Aerosol-forming substrate having expanded graphite

Abstract

An aerosol-forming substrate for use in a heated aerosol-generating article includes expanded graphite particles, which have high thermal conductivity and low density and can improve the efficiency of aerosol delivery from the substrate.

Description

[Technical field]

[0001] The present disclosure relates to an aerosol-forming substrate. The present disclosure also relates to a method of making the aerosol-forming substrate, an aerosol-generating article, and an aerosol-generating system. [Background technology]

[0002] A typical aerosol generating system comprises an aerosol generating device and an aerosol-generating article that includes an aerosol-forming substrate. In use, the aerosol generating device interacts with the aerosol-generating article to heat the aerosol-forming substrate, causing the aerosol-forming substrate to release volatile compounds. These compounds then cool to form an aerosol, which is inhaled by the user.

[0003] Known aerosol-forming substrates typically have a relatively low thermal conductivity. This may be particularly undesirable in aerosol generating systems where a blade is inserted into the aerosol-forming substrate and heated to heat the aerosol-forming substrate. This is because the low thermal conductivity of the aerosol-forming substrate may cause a relatively large temperature gradient in the aerosol-forming substrate during use. This may mean that the part of the aerosol-forming substrate located farthest from the blade does not reach high temperatures and therefore does not release as many volatile compounds as if the aerosol-forming substrate had a higher thermal conductivity. In other words, aerosol-forming substrates with low thermal conductivity may undesirably lead to a low usage efficiency of the aerosol-forming substrate.

[0004] Furthermore, known aerosol-forming substrates are typically not inductively heatable to operating temperatures. This means that a separate susceptor element is typically required for inductive heating, which can increase costs. Furthermore, this can result in the same problems as described above. For example, if an inductively heated susceptor element is placed in a central position on the substrate, the part of the aerosol-forming substrate that is located furthest from the susceptor element may not reach high temperatures and therefore not emit many volatile compounds.

[0005] Attempts have been made to increase the thermal conductivity of aerosol-forming substrates, but so far these attempts have been inadequate in one or more respects.

[0006] It is an object of the present invention to provide an improved aerosol-forming substrate, for example an aerosol-forming substrate having increased thermal conductivity. Summary of the Invention

[0007] According to the present disclosure, an aerosol-forming substrate is provided that includes expanded graphite particles. The aerosol-forming substrate may include an aerosol-forming material, such as expanded graphite particles and an aerosol former. The aerosol-forming substrate may include more than 0.1 weight percent (wt.%) of expanded graphite particles. The volume average particle size of the expanded graphite particles may be more than 5 microns, such as more than 10 microns. The aerosol-forming substrate may have a thermal conductivity greater than that of a homogenized tobacco substrate. The aerosol-forming substrate may have a thermal conductivity in at least one direction, e.g., when measured at a temperature of 25 degrees Celsius, of more than 0.12 W / mk. In some specific embodiments, the aerosol-forming substrate may have a thermal conductivity in at least one direction, e.g., when measured at a temperature of 25 degrees Celsius, of more than 0.22 W / mk.

[0008] An exemplary aerosol-forming substrate may comprise, on a dry weight basis, 1-90% by weight expanded graphite particles, each expanded graphite particle having a thermal conductivity of at least 1 W / (mK) in at least one direction at 25 degrees Celsius, 7-60% by weight aerosol former, 2-20% by weight fibers, and 2-10% by weight binder, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12 W / (mK) in at least one direction at 25 degrees Celsius. For example, an exemplary aerosol-forming substrate may comprise, on a dry weight basis, 1-10% by weight of expanded graphite particles, each expanded graphite particle having a thermal conductivity of at least 1 W / (mK) in at least one direction at 25 degrees Celsius, 7-20% by weight of an aerosol former, 2-20% by weight of fibers, and 2-10% by weight of a binder, the aerosol-forming substrate having a thermal conductivity of at least 0.12 W / (mK) in at least one direction at 25 degrees Celsius. The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco.

[0009] Advantageously, the expanded graphite particles may increase the thermal conductivity of the aerosol-forming substrate. The increased thermal conductivity of the substrate may provide a more uniform temperature distribution throughout the substrate during use. This may allow a greater proportion of the aerosol-forming substrate to reach a temperature high enough to release the volatile compound, and therefore a more efficient use of the aerosol-forming substrate. Furthermore, the increased thermal conductivity of the substrate may allow a heater, e.g., a heating blade configured to heat the substrate, to operate at a lower temperature and therefore require less power. Furthermore, the increased thermal conductivity of the substrate may allow the heater to heat the substrate to a temperature at which the volatile compound is released in a shorter time. Thus, the increased thermal conductivity may reduce the time required to form an aerosol that can be inhaled by a user.

[0010] Expanded graphite is a modified graphite material. Expanded graphite has a layer structure similar to graphite, but the spacing between the layers is increased or expanded. Particularly advantageously, expanded graphite has a lower density than graphite. Thus, an aerosol-forming substrate made of expanded graphite particles can be formed at a lower density compared to a similar substrate made using a comparable particle size of regular, unexpanded, graphite or other conductive particles. A low density substrate can allow aerosol-generating articles to be made with a lower total weight while providing comparable aerosol delivery. This can advantageously reduce shipping costs. Even a lower density aerosol-forming substrate, if it has the same or higher thermal conductivity, can have a lower thermal inertia, which can reduce preheat time and time to first puff.

[0011] Advantageously, one or both of the fibers and the binder may increase the tensile strength of the aerosol-forming substrate. Increasing the tensile strength may allow for the production of sheets of the aerosol-forming substrate that do not tear easily. Increasing the tensile strength may allow for the production of sheets of the aerosol-forming substrate using existing manufacturing machinery.

[0012] As mentioned above, the aerosol-forming substrate may have a thermal conductivity of at least 0.12 W / (mK), such as at least 0.22 W / mK, in at least one direction at 25 degrees Celsius. This thermal conductivity may be measured when the moisture content of the substrate is 0-20%, or 5-15%, such as about 10%. This thermal conductivity may also be measured when the substrate contains 0-20% by weight, or 5-15% by weight, such as about 10% by weight water. The moisture or moisture content of the substrate may be measured using a titration method. The moisture or moisture content of the substrate may be measured using the Karl Fisher method.

[0013] The expanded graphite particles may have anisotropic thermal conductivity values, for example, some or each of the expanded graphite particles may have a thermal conductivity of greater than 2, 5, 10, 20, 50, 100, 200, 500, or 1000 W / mK in at least one direction when measured at 25 degrees Celsius.

[0014] Expanded graphite can be expanded up to 100 to 300 times compared to unexpanded graphite. Expanded graphite can be expanded in amounts of 2, 1.8, 1.5, 1.2, 1, 0.8, or 0.5, 0.2, 0.1, 0.05, or 0.02 grams per cubic centimeter (g / cm 3 The expanded graphite may have a density of less than 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, or 1.8 grams per cubic centimeter (g / cm 3 ) The expanded graphite may have a density of 0.01-3, 0.01-2, 0.01-1.8, 0.01-1.5, 0.01-1.2, 0.01-1, 0.01-0.8, 0.01-0.5, 0.02-3, 0.02-2, 0.02-1.8, 0.02-1.5, 0.02-1.2, 0.02-1, 0.02-0.8, 0.02-0.5, 0.01-3, 0.05-2, 0.05-1.8, 0.05-1.5, 0.05-1.2, 0.05-1, 0.05-0.8, 0.05-0.5 g / cm 3、 0.1~3, 0.1~2, 0.1~1.8, 0.1~1.5, 0.1~1.2, 0.1~1, 0.1~0.8, 0.1~0.5, 0.2~3, 0.2~2, 0.2~1.8, 0.2~1.5, 0.2~1.2, 0.2~1, 0.2~0.8, 0.2~0.5, 0.5~3, 0.5~2, 0.5~1.8, 0.5~1.5, 0.5~1.2, 0.5~1, 0.5~0.8, 0.8~3, 0.8~2, 0.8~1.8, 0.8~1.5, 0.8~1.2, 0.8~1 grams per cubic centimeter (g / cm 3 )

[0015] The expanded graphite particles may each have a certain "particle size." The meaning of the term "particle size" and the method for measuring particle size are explained below.

[0016] The expanded graphite particles may be characterized by a particle size distribution. The particle size distribution may have a number D10, D50, and D90 particle size. The number D10 particle size is defined such that 10% of the particles have a particle size equal to or smaller than the number D10 particle size. Similarly, the number D50 particle size is defined such that 50% of the particles have a particle size equal to or smaller than the number D50 particle size. Thus, the number D50 particle size may also be referred to as the median particle size. The number D90 particle size is defined such that 90% of the particles have a particle size equal to or smaller than the number D90 particle size. Thus, if there are 1,000 particles in a distribution and the particles are ordered by increasing size, the number D10 particle size is expected to be approximately equal to the 100th particle size, the number D50 particle size is expected to be approximately equal to the 500th particle size, and the number D90 particle size is expected to be approximately equal to the 900th particle size.

[0017] The particle size distribution may have volume D10, D50, and D90 particle sizes. The volume D10 particle size is defined such that 10% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D10 particle size. Similarly, the volume D50 particle size is defined such that 50% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D50 particle size. Also, the volume D90 particle size is defined such that 90% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D90 particle size.

[0018] Optionally, the expanded graphite particles have a particle size distribution with a number D10 particle size, the number D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0019] Optionally, the thermally conductive particles have a particle size distribution with a particle size number D10, the particle size number D10 being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0020] A compromise must be made in determining particle size. Larger expanded graphite particles can advantageously increase the thermal conductivity of an aerosol-forming substrate more than smaller expanded graphite particles. However, larger expanded graphite particles can reduce the space within the substrate available to the aerosol-forming material.

[0021] Optionally, the expanded graphite particles have a particle size distribution with a number D50 particle size, the number D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0022] Optionally, the thermally conductive particles have a particle size distribution with a particle size number D50, the particle size number D50 being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0023] Optionally, the expanded graphite particles have a particle size distribution with a number D90 particle size, the number D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0024] Optionally, the thermally conductive particles have a particle size distribution with a particle size number D90, the particle size number D90 being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0025] Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size and a number D90 particle size, the number D90 particle size being no greater than 50, 40, 30, 20, 10, or 5 times the number D10 particle size.

[0026] Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size and a number D90 particle size, the number D90 particle size being at least 1.5, 2, 3, 5, 10, or 20 times the number D10 particle size.

[0027] A compromise must be made regarding particle size distribution. A tighter particle size distribution, characterized by a smaller ratio between D90 and D10 particle sizes, may advantageously provide a more uniform thermal conductivity throughout the aerosol-forming substrate. This is because there is less variation in particle size at different locations within the substrate. This may advantageously allow for more efficient use of the aerosol-forming material throughout the aerosol-forming substrate. However, a tight particle size distribution may be disadvantageously more difficult and expensive to achieve. The inventors have found that the particle size distribution described above may provide an optimal compromise between these two factors.

[0028] Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size, the volume D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0029] Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size that is less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0030] Optionally, the expanded graphite particles have a particle size distribution having a volume D50 particle size, the volume D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0031] Optionally, the expanded graphite particles have a particle size distribution having a volume D50 particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0032] Optionally, the expanded graphite particles have a particle size distribution having a volume D90 particle size, the volume D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0033] Optionally, the expanded graphite particles have a particle size distribution having a volume D90 particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0034] It may be particularly preferred that the expanded graphite particles have a particle size distribution with a volume D10 particle size of 1 to 20 microns. Alternatively, or additionally, it may be particularly preferred that the expanded graphite particles have a particle size distribution with a volume D90 particle size of 50 to 300 microns, or 50 to 200 microns.

[0035] Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, the volume D90 particle size being no greater than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size.

[0036] Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, the volume D90 particle size being at least 1.5, 2, 3, 5, 10, or 20 times the volume D10 particle size.

[0037] The expanded graphite can have a volume average particle size of 1, 2, 3, 5, 10, 20, 30, 35, 50, 75, 100, 150, 200, 250, 500, or 900 micrometers or more.

[0038] It may be particularly preferred that the expanded graphite particles have a volume average particle size of greater than 10 micrometers.

[0039] The expanded graphite particles may have a volume average particle size of 1000, 900, 500, 200, 100, 150, 100, 75, 50, 35, 30, 20, 10, 5, 3, or 2 micrometers or less. The expanded graphite particles may have a volume average particle size of 1 to 1000, 35 to 1000, or 100 to 900 micrometers. These particle size ranges may be particularly preferred when the aerosol-forming material includes or is in the form of one or more of cut filler, powder particles, granules, pellets, pieces, spaghetti, strips, or sheets.

[0040] The expanded graphite particles may have a volume average particle size of 1 to 1000, 10 to 200, 30 to 150, or 50 to 75 micrometers. These volume average particle size ranges may be particularly preferred when the aerosol-forming material includes or is in the form of a sheet, such as an assembly of sheets.

[0041] The expanded graphite particles can have a volume average particle size that is at least 2, 3, 5, 8, 10, 15, or 20 times the number average particle size.

[0042] As explained above, a compromise has to be made with respect to particle size distribution and the inventors have found that the particle size distribution described above may provide an optimal compromise.

[0043] Optionally, each of the expanded graphite particles has a particle size of at least 0.01, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Optionally, each of the expanded graphite particles has a particle size of 1,000, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less. It may be particularly preferred that each of the expanded graphite particles has a particle size of at least 1 micron. Alternatively, or additionally, it may be particularly preferred that each of the expanded graphite particles has a particle size of 300 microns or less. Particles smaller than 1 micron may be difficult to handle during manufacturing. Particles larger than 300 microns may occupy a significant amount of space within a substrate that may be used for the aerosol-forming material. Thus, it may be particularly advantageous for each of the expanded graphite particles to have a particle size of at least 1 micron, or a particle size of no greater than 300 microns, or both.

[0044] Optionally, each of the expanded graphite particles has three mutually orthogonal dimensions, with the largest of the three dimensions being no greater than 10, 8, 5, 3, or 2 times the smallest of the three dimensions. Optionally, each of the expanded graphite particles has three mutually orthogonal dimensions, with the largest of the three dimensions being no greater than 10, 8, 5, 3, or 2 times the second largest of the three dimensions. Optionally, each of the expanded graphite particles is substantially spherical.

[0045] Optionally, the aerosol-forming substrate comprises at least 10, 20, 50, 100, 200, 500, or 1000 expanded graphite particles. Advantageously, a greater number of expanded graphite particles in the aerosol-forming substrate may allow for a more uniform thermal conductivity of the substrate.

[0046] In some embodiments, the aerosol-forming substrate may have a relatively low proportion of expanded graphite particles. For example, the substrate may comprise an aerosol-forming material such as homogenized tobacco containing 0.1-25% by weight of expanded graphite particles. The expanded graphite particles may comprise 80, 50, 20, 10, or 5% or less by weight of the aerosol-forming substrate. The expanded graphite particles may comprise 0.1, 0.2, 0.5, 1, 2, 3, 5, 10, 20, or 50% or more by weight of the aerosol-forming substrate. The expanded graphite particles may comprise 0.1-20, 0.2-20, 0.5-20, 1-20, 2-20, 3-20, 5-20, 0.1-15, 0.2-15, 0.5-15, 1-15, 2-15, 3-15, 5-15, 0.1-10, 0.2-10, 0.5-10, 1-10, 2-10, 3-10, or 5-10% by weight of the aerosol-forming substrate. The expanded graphite particles may comprise 0.1-20, 0.2-20, 0.5-20, 1-20, 2-20, 3-20, 5-20, 0.1-15, 0.2-15, 0.5-15, 1-15, 2-15, 3-15, 5-15, 0.1-10, 0.2-10, 0.5-10, 1-10, 2-10, 3-10, or 5-10% by weight of the aerosol-forming substrate.

[0047] It may be particularly preferred that the expanded graphite particles account for more than 1% by weight of the aerosol-forming substrate. It may also be preferred that the expanded graphite particles account for less than 20% by weight of the aerosol-forming substrate. Advantageously, the inventors have found that such weight percentages provide an optimal compromise between increasing the thermal conductivity of the aerosol-forming substrate and maintaining sufficient aerosol-forming material, e.g. homogenized tobacco, to form a suitable amount of aerosol. It may be particularly preferred that the expanded graphite particles account for 1-20, 2-15, or 3-10% by weight of the aerosol-forming substrate. This is because the inventors have found that for a particular aerosol-forming substrate, these weight percentage ranges may provide a more consistent glycerol and nicotine delivery over approximately 12 puffs. Without wishing to be bound by theory, it is believed that this is because having less than 1, 2 or 3 wt% of expanded graphite particles does not have a large enough effect on the thermal conductivity of the substrate, while more than 10, 15 or 20 wt% of expanded graphite particles raises the local substrate temperature too high and too fast, resulting in relatively high glycerol and nicotine delivery in the initial puff, but relatively low glycerol and nicotine delivery in subsequent puffs. In addition, the inventors have surprisingly found that for a particular aerosol-forming substrate, the total yield of glycerol and nicotine over approximately 12 puffs appears to reach a maximum for substrates having 1-20, 2-15 or 3-10 wt% of expanded graphite particles. This may be advantageous, since less substrate may be required to deliver an equal amount of glycerol and nicotine to the user.

[0048] In some embodiments, the aerosol-forming substrate may include a relatively high percentage of expanded graphite particles, e.g., expanded graphite particles, binder, fiber component, and aerosol former. Optionally, the substrate includes at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85% by weight of expanded graphite particles on a dry weight basis. Optionally, the substrate includes 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15% by weight of expanded graphite particles on a dry weight basis. Optionally, the substrate comprises 10-90, 20-90, 30-90, 40-90, 50-90, 60-90, 70-90, 80-90, 10-80, 20-80, 30-80, 40-80, 50-80, 60-80, 70-80, 10-70, 20-70, 30-70, 40-70, 50-70, 60-70, 10-60, 20-60, 30-60, 40-60, 50-60, 10-50, 20-50, 30-50, 40-50, 10-40, 20-40, 30-40, 10-30, 20-30, or 10-20 weight percent of expanded graphite particles on a dry weight basis. It may be particularly preferred that the substrate comprises 50 to 90, or more preferably 60 to 90, or even more preferably 65 to 85, weight percent of the expanded graphite particles on a dry weight basis.

[0049] A compromise may need to be made regarding the weight percentage of expanded graphite particles in the substrate. Increasing the weight percentage of particles in the aerosol-forming substrate may advantageously increase the thermal conductivity of the substrate. However, increasing the weight percentage of particles in the aerosol-forming substrate may also reduce the space available to one or more of the aerosol formers, binders, and fibers, which may result in a substrate that forms less aerosol or has lower tensile strength.

[0050] Optionally, the substrate comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55% by weight of the aerosol former on a dry weight basis. Optionally, the substrate comprises no more than 55, 50, 45, 40, 35, 30, 25, 20, or 15% by weight of the aerosol former on a dry weight basis. Optionally, the substrate comprises 7-60, 10-60, 20-60, 30-60, 40-60, 50-60, 7-50, 10-50, 20-50, 30-50, 40-50, 7-40, 10-40, 20-40, 30-40, 7-30, 10-30, 20-30, 7-20, 10-20, or 7-10% by weight of the aerosol former on a dry weight basis. It may be particularly preferred for the substrate to contain from 15 to 25 weight percent of the aerosol former on a dry weight basis.

[0051] Optionally, the aerosol former comprises or consists of one or more of polyhydric alcohols (such as propylene glycol, polyethylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol), mono-, di-, or tri-acetates, and aliphatic esters or mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Optionally, the aerosol-forming substrate comprises one or both of glycerin and glycerol.

[0052] Optionally, the substrate comprises at least 2, 4, 6, 8, 10, 12, 14, 16, or 18% by weight of fibers on a dry weight basis. Optionally, the substrate comprises no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4% by weight of fibers on a dry weight basis. Optionally, the substrate comprises 4-20, 6-20, 8-20, 10-20, 12-20, 14-20, 16-20, 18-20, 2-18, 4-18, 6-18, 8-18, 10-18, 12-18, 14-18, 16-18, 2-16, 4-16, 6-16, 8-16, 10 % fibers by weight. It may be particularly preferred that the substrate comprises 2.1 to 9.8% fibers by weight, on a dry weight basis.

[0053] Optionally, the fibers are cellulose fibers. Advantageously, cellulose fibers are not overly expensive and can increase the tensile strength of the substrate.

[0054] Optionally, each of the fibers has three mutually orthogonal dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than the smallest of the three dimensions. Optionally, each of the fibers has three mutually orthogonal dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than a second largest of the three dimensions.

[0055] Optionally, the substrate comprises at least 4, 6, or 8% by weight of binder on a dry weight basis. Optionally, the substrate comprises no more than 8, 6, or 4% by weight of binder on a dry weight basis. Optionally, the substrate comprises 4-10, 6-10, 8-10, 2-8, 4-8, 6-8, 2-6, 4-6, 2-4% by weight of binder on a dry weight basis. It may be particularly preferred that the substrate comprises 2.1-10% by weight of binder on a dry weight basis.

[0056] Preferred binders are well known in the art and include, but are not limited to, natural pectins (such as fruit pectins, citrus pectins, or tobacco pectins), guar gums (such as hydroxyethyl guar and hydroxypropyl guar), locust bean gums (such as hydroxyethyl and hydroxypropyl locust bean gums), alginates, starches (such as modified or derivatized starches), celluloses (such as methylcellulose, ethylcellulose, ethylhydroxymethylcellulose, and carboxymethylcellulose), tamarind gum, dextran, pralon, konjac flour, xanthan gum, and the like. It may be particularly preferred that the binder is or comprises guar. It may be particularly preferred that the binder comprises or consists of one or more of carboxymethylcellulose or hydroxypropylcellulose, or a gum such as guar gum.

[0057] Optionally, the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the aerosol formers are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the fibers are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Advantageously, the homogeneous distribution of the substrate's components may result in the substrate having more spatially uniform properties. For example, substantially homogeneously distributed expanded graphite particles may result in a substrate having a substantially uniform thermal conductivity. As another example, substantially homogeneously distributed binder or fibers may result in a substrate having a substantially uniform tensile strength.

[0058] Optionally, the substrate comprises nicotine. Optionally, the substrate comprises at least 0.01, 1, 2, 3, or 4% by weight of nicotine on a dry weight basis. Optionally, the substrate comprises no more than 5, 4, 3, 2, or 1% by weight of nicotine on a dry weight basis. Optionally, the substrate comprises 0.01-5, 1-5, 2-5, 3-5, 4-5, 0.01-4, 1-4, 2-4, 3-4, 0.01-3, 1-3, 2-3, 0.01-2, 1-2, 0.01-1% by weight of nicotine on a dry weight basis. It may be particularly preferred that the substrate comprises 0.5-3% by weight of nicotine on a dry weight basis.

[0059] Optionally, the nicotine is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0060] Optionally, the substrate comprises an acid. Optionally, the substrate comprises at least 0.01, 1, 2, 3, or 4% by weight of acid on a dry weight basis. Optionally, the substrate comprises no more than 5, 4, 3, 2, or 1% by weight of acid on a dry weight basis. Optionally, the substrate comprises 0.01-5, 1-5, 2-5, 3-5, 4-5, 0.01-4, 1-4, 2-4, 3-4, 0.01-3, 1-3, 2-3, 0.01-2, 1-2, 0.01-1% by weight of acid on a dry weight basis. It may be particularly preferred that the substrate comprises 0.5-3% by weight of acid on a dry weight basis.

[0061] Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0062] Optionally, the acid is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0063] Optionally, the substrate comprises at least one plant. Optionally, the substrate comprises at least 0.01, 1, 2, 5, 10, or 15% by weight, on a dry weight basis, of at least one plant. Optionally, the substrate comprises no more than 20, 15, 10, 5, 2, or 1% by weight, on a dry weight basis, of at least one plant. Optionally, the substrate comprises 0.01-20, 1-20, 2-20, 5-20, 10-20, 15-20, 0.01-15, 1-15, 2-15, 5-15, 10-15, 0.01-10, 1-10, 2-10, 5-10, 0.01-5, 1-5, 2-5, 0.01-2, 1-2, 0.01-1% by weight, on a dry weight basis, of at least one plant. It may be particularly preferred that the substrate comprises from 5 to 15% by weight, on a dry weight basis, of at least one plant component.

[0064] Optionally, the at least one plant includes or consists of one or both of clove and rosmarinus.

[0065] Optionally, the at least one plant is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0066] Optionally, the substrate comprises at least one flavorant. Optionally, the substrate comprises at least 0.1, 1, 2, or 5% by weight, on a dry weight basis, of at least one flavorant. Optionally, the substrate comprises no more than 10, 5, 2, or 1% by weight, on a dry weight basis, of at least one flavorant. Optionally, the substrate comprises 0.1-10, 1-10, 2-10, 5-10, 0.1-5, 1-5, 2-5, 0.1-2, 1-2, 0.1-1% by weight, on a dry weight basis, of at least one flavorant. It may be particularly preferred that the substrate comprises 0.5-4.0% by weight, on a dry weight basis, of at least one flavorant.

[0067] Optionally, the at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate. Alternatively, or additionally, the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0068] Optionally, the aerosol-forming substrate comprises at least one organic material, such as tobacco. The at least one organic material comprises one or more of herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the at least one organic material is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0069] The substrate may comprise less than 10, 5, 3, 2 or 1% by weight of tobacco on a dry weight basis.Optionally, the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

[0070] The aerosol-forming substrate may be in the form of a rod, so that a rod of the aerosol-forming substrate may be provided.

[0071] The susceptor element may be located within the rod of the aerosol-forming substrate. The susceptor element may be an elongated susceptor element. The susceptor element may extend longitudinally within the rod of the aerosol-forming substrate. The rod may be substantially cylindrical, for example, right cylindrical. The susceptor element may be located at a radially central position within the rod of the aerosol-forming substrate. The susceptor element may extend along a central longitudinal axis of the rod of the aerosol-forming substrate. The susceptor element may extend all the way to the downstream end of the rod of the aerosol-forming substrate. The susceptor element may extend all the way to the upstream end of the rod of the aerosol-forming substrate. The susceptor element may have substantially the same length as the rod of the aerosol-forming substrate. The susceptor element may extend from the upstream end to the downstream end of the rod of the aerosol-forming substrate. The susceptor element may be in the form of a pin, rod, strip, or blade. The susceptor element may have a length of 5 to 15 millimeters, 6 to 12 millimeters, or 8 to 10 millimeters. The susceptor element may have a width of 1 to 5 millimeters. The susceptor element may have a thickness of 0.01 to 2 millimeters, 0.5 to 2 millimeters, or 0.5 to 1 millimeter.

[0072] Alternatively, there may be no susceptor material within the aerosol-forming substrate or within the rod of the aerosol-forming substrate.

[0073] Optionally, some or each of the expanded graphite particles may be inductively heatable, for example to a temperature of at least 100 degrees Celsius, 150 degrees Celsius, or 200 degrees Celsius. The expanded graphite particles may comprise or be the only susceptor material present within the aerosol-forming substrate or within the rod of the aerosol-forming substrate, i.e., there may be cases where there are no susceptor elements present within the aerosol-forming substrate or within the rod of the aerosol-forming substrate, other than the expanded graphite particles.

[0074] Optionally, the aerosol-forming substrate has a thermal conductivity in at least one direction greater than 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.25, 1.5, 2, 5, 10, 20, 50, 100, 200, or 500 W / (mK) at 25 degrees Celsius.

[0075] Optionally, the aerosol-forming substrate has a viscosity of 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, 650, or 600 kg / m 3 Optionally, the aerosol-forming substrate has a density of from 600 to 1400 kg / m 3 , 800~1200kg / m 3 , or 900-1100kg / m 3 Advantageously, by reducing the density of the substrate, the cost of shipping the substrate may be reduced.

[0076] Optionally, the aerosol-forming substrate has a moisture content of 1-20, or 3-15% by weight. The moisture content may be measured after 48 hours of equilibration at 50% relative humidity and 20 degrees Celsius. Optionally, the aerosol-forming substrate comprises 1-20, or 3-15% water by weight. The moisture or moisture content of the substrate may be measured using a titration method. The moisture or moisture content of the substrate may be measured using the Karl Fisher method.

[0077] Optionally, the aerosol-forming substrate comprises or is in the form of one or more of cut filler, powder particles, granules, pellets, pieces, spaghetti, strips, threads, ribbons, or sheets. Optionally, the aerosol-forming substrate comprises or is in the form of one or more sheets or strips.

[0078] Optionally, the aerosol-forming substrate comprises or is in the form of one or more sheets, such as a collection of sheets or a roll of sheets. Optionally, the aerosol-forming substrate comprises or is in the form of a plurality of strips. Optionally, the aerosol-forming substrate may be in the form of a tube.

[0079] Optionally, the or each sheet or strip has a thickness of at least 5, 10, 20, 50, 100, 150, or 200 microns. Optionally, the or each sheet or strip has a thickness of no more than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the or each sheet or strip has a thickness of 100-350 microns, or 150-300 microns.

[0080] Optionally, the or each sheet or strip has a width of at least 100, 200, 500, or 1000 microns. Optionally, the or each sheet or strip has a width of no more than 2000, 1000, 500, 400, 300, 250, or 200 microns. Optionally, the or each sheet or strip has a width of 100-2000 microns, or 500-1000 microns, or 600-1000 microns.

[0081] Optionally, the sheets or strips, or each of them, have a length of at least 100, 200, 500, 1000, 2000, or 3000 microns. Optionally, the sheets or strips, or each of them, have a length of no more than 6000, 5000, 3000, 2000, 1000, 500, or 200 microns. Optionally, the sheets or strips, or each of them, have a length of 100-6000 microns, or 500-5000 microns, or 1000-4000 microns.

[0082] Optionally, the sheet or strip, or each, has a density of at least 20, 50, or 100 g / m 2 Optionally, the sheet or strip, or each, has a basis weight of 300 g / m 2 Optionally, the sheet or strip, or each, has a basis weight of from 20 to 300 g / m 2 , 50~250g / m 2 , or 100~250g / m 2 The sheet has a basis weight of 1.0 g.

[0083] Optionally, the sheet or strip, or each, has a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 Optionally, the sheet or strip, or each, has a density of 2, 1.5, 1.2, or 1 g / m 3 Optionally, the sheet or strip, or each, has a density of from 0.1 to 2 g / m 3 , 0.2~2g / m 3 , 0.3~2g / m 3, 0.3~1.5g / m 3 , or 0.3 to 1.2 g / m 3 has a density of

[0084] When the substrate comprises one or more collections of sheets, the or each collection of sheets may have a width of at least about 1, 2, 5, 10, 25, 50, or 100 mm.

[0085] Optionally, the aerosol-forming substrate comprises an aerosol former and expanded graphite particles constituting 3% to 90% by weight of a second material on a dry weight basis, the second material configured to generate an aerosol when heated to a temperature of 120 degrees Celsius to 395 degrees Celsius. Optionally, the aerosol-forming substrate comprises tobacco, an aerosol former and expanded graphite particles constituting 3% to 90% by weight of the second material on a dry weight basis, the second material configured to generate an aerosol when heated to a temperature of 120 degrees Celsius to 395 degrees Celsius. Optionally, the aerosol-forming substrate is a thermally conductive homogenized tobacco material comprising expanded graphite particles, and further comprising fibers and a binder.

[0086] Optionally, the aerosol-forming substrate is tobacco-free, for example the substrate is a thermally conductive tobacco-free material comprising expanded graphite particles, and further comprises fibres and a binder.

[0087] According to a second aspect of the present disclosure, there is also provided an aerosol-generating article.

[0088] The article may comprise an aerosol-forming substrate as described above, for example an aerosol-forming substrate according to the first aspect.

[0089] Optionally, the article is in the form of a rod and comprises an aerosol-forming substrate assembled within a wrapper or casing or multiple components including combined aerosol-forming substrates.

[0090] Optionally, the aerosol-generating article comprises a front plug. Optionally, the aerosol-generating article comprises a first hollow tube, e.g., a first hollow acetate tube. Optionally, the aerosol-generating article comprises a second hollow tube, e.g., a second hollow acetate tube. Optionally, the second hollow tube comprises one or more vent holes. Optionally, the aerosol-generating article comprises a mouth-side plug filter. Optionally, the aerosol-generating article comprises a wrapper, e.g., a paper wrapper.

[0091] Optionally, the front plug is disposed at the most upstream end of the article. Optionally, the aerosol-forming substrate is disposed downstream of the front plug. Optionally, the first hollow tube is disposed downstream of the aerosol-forming substrate. Optionally, the second hollow tube is disposed downstream of the first hollow tube. Optionally, the mouth plug filter is disposed downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth plug filter is disposed at the most downstream end of the article. Optionally, the most downstream end of the article, which may be referred to as the mouth end of the article, may be configured to be inserted into the mouth of a user. The user may, for example, be able to directly inhale the mouth end of the article.

[0092] Optionally, the front plug, the aerosol-forming substrate, one or both of the first and second hollow tubes, and the oral plug filter are surrounded by a wrapper, for example a paper wrapper.

[0093] Optionally, the front plug has a length of 2-10 mm, 3-8 mm, or 4-6 mm, for example about 5 mm. Optionally, the aerosol-forming substrate has a length of 5-20 mm, 8-15 mm, or 10-15 mm, for example about 12 mm. Optionally, the first hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, for example about 8 mm. Optionally, the second hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, for example about 8 mm. Optionally, the mouth plug filter has a length of 5-20 mm, 8-15 mm, or 10-15 mm, for example about 12 mm. The length of one or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter may extend longitudinally.

[0094] One or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the oral plug filter may be substantially cylindrical in shape, for example a right cylinder.

[0095] According to a third aspect of the present disclosure, an aerosol generation system is provided.

[0096] The system may comprise an aerosol generating article and an electrical aerosol generating device. The article may be as described above, for example an article according to the second aspect.

[0097] Optionally, the electrical aerosol generating device is configured to resistively heat the aerosol-generating article in use.

[0098] Optionally, the electrical aerosol generating device is configured, in use, to inductively heat the aerosol-generating article, for example an aerosol-forming substrate of the aerosol-generating article.

[0099] According to the present disclosure, there is provided a method of forming an aerosol-forming substrate, such as the substrate described above, such as the substrate according to the first aspect. The method may include forming a slurry including one or more or all of the expanded graphite particles, the aerosol former, fibers, and a binder. The method may include casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming into the aerosol-forming substrate.

[0100] Thus, according to a fourth aspect of the present disclosure there is provided a method of forming an aerosol-forming substrate, for example a substrate as described above, such as a substrate according to the first aspect, the method comprising: forming a slurry including expanded graphite particles, an aerosol former, fibers, and a binder; Casting and drying the slurry to form an aerosol-forming substrate or a precursor for forming into an aerosol-forming substrate.

[0101] Optionally, the slurry comprises water. Optionally, the slurry comprises 20-90, 30-90, 40-90, 40-85, 50-80, 60-80, or 60-75 wt % water.

[0102] Optionally, the slurry comprises an acid. Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0103] Optionally, the slurry includes nicotine.

[0104] Optionally, forming the slurry includes forming a first mixture. The first mixture may include an aerosol former. The first mixture may include fibers. The first mixture may include water. The first mixture may include an acid. The first mixture may include nicotine. Forming the slurry may include forming a second mixture. The second mixture may include expanded graphite particles. The second mixture may include a binder. Forming the slurry may include adding the second mixture to the first mixture to form a combined mixture.

[0105] Thus, forming a slurry includes: forming a first mixture including an aerosol former, fibers, water, optionally an acid, and optionally nicotine; forming a second mixture comprising expanded graphite particles and a binder; adding the second mixture to the first mixture to form a combined mixture.

[0106] The combined mixture may then be formed into a slurry, for example by mixing.

[0107] Optionally, forming the first mixture includes providing an aerosol former, or a solution including an aerosol former and nicotine.

[0108] Optionally, forming the first mixture includes adding an acid to an aerosol former, or a solution including an aerosol former and nicotine, to form a first pre-mixture.

[0109] Optionally, forming the first mixture includes adding water to the aerosol former, or to a solution comprising the aerosol former and nicotine, or to the first pre-mixture to form a second pre-mixture.

[0110] Optionally, forming the first mixture includes adding fibers to the second pre-mixture.

[0111] Optionally, forming the second mixture includes mixing expanded graphite particles with a binder.

[0112] Optionally, the method, e.g., forming a slurry, includes a first mixing of the combined mixture. Optionally, the first mixing is performed under a first pressure of less than or equal to 500, 400, 300, 250, or 200 mbar. Optionally, the first mixing is performed for 1-10 minutes, 2-8 minutes, or 3-6 minutes, e.g., about 4 minutes.

[0113] Optionally, the method, e.g., forming a slurry, includes a second mixing after the first mixing. Optionally, the second mixing is performed under a second pressure less than the first pressure. Optionally, the second pressure is less than or equal to 500, 400, 300, 200, 150, or 100 mbar. Optionally, the second mixing is performed for 5-120 seconds, 5-80 seconds, 5-40 seconds, or 10-30 seconds, e.g., about 20 seconds.

[0114] Optionally, casting the slurry includes casting the slurry onto a flat support, such as a flat steel support.

[0115] Optionally, after casting the slurry and before drying the slurry, the method includes setting a thickness of the slurry, for example setting a thickness of the slurry between 100 and 1200 microns, between 200 and 1000 microns, between 300 and 900 microns, between 500 and 700 microns, for example about 600 microns.

[0116] Optionally, drying the slurry includes providing a flow of gas, such as air, over or through the slurry. Optionally, the flow of gas is heated. Optionally, the flow of gas is heated to a temperature of 100-160 degrees Celsius, or 120-140 degrees Celsius. Optionally, the flow of gas is provided for 1-10 minutes, or 2-5 minutes. Optionally, drying the slurry includes drying the slurry until the slurry has a moisture content of 1-20, 2-15, 2-10, or 3-7% by weight.

[0117] Optionally, the slurry is dried to form a precursor for forming into an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method includes cutting the sheet of aerosol-forming material.

[0118] As will be understood by those of skill in the art upon reading this disclosure, features described herein in relation to one embodiment may be applicable to any other embodiment, for example features described in relation to the combined aerosol-forming substrate of the second embodiment, or in relation to the first and second materials of the combined aerosol-forming substrate of the second embodiment, may be applicable to the aerosol-forming substrate of the first embodiment, and vice versa.

[0119] As used herein, the term "aerosol-forming substrate" may refer to a substrate capable of emitting an aerosol or volatile compound capable of forming an aerosol. Such a volatile compound may be emitted by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise an aerosol-forming material. The aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or support. The aerosol-forming substrate may conveniently be part of an aerosol-generating article or a smoking article.

[0120] As used herein, the term "thermally conductive particles" may refer to particles having a thermal conductivity of greater than 1 W / (MK) in at least one direction at 25 degrees Celsius, such as in all directions at 25 degrees Celsius. The particles may exhibit anisotropic or isotropic thermal conductivity.

[0121] As used herein, the term "expanded graphite" may refer to a graphite-based material or a material having a graphite-like structure. Expanded graphite may have carbon layers (e.g., similar to graphite) where the spacing between the carbon layers is greater than the spacing found between the carbon layers of regular graphite. Expanded graphite may have carbon layers with elements or compounds interposed within the spaces between the carbon layers.

[0122] As used herein, the term "particle size" may refer to a single dimension and may be used to characterize a given particle size. The dimension may be the diameter of a spherical particle that occupies the same volume as the given particle. All particle sizes and particle size distributions herein may be obtained using standard laser diffraction techniques. The particle sizes and particle size distributions described herein may be obtained using commercially available sensors, such as Sympatec's HELOS laser diffraction sensor.

[0123] As used herein, unless otherwise specified, the term "density" may be used to refer to true density. Thus, unless otherwise specified, the density of a powder or particles may refer to the true density of the powder or particles (rather than the bulk density of the powder or particles, which may vary greatly depending on how the powder or particles are handled). Measurement of true density can be performed using many standard methods, which are often based on Archimedes' principle. The most widely used method used to measure the true density of a powder involves the powder being placed and weighed inside a container of known volume (pycnometer). The pycnometer is then filled with a fluid of known density in which the powder is not volatile. The volume of the powder is determined by the difference between the volume indicated by the pycnometer and the volume to which the liquid is added (i.e., the volume of air displaced).

[0124] As used herein, the term "aerosol-generating article" may refer to an article that is capable of generating or releasing an aerosol, for example, upon heating.

[0125] As used herein, the term "longitudinal direction" may refer to the direction extending between a downstream or proximal end and an upstream or distal end of a component, such as an aerosol-forming substrate or an aerosol-generating article.

[0126] As noted above, the term "transverse" may refer to a direction perpendicular to the longitudinal axis.

[0127] As used herein, the term "aerosol-generating device" may refer to a device used in conjunction with an aerosol-generating article to enable the generation or emission of an aerosol.

[0128] As used herein, the term "assembly of a sheet" may refer to an aerosol-forming substrate, or a sheet of an aerosol-generating article that is spiralled, folded, or otherwise compressed or contracted in a direction substantially transverse to the longitudinal axis of the aerosol-forming substrate, or the aerosol-generating article.

[0129] As used herein, the term "sheet" can refer to a generally planar, laminar element having a width and length substantially greater than, for example, at least 2, 3, 5, 10, 20, or 50 times its thickness.

[0130] As used herein, the term "strip" may refer to a generally planar, laminar element having a width and length substantially greater than its thickness. The width of a strip may be greater than its thickness, e.g., at least 2, 3, 5, or 10 times its thickness. The length of a strip may be greater than its width, e.g., at least 2, 3, 5, or 10 times its width.

[0131] As used herein, the term "aerosol former" may refer to any suitable known compound or mixture of compounds that facilitates the formation of an aerosol upon use. The aerosol may be a dense and stable aerosol. The aerosol may be substantially resistant to thermal decomposition at the operating temperature of the aerosol-forming substrate or aerosol-generating article.

[0132] As used herein, the term "aerosol cooling element" may refer to a component of an aerosol-generating article that is located downstream of an aerosol-forming substrate such that, in use, an aerosol formed by the substrate or by volatile compounds released from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by a user.

[0133] As used herein, the term "rod" may refer to a generally cylindrical element, for example a right cylindrical element of substantially circular, oval, or elliptical cross-section.

[0134] As used herein, the term "crimped" may refer to a sheet having one or more ridges or corrugations. The ridges or corrugations may be substantially parallel. When present in a component of an aerosol-generating article, the ridges or corrugations may extend longitudinally relative to the aerosol-generating article.

[0135] As used herein, the term "aeration level" can refer to the volume ratio of the airflow entering the aerosol-generating article via the ventilation zone (ventilation airflow) to the sum of the aerosol airflow and the ventilation airflow. The higher the aeration level, the higher the dilution of the aerosol stream delivered to the consumer. EXAMPLES

[0136] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0137] Example 1. 1. An aerosol-forming substrate for use in an aerosol-generating article, the aerosol-forming substrate comprising expanded graphite particles. Example 2. For example, the aerosol-forming substrate according to Example 1 further comprising an aerosol-forming material such as an aerosol former. Example 3. An aerosol-forming substrate according to example 1 or 2, wherein the expanded graphite particles constitute no more than 80, 50, 20, 10, or 5% by weight of the aerosol-forming substrate. Example 4. An aerosol-forming substrate according to any of Examples 1 to 3, wherein the expanded graphite particles constitute 0.1, 0.2, 0.5, 1, 2, 3, 5, 10, 20, or 50% or more by weight of the aerosol-forming substrate. Example 5. An aerosol-forming substrate according to any of Examples 1 to 4, wherein the expanded graphite particles comprise 1 to 20, 2 to 20, 3 to 20, 5 to 20, 3 to 15, 5 to 15, or 3 to 10% by weight of the aerosol-forming substrate. Example 6. On a dry weight basis, 1 to 90% by weight of expanded graphite particles; 7 to 60% by weight of an aerosol former; 2 to 20% by weight of fiber; 2-10% by weight of a binder. Example 7. On a dry weight basis, 10 to 90 weight percent expanded graphite particles; 7 to 60% by weight of an aerosol former; 2 to 20% by weight of fiber; 2-10% by weight of a binder. Example 8. An aerosol-forming substrate according to any of Examples 1 to 7, wherein the expanded graphite particles have a thermal conductivity in at least one direction of at least 0.3, 0.5, 1, 2, 5, or 10 W / (mK) at 25 degrees Celsius. Example 9. On a dry weight basis, 1 to 90% by weight of expanded graphite particles; 7 to 60% by weight of an aerosol former; 2 to 20% by weight of fiber; 2 to 10% by weight of a binder; An aerosol-forming substrate according to any of Examples 1 to 8, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.22 W / (mK) at 25 degrees Celsius in at least one direction. Example 10. On a dry weight basis, 10 to 90 weight percent expanded graphite particles; 7 to 60% by weight of an aerosol former; 2 to 20% by weight of fiber; 2 to 10% by weight of a binder; An aerosol-forming substrate according to any of Examples 1 to 9, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.22 W / (mK) at 25 degrees Celsius in at least one direction. Example 11. An aerosol-forming substrate according to any of Examples 1 to 10, comprising 1 to 15% by weight of expanded graphite particles. Example 12. An aerosol-forming substrate according to any of Examples 1 to 11, comprising 3 to 6% by weight of expanded graphite particles. Example 13. 13. An aerosol-forming substrate according to any of Examples 1 to 12, wherein the expanded graphite particles have a particle size distribution with a number D10 particle size, the number D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 14. 14. An aerosol-forming substrate according to any of Examples 1-13, wherein the expanded graphite particles have a particle size distribution with a number D10 particle size, the number D10 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 15. 15. An aerosol-forming substrate according to any of Examples 1-14, wherein the expanded graphite particles have a particle size distribution with a number D50 particle size, the number D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 16. 16. An aerosol-forming substrate according to any of Examples 1-15, wherein the expanded graphite particles have a particle size distribution with a number D50 particle size, the number D50 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 17. 17. An aerosol-forming substrate according to any of Examples 1-16, wherein the expanded graphite particles have a particle size distribution with a number D90 particle size, the number D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 18. 18. An aerosol-forming substrate according to any of Examples 1-17, wherein the expanded graphite particles have a particle size distribution with a number D90 particle size, the number D90 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 19. 19. An aerosol-forming substrate according to any of Examples 1-18, wherein the expanded graphite particles have a particle size distribution with a volume D10 particle size, the volume D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 20. 20. An aerosol-forming substrate according to any of Examples 1-19, wherein the expanded graphite particles have a particle size distribution with a volume D10 particle size, the volume D10 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 21. 21. An aerosol-forming substrate according to any of Examples 1-20, wherein the expanded graphite particles have a particle size distribution with a volume D50 particle size, the volume D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 22. 22. An aerosol-forming substrate according to any of Examples 1-21, wherein the expanded graphite particles have a particle size distribution with a volume D50 particle size, the volume D50 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 23. 23. An aerosol-forming substrate according to any of Examples 1-22, wherein the expanded graphite particles have a particle size distribution with a volume D90 particle size, the volume D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 24. 24. An aerosol-forming substrate according to any of Examples 1-23, wherein the expanded graphite particles have a particle size distribution with a volume D90 particle size, the volume D90 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 25. the expanded graphite particles have a particle size distribution having a number D10 particle size, a number D90 particle size, a volume D10 particle size, and a volume D90 particle size; The number D90 particle size is 50, 40, 30, 20, 10, or 5 times smaller than the number D10 particle size; or the volume D10 particle size is 50, 40, 30, 20, 10, or 5 times or less than the volume D10 particle size; Or, an aerosol-forming substrate according to any of Examples 1 to 24, wherein the number D90 particle size is 50, 40, 30, 20, 10, or 5 times or less than the number D10 particle size, and the volume D10 particle size is 50, 40, 30, 20, 10, or 5 times or less than the volume D10 particle size. Example 26. An aerosol-forming substrate according to any of Examples 1 to 26, wherein the expanded graphite particles have a particle size distribution, one or both of the number D10 particle size and the volume D1 particle size being between 1 and 20 microns. Example 27. 27. An aerosol-forming substrate according to any of Examples 1 to 26, wherein the expanded graphite particles have a particle size distribution, and one or both of the number D90 particle size and the volume D90 particle size are from 50 to 300 microns, or from 50 to 200 microns. Example 28. An aerosol-forming substrate according to any of Examples 1-27, wherein each of the expanded graphite particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 29. An aerosol-forming substrate according to any of Examples 1-28, wherein each of the thermally conductive particles has a particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 30. 30. An aerosol-forming substrate according to any of Examples 1-29, wherein each of the expanded graphite particles has three mutually perpendicular dimensions, and the largest of the three dimensions is no more than 10, 8, 5, 3, or 2 times greater than one or both of the smallest of the three dimensions and a second largest of the three dimensions. Example 31. An aerosol-forming substrate according to any of Examples 1 to 30, wherein each of the expanded graphite particles is substantially spherical. Example 32. An aerosol-forming substrate according to any of Examples 1-31, comprising at least 10, 20, 50, 100, 200, 500, or 1000 expanded graphite particles. Example 33. An aerosol-forming substrate according to any of Examples 1-32, wherein the substrate comprises at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85% by weight of expanded graphite particles on a dry weight basis. Example 34. 34. The aerosol-forming substrate according to any of Examples 1-33, wherein the substrate comprises no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 weight percent of expanded graphite particles on a dry weight basis. Example 35. The substrate is, on a dry weight basis, 1-95, 4-94, 10-90, 20-90, 30-90, 40-90, 50-90, 60-90, 70-90, 80-90, 10-80, 20-80, 30-80, 40-80, 50-80, 60-80, 70-80, 10-70, 20-70, 30-70, 40-70, 50- 35. An aerosol-forming substrate according to any of Examples 1-34 comprising 70, 60-70, 10-60, 20-60, 30-60, 40-60, 50-60, 10-50, 20-50, 30-50, 40-50, 10-40, 20-40, 30-40, 10-30, 20-30, or 10-20 weight percent of expanded graphite particles. Example 36. The aerosol-forming substrate according to any of Examples 1-35, wherein the substrate comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55% by weight of the aerosol former on a dry weight basis. Example 37. The aerosol-forming substrate according to any of Examples 1-36, wherein the substrate comprises no more than 55, 50, 45, 40, 35, 30, 25, 20, or 15% by weight of the aerosol former on a dry weight basis. Example 38. 38. The aerosol-forming substrate according to any of Examples 1-37, wherein the substrate comprises 7-60, 10-60, 20-60, 30-60, 40-60, 50-60, 7-50, 10-50, 20-50, 30-50, 40-50, 7-40, 10-40, 20-40, 30-40, 7-30, 10-30, 20-30, 7-20, 10-20, or 7-10% by weight of aerosol formers, on a dry weight basis, particularly preferably 15-25% by weight of aerosol formers. Example 39. The aerosol-forming substrate according to any of Examples 1-38, wherein the aerosol former comprises or consists of one or more of polyhydric alcohols (such as propylene glycol, polyethylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol), mono-, di-, or tri-acetates, and aliphatic esters or mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Example 40. An aerosol-forming substrate according to any of Examples 1-39, wherein the aerosol-forming substrate comprises one or both of glycerin and glycerol. Example 41. An aerosol-forming substrate according to any of Examples 1-40, wherein the substrate comprises at least 2, 4, 6, 8, 10, 12, 14, 16, or 18% by weight of fibers on a dry weight basis. Example 42. An aerosol-forming substrate according to any of Examples 1-41, wherein the substrate comprises no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt. % fibers on a dry weight basis. Example 43. The substrate is, on a dry weight basis, 4-20, 6-20, 8-20, 10-20, 12-20, 14-20, 16-20, 18-20, 2-18, 4-18, 6-18, 8-18, 10-18, 12-18, 14-18, 16-18, 2-16, 4-16, 6-16, 8-16, 10-16, 12-16, 14-16, 2-14, 4-1 4, 6-14, 8-14, 10-14, 12-14, 2-12, 4-12, 6-12, 8-12, 10-12, 2-10, 4-10, 6-10, 8-10, 2-8, 4-8, 6-8, 2-6, 4-6, or 2-4% by weight of fibres, preferably 2-10% by weight of fibres. Example 44. An aerosol-forming substrate according to any one of Examples 1 to 43, wherein the fibres are cellulose fibres. Example 45. An aerosol-forming substrate according to any of Examples 1-44, wherein each of the fibers has three mutually perpendicular dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than the smallest of the three dimensions. Example 46. An aerosol-forming substrate according to any of Examples 1-45, wherein each of the fibers has three mutually perpendicular dimensions, and the largest of the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times greater than the second largest of the three dimensions. Example 47. An aerosol-forming substrate according to any of Examples 1-46, wherein the substrate comprises at least 4, 6, or 8% by weight of binder on a dry weight basis. Example 48. An aerosol-forming substrate according to any of Examples 1-47, wherein the substrate comprises no more than 8, 6, or 4 weight percent binder on a dry weight basis. Example 49. An aerosol-forming substrate according to any of Examples 1 to 48, wherein the substrate comprises 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, 2 to 4 wt. % of binder, particularly preferably 2 to 10 wt. % of binder, on a dry weight basis. Example 50. An aerosol-forming substrate according to any of Examples 1-49, wherein the binder comprises or consists of one or both of carboxymethylcellulose or hydroxypropylcellulose. Example 51. An aerosol-forming substrate according to any of Examples 1-50, wherein the binder comprises or consists of one or more gums, such as guar gum. Example 52. An aerosol-forming substrate according to any of Examples 1 to 51, wherein the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 53. An aerosol-forming substrate according to any of Examples 1 to 52, wherein the aerosol formers are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 54. An aerosol-forming substrate according to any of Examples 1 to 53, wherein the fibers are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 55. An aerosol-forming substrate according to any of Examples 1 to 54, wherein the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 56. An aerosol-forming substrate according to any of Examples 1-55, wherein the substrate comprises nicotine. Example 57. An aerosol-forming substrate according to Example 56, wherein the substrate comprises at least 0.01, 1, 2, 3, or 4% by weight of nicotine on a dry weight basis. Example 58. 58. An aerosol-forming substrate according to any of Examples 56-57, wherein the substrate comprises no more than 5, 4, 3, 2, or 1% by weight of nicotine on a dry weight basis. Example 59. An aerosol-forming substrate according to any of Examples 1-58, wherein the substrate comprises, on a dry weight basis, 0.01-5, 1-5, 2-5, 3-5, 4-5, 0.01-4, 1-4, 2-4, 3-4, 0.01-3, 1-3, 2-3, 0.01-2, 1-2, 0.01-1% by weight of nicotine, particularly preferably 0.5-4% by weight of nicotine. Example 60. An aerosol-forming substrate according to any of Examples 56 to 58, wherein the nicotine is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 61. An aerosol-forming substrate according to any of Examples 1 to 60, wherein the substrate comprises an acid. Example 62. 62. The aerosol-forming substrate according to Example 61, wherein the substrate comprises at least 0.01, 1, or 2% by weight of an acid on a dry weight basis. Example 63. The aerosol-forming substrate according to any of Examples 61-62, wherein the substrate comprises no more than 3, 2, or 1 weight percent acid on a dry weight basis. Example 64. 64. An aerosol-forming substrate according to any of Examples 61 to 63, wherein the substrate comprises, on a dry weight basis, 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1% by weight of acid, particularly preferably 0.5 to 5% by weight of acid. Example 65. An aerosol-forming substrate according to any of Examples 61-64, wherein the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid. Example 66. An aerosol-forming substrate according to any of Examples 61 to 65, wherein the acid is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 67. An aerosol-forming substrate according to any of Examples 1-66, wherein the substrate comprises at least one plant. Example 68. 68. The aerosol-forming substrate according to example 67, wherein the substrate comprises at least 0.01, 1, 2, 5, 10, or 1% by weight of at least one plant, on a dry weight basis. Example 69. 69. The aerosol-forming substrate according to any of Examples 67-68, wherein the substrate comprises no more than 20, 15, 10, 5, 2, or 1% by weight, on a dry weight basis, of at least one plant. Example 70. 70. The aerosol-forming substrate according to any of Examples 67 to 69, wherein the substrate comprises, on a dry weight basis, 0.01 to 20, 1 to 20, 2 to 20, 5 to 20, 10 to 20, 15 to 20, 0.01 to 15, 1 to 15, 2 to 15, 5 to 15, 10 to 15, 0.01 to 10, 1 to 10, 2 to 10, 5 to 10, 0.01 to 5, 1 to 5, 2 to 5, 0.01 to 2, 1 to 2, 0.01 to 1% by weight of at least one plant, particularly preferably 1 to 15% by weight of at least one plant. Example 71. An aerosol-forming substrate according to any of Examples 67-70, wherein the at least one plant comprises or consists of one or both of clove and rosmanus. Example 72. An aerosol-forming substrate according to any of Examples 67 to 71, wherein the at least one plant is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 73. An aerosol-forming substrate according to any of Examples 1 to 72, wherein the substrate comprises at least one flavourant. Example 74. An aerosol-forming substrate according to Example 73, wherein the substrate comprises at least 0.1, 1, 2, or 5% by weight, on a dry weight basis, of at least one flavorant. Example 75. An aerosol-forming substrate according to any of Examples 73-74, wherein the substrate comprises no more than 10, 5, 2, or 1% by weight, on a dry weight basis, of at least one flavorant. Example 76. 76. An aerosol-forming substrate according to any of Examples 73 to 75, wherein the substrate comprises, on a dry weight basis, 0.1 to 10, 1 to 10, 2 to 10, 5 to 10, 0.1 to 5, 1 to 5, 2 to 5, 0.1 to 2, 1 to 2, 0.1 to 1% by weight of at least one flavourant, particularly preferably 0.1 to 5% by weight of at least one flavourant. Example 77. An aerosol-forming substrate according to any of Examples 73-76, wherein at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate. Example 78. An aerosol-forming substrate according to any of Examples 73 to 77, wherein the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 79. An aerosol-forming substrate according to any of Examples 1-78, wherein the aerosol-forming substrate comprises one or more organic materials, such as tobacco. Example 80. The aerosol-forming substrate according to any of Examples 1-79, wherein the organic material comprises one or more of herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Example 81. An aerosol-forming substrate according to any of Examples 1 to 80, wherein the organic material is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 82. The aerosol-forming substrate according to any one of Examples 1 to 81, wherein the aerosol-forming substrate is an aerosol-forming substrate that does not contain tobacco. Example 83. An aerosol-forming substrate according to any of Examples 1-82, wherein the or each of the expanded graphite particles acts as a susceptor material. Example 84. An aerosol-forming substrate according to any of Examples 1 to 83, wherein the aerosol-forming substrate has a thermal conductivity in at least one direction, or in all directions, of at least 0.15, 0.2, 0.22, 0.3, 0.4, 0.5, 0.75, 1, 1.25, or 1.5 W / (mK) at 25 degrees Celsius. Example 85. The aerosol-forming substrate may have a viscosity of 1500, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, or 650 kg / m 3 An aerosol-forming substrate according to any of Examples 1 to 84 having a density of less than 100 nm. Example 86. The aerosol-forming substrate is 500 to 900 kg / m 3 , or 600-800kg / m 3 An aerosol-forming substrate according to any of Examples 1 to 85, having a density of Example 87. An aerosol-forming substrate according to any of Examples 1 to 86, wherein the aerosol-forming substrate has a water content of from 1 to 20, or from 3 to 15% by weight. Example 88. An aerosol-forming substrate according to any of Examples 1 to 87, wherein the aerosol-forming substrate comprises 1 to 20, or 3 to 15 wt. % water. Example 89. The aerosol-forming substrate according to any of Examples 1 to 88, wherein the aerosol-forming substrate comprises or is in the form of one or more of cut filler, powder particles, granules, pellets, pieces, spaghetti, strips, sheets, sheet rolls, collections of sheets, or tubes. Example 90. An aerosol-forming substrate according to any of Examples 1-89, wherein the aerosol-forming substrate comprises or is in the form of one or more sheets or strips. Example 91. An aerosol-forming substrate according to any of Examples 1 to 90, wherein the aerosol-forming substrate comprises or is in the form of an assembly of one or more sheets. Example 92. An aerosol-forming substrate according to Example 91, wherein the, or each, of the collection of sheets has a width of at least about 5, 10, 25, 50, or 100 mm. Example 93. An aerosol-forming substrate according to any of Examples 1 to 92, wherein the aerosol-forming substrate comprises or is in the form of a plurality of strips. Example 94. An aerosol-forming substrate according to any of Examples 93, wherein each of the plurality of strips has a length of at least about 3, 5, or 10 mm. Example 95. An aerosol-forming substrate according to any of Examples 93-94, wherein each of the plurality of strips has a width of less than about 3, 2, or 1 mm. Example 96. An aerosol-forming substrate according to any of Examples 90-95, wherein the sheet or strip, or each thereof, has a thickness of at least 100, 150, or 200 microns. Example 97. An aerosol-forming substrate according to any of Examples 90-96, wherein the sheet or strip, or each thereof, has a thickness of 300, or 250 microns or less. Example 98. An aerosol-forming substrate according to any of Examples 90 to 97, wherein the sheet or strip, or each thereof, has a thickness of from 100 to 300 microns, or from 150 to 250 microns, or from 200 to 250 microns. Example 99. The sheets or strips, or each of them, have a mass of at least 20, 50, or 100 g / m 297. An aerosol-forming substrate according to any one of Examples 90 to 98, having a basis weight of Example 100. The sheets or strips, or each of them, are 300 g / m 2 An aerosol-forming substrate according to any of Examples 90 to 99, having the following basis weight: Example 101. The sheets or strips, or each of them, are 20 to 300 g / m 2 , 50~250g / m 2 , or 100~250g / m 2 An aerosol-forming substrate according to any one of Examples 90 to 100, having a basis weight of Example 102. The sheets or strips, or each of them, have a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 2. An aerosol-forming substrate according to any of Examples 90 to 101, having a density of Example 103. The sheets or strips, or each of them, have a density of 2, 1.5, 1.2, or 1 g / m 3 An aerosol-forming substrate according to any of Examples 90 to 102, having the following density: Example 104. The sheets or strips, or each of them, are 0.1 to 2 g / m 2 , 0.2~2g / m 2 , 0.3~2g / m 2 , 0.3~1.5g / m 2 , or 0.3 to 1.2 g / m 3 An aerosol-forming substrate according to any of Examples 90 to 103, having a density of Example 105. An aerosol-generating article comprising an aerosol-forming substrate as defined in any one of Examples 1 to 104. Example 106. The aerosol-generating article according to example 105, wherein the article is in the form of a rod and comprises a plurality of components including the aerosol-forming substrate assembled within a wrapper or casing. Example 107. An aerosol-generating article comprising an assembly or roll of sheets of an aerosol-forming substrate according to any of Examples 1-106. Example 108. The aerosol-generating article according to any of Examples 105-107, wherein the aerosol-generating article comprises a front plug. Example 109. The aerosol-generating article according to any of Examples 105-108, wherein the aerosol-generating article comprises a first hollow tube, such as a first hollow acetate tube. Example 110. The aerosol-generating article according to example 109, wherein the aerosol-generating article comprises a second hollow tube, such as a second hollow acetate tube. Example 111. The aerosol-generating article according to example 110, wherein the second hollow tube comprises one or more vent holes. Example 112. An aerosol-generating article according to any one of Examples 105 to 111, wherein the aerosol-generating article comprises a mouth-side plug filter. Example 113. The aerosol-generating article according to any of Examples 105-112, wherein the aerosol-generating article comprises a wrapper, such as a paper wrapper. Example 114. An aerosol-generating article according to any of Examples 105 to 113, comprising a front plug, an aerosol-forming substrate disposed downstream of the front plug, a first hollow tube disposed downstream of the aerosol-forming substrate, a second hollow tube disposed downstream of the first hollow tube, and an oral plug filter disposed downstream of the second hollow tube. Example 115. The aerosol-generating article according to example 114, wherein the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the oral plug filter are surrounded by a wrapper, such as a paper wrapper. Example 116. The aerosol-generating article according to any of Examples 108-115, wherein the front plug has a length of 2-10, 3-8, or 4-6 mm, for example about 5 mm. Example 117. The aerosol-generating article according to any of Examples 105 to 116, wherein the aerosol-forming substrate has a length of 5 to 20, 8 to 15, or 10 to 15 mm, for example about 12 mm. Example 118. The aerosol-generating article according to Example 109 or 110-117 when dependent on Example 109, wherein the first hollow tube has a length of 2-20, 5-15, or 5-10 mm, for example about 8 mm. Example 119. The aerosol-generating article according to any of Examples 110 or 111-118 when dependent on Example 110, wherein the second hollow tube has a length of 2-20, 5-15, or 5-10 mm, e.g., about 8 mm. Example 120. The aerosol-generating article according to any of Examples 112 or 113-119 when dependent on Example 112, wherein the oral plug filter has a length of 5-20, 8-15, or 10-15 mm, e.g., about 12 mm. Example 121. An aerosol generating system comprising an aerosol generating article according to any one of Examples 105 to 120 and an electrical aerosol generating device. Example 122. An aerosol generating system according to Example 121, wherein the electrical aerosol generating device is configured to resistively heat the aerosol generating article during use. Example 123. An aerosol generating system according to any of Examples 121-122, wherein the electrical aerosol generating device is configured, in use, to inductively heat an aerosol-generating article, such as an aerosol-forming substrate of the aerosol-generating article. Example 124. A method of forming an aerosol-forming substrate according to any one of Examples 1 to 123, for example, any one of Examples 1 to 104, comprising the steps of: forming a slurry including expanded graphite particles, an aerosol former, fibers, and a binder; casting and drying the slurry to form an aerosol-forming substrate or a precursor for formation into an aerosol-forming substrate. Example 125. The process according to example 124, wherein the slurry comprises water. Example 126. The process according to any of embodiments 124-125, wherein the slurry comprises 40-90, 40-85, 50-80, 60-80, or 60-75 wt.% water. Example 127. The process according to any of examples 124-126, wherein the slurry comprises an acid, such as fumaric acid. Example 128. The method according to any of Examples 124-127, wherein the slurry comprises nicotine. Example 129. forming a slurry an aerosol former; Fibers and Water, Optionally, an acid, forming a first mixture, optionally including nicotine; Expanded graphite particles; forming a second mixture comprising a binder; The method according to any of Examples 124-128, comprising adding the second mixture to the first mixture to form a combined mixture. Example 130. The method according to example 129, wherein forming the first mixture includes providing an aerosol former, or a solution including an aerosol former and nicotine. Example 131. The method according to example 130, wherein forming the first mixture comprises adding an acid to an aerosol former, or a solution comprising an aerosol former and nicotine, to form a first pre-mixture. Example 132. The method according to any of Examples 129-131, wherein forming the first mixture comprises adding water to the aerosol former, or to a solution comprising the aerosol former and nicotine, or to the first pre-mixture to form a second pre-mixture. Example 133. The method according to any of Examples 129-132, wherein forming the first mixture includes adding fibers to the second pre-mixture. Example 134. The method according to any of Examples 129-133, wherein forming the second mixture includes mixing expanded graphite particles and a binder. Example 135. The method according to any of Examples 129-134, wherein the method comprises first mixing the combined mixture. Example 136. The process according to example 135, wherein the first mixing is carried out under a first pressure of not more than 500, 400, 300, 250, or 200 mbar. Example 137. The method according to example 135 or 136, wherein the first mixing is carried out for 1 to 10 minutes, 2 to 8 minutes, or 3 to 6 minutes, e.g., about 4 minutes. Example 138. The method according to any of examples 135-137, wherein the method comprises, after the first mixing, a second mixing. Example 139. The process according to example 138, wherein the second mixing is conducted under a second pressure less than the first pressure. Example 140. The method according to example 139, wherein the second pressure is less than or equal to 500, 400, 300, 200, 150, or 100 mbar. Example 141. The method according to example 138 or 139 or 140, wherein the second mixing is carried out for 5 to 120, 5 to 80, 5 to 40, or 10 to 30 seconds, e.g., for about 20 seconds. Example 142. The method according to any of Examples 124-141, wherein casting the slurry includes casting the slurry onto a flat support, such as a flat steel support. Example 143. The method according to any of Examples 124-142, wherein after casting the slurry and before drying the slurry, the method comprises setting a thickness of the slurry, e.g., setting a thickness of the slurry to between 100 and 1,000 microns, between 200 and 900 microns, between 300 and 800, between 500 and 700 microns, e.g., about 600 microns. Example 144. The method according to any of Examples 124-143, wherein drying the slurry comprises providing a flow of gas, such as air, over or through the slurry. Example 145. The method according to embodiment 144, wherein the gas stream is heated. Example 146. The method according to example 145, wherein the gas stream is heated to a temperature of 100 to 160 degrees Celsius, or 120 to 140 degrees Celsius. Example 147. The method according to any of Examples 144-146, wherein the flow of gas is provided for 1 to 10 minutes or 2 to 5 minutes. Example 148. The method according to any of Examples 124-147, wherein drying the slurry comprises drying the slurry until the slurry has a moisture content of 1-20, 2-15, 2-10, or 3-7 wt.%. Example 149. The method according to any of Examples 124-148, wherein drying the slurry forms a precursor for formation into an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Example 150. The method according to example 149, wherein the method comprises cutting a sheet of aerosol-forming material.

[0138] The embodiments will now be further described with reference to the following figures: [Brief description of the drawings]

[0139] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article. [Diagram 2] FIG. 2 shows a schematic cross-sectional view of a first embodiment of an aerosol generation system comprising a first aerosol generation device. [Diagram 3] FIG. 3 shows a schematic cross-sectional view of a second embodiment of an aerosol generation system including a second aerosol generating device. [Figure 4] FIG. 4 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article. [Diagram 5] FIG. 5 is a bar graph illustrating nicotine yield from the aerosol-generating article of the first embodiment when used in the aerosol generating device of FIG. 2 compared to two alternative aerosol-generating articles. [Figure 6] FIG. 6 is a bar graph showing the yield of glycerin from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of FIG. 2 compared to two alternative aerosol-generating articles. [Figure 7] FIG. 7 is a bar graph showing the delivery efficiency of nicotine and glycerin from the aerosol-generating article of the first embodiment when used in the aerosol generating device of FIG. 2 in comparison with two alternative aerosol-generating articles. [Figure 8] FIG. 8 is a bar graph illustrating nicotine yield from the aerosol-generating article of the first embodiment when used in the aerosol generating device of FIG. 3 compared to two alternative aerosol-generating articles. [Figure 9] FIG. 9 is a bar graph showing the yield of glycerin from the aerosol-generating article of the first embodiment when used in the aerosol generating device of FIG. 3 compared to two alternative aerosol-generating articles. [Figure 10] FIG. 10 is a bar graph showing the delivery efficiency of nicotine and glycerin from the aerosol-generating article of the first embodiment when used in the aerosol generating device of FIG. 3 in comparison with two alternative aerosol-generating articles. [Figure 11]FIG. 11 shows an alternative embodiment of an aerosol-generating article comprising a thermally enhanced aerosol-forming substrate comprising discrete elements of a first material and discrete elements of a second material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0140] 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article 10. The aerosol-generating article 10 comprises a rod of aerosol-forming substrate 12 and a downstream section 14 located downstream of the rod of aerosol-forming substrate 12. Furthermore, the aerosol-generating article 10 comprises an upstream section 16 located upstream of the rod of aerosol-forming substrate 12. The aerosol-generating article 10 thus extends from an upstream or distal end 18 to a downstream or proximal or oral end 20.

[0141] The aerosol-generating article has a total length of about 45 millimeters.

[0142] The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of the aerosol-forming substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the upstream end of the support element 22 abuts the downstream end of the rod 12 of the aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol cooling element 24 located immediately downstream of the support element 22, the aerosol cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of Figure 1, the upstream end of the aerosol cooling element 24 abuts the downstream end of the support element 22.

[0143] As will become apparent from the following description, the support element 22 and the aerosol cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 10. Taken as a whole, the intermediate hollow section 50 does not substantially contribute to the overall RTD of the aerosol-generating article. The RTD of the intermediate hollow section 26 as a whole is substantially less than 0 millimeters H 2 It is O.

[0144] The support element 22 may include a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 extending entirely from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 20. The interior cavity 28 is substantially empty, thereby allowing substantially unrestricted airflow therealong. The first hollow tubular segment 26, and consequently the support element 22, does not substantially contribute to the overall RTD of the aerosol-generating article 10. More specifically, the RTD of the first hollow tubular segment 26 (which is substantially the RTD of the support element 22) is substantially less than 0 millimeters H. 2 It is O.

[0145] The first hollow tubular segment 26 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D FTS ), the peripheral wall thickness of the first hollow tubular segment 26 is therefore approximately 2.67 millimeters.

[0146] The aerosol cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 extending entirely from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The interior cavity 36 is substantially empty, thereby allowing substantially unrestricted airflow therealong. The second hollow tubular segment 28, and consequently the aerosol cooling element 24, does not substantially contribute to the overall RTD of the aerosol-generating article 10. More specifically, the RTD of the second hollow tubular segment 34 (which is essentially the RTD of the aerosol cooling element 24) is substantially equal to or less than 0 millimeters H. 2 It is O.

[0147] The second hollow tubular segment 34 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D STS ) of the peripheral wall of the second hollow tubular segment 34 is approximately 2 millimeters. FTS ) and the inner diameter (D STS ) is about 0.75.

[0148] The aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. More specifically, the ventilation zone is provided approximately 2 millimeters from the upstream end of the second hollow tubular segment 34. In this embodiment, the ventilation zone 60 comprises a circumferential row of perforations through the paper wrapper 70, and the ventilation level of the aerosol-generating article 10 is approximately 25%.

[0149] 1, the downstream section 14 further comprises a mouthpiece element 42 located downstream of the intermediate hollow section 50. More specifically, the mouthpiece element 42 is positioned immediately downstream of the aerosol cooling element 24. As shown in the drawing of FIG.

[0150] Mouthpiece element 42 is provided in the form of a cylindrical plug of low density cellulose acetate.

[0151] Mouthpiece element 42 has a length of about 12 millimeters and an outer diameter of about 7.25 millimeters. The RTD of mouthpiece element 42 is about 12 millimeters H 2 The ratio of the length of the mouthpiece element 42 to the length of the intermediate hollow section 50 is about 0.6.

[0152] The rod 12 of the aerosol-forming substrate has an outer diameter of about 7.25 millimeters, and a length of about 12 millimeters.

[0153] The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of the aerosol-forming substrate, the upstream element 46 being longitudinally aligned with the rod 12. In the embodiment of FIG. 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of the aerosol-forming substrate. The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate. The upstream element 46 has a length of about 5 millimeters. The RTD of the upstream element 46 is about 30 millimeters H. 2 It is O.

[0154] The upstream element 46 , the rod of aerosol-forming substrate 12 , the support element 22 , the aerosol cooling element 24 , and the mouthpiece element 42 are enclosed by a paper wrapper 70 .

[0155] The rod 12 of the aerosol-forming substrate comprises an aerosol-forming material and thermally conductive particles 44. The aerosol-forming material comprises a reconstituted and assembled sheet comprising tobacco material and glycerin. The thermally conductive particles 44 are carbon particles, specifically expanded graphite particles, having a particle size distribution with a D10 particle size of 6.6 micrometers, a D50 particle size of 20 micrometers, and a D90 particle size of 56 micrometers. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume average particle size of about 35 microns. Each of the expanded graphite particles is substantially spherical in shape. The expanded graphite particles have a density less than 1000 kilograms per cubic meter. The aerosol-forming substrate comprising the aerosol-forming material and the thermally conductive particles 44 has a combined density of approximately 760 kilograms per cubic meter. The expanded graphite particles make up approximately 4.6% by weight of the aerosol-forming substrate. Glycerin constitutes approximately 1.7% by weight of the aerosol-forming substrate.

[0156] The rod 12 of aerosol-forming substrate is formed by a process which includes the following steps: premixing a binder, guar gum, with an aerosol former, glycerin, to form a first premix; premixing the finely shredded tobacco material with a powder comprised of expanded graphite particles 44 and having a bulk density of approximately 0.065 grams per cubic centimeter to form a second premix; mixing the first premix and the second premix with water to form a slurry; homogenizing the slurry using a high shear mixer; Casting the slurry onto a conveyor belt; controlling the thickness of the slurry and drying the slurry to form large sheets of the aerosol-forming substrate; and Assembling and cutting large sheets of the aerosol-forming substrate to form rods 12 of the aerosol-forming substrate.

[0157] After forming the rod 12 of aerosol-forming substrate, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and packaging the components within a wrapper 70.

[0158] 2 shows a schematic cross-sectional view of a first embodiment of an aerosol generating system 100. The system 100 comprises an aerosol generating device 102 and the aerosol-generating article 10 of FIG.

[0159] The aerosol generating device 102 comprises a battery 104, a controller 106, a heating blade 108 coupled to the battery, and a puff detection mechanism (not shown). The controller 106 is coupled to the battery 104, the heating blade 108, and the puff detection mechanism.

[0160] The aerosol generating device 102 further comprises a housing 110 defining a substantially cylindrical cavity for receiving a portion of the article 10. The heating blade 108 is centrally positioned within the cavity and extends longitudinally from the base of the cavity.

[0161] In this embodiment, the heating blade 108 includes a substrate and an electrically resistive track located on the substrate. The battery 104 is coupled to the heating blade 108 such that a current can be passed through the electrically resistive track to heat the electrically resistive track and the heating blade 108 to an operating temperature.

[0162] In use, a user inserts the article 10 into the cavity and causes the heating blade 108 to penetrate the upstream element 46 and rod 12 of the aerosol-forming substrate of the article 10. FIG.

[0163] The user then takes a puff at the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 102, then through the article 10, from the upstream end 18 to the downstream end 20, and into the user's mouth.

[0164] When a user puffs on the article 10, air flows through the air inlet of the device. The puff detection mechanism detects when the airflow rate through the air inlet increases above a non-zero threshold flow rate. The puff detection mechanism sends a signal to the controller 106 in response. The controller 106 then controls the battery 104 to apply a current to the electrically resistive track, heating the heating blade 108. This heats the rod 12 of the aerosol-forming substrate, which is in contact with the heating blade 108.

[0165] The expanded graphite particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. As such, these particles may act as localized hot spots and provide a more uniform temperature across the aerosol-forming substrate, particularly in the radial direction from the heating blade 108, whereas in prior art substrates there may be significant temperature gradients. This may allow a greater proportion of the aerosol-forming substrate to reach a temperature high enough to release volatile compounds, and therefore a more efficient use of the aerosol-forming substrate.

[0166] Heating of the aerosol-forming substrate causes it to release volatile compounds. These compounds are entrained in air flowing from the upstream end 18 of the article 10 toward the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as it passes through the internal cavities 28, 36 of the support element and the aerosol cooling element. The aerosol then passes through the mouthpiece element 42, which may remove undesirable particles that may be entrained in the airflow and enter the user's mouth.

[0167] When the user stops inhaling on the article 10, the airflow rate through the air inlet of the device decreases below a non-zero threshold flow rate. This is detected by the puff detection mechanism, which in response sends a signal to the controller 106. The controller 106 then controls the battery 104 to reduce the current passing through the electrically resistive track to zero.

[0168] After taking a number of puffs on the article 10, the user may choose to replace the article 10 with a new article.

[0169] 3 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system 200. System 200 comprises an aerosol-generating device 202 and the aerosol-generating article 11 of FIG.

[0170] The aerosol generating device 202 includes a battery 204, a controller 206, an inductor coil 208, and a puff detection mechanism (not shown). The controller 206 is coupled to the battery 204, the inductor coil 208, and the puff detection mechanism.

[0171] The aerosol generating device 202 further comprises a housing 210 defining a substantially cylindrical cavity for receiving a portion of the article 10. An inductor coil 208 spirals around the cavity.

[0172] The battery 204 is coupled to the inductor coil 208 such that an alternating current can be applied to the inductor coil 208 .

[0173] In use, a user inserts an item 11 into the cavity. Figure 3 shows an item 10 inserted into the cavity of the device 202.

[0174] The user then takes a puff at the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 202, then through the article 10, from the upstream end 18 to the downstream end 20, and into the user's mouth.

[0175] When a user puffs on the article 10, air flows through the air inlet of the device. The puff detection mechanism detects that the airflow rate through the air inlet has increased above a non-zero threshold flow rate. The puff detection mechanism accordingly sends a signal to the controller 206. The controller 206 then controls the battery 204 to apply an alternating current to the inductor coil 208, which in turn generates a varying electromagnetic field. The rod 13 of the aerosol-forming substrate is located within this varying electromagnetic field, and the material of the particles 44, expanded graphite, is a susceptor material. The varying electromagnetic field thus induces eddy currents in the particles 44. This heats the particles 44, which in turn heats the nearby aerosol-forming material.

[0176] Heating of the aerosol-forming material causes it to release volatile compounds. These compounds are entrained in air flowing from the upstream end 18 of the article 10 toward the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol cooling element. The aerosol then passes through the mouthpiece element 42, which may remove undesirable particles that may be entrained in the airflow and enter the user's mouth.

[0177] When the user stops inhaling on the article 10, the airflow rate through the air inlet of the device decreases below a non-zero threshold flow rate. This is detected by the puff detection mechanism, which in response sends a signal to the controller 206. The controller 206 then controls the battery 204 to reduce the current passing through the electrically resistive track to zero.

[0178] After taking a number of puffs on the article 11, the user may choose to replace the article 11 with a new article.

[0179] Figure 4 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article 510. This second embodiment is identical to the first embodiment of Figure 1, except that the rod of aerosol-forming substrate 12 is replaced by an alternative rod of aerosol-forming substrate 512. The same reference numbers have been used for identical components in the embodiments of Figures 1 and 3.

[0180] The rod 512 of the aerosol-forming substrate of the second embodiment in FIG. 4 is identical to the rod 12 of the aerosol-forming substrate of the first embodiment in FIG. 1, except that the rod 512 of the aerosol-forming substrate of the third embodiment in FIG. 4 additionally includes an elongated susceptor element 580.

[0181] The susceptor element 580 is disposed substantially longitudinally within the aerosol-forming substrate rod 512 such that it is approximately parallel to the longitudinal axis of the aerosol-forming substrate rod 512. As shown in the drawing in Figure 4, the susceptor element 580 is located at a radially central position within the rod and extends along the longitudinal axis of the rod 12.

[0182] The susceptor element 580 extends completely from the upstream end to the downstream end of the aerosol-forming substrate rod 512. Thus, the susceptor element 580 has substantially the same length as the aerosol-forming substrate rod 512.

[0183] In the embodiment of FIG. 4, the susceptor element 580 is provided in the form of a strip of ferromagnetic steel and has a length of about 12 millimeters, a thickness of about 60 micrometers, and a width of about 4 millimeters.

[0184] The aerosol-generating article 510 of Figure 4 may be used with the aerosol-generating apparatus 202 of Figure 3 in the same manner as the aerosol-generating article 10 of Figure 1. In particular, the inclusion of a susceptor element 580 means that the article 510 may be inductively heated. In the example shown in Figure 4, both the expanded graphite particles and the susceptor element 580 are inductively heatable. Thus, both the susceptor element 580 and the expanded graphite particles 44 contribute to heating during use.

[0185] The rod of aerosol-forming substrate 12, 512 of the aerosol-generating article 10, 510 contains 4.6% by weight of expanded graphite particles and is therefore said to be thermally enhanced. The inventors have found that such an aerosol-generating article according to the present disclosure exhibits improved yield and delivery efficiency of nicotine and glycerin compared to an aerosol-generating article comprising a rod of aerosol-forming substrate that does not contain expanded graphite particles.

[0186] The inventors have measured the yields of nicotine and glycerin from an aerosol-generating article 602 that does not contain thermally conductive particles, an aerosol-generating article 604 in which 4.6% of the tobacco in the aerosol-generating article 602 has been replaced with graphite particles, and an aerosol-generating article 606 in which 4.6% of the tobacco in the aerosol-generating article 602 has been replaced with expanded graphite particles. In other words, the aerosol-generating article 606 is an aerosol-generating article according to the present disclosure and may be the aerosol-generating article shown in FIG.

[0187] 5-7 show the results when aerosol-generating articles 602-606 are used in conjunction with a resistive aerosol-generating device (such as the device shown in FIG. 2).

[0188] FIG. 5 is a bar graph 600 showing the nicotine yield per aerosol-generating article on the Y-axis. Yield is measured in micrograms per article and is the total yield achieved during a use session. On the X-axis are bars for each of the aerosol-generating articles 602-606. The nicotine yield from the aerosol-generating article 602, which does not contain thermally conductive particles, is 1150 micrograms per article. The nicotine yield from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 1190 micrograms per article. The nicotine yield from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 1125 micrograms per article.

[0189] FIG. 6 is a bar graph 700 showing the yield of glycerine per aerosol-generating article on the Y-axis. Yield is measured in micrograms per article and is the total yield achieved during a use session. On the X-axis are bars for each of the aerosol-generating articles 602-606. The yield of glycerine from the aerosol-generating article 602, which does not contain thermally conductive particles, is 3640 micrograms per article. The yield of glycerine from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 4150 micrograms per article. The yield of glycerine from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 4540 micrograms per article.

[0190] 7 is a bar graph 800 showing the nicotine and glycerin delivery efficiency of each aerosol-generating article 602-608 during a use session. Efficiency is shown on the Y-axis and is a percentage. In particular, efficiency is the fraction of the total initial nicotine or glycerin contained in the aerosol-generating article that is delivered to the user or smoking machine over a use session of that article. The bar 802 showing nicotine delivery efficiency is hatched diagonally. The bar 804 showing glycerin delivery efficiency is hatched vertically with dashed lines.

[0191] The nicotine delivery efficiency from the aerosol-generating article 602, which does not contain thermally conductive particles, is 29%. The nicotine delivery efficiency from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 31.5%. The nicotine delivery efficiency from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 35.4%.

[0192] The efficiency of glycerin delivery from the aerosol-generating article 602, which does not contain thermally conductive particles, is 9.3%. The efficiency of glycerin delivery from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 10.6%. The efficiency of nicotine delivery from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 12.1%.

[0193] 8-10 show the results when aerosol-generating articles 602-606 are used in conjunction with an induced aerosol generating device (such as the device shown in FIG. 3).

[0194] FIG. 8 is a bar graph 900 showing the nicotine yield per aerosol-generating article on the Y-axis. Yield is measured in micrograms per article and is the total yield achieved during a use session. On the X-axis are bars for each of the aerosol-generating articles 602-606. The nicotine yield from the aerosol-generating article 602, which does not contain thermally conductive particles, is 790 micrograms per article. The nicotine yield from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 886 micrograms per article. The nicotine yield from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 1197 micrograms per article.

[0195] FIG. 9 is a bar graph 1000 showing the yield of glycerine per aerosol-generating article on the Y-axis. The yield is measured in micrograms per article and is the total yield achieved during a use session. On the X-axis are bars for each of the aerosol-generating articles 602-606. The yield of glycerine from the aerosol-generating article 602, which does not contain thermally conductive particles, is 3100 micrograms per article. The yield of glycerine from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 3840 micrograms per article. The yield of glycerine from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 4800 micrograms per article.

[0196] FIG. 10 is a bar graph 1100 showing the nicotine and glycerin delivery efficiency of each aerosol-generating article 602-608 during a use session. Efficiency is shown on the Y-axis and is a percentage. In particular, efficiency is the fraction of the total initial nicotine or glycerin contained in the aerosol-generating article that is delivered to a user or smoking machine over a use session of that article. The bar 1102 showing the nicotine delivery efficiency is hatched diagonally. The bar 1104 showing the glycerin delivery efficiency is hatched vertically with dashed lines.

[0197] The nicotine delivery efficiency from the aerosol-generating article 602, which does not contain thermally conductive particles, is 19.1%. The nicotine delivery efficiency from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 23.8%. The nicotine delivery efficiency from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 31.4%.

[0198] The efficiency of glycerin delivery from the aerosol-generating article 602, which does not contain thermally conductive particles, is 7.6%. The efficiency of glycerin delivery from the aerosol-generating article 604, which contains 4.6% by weight of graphite particles, is 9.9%. The efficiency of nicotine delivery from the aerosol-generating article 606, which contains 4.6% by weight of expanded graphite particles, is 12.1%.

[0199] Thus, the bar graphs of Figures 5, 6, 8 and 9 show that the yield of both nicotine and glycerin is increased when the aerosol-forming substrate is thermally enhanced by replacing a small amount of tobacco with expanded graphite, and that the increase in yield is greater when expanded graphite particles are used to thermally enhance the substrate rather than graphite particles. The increase in aerosol is achieved whether the aerosol is generated as a result of resistive or inductive heating of the substrate.

[0200] Similarly, the bar graphs in Figure 7 show that the efficiency of delivery of both nicotine and glycerin is increased when the aerosol-forming substrate is thermally enhanced by replacing a small amount of tobacco with expanded graphite, and that the increase in efficiency is even greater when expanded graphite particles are used to thermally enhance the substrate rather than graphite particles. The increase in aerosol is achieved whether the aerosol is generated as a result of resistive or inductive heating of the substrate.

[0201] An aerosol-forming substrate comprising expanded graphite particles according to one particular embodiment has been described above. Of course, the aerosol-forming substrate may be different in other embodiments. For example, the aerosol-forming substrate may comprise an amount, ratio, size or density of expanded graphite particles different from the particular embodiment described above. In either case, the presence of the expanded graphite particles may thermally enhance the substrate. Furthermore, other characteristics of the substrate may be different, such as other characteristics of the substrate's chemical composition.

[0202] Figure 11 shows an alternative embodiment of an aerosol-generating article 1110 comprising a thermally enhanced aerosol-forming substrate 1112 comprising individual elements of a first material 1113 and individual elements of a second material 1114. Each individual element of the second material 1114 may be in contact with many individual elements of the first material 1113 and can therefore act as a thermal path through the substrate. The ratio of the first and second materials can vary depending on the particular properties of the first and second materials and the desired properties of the aerosol-forming substrate 1112. Other than the differences in the substrate itself, the aerosol-generating article 1110 is identical to the aerosol-generating article 10 of Figure 1, with like features numbered accordingly.

[0203] Some specific thermally enhanced aerosol-forming substrates are identified as examples, which use combinations of three specific materials, Material A, Material B, and Material C, identified below.

[0204] Material A Material A is a standard homogenized tobacco material. Material A includes tobacco powder, about 4% by weight cellulose fiber, about 3% by weight guar as a binder, and about 15% by weight glycerin as an aerosol former.

[0205] Material A is formed by a process that includes the following steps: premixing a binder, guar gum, with an aerosol former, glycerin, to form a first premix; premixing tobacco powder and water to form a second premix; mixing the first and second premixes to form a slurry; homogenizing the slurry using a high shear mixer; Casting the slurry onto a conveyor belt; controlling the thickness of the slurry and drying the slurry to form large sheets of reconstituted, substantially homogenous, tobacco-containing aerosol-forming material; and Crimping and chopping the large sheets of the reconstituted and substantially homogeneous aerosol-forming material to form cut fillers.

[0206] Material A has a thermal conductivity of 0.12 W / mK.

[0207] Material B Material B is a homogenized tobacco material with enhanced thermal conductivity. Material B includes tobacco powder, about 5% by weight of expanded graphite particles, about 4% by weight of cellulose fibers, about 3% by weight of guar as a binder, and about 15% by weight of glycerin as an aerosol former.

[0208] The expanded graphite particles have a particle size distribution having a D10 particle size of 6.6 microns, a D50 particle size of 20 microns, and a D90 particle size of 56 microns. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume average particle size of about 35 microns. Each of the expanded graphite particles is substantially spherical in shape. The expanded graphite particles have a density less than 1000 kilograms per cubic meter.

[0209] Material B is formed by a process that includes the following steps: premixing a binder, guar gum, with an aerosol former, glycerin, to form a first premix; premixing tobacco powder, expanded graphite particles, and water to form a second premix; mixing the first and second premixes to form a slurry; homogenizing the slurry using a high shear mixer; Casting the slurry onto a conveyor belt; controlling the thickness of the slurry and drying the slurry to form large sheets of reconstituted, substantially homogenous, tobacco-containing aerosol-forming material; and Crimping and chopping the large sheets of the reconstituted and substantially homogeneous aerosol-forming material to form cut fillers.

[0210] Material B has a thermal conductivity at least 10% higher than that of material A, for example, 0.14 W / mK to 0.25 W / mK. Replacing 5 wt% of tobacco powder with expanded graphite particles slightly reduces the overall tobacco content, and therefore the nicotine content. However, the thermal conductivity of the material increases. In experiments, the addition of 4.5 wt% to 10 wt% expanded graphite particles to homogenized tobacco material increased thermal conductivity by 20% to 50%.

[0211] Material C Material C is a non-tobacco aerosol forming material having high thermal conductivity. Material C comprises, on a dry weight basis, about 76.1% by weight of expanded graphite particles.

[0212] Material C further comprises about 17.7% by weight of an aerosol former, in this embodiment, the aerosol former is glycerol, in particular ICOF European food grade (>99.5% purity) glycerol.

[0213] Material C further comprises about 3.9% by weight of fibers on a dry weight basis. In this embodiment, the fibers are cellulose fibers, in particular birch cellulose fibers from Stora Enso OYJ.

[0214] Material C further comprises about 2.3% by weight of a binder on a dry weight basis. In this embodiment, the binder is guar gum, specifically Gumix International Inc's guar gum.

[0215] Ingredient C may further include one or more of nicotine, an acid such as fumaric acid, a botanical ingredient such as clove or rosmarinus, water, and a flavoring agent.

[0216] Material C is formed by the process described below.

[0217] The slurry is formed using a laboratory spasser, which has the ability to mix viscous liquids, disperse powders through liquids, and remove gas from the mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a laboratory spasser commercially available from PC Laborsystem was used.

[0218] To form the slurry, a first mixture is formed by adding about 7.11 grams of aerosol former, then about 157.5 grams of water, then about 1.57 grams of fiber to a lab dispenser. These first components are then mixed at 600-700 rpm for 5 minutes at 25 degrees Celsius to ensure a homogenous mixture and to hydrate the fiber. A second mixture is then formed by manually mixing about 32.95 grams of thermally conductive particles and about 0.92 grams of binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. The second mixture is then added to the first mixture to form a combined mixture. The combined mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of about 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are homogenously dispersed in the mixture and that there is little trapped air and few lumps in the combined mixture. The combined mixture is then mixed at 5000 rpm for 20 seconds at 25 degrees Celsius and a second reduced pressure of about 100 mbar. This second reduced pressure may help remove any remaining air bubbles. This forms a slurry for casting.

[0219] The slurry is then cast and dried using a suitable device. In this embodiment, a commercially available Labcoater Mathis device is used. The device includes a stainless steel, flat support, and a castor blade to control the thickness of the slurry cast onto the flat support.

[0220] The slurry is cast onto a flat support and the gap between the caster blade and the flat support is set at 0.6 millimeters, ensuring that the thickness of the slurry at any given point is no more than 0.6 millimeters.

[0221] The slurry is then dried with hot air at 120-140 degrees Celsius for 2-5 minutes. After this drying, a sheet of aerosol-forming substrate is formed. The sheet has a thickness of about 159 microns, a basis weight of about 125.7 grams per square meter, and a density of about 0.79 kilograms per cubic meter.

[0222] The sheet is then crimped and cut to form Material C. Material C has a thermal conductivity of at least 0.28 W(mK).

[0223] It will be appreciated that a wide range of different aerosol-forming substrates can be produced simply by combining materials A, B, and C in different ratios.

[0224] Thus, the first exemplary aerosol-forming substrate 12 may comprise a mixture of 60% by weight individual elements of material A and 40% by weight individual elements of material B. Both material A and material B are homogenized tobacco materials, but material B has had its thermal conductivity increased by the presence of expanded graphite particles. The presence of material B in the first exemplary aerosol-forming substrate provides individual elements with increased thermal conductivity and resulting improved aerosol delivery and nicotine delivery.

[0225] The second exemplary aerosol-forming substrate 12 may include a mixture of 70% by weight of individual elements of material A and 30% by weight of individual elements of material C. The presence of material C in the second exemplary aerosol-forming substrate reduced the overall amount of tobacco in the substrate but significantly improved the thermal conductivity. Material C also contributes to the generation of aerosol.

[0226] A third exemplary aerosol-forming substrate 12 may comprise a mixture of 80% by weight of the individual components of material B and 20% by weight of the individual components of material C. In this example, the first material is material B, a homogenized tobacco material with enhanced thermal conductivity, and the second material is material C.

[0227] Any of these three exemplary aerosol-forming substrates may be used as the substrate of the aerosol-generating article 10 of FIG. 1 or the aerosol-generating article 1110 of FIG.

[0228] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like, should be understood in all cases as modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A±10%. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some cases as used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel property(ies) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. An aerosol-forming substrate for use in aerosol-generating articles, the aerosol-forming substrate comprising expanded graphite particles.

2. The aerosol-forming substrate according to claim 1, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12 W / (mK).

3. The aerosol-generating article according to claim 1, wherein the expanded graphite particles occupy at least 1% by weight of the aerosol-forming substrate.

4. On a dry weight basis, 1 to 90% by weight of expanded graphite particles, 7 to 60% by weight of an aerosol-forming matrix, 2 to 20% by weight of fibers, 2 to 10% by weight of a binder, and the aerosol-forming substrate according to claim 1.

5. The aerosol-forming substrate according to claim 1, comprising 1 to 15% by weight of expanded graphite particles.

6. The aerosol-forming substrate according to claim 1, wherein the expanded graphite particles have a particle size distribution with a volume D10 particle size of 1 to 20 microns.

7. The aerosol-forming substrate according to claim 1, wherein the expanded graphite particles have a particle size distribution with a volume D90 particle size of 50 to 300 microns.

8. The aerosol-forming substrate according to claim 1, wherein the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate.

9. The aerosol-forming substrate according to claim 1, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

10. The aerosol-generating substrate according to claim 1, comprising tobacco particles.

11. A method of forming an aerosol-forming substrate according to claim 1, comprising: forming a slurry comprising expanded graphite particles, an aerosol-forming matrix, fibers, and a binder; and casting and drying the slurry to form the aerosol-forming substrate or a precursor of the aerosol-forming substrate.

12. Forming the slurry comprises the aerosol-forming matrix, the fibers, water, optionally, an acid, optionally, nicotine, to form a first mixture; forming a second mixture comprising the expanded graphite particles and the binder; and adding the second mixture to the first mixture to form a combined mixture. The method according to claim 11.

13. An aerosol-generating article comprising the aerosol-forming substrate according to claim 1, or an aerosol-forming substrate formed by the method according to claim 11. ​

14. The aerosol generating article according to claim 13, comprising a plurality of elements including the aerosol forming substrate assembled within a wrapper.

15. An aerosol generating system comprising the aerosol generating article according to claim 13 and an electric aerosol generating device for heating the aerosol forming substrate.

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