A gas cylinder liner and a preparation method and application thereof

Abstract

The present application relates to a kind of gas cylinder liner and its preparation method and application, preparation method is: using nylon microspheres is processed according to rotational molding process and is obtained gas cylinder liner;The number average molecular weight of nylon microspheres is greater than or equal to 20,000 g / mol;The average particle size of nylon microspheres is 0.1-50 μm;The loose bulk density of nylon microspheres is greater than 0.65 g / cm 3 ;Nylon microspheres has high sphericity and smooth surface morphology, high sphericity is 90% or more;The thickness of the prepared gas cylinder liner is 100 μm-5 mm;The hydrogen permeation coefficient of gas cylinder liner is less than 3.5 × 10 ‑11 cm 3 ·cm / cm 2 ·s·cmHg, excellent repeated loading / unloading capacity, excellent mechanical properties;Application is: the prepared gas cylinder liner is used to make gas cylinder, and the pressure bearing capacity of gas cylinder is greater than 75 MPa.The nylon microspheres used in the present application have high sphericity, good flowability, the obtained liner structure is dense, the hydrogen permeation resistance is excellent, the repeated loading / unloading capacity is excellent, and can meet the requirements of gas cylinder with higher pressure bearing capacity.

Description

Technical Field

[0001] This invention belongs to the field of gas cylinder technology, and relates to a gas cylinder liner, its preparation method, and its application. Background Technology

[0002] In recent years, to address the depletion of petroleum fuels and the need to reduce harmful gas emissions, fuel cells and electric vehicles have rapidly developed and become industrialized, bringing significant attention to high-pressure gas tanks used in automobiles. The inner liner is the core component of the high-pressure gas tank, requiring it to withstand high mechanical stress and operating within a temperature range of -60°C to +120°C. The quality of the inner liner directly determines the safety and lifespan of the high-pressure gas tank.

[0003] Lightweight Type IV gas cylinders, specifically those with fully wound plastic liner fibers, represent a current and future research direction. Numerous patents have already reported on thermoplastic resin liners. Polyamide resin (PA) possesses excellent mechanical and electrical properties, along with resistance to friction, wear, oil, and organic solvents, making it widely used and one of the highest-volume engineering plastics. Existing technologies commonly use polyamide resin to prepare liner materials. For example, patent CN103261325A discloses the blow molding process of liner materials by adding other additives to polyamide, and patent CN106255726A studies a hydrogen tank liner material formed from a polyamide resin composition containing polyamide 6, copolyamide, and impact-resistant materials.

[0004] Rotational molding involves adding plastic powder into a mold, which is then rotated and heated along two perpendicular axes. Under the influence of gravity and heat, the plastic powder gradually and evenly coats and melts onto the entire surface of the mold cavity, shaping it into the desired form. After cooling and setting, the product is demolded. Rotational molding differs from all other processing methods in that the heating, melting, molding, and cooling stages all occur after the polymer is placed in the mold. Furthermore, no external pressure is used to force the molten polymer into the mold. Rotationally molded products are essentially stress-free, have no weld lines, and can be produced in complex shapes. In addition, the mold cost is relatively low, allowing for the economical production of large products, capable of manufacturing components up to 150 liters or even larger.

[0005] However, the number of polymer materials that can be used in rotational molding is limited. The most widely used polymer is polyethylene, especially medium-density polyethylene. Other polymers that can be used include polypropylene, polyvinyl chloride and, to a lesser extent, polyamide (i.e., nylon), polyethylene-co-vinyl acetate, and polycarbonate. Rotationally molded products have low density and are prone to defects; high melt flow rates are required, and raw materials are generally in powder form.

[0006] In existing technologies, nylon resins such as PA6 have poor applicability to rotational molding processes. It is difficult to produce inner liners with excellent gas barrier properties, pressure resistance, and repeated filling / unloading capabilities using nylon resins via rotational molding. This is because meeting the melt flow rate requirements of rotational molding necessitates the use of polyamides with good flowability. However, polyamides with good flowability often have low molecular weight and poor crystallinity, directly resulting in poor product strength and difficulty in forming a dense inner liner. Lower inner liner density leads to insufficient barrier properties against low-molecular-weight gases such as hydrogen, allowing hydrogen to easily permeate the resin. Furthermore, high-pressure hydrogen accumulates in the resin in greater quantities than hydrogen at normal pressure. Therefore, polyamide resin inner liners lack sufficient pressure resistance during repeated high-pressure hydrogen filling and unloading, making the can prone to deformation or damage.

[0007] Therefore, there is indeed a need for a method that can overcome these defects, shortcomings and obstacles in the existing technology, especially a method that can obtain a hydrogen storage cylinder liner that does not exhibit the aforementioned defects. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and to provide a gas cylinder liner, its preparation method and application. The gas cylinder liner is prepared by nylon microspheres through rotational molding. The resulting gas cylinder liner has excellent gas barrier effect, pressure bearing capacity and repeated filling / unloading capacity.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a gas cylinder liner involves processing nylon microspheres using a rotational molding process. The number-average molecular weight of the nylon microspheres is greater than or equal to 20,000 g / mol. Existing technologies disclose that the mechanical properties of nylon resin increase rapidly around 20,000 g / mol, but processing becomes difficult above 30,000 g / mol. Rotational molding places higher demands on resin flowability than other processing methods because excessively high molecular weight leads to high viscosity, low melt flowability, requiring high melting temperatures and extended heating times. Prolonged heating times can cause material aging, affecting product performance and increasing costs. The nylon resin used in this invention has a number-average molecular weight greater than or equal to 20,000 g / mol because it is added in microsphere form, rather than the large powder form used in existing technologies. The nylon microspheres have better flowability and are not affected by excessively high molecular weight. They require shorter heating times, avoiding material aging, thus resulting in a liner product with excellent mechanical properties and a dense structure.

[0011] As a preferred technical solution:

[0012] In the gas cylinder liner preparation method described above, the number-average molecular weight of the nylon microspheres is greater than or equal to 30,000 g / mol.

[0013] In the gas cylinder liner preparation method described above, the number-average molecular weight of the nylon microspheres is greater than or equal to 50,000 g / mol.

[0014] The gas cylinder liner preparation method described above uses nylon microspheres composed of polymers with amide bonds, primarily composed of lactams or diamines and dicarboxylic acids. Typical examples of raw materials include lactams such as ε-caprolactam, octyllactam, and ω-dodecyllactam; aliphatic diamines such as tetramethylenediamine, hexamethylenediamine, undecylmethylenediamine, and dodecylmethylenediamine; aromatic diamines such as m-phenylenediamine and terephthalic acid; aliphatic dicarboxylic acids such as adipic acid, octanoic acid, azelaic acid, sebacic acid, and dodecanoic acid; and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid. In this invention, polyamide homopolymers or copolymers derived from these raw materials can be used.

[0015] Preferred nylon microspheres include nylon 6 (polycaprolactam) microspheres, nylon 12 (polydodecanolactam) microspheres, or nylon 6 / 12 (polycaprolactam / dodecanolactam) microspheres; furthermore, it is suitable to use these nylon microspheres as a mixture, provided that the effects of the present invention are not impaired.

[0016] The preparation methods of nylon microspheres include physical methods and chemical methods. Physical methods include mechanical pulverization, solvent precipitation, and melt blending. Chemical methods include precipitation polymerization, suspension polymerization, emulsion polymerization, and reaction-induced phase separation. The nylon microspheres used in this invention can be prepared by any of these methods, but microspheres prepared by reaction-induced phase separation are preferred. This method produces nylon microspheres with higher sphericity, more uniform particle size, and higher yield.

[0017] In the gas cylinder liner preparation method described above, the average particle size of the nylon microspheres is 0.1–50 μm.

[0018] According to the above-described method for preparing a gas cylinder liner, the loose bulk density of the nylon microspheres, as determined by a loose bulk density measuring instrument, is greater than 0.65 g / cm³. (Loose bulk density includes the average density of a loosely packed aggregate of particles, encompassing internal and external pores and inter-particle voids, and is calculated by dividing the total mass of uncompacted granular material in a naturally packed state by the total volume of the aggregate.) 3 A higher loose bulk density indicates a wider particle size distribution. The combination of different particle sizes results in a sufficiently high bulk density. The wide particle size distribution of nylon microspheres allows smaller microspheres to enter the voids, making the structure of the gas cylinder liner more compact, with higher precision and strength.

[0019] The gas cylinder liner preparation method described above uses nylon microspheres with high sphericity and a smooth surface morphology. High sphericity means a sphericity of 90% or more, preferably 95% or more, more preferably 98% or more, with an upper limit of 100%. The higher the sphericity, the smaller the gaps during stacking, and the easier it is to roll, resulting in better powder flowability. The nylon microspheres used in this invention have smooth surfaces. The smoother the surface of the microspheres, the lower the friction between the microspheres and the better the flowability.

[0020] The gas cylinder liner preparation method described above uses a conventional rotational molding machine. The mold is set to rotate along two axes, which can be performed on a conventional rotational molding machine. The specific steps are as follows:

[0021] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature (preferably 100-150℃) to preheat the mold body to ensure uniform mold temperature and avoid the impact of mold wall thickness on temperature uniformity.

[0022] (2) After reaching the preheating temperature, nylon microspheres are inserted into the mold;

[0023] (3) Set the heating temperature to be higher than the melting point of the nylon microspheres, and set the dual-axis rotation speed to a constant value. After reaching the set heating temperature, rotate at a constant temperature.

[0024] (4) Stop heating, continue rotating, and cool with water mist (other cooling methods can also be used);

[0025] (5) Continue rotating and allow to cool naturally to room temperature;

[0026] (6) Open the mold, take out the product, and obtain the gas cylinder liner;

[0027] There is no particular limitation on the rotational speed in rotational molding, but it can be appropriately selected by those skilled in the art. Since the fluidity of nylon microspheres is greater than that of conventional nylon powder, their rotational speed can be appropriately higher than the conventional speed. For example, in the prior art, the rotational speed of the main shaft and the secondary shaft is 1 to 20 rpm, usually 2 to 10 rpm. In the method of the present invention, the rotational speed can be 5 to 30 rpm, preferably 10 to 20 rpm.

[0028] The gas cylinder liner preparation method described above uses a conventional rotational molding machine. The mold is set to rotate along two axes, which can be performed on a conventional rotational molding machine. The specific steps are as follows:

[0029] (I) Insert nylon microspheres into the mold, start the dual-axis rotation, and control the speed of the dual-axis mold until the nylon microspheres are evenly coated on the inner surface of the mold.

[0030] (II) Turn on the heating system and set the heating temperature to be higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature.

[0031] (III) Stop heating, continue rotating, and cool with water mist (other cooling methods may also be used);

[0032] (IV) Continue rotating and allow to cool naturally to room temperature;

[0033] (V) Open the mold, remove the product, and obtain the gas cylinder liner;

[0034] There is no particular limitation on the rotational speed in rotational molding, but it can be appropriately selected by those skilled in the art. Since the fluidity of nylon microspheres is greater than that of conventional nylon powder, their rotational speed can be appropriately higher than the conventional speed. For example, in the prior art, the rotational speed of the main shaft and the secondary shaft is 1 to 20 rpm, usually 2 to 10 rpm. In the method of the present invention, the rotational speed can be 5 to 30 rpm, preferably 10 to 20 rpm.

[0035] The present invention also provides a gas cylinder liner prepared by the method described in any of the preceding claims, wherein the thickness (i.e., wall thickness) of the gas cylinder liner is 100 μm to 5 mm, preferably 0.5 mm to 3 mm; and the hydrogen permeability coefficient of the gas cylinder liner is less than 3.5 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It has excellent repeated charging / unloading capabilities and excellent mechanical properties.

[0036] The present invention also provides a gas cylinder, comprising a gas cylinder liner, wherein the gas cylinder liner is as described above; the gas cylinder can withstand a pressure greater than 75 MPa.

[0037] The aforementioned gas cylinder is a gas cylinder made by laminating a carbon fiber reinforced resin (CFRP) reinforcing layer on the outer surface of the inner liner of the gas cylinder of the present invention.

[0038] The matrix resin constituting the CFRP reinforcing layer can be a thermosetting resin or a thermoplastic resin; when the matrix resin is a thermosetting resin, examples of its main materials include epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, polyurethane resin, and silicone resin; only one of these types can be used, or two or more can be used in combination; epoxy resin is particularly preferred; when the matrix resin is a thermoplastic resin, its main materials are polyethylene resin, polypropylene resin, polyvinyl chloride resin, ABS resin, polystyrene resin, AS resin, polyamide resin, polyacetal resin, polycarbonate resin, thermoplastic polyester resin, and PPS resin; these thermoplastic resins can be used alone or as a mixture of two or more.

[0039] The principle of this invention is as follows:

[0040] Polyamide resin (PA) possesses excellent mechanical and electrical properties, along with resistance to friction, wear, oil, and organic solvents, making it widely used and one of the most produced engineering plastics. Ultrafine nylon spherical powders, due to their unique spherical shape, smooth surface, soft texture, and abundant functional groups such as amine (-NH2) and carboxyl (-COOH) groups, have broad application prospects in medical engineering, biomaterials, liquid crystal displays, coatings, and cosmetics. However, currently, over 95% of the powder materials used in selective laser sintering (SLS) are nylon powders; however, these powders do not have high sphericity and cannot be called nylon microspheres, and are mostly PA12 powders.

[0041] The nylon microspheres used in this application have small particle size, are monodisperse (i.e., single particle size), and have high positive sphericity. Monodispersity and high positive sphericity allow for controllable particle size, enabling the preparation of microspheres with a single particle size, which can then be formulated according to requirements. The number average molecular weight of the nylon resin is greater than or equal to 20,000 g / mol, preferably greater than or equal to 30,000 g / mol, and more preferably greater than or equal to 50,000 g / mol; the microsphere particle size can be adjusted in the range of 0.1–50 μm, exhibiting good flowability.

[0042] Rotational molding requires high polymer flowability, and the polymer crystallization rate cannot be too fast to obtain products with uniform thickness. Therefore, polyamides with good flowability (i.e., lower molecular weight polyamides) often sacrifice crystallinity and strength. This invention uses high molecular weight nylon microspheres, which have excellent flowability and can be uniformly coated into the mold in a very short time through rotational molding. During this process, the degradation of polyamide is minimal, so the gas cylinder liner is still composed of high molecular weight polyamide, resulting in good mechanical properties. Furthermore, existing rotational molding technologies use plastic powder. The raw materials used for rotational molding nylon parts on the market are mostly irregular powders of nylon 6 chips pulverized to about 100 mesh, which are rolled, spread, and melted on the inner surface of a heated rotational molding mold. This invention uses spherical powder instead of irregularly shaped pulverized nylon powder. The former has better powder flow and spreadability, resulting in higher packing density on the inner surface of the mold. Before melting, it is evenly and densely coated on the mold surface, which is more conducive to forming a dense (porosity and defect-free) rotational molding product during the melting and plasticizing process. After melting, the cooling and crystallization are also uniform and dense. Therefore, the gas cylinder liner has high density and uniform thickness, which can inhibit hydrogen permeation and dissolution in the resin. It can effectively suppress the appearance of defects during repeated filling / unfilling, and the molded product has excellent demolding properties. Furthermore, the amount of nylon microspheres used is small, reducing costs.

[0043] This invention combines nylon microspheres with rotational molding, which can overcome the low density of rotational molded products while obtaining the advantages of rotational molding. It can also produce gas cylinder liners with excellent gas barrier properties and good pressure resistance.

[0044] Beneficial effects:

[0045] (1) The nylon microspheres used in this invention have high molecular weight, resulting in excellent mechanical properties of the gas cylinder liner.

[0046] (2) The nylon microspheres used in this invention have high sphericity and good fluidity, and the resulting gas cylinder liner has a dense structure and excellent hydrogen permeation (gas barrier) performance.

[0047] (3) The present invention uses less nylon microspheres and has a shorter processing time, which can effectively reduce costs. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0049] The test methods for some performance indicators in the following embodiments and comparative examples are as follows:

[0050] Number-average molecular weight of nylon microspheres: Number-average molecular weight (Mn) was measured using a Water-991 GPC.

[0051] The sphericity of nylon microspheres: 30 particles were randomly selected from scanning electron microscope images, and their minor and major axes were determined using the following mathematical formula:

[0052]

[0053] Where S is the sphericity, a is the major axis, b is the minor axis, and n is the number of measurements (30).

[0054] Loose bulk density is characterized by a loose bulk density measuring instrument.

[0055] Hydrogen permeability coefficient: According to the JIS K7126A method (differential pressure method), the inner liner sample was tested at 35℃ using a Labthink G2 / 131 gas permeability tester.

[0056] High-pressure hydrogen repeated filling / unloading capability: A sample measuring 10mm longitudinally and 30mm circumferentially was taken from the cylinder liner product obtained by rotational molding. X-ray CT analysis was performed on the sample to observe the presence or absence of defects. A defect-free sample was placed in an autoclave, and hydrogen was injected into the autoclave over 3 minutes to a pressure of 30MPa, maintained for 2 hours, and then depressurized for 1 minute until the pressure returned to normal. This was considered one cycle, and repeated 700 cycles. Similarly, X-ray CT analysis was performed on the sample after 700 cycles to observe the presence or absence of defects larger than 10μm.

[0057] Tensile strength: Refer to ISO-527-1, 2, test temperature is 23℃.

[0058] Tensile modulus: Refer to ISO-527-1, 2, test temperature is 23℃.

[0059] Bending strength: Refer to ISO 178, test temperature is 23℃.

[0060] Flexural modulus: Refer to ISO 178, test temperature is 23℃.

[0061] Impact strength: Refer to ISO 179-1, test temperature is 23℃.

[0062] The pressure that the gas cylinder can withstand is determined by the ambient temperature pressure cycling test and the extreme temperature pressure cycling test in GB / T35544-2017.

[0063] Example 1

[0064] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0065] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 100℃ to preheat the mold body.

[0066] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein the nylon microspheres are nylon 6 microspheres; the number-average molecular weight of the nylon microspheres is 20,000 g / mol; the average particle size of the nylon microspheres is 0.1 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 92%; the loose bulk density of the nylon microspheres is 0.7 g / cm³. 3 ;

[0067] (3) Set the heating temperature to be 10°C higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 30 rpm. After reaching the set heating temperature, rotate at a constant temperature for 5 minutes.

[0068] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 70°C;

[0069] (5) Continue rotating and allow to cool naturally to room temperature;

[0070] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0071] The thickness of the prepared gas cylinder liner is 1 mm; the hydrogen permeability coefficient of the gas cylinder liner is 2.3 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 50 MPa, tensile modulus of 0.3 GPa, flexural strength of 25 MPa, flexural modulus of 0.5 GPa, and impact strength of 20 KJ / m. 2 .

[0072] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 75 MPa.

[0073] Comparative Example 1

[0074] A method for preparing a gas cylinder liner is basically the same as in Example 1, except that instead of nylon microspheres, nylon 6 chips with a number average molecular weight of 20,000 g / mol are pulverized into irregular powder with a mesh size of 100 instead of nylon microspheres.

[0075] The resulting gas cylinder liner has a rough surface and uneven wall thickness; the hydrogen permeability coefficient of the gas cylinder liner is 23 × 10⁻⁶. - 11 cm 3 ·cm / cm 2 • s·cmHg, poor repeated filling / unloading capacity, tensile strength of 30MPa, tensile modulus of 0.1GPa, flexural strength of 10MPa, flexural modulus of 0.2GPa, impact strength of 10KJ / m 2 .

[0076] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made by the above method, and the gas cylinder can withstand a pressure of 45 MPa.

[0077] Compared with Example 1, the gas cylinder liner of Comparative Example 1 has poorer gas barrier properties, repeated filling / unloading capacity, and mechanical properties. This is because Example 1 uses nylon microspheres as raw material, which have good fluidity and dense packing. Before melting, they are evenly and densely coated on the mold surface, and after melting, they are also evenly and densely crystallized upon cooling. Therefore, the gas cylinder liner has high density and uniform thickness, which can inhibit hydrogen permeation and hydrogen dissolution in the resin, and can effectively suppress the occurrence of defects during repeated filling / unloading.

[0078] Example 2

[0079] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0080] (1) Nylon microspheres are added into the mold body, and the dual-axis rotation is started. The rotational speed of the mold around the X-axis and the rotational speed around the Y-axis are controlled to be 1:2.5, and the rotational speed around the Y-axis is 10 rpm, until the nylon microspheres are evenly coated on the surface of the mold body; wherein, the nylon microspheres are nylon 6 microspheres; the number average molecular weight of the nylon microspheres is 30,000 g / mol; the average particle size of the nylon microspheres is 0.1 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 94%; the loose bulk density of the nylon microspheres is 1.0 g / cm³. 3 ;

[0081] (2) Turn on the heating system and set the heating temperature to be 12°C higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature for 5 minutes.

[0082] (3) Stop heating, continue rotating, and cool with water mist until the temperature drops to 80°C;

[0083] (4) Continue rotating and allow to cool naturally to room temperature;

[0084] (5) Open the mold, take out the product, and obtain the gas cylinder liner.

[0085] The thickness of the prepared gas cylinder liner is 2 mm; the hydrogen permeability coefficient of the gas cylinder liner is 3.4 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 60 MPa, tensile modulus of 0.5 GPa, flexural strength of 40 MPa, flexural modulus of 0.7 GPa, and impact strength of 40 KJ / m. 2 .

[0086] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 80MPa.

[0087] Example 3

[0088] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0089] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 120℃ to preheat the mold body.

[0090] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein the nylon microspheres are nylon 6 microspheres; the number-average molecular weight of the nylon microspheres is 70,000 g / mol; the average particle size of the nylon microspheres is 20 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 96%; the loose bulk density of the nylon microspheres is 0.9 g / cm³. 3 ;

[0091] (3) Set the heating temperature to be 18°C ​​higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 10 revolutions / minute. After reaching the set heating temperature, rotate at a constant temperature for 6 minutes.

[0092] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 90°C;

[0093] (5) Continue rotating and allow to cool naturally to room temperature;

[0094] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0095] The thickness of the prepared gas cylinder liner is 3 mm; the hydrogen permeability coefficient of the gas cylinder liner is 1.3 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 85 MPa, tensile modulus of 1.1 GPa, flexural strength of 80 MPa, flexural modulus of 1 GPa, and impact strength of 80 KJ / m. 2 .

[0096] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 95MPa.

[0097] Example 4

[0098] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0099] (1) Nylon microspheres are added into the mold body, and the dual-axis rotation is started. The rotational speed of the mold around the X-axis and the rotational speed around the Y-axis are controlled to be 1:2.5, and the rotational speed around the Y-axis is 20 rpm, until the nylon microspheres are evenly coated on the surface of the mold body; wherein, the nylon microspheres are nylon 6 microspheres; the number average molecular weight of the nylon microspheres is 130,000 g / mol; the average particle size of the nylon microspheres is 50 μm, with high sphericity and smooth surface morphology, and the high sphericity is 95%; the loose bulk density of the nylon microspheres is 0.8 g / cm³. 3 ;

[0100] (2) Turn on the heating system and set the heating temperature to be 22°C higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature for 9 minutes.

[0101] (3) Stop heating, continue rotating, and cool with water mist until the temperature drops to 110°C;

[0102] (4) Continue rotating and allow to cool naturally to room temperature;

[0103] (5) Open the mold, take out the product, and obtain the gas cylinder liner.

[0104] The thickness of the gas cylinder liner is 0.5 mm; the hydrogen permeability coefficient of the gas cylinder liner is 3.5 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 80 MPa, tensile modulus of 0.8 GPa, flexural strength of 60 MPa, flexural modulus of 0.9 GPa, and impact strength of 75 KJ / m. 2 .

[0105] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 90MPa.

[0106] Example 5

[0107] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0108] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 115℃ to preheat the mold body.

[0109] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein, the nylon microspheres are nylon 6 / 12 microspheres; the number-average molecular weight of the nylon microspheres is 50,000 g / mol; the average particle size of the nylon microspheres is 1 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 95%; the loose bulk density of the nylon microspheres is 0.68 g / cm³. 3 ;

[0110] (3) Set the heating temperature to be 15°C higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 10 revolutions / minute. After reaching the set heating temperature, rotate at a constant temperature for 5 minutes.

[0111] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 80°C;

[0112] (5) Continue rotating and allow to cool naturally to room temperature;

[0113] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0114] The thickness of the prepared gas cylinder liner is 1.5 mm; the hydrogen permeability coefficient of the gas cylinder liner is 2.8 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 70 MPa, tensile modulus of 0.6 GPa, flexural strength of 50 MPa, flexural modulus of 0.8 GPa, and impact strength of 50 KJ / m. 2 .

[0115] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 85MPa.

[0116] Example 6

[0117] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0118] (1) Nylon microspheres are introduced into the mold body, and the dual-axis rotation is started. The rotational speed of the mold around the X-axis is controlled to be 1:2.5 with the rotational speed around the Y-axis being 25 rpm, until the nylon microspheres are evenly coated on the surface of the mold body. The nylon microspheres are nylon 6 / 12 microspheres. The number-average molecular weight of the nylon microspheres is 100,000 g / mol. The average particle size of the nylon microspheres is 15 μm, with high sphericity and a smooth surface morphology. The high sphericity is 96%. The loose bulk density of the nylon microspheres is 0.75 g / cm³. 3 ;

[0119] (2) Turn on the heating system and set the heating temperature to be 22°C higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature for 8 minutes.

[0120] (3) Stop heating, continue rotating, and cool with water mist until the temperature drops to 100°C;

[0121] (4) Continue rotating and allow to cool naturally to room temperature;

[0122] (5) Open the mold, take out the product, and obtain the gas cylinder liner.

[0123] The thickness of the gas cylinder liner is 3 mm; the hydrogen permeability coefficient of the gas cylinder liner is 2.5 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 90 MPa, tensile modulus of 1.1 GPa, flexural strength of 80 MPa, flexural modulus of 1.1 GPa, and impact strength of 70 KJ / m. 2 .

[0124] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 95MPa.

[0125] Example 7

[0126] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0127] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 140℃ to preheat the mold body.

[0128] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein, the nylon microspheres are nylon 6 / 12 microspheres; the number-average molecular weight of the nylon microspheres is 150,000 g / mol; the average particle size of the nylon microspheres is 20 μm, and they have high sphericity and a smooth surface morphology, with high sphericity meaning 100% sphericity; the loose bulk density of the nylon microspheres is 0.95 g / cm³. 3 ;

[0129] (3) Set the heating temperature to be 28°C higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 20 revolutions / minute. After reaching the set heating temperature, rotate at a constant temperature for 10 minutes.

[0130] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 115°C;

[0131] (5) Continue rotating and allow to cool naturally to room temperature;

[0132] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0133] The thickness of the prepared gas cylinder liner is 4 mm; the hydrogen permeability coefficient of the gas cylinder liner is 1.2 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 110 MPa, tensile modulus of 1.3 GPa, flexural strength of 90 MPa, flexural modulus of 1.3 GPa, and impact strength of 85 KJ / m. 2 .

[0134] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 98MPa.

[0135] Example 8

[0136] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0137] (1) Nylon microspheres are introduced into the mold body, and the dual-axis rotation is started. The rotational speed of the mold around the X-axis and the rotational speed around the Y-axis are controlled to be 1:2.5, and the rotational speed around the Y-axis is 25 rpm, until the nylon microspheres are evenly coated on the surface of the mold body; wherein, the nylon microspheres are nylon 12 microspheres; the number average molecular weight of the nylon microspheres is 80,000 g / mol; the average particle size of the nylon microspheres is 5 μm, with high sphericity and smooth surface morphology, and the high sphericity is 97%; the loose bulk density of the nylon microspheres is 0.72 g / cm³. 3 ;

[0138] (2) Turn on the heating system and set the heating temperature to be 20°C higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature for 7 minutes.

[0139] (3) Stop heating, continue rotating, and use water mist to cool until the temperature drops to 90°C;

[0140] (4) Continue rotating and allow to cool naturally to room temperature;

[0141] (5) Open the mold, take out the product, and obtain the gas cylinder liner.

[0142] The thickness of the gas cylinder liner is 2 mm; the hydrogen permeability coefficient of the gas cylinder liner is 2.6 × 10⁻⁶. -11 cm 3 ·cm / cm 2It exhibits excellent repeated filling / unloading capacity, tensile strength of 72 MPa, tensile modulus of 1 GPa, flexural strength of 70 MPa, flexural modulus of 1 GPa, and impact strength of 65 KJ / m. 2 .

[0143] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 94 MPa.

[0144] Example 9

[0145] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0146] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 135℃ to preheat the mold body.

[0147] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein, the nylon microspheres are nylon 12 microspheres; the number-average molecular weight of the nylon microspheres is 120,000 g / mol; the average particle size of the nylon microspheres is 30 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 97%; the loose bulk density of the nylon microspheres is 0.85 g / cm³. 3 ;

[0148] (3) Set the heating temperature to be 25°C higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 20 revolutions / minute. After reaching the set heating temperature, rotate at a constant temperature for 9 minutes.

[0149] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 110°C;

[0150] (5) Continue rotating and allow to cool naturally to room temperature;

[0151] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0152] The thickness of the gas cylinder liner is 3.5 mm; the hydrogen permeability coefficient of the gas cylinder liner is 3 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 100 MPa, tensile modulus of 1.2 GPa, flexural strength of 85 MPa, flexural modulus of 1.1 GPa, and impact strength of 80 KJ / m. 2 .

[0153] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 96MPa.

[0154] Example 10

[0155] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0156] (1) Nylon microspheres are introduced into the mold body, and the dual-axis rotation is started. The rotational speed of the mold around the X-axis is controlled to be 1:2.5 with the rotational speed around the Y-axis being 20 rpm, until the nylon microspheres are evenly coated on the surface of the mold body. The nylon microspheres are nylon 12 microspheres. The number-average molecular weight of the nylon microspheres is 200,000 g / mol. The average particle size of the nylon microspheres is 25 μm, with high sphericity and a smooth surface morphology. The high sphericity is 98%. The loose bulk density of the nylon microspheres is 1.0 g / cm³. 3 ;

[0157] (2) Turn on the heating system and set the heating temperature to be 30°C higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature for 10 minutes.

[0158] (3) Stop heating, continue rotating, and cool with water mist until the temperature drops to 115°C;

[0159] (4) Continue rotating and allow to cool naturally to room temperature;

[0160] (5) Open the mold, take out the product, and obtain the gas cylinder liner.

[0161] The thickness of the gas cylinder liner is 5 mm; the hydrogen permeability coefficient of the gas cylinder liner is 1×10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 120 MPa, tensile modulus of 1.5 GPa, flexural strength of 100 MPa, flexural modulus of 1.5 GPa, and impact strength of 90 KJ / m. 2 .

[0162] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 100MPa.

[0163] Example 11

[0164] A method for preparing a gas cylinder liner, using a conventional rotational molding machine, wherein the mold is set to rotate along two axes, and the specific steps are as follows:

[0165] (1) Start the dual-axis rotation and simultaneously turn on the heating system. Set the preheating temperature to 140℃ to preheat the mold body.

[0166] (2) After reaching the preheating temperature, nylon microspheres are added into the mold; wherein, the nylon microspheres are nylon 8 microspheres; the number-average molecular weight of the nylon microspheres is 140,000 g / mol; the average particle size of the nylon microspheres is 100 μm, with high sphericity and a smooth surface morphology, and the high sphericity is 98%; the loose bulk density of the nylon microspheres is 0.65 g / cm³. 3 ;

[0167] (3) Set the heating temperature to be 28°C higher than the melting point of the nylon microspheres, control the ratio of the rotation speed of the mold around the X-axis to that around the Y-axis to be 1:2.5, and the rotation speed around the Y-axis to be 20 revolutions / minute. After reaching the set heating temperature, rotate at a constant temperature for 10 minutes.

[0168] (4) Stop heating, continue rotating, and cool with water mist until the temperature drops to 115°C;

[0169] (5) Continue rotating and allow to cool naturally to room temperature;

[0170] (6) Open the mold, take out the product, and obtain the gas cylinder liner.

[0171] The thickness of the gas cylinder liner is 1.5 mm; the hydrogen permeability coefficient of the gas cylinder liner is 2 × 10⁻⁶. -11 cm 3 ·cm / cm 2 It exhibits excellent repeated filling / unloading capacity, tensile strength of 100 MPa, tensile modulus of 1.2 GPa, flexural strength of 84 MPa, flexural modulus of 1 GPa, and impact strength of 80 KJ / m. 2 .

[0172] A gas cylinder with a structure basically the same as the existing Type IV hydrogen storage cylinder, the only difference being that the inner liner of the gas cylinder is made according to the above steps, and the gas cylinder can withstand a pressure of 95MPa.

Claims

1. A method for preparing a gas cylinder liner, characterized in that, The inner liner of the gas cylinder was manufactured using nylon microspheres via rotational molding. The number-average molecular weight of the nylon microspheres was greater than or equal to 20,000 g / mol; the average particle size of the nylon microspheres was 0.1–50 μm; and the loose bulk density of the nylon microspheres was greater than 0.65 g / cm³. 3 Nylon microspheres have high sphericity and a smooth surface morphology, with high sphericity meaning a sphericity of over 90%.

2. The method for preparing a gas cylinder liner according to claim 1, characterized in that, The number-average molecular weight of nylon microspheres is greater than or equal to 30,000 g / mol.

3. The method for preparing a gas cylinder liner according to claim 2, characterized in that, The number-average molecular weight of nylon microspheres is greater than or equal to 50,000 g / mol.

4. The method for preparing a gas cylinder liner according to claim 1, characterized in that, The inner liner of the gas cylinder is prepared using a rotational molding machine, with the mold set to rotate along two axes. The specific steps are as follows: (1) Start the dual-axis rotation and simultaneously turn on the heating system, set the preheating temperature, and preheat the mold body; (2) After reaching the preheating temperature, nylon microspheres are inserted into the mold; (3) Set the heating temperature to be higher than the melting point of the nylon microspheres, and set the dual-axis rotation speed to a constant value. After reaching the set heating temperature, rotate at a constant temperature. (4) Stop heating, continue rotating, and cool with water mist; (5) Continue rotating and allow to cool naturally to room temperature; (6) Open the mold, take out the product, and obtain the gas cylinder liner.

5. The method for preparing a gas cylinder liner according to claim 1, characterized in that, The inner liner of the gas cylinder is prepared using a rotational molding machine, with the mold set to rotate along two axes. The specific steps are as follows: (I) Insert nylon microspheres into the mold, start the dual-axis rotation, and control the rotation speed of the dual-axis mold until the nylon microspheres are evenly coated on the inner surface of the mold. (II) Turn on the heating system and set the heating temperature to be higher than the melting point of the nylon microspheres. After reaching the set heating temperature, rotate at a constant temperature. (III) Stop heating, continue rotating, and allow water mist cooling; (IV) Continue rotating and allow to cool naturally to room temperature; (V) Open the mold, remove the product, and obtain the gas cylinder liner.

6. A gas cylinder liner prepared by the method described in any one of claims 1 to 5, characterized in that, The thickness of the inner liner of the gas cylinder is 100μm~5mm; the hydrogen permeability coefficient of the inner liner is less than 3.5×10. -11 cm 3 ·cm / cm 2 ·s·cmHg.

7. A gas cylinder comprising a cylinder liner, characterized in that, The cylinder liner is as described in claim 6; the cylinder can withstand a pressure greater than 75 MPa.

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