Sheet

Abstract

A sheet comprising a body comprising the reaction product of: a first component comprising a methylene diphenyl diisocyanate, and a second component comprising a polyol, wherein the ratio of the first

Description

Technical Field The present invention relates to a sheet. The present invention also relates to a process for producing a sheet, a sheet comprising a body formed by a process, a combination for forming a sheet and a use of a combination for forming a sheet. Background Insoles can in some specific instances be made from sheets. Ethylene-vinyl acetate (EVA), also known as poly(ethylene-vinyl acetate), is conventionally used for insoles. Typically, insoles of EVA foam are formed by an injection moulding process. EVA foam can be flexible, light, and somewhat shock absorbent. However, air or liquid cannot pass through the foam cells, so EVA foam insoles retain heat and moisture. Further, whilst EVA foam cells can provide cushioning properties, with regular use the cushioning properties tend to degrade over time. Deterioration with heavy use can lead to discomfort and reduce shock absorption. Alternatively, gel insoles are formed from a mixture of silicone and synthetic rubber. Gel insoles can provide shock absorption and pressure distribution but lose their shape over time and retain heat. For ball sports, aside from being lightweight, an insole may both stabilise the foot and provide a solid platform during a sports swing and during running backwards and forwards. To stabilise the foot, the insole may provide an optimum level of pronation and supination when running for the ball. To provide a solid platform, the insole may provide support for the medial and lateral arches. If other orthopaedic or protective devices are made from sheets, they suffer from the same drawbacks as insoles made from such sheets. Summary of Invention The present invention is directed to a sheet. Accordingly, there is provided a sheet comprising: a body comprising the reaction product of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less, preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. A further aspect provides a sheet comprising: a body comprising a polymer or foam formed by the reaction of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. In some embodiments, the ratio of the first component to the second component is about 3:5. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. For example, the at least a portion of the body has a thickness of from about 1mm to about 3mm. Preferably, at least a portion of the body has a thickness of less than about 3mm. In some embodiments, the second component comprises a first polyol, a second polyol or any combination of a first polyol and a second polyol. In some embodiments, the first polyol has a viscosity of from about 300 to about 2000 mPa.s, and / or the second polyol has a viscosity of from about 1000 to about 7000 mPa.s; and the first polyol has a hydroxyl number of from about 15 to about 80 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 20 to about 90 mg KOH / g; and optionally the first polyol has a molecular weight of from about 2000 to about 9000 g / mol, and / or optionally the second polyol has a molecular weight of from about 500 to about 5000 g / mol. In some embodiments, the first component comprises a first methylene diphenyl diisocyanate (MDI), a second methylene diphenyl diisocyanate (MDI), or any combination of a first methylene diphenyl diisocyanate and a second methylene diphenyl diisocyanate. In some embodiments, the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate; and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate; and the first MDI has an average NCO% of from about 13 to about 42 %, and / or the second MDI has an average NCO% of from about 10 to about 40%; and the first MDI has a viscosity of from about 50 to about 350 mPa.s, and / or the second MDI has a viscosity of from about 10-100 mPa.s; and optionally the first MDI has an average functionality of from about 2.1 to about 2.3, and / or optionally the second MDI has an average functionality of from about 2.0 to about 2.2. In some embodiments, the body comprises a foam comprising an open cell structure formed by a foaming agent. In some embodiments, the portion of the body has a thickness of 4mm or less. In some embodiments, the body comprises at least one raised feature, and optionally wherein the at least one raised feature is located approximately centrally within the body. In some embodiments, the at least one raised feature is substantially dome-shaped. In some embodiments, the at least one raised feature is formed of the reaction product of the first component and the second component. In some embodiments, the average density of the body is from about 150kg / m3 to about 400kg / m3; and / or wherein the body has a material hardness from about 20 to about 40A Shore A points; and / or wherein the body has a maximum tensile stress of greater than about 0.8MPa. For example, the average density of the body is from about 150kg / m3 to about 400kg / m3, preferably from about 250kg / m3 to about 300kg / m3. For example, at least a portion of the body has a thickness of about 3 mm or less, the tensile strength is from about 1.2 to about 2 MPa at an elongation of greater than 170%, and the density is from about 250 kg / m3 to about 300 kg / m3. A further aspect provides a process for producing a sheet, the sheet comprising a body, the process comprising: a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; c) Mixing the first substance and the second substance to form a mixture; and d) Applying the mixture to a mould to provide a sheet, optionally wherein at least a portion of the body has a thickness of about 4mm or less; preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. wherein the ratio of the first component to the second component is from about 1:3 to about 3:1. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any second component as described herein in relation to any aspect or embodiment. In some embodiments, the mixture has a weight of from about 100 g to about 150 g. Preferably, the mixture has a weight of from about 110 g to about 130 g. For example, the mixture has a weight of about 125 g. In some embodiments, the first substance comprises from about 50 to about 100 wt% of the first component. For example, the first substance comprises from about 70 to about 100 wt% of the first component. Preferably, the first substance comprises from about 80 to about 100wt% of the first component. In some embodiments, the second substance comprises from about 50 to about 95 wt% of the second component. For example, the second substance comprises from about 70 to about 90 wt% of the second component. Preferably, the second substance comprises from about 80 to about 90 wt% of the second component. In some embodiments, the second substance comprises from about 50 to about 95 wt% of the second component, from about from about 0.1 to about 3 wt% water, from about 1 to about 20 wt% DEG, from about 0.01 to about 0.5 wt% first surfactant, and from about 0.01 to about 0.4 wt% second surfactant, and from about 0.1 to about 3.0 wt% first catalyst, from about 0.01 wt% to about 2 wt% second catalyst. In some embodiments, the ratio of the first component and the second component is about 3:5. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. For example, the at least a portion of the body has a thickness of from about 1mm to about 3mm. Preferably, at least a portion of the body has a thickness of less than about 3mm. In some embodiments, the process further comprises heating the mould to a temperature from about 30°C to about 50°C before the mixture is applied to the mould. In some embodiments, the process further comprises curing the mixture to form the body. In some embodiments, curing is carried out from about 1 to about 120 minutes within the mould at the temperature of the mould, optionally wherein curing further comprises removing the body from the mould and maintaining the body at a temperature of from about 15 °C to about 60°C. In some embodiments, the process further comprises providing a third component, the third component being a diethylene glycol, and providing a fourth component, the fourth component being water; wherein the ratio of the third component to the fourth component is from about 20:1 to about 20:3. In some embodiments, the mould comprises a cavity, wherein at least a portion of the cavity has a thickness of about 4mm. In some embodiments, the mould comprises at least one fastening positioned within an upper part of the mould, and wherein the process further comprises placing and fastening a fabric comprising a coating of thermoplastic polyurethane within the mould using the at least one fastening prior to the mixture being applied to the mould. In some embodiments, mixing of the first substance and the second substance is carried out for a duration of from about 1 second to about 60 seconds. A further aspect provides a sheet, the sheet comprising a body, the body being formed by a process comprising: a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; c) Mixing the first substance and the second substance to form a mixture; and d) Applying the mixture to a mould to provide a sheet, optionally wherein at least a portion of the body has a thickness of about 4mm or less; preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1. A further aspect provides a sheet, the sheet comprising a body comprising polyurethane, optionally wherein at least a portion of the body has a thickness of about 4mm or less. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. For example, at least a portion of the body has a thickness of from about 1mm to about 3mm. Preferably, at least a portion of the body has a thickness of less than about 3mm. More preferably, at least a portion of the body has a thickness of from about 2mm to about 3mm. A further aspect provides a combination for forming a sheet, the combination comprising: i) a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; and ii) a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1. A further aspect provides a use of a combination described herein, for forming a sheet. A further aspect provides, an insole comprising: a body comprising the reaction product of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less. A further aspect provides an insole comprising: a body comprising a polymer or foam formed by the reaction of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less. For example, at least a portion of the body has a thickness of from about 1mm to about 3mm. Preferably, at least a portion of the body has a thickness of less than about 3mm. More preferably, at least a portion of the body has a thickness of from about 2mm to about 3mm. In one aspect, there is provided an insole formed from the sheet defined herein. In one aspect, there is provided an orthopaedic device formed from the sheet defined herein. In one aspect, there is provided an orthopaedic device comprising a part or the whole of a sheet defined herein. In one aspect, there is provided a protective device formed from the sheet defined herein. In one aspect, there is provided a protective device comprising a part or the whole of a sheet defined herein. Brief Description of the Drawings The present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a sheet according to the invention. Figure 2 is a sheet displaying developmental challenges including air bubbles. Figure 3 is a sheet displaying developmental challenges including air bubbles. Figure 4 is a sheet displaying developmental challenges. Figure 5 is a top view of an insole as described herein. Figure 6 is a front view of the insole of Figure 5 from a forefoot end of the insole. Figure 7 is a side view of the insole of Figures 5 and 6 from a medial side of the insole. Figure 8 is a perspective view of the insole of Figures 5, 6 and 7 showing the contours of an upper surface of the insole. Figure 9 is a cross-sectional view through the thickness of a polyurethane foam body of an insole, as described herein. Figure 10 is a cross-sectional view through the thickness of an EVA foam body, for comparison with Figure 9. Figure 11 is a schematic of an apparatus for forming a sheet or an insole, as described herein. Detailed Description Many materials can be used for sheets (for example, EVA). However, it has not been possible to produce a sheet that meets the high performance needs of certain sports. In sports such as badminton, high shock absorption and cushioning is preferred. However, when producing sheets that provide such properties, it has conventionally been required to produce sheets that are thicker than the sheets provided by the present invention. The properties of the sheets of the present invention are in part provided by their composition. In particular, the sheets of the present invention can be made to have a slim profile whilst retaining excellent shock absorption / cushioning or providing improved shock absorption / cushioning. These properties are retained even after prolonged wear, ensuring consistent comfort and performance for the user. Not only do the sheets of the present invention have improved properties attributable to their composition, they can also be made such they provide improved support which is in part provided by their profile. The profile of the sheet can act synergistically with the composition of the sheet to provide excellent shock absorption / cushioning as well as excellent support for the user. The sheet according to the present invention is suitable for use as an insole for a shoe (or a section of an insole for a shoe), particularly a ball sport specific shoe, particularly a badminton shoe. The sheet according to the invention is suitable for use as an insole, or as part of an insole, for example the heel or arch. The sheet is substantially thinner, by approximately 25% compared to existing sheets, whilst retaining excellent shock absorption / cushioning or providing improved shock absorption / cushioning. This meets the preferences of badminton footwear users, who prefer both high performance and slim profiles. The sheet according to the present invention is suitable for use as (or in) a protective device, for example in an elbow or knee protector. The sheet according to the present invention is also suitable for use as (or in) an orthopaedic device. The sheet according to the present invention is suitable for use in orthotic insoles, for example bespoke orthotic insoles. The sheet according to the present invention is suitable for use as a shock absorbent layer in any normal footwear, or, for example, in children’s insoles. The sheet according to the present invention is suitable for use in products where the material properties of shock absorption and energy return are needed, for example in bicycle seat covers and cricket wicket keeping gloves or similar products. In one aspect, there is provided a sheet comprising: a body comprising the reaction product of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less; preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. A further aspect provides a sheet comprising: a body comprising a polymer or foam formed by the reaction of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. In some embodiments, the sheet is approximately rectangular (for example, rectangular). The length, width and thickness of the sheet are perpendicular to each other. The thickness of the sheet is equivalent to the height of the sheet. In some embodiments, the sheet has a length of from about 300 to about 600 mm. Preferably, the sheet has a length of from about 300 to about 500 mm. More preferably, the sheet has a length of from about 300 to about 400 mm. Even more preferably, the sheet has a length of from about 325 to about 375 mm. For example, the sheet has a length of about 350 mm. In some embodiments, the sheet has a width of from about 200 to about 500 mm. Preferably, the sheet has a width of from about 200 to about 400 mm. More preferably, the sheet has a width of from about 220 to about 300 mm. Even more preferably, the sheet has a width of from about 220 to about 250 mm. For example, the sheet has a width of about 220 mm. For example, the sheet has a width of about 250 mm. In some embodiments, at least a portion of the body has a thickness of from about 0.1 to about 4 mm. In some embodiments, at least a portion of the body has a thickness of from about 1 mm to about 4 mm. For example, the at least a portion of the body has a thickness of from about 1 mm to about 3 mm. Preferably, at least a portion of the body has a thickness of less than about 3 mm. Preferably the thickness is about 3 mm, 2.5 mm, 2.4 mm or 2.3 mm. In one embodiment, the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. In one embodiment, the sheet has a length of from about 300 to about 500 mm, a width of from about 200 to about 400 mm, and a thickness of from about 1 mm to about 4 mm. In one embodiment, the sheet has a length of from about 300 to about 400 mm, a width of from about 220 to about 300 mm, and a thickness of from about 1 mm to about 3 mm. In one embodiment, the sheet has a length of from about 325 to about 375 mm, a width of from about 220 to about 250 mm, and a thickness of less than about 3 mm. In one embodiment, the sheet has a length of about 350 mm, a width of about 220 mm, and a thickness of about 3 mm. In one embodiment, the sheet has a length of about 350 mm, a width of about 250 mm, and a thickness of about 3 mm. In one embodiment, the sheet has a length of 350 mm, a width of 250 mm, and a thickness of about 3 mm. In one embodiment, the sheet has a length of 350 mm, a width of 250 mm, and a thickness of about 2.5 mm. In one embodiment, the sheet has a length of 350 mm, a width of 250 mm, and a thickness of about 2.4 mm. In one embodiment, the sheet has a length of 350 mm, a width of 250 mm, and a thickness of about 2.3 mm. In one embodiment, the sheet has a length of 350 mm, a width of 250 mm, and a thickness of from about 2 mm to about 3 mm. The combination of the first component and the second component in the ratio of from about 1:3 to about 3:1 results in flow characteristics that can result in a thickness that is far thinner than standard sheets, by up to about 25%. The flow characteristics of the combination are important as they allow for the combination to consistently fill a mould cavity, even when the mould cavity is particularly thin or narrow. Specifically, a portion of the body comprising the reaction product may have a thickness of about 4mm or less. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. This slim profile is particularly useful for ball sport specific shoes, such as for badminton, because the sheet is lightweight and more flexible, enabling a more tailored fit in the shoe and requiring less space in the shoe to ensure that the user is comfortable. The first component may be in liquid form, in particular the methylene diphenyl diisocyanate may be in liquid form. The second component may be in liquid form, in particular the polyol may be in liquid form. Preferably, the body of the sheet may be formed by reaction injection moulding or compression moulding in which the first component in the form of a liquid and the second component in the form of a liquid are mixed together and then provided in a mould to react, polymerise and form the body of the sheet. The ratio of the first component to the second component may be from about 1:3 to about 3:1, for example from about 2:5 to about 5:2. Preferably, the ratio of the first component to the second component may be about 3:5. This range of ratios provides optimum flow characteristics to more easily form the body of the insole. The second component may comprise one or more polyols. Preferably, the second component comprises one or more polyols. More preferably, the second component comprises two or more polyols. For example, the second component comprises two polyols. The second component may comprise a first polyol, a second polyol, or any combination of a first polyol and a second polyol. For example, the second component comprises a first polyol and a second polyol. The second component may comprise a first polyol. The first polyol may have a viscosity of from about 300 to about 2000 mPa.s. For example, the first polyol has a viscosity of from about 500 to about 1500 mPa.s. Preferably, the first polyol has a viscosity of from about 750 to about 950 mPa.s. The first polyol may have a molecular weight of from about 2000 to about 9000 g / mol. For example, the first polyol has a molecular weight of from about 3000 to about 7000 g / mol. Preferably, the first polyol has a molecular weight of from about 4500 to about 5000 g / mol. The first polyol may have a hydroxyl number of from about 15 to about 80 mg KOH / g. For example, the first polyol has a hydroxyl number of from about 25 to about 60 mg KOH / g. Preferably, the first polyol has a hydroxyl number of from about 33 to about 37 mg KOH / g. In some embodiments, the first polyol may have a viscosity of from about 300 to about 2000 mPa.s, a molecular weight of from about 2000 to about 9000 g / mol and / or a hydroxyl number of from about 15 to about 80 g / mol. For example, the first polyol has a viscosity of from about 500 to about 1500 mPa.s, a molecular weight of from about 3000 to about 7000 g / mol and / or a hydroxyl number of from about 25 to about 60 mg KOH / g. Preferably, the first polyol has a viscosity of from about 750 to about 950 mPa.s, a molecular weight of from about 4500 to about 5000 g / mol and / or a hydroxyl number of from about 33 to about 37 mg KOH / g. The second component may comprise a second polyol. The second polyol may have a viscosity of from about 1000 to about 7000 mPa.s. For example, the second polyol has a viscosity of from about 3000 to about 4000 mPa.s. Preferably, the second polyol has a viscosity of from about 3600 to about 3700 mPa.s. The second polyol may have a molecular weight of from about 500 to about 5000 g / mol. For example, the second polyol has a molecular weight of from about 1500 to about 3000 g / mol. Preferably, the second polyol has a molecular weight of from about 2000 to about 2500 g / mol. The second polyol may have a hydroxyl number of from about 20 to about 90 mg KOH / g. For example, the second polyol has a hydroxyl number of from about 40 to about 70 mg KOH / g. Preferably, the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g. In some embodiments, the second polyol may have a viscosity of from about 1000 to about 7000 mPa.s, a molecular weight of from about 500 to about 5000 g / mol and / or a hydroxyl number of from about 20 to about 90 mg KOH / g. For example, the second polyol has a viscosity of from about 3000 to about 4500 mPa.s, a molecular weight of from about 1500 to about 3000 g / mol and / or a hydroxyl number of from about 40 to about 70 mg KOH / g. Preferably, the second polyol has a viscosity of from about 3600 to about 3700 mPa.s, a molecular weight of from about 2000 to about 2500 g / mol and / or a hydroxyl number of from about 50 to about 55 mg KOH / g. In some embodiments, the first polyol may have a viscosity of from about 300 to about 2000 mPa.s, and / or the second polyol may have a viscosity of from about 1000 to about 7000 mPa.s. For example, the first polyol has a viscosity of from about 500 to about 1500 mPa.s, and / or the second polyol has viscosity of from about 3000 to about 4000 mPa.s. Preferably,, the first polyol has a viscosity of from about 750 to about 950 mPa.s, and / or the second polyol has a viscosity of from about 3600 to about 3700 mPa.s. In some embodiments, the first polyol may have a molecular weight of from about 2000 to about 9000 g / mol, and / or the second polyol may have a molecular weight of from about 500 to about 5000 g / mol. For example, the first polyol has a molecular weight of from about 3000 to about 7000 g / mol, and / or the second polyol has a molecular weight of from about 1500 to about 3000 g / mol. Preferably, the first polyol has a molecular weight of from about 4500 to about 5000 g / mol, and / or the second polyol has a molecular weight of from about 2000 to about 2500 g / mol. In some embodiments, the first polyol may have a hydroxyl number of from about 15 to about 80 mg KOH / g, and / or the second polyol may have a hydroxyl number of from about 20 mg KOH / g to about 90 mg KOH / g. For example, the first polyol has a hydroxyl number of from about 25 to about 60 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 40 to about 70 mg KOH / g. Preferably, the first polyol has a hydroxyl number of from about 33 to about 37 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g. In some embodiments,, the first polyol may have a viscosity of from about 300 to about 2000 mPa.s, and / or the second polyol may have a viscosity of from about 1000 to about 7000 mPa.s; and the first polyol may have a molecular weight of from about 2000 to about 9000 g / mol, and / or the second polyol may have a molecular weight of from about 500 to about 5000 g / mol; and, the first polyol may have a hydroxyl number of from about 15 to about 80 mg KOH / g, and / or the second polyol may have a hydroxyl number of from about 20 to about 90 mg KOH / g. For example,, the first polyol has a viscosity of from about 500 to about 1500 mPa.s, and / or the second polyol has viscosity of from about 3000 to about 4000 mPa.s; and the first polyol has a molecular weight of from about 3000 to about 7000 g / mol, and / or the second polyol has a molecular weight of from about 1500to about 3000 g / mol; and the first polyol has a hydroxyl number of from about 25 to about 60 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g. Preferably, the first polyol has a viscosity of from about 750 to about 950 mPa.s, and / or the second polyol has a viscosity of from about 3600 to about 3700 mPa.s; and the first polyol has a molecular weight of from about 4500 to about 5000 g / mol, and / or the second polyol has a molecular weight of from about 2000 to about 2500 g / mol; and the first polyol has a hydroxyl number of from about 33 to about 37 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g. In some embodiments, the first polyol may have a viscosity of from about 300 to about 2000 mPa.s, and the second polyol may have a viscosity of from about 1000 to about 7000 mPa.s; and the first polyol may have a molecular weight of from about 2000 to about 9000 g / mol, and the second polyol may have a molecular weight of from about 500 to about 5000 g / mol; and the first polyol may have a hydroxyl number of from about 15 to about 80 mg KOH / g, and the second polyol may have a hydroxyl number of from about 20 to about 90 mg KOH / g. For example, the first polyol has a viscosity of from about 500 to about 1500 mPa.s, and the second polyol has viscosity of from about 3000 to about 4000 mPa.s; and the first polyol has a molecular weight of from about 3000 to about 7000 g / mol, and the second polyol has a molecular weight of from about 1500 to about 3000 g / mol; and the first polyol has a hydroxyl number of from about 25 to about 60 mg KOH / g, and the second polyol has a hydroxyl number of from about 40 to about 70 mg KOH / g. Preferably, the first polyol has a viscosity of from about 750 to about 950 mPa.s, and the second polyol has a viscosity of from about 3600 to about 3700 mPa.s; and the first polyol has a molecular weight of from about 4500 to about 5000 g / mol, and the second polyol has a molecular weight of from about 2000 to about 2500 g / mol; and the first polyol has a hydroxyl number of from about 33 to about 37 mg KOH / g, and the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g. In some embodiments, the second component comprises a mixture or blend of polyols. The mixture or blend may comprise two or more polyols (for example two polyols). Preferably, the mixture or blend comprises the first polyol and the second polyol. In some embodiments, the ratio of the first polyol to the second polyol is from about 1:20 to about 20:1. For example, the ratio of the first polyol to the second polyol is from about 1:15 to about 15:1. Preferably, the ratio of the first polyol to the second polyol is from about 1:8 to about 8:1. More preferably, the ratio of the first polyol to the second polyol is from about 1:4 to about 4:1. Even more preferably, the ratio of the first polyol to the second polyol is from about 1:2 to about 2:1. For example, the ratio of the first polyol to the second polyol is about 1:1. In some embodiments, at least one of the polyols comprises glycerine, and this is particularly useful for moulding processes. For example, the first polyol may comprise glycerine. In some embodiments, at least one of the polyols comprises from about 0.05 to about 0.08 wt% of water. For example, at least one of the polyols comprises less than about 0.05% of water. For example, each of the polyols comprises from about 0.05 to about 0.08 wt% of water. In some embodiments, the mixture of polyols comprises styrene acrylonitrile. Preferably, at least one of the polyols comprises styrene acrylonitrile (SAN). Incorporating styrene acrylonitrile into the sheet helps to enhance the load bearing capacity of the sheet. The first component comprises a methylene diphenyl diisocyanate (MDI). In this context “a methylene diphenyl diisocyanate” is a term of art which refers to methylene diphenyl diisocyanate (e.g. a monomer), an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate. Preferably, the first component comprises oligomeric methylene diphenyl diisocyanate and / or polymeric methylene diphenyl diisocyanate. The first component may comprise one or more methylene diphenyl diisocyanates. Preferably, the first component comprises two or more methylene diphenyl diisocyanates (for example, two methylene diphenyl diisocyanates). The first component may comprise a first methylene diphenyl diisocyanate (MDI), a second methylene diphenyl diisocyanate (MDI), or any combination of a first methylene diphenyl diisocyanate and a second methylene diphenyl diisocyanate. For example, the first component comprises a first methylene diphenyl diisocyanate and a second methylene diphenyl diisocyanate. Preferably, the first component consists of a first methylene diphenyl diisocyanate and a second methylene diphenyl diisocyanate. The first MDI may be methylene diphenyl diisocyanate (e.g. a monomer), an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate. Preferably, the first MDI comprises an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average NCO% of from about 13 to about 42 %. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 23 to about 28 %. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 25 to 26 %. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have a viscosity of from about 50 to about 350 mPa.s. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has a viscosity of from about 150 to about 250 mPa.s. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has a viscosity of from about 190 to about 210 mPa.s. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average functionality of from about 2.1 to about 2.3. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average functionality of from about 2.2 to about 2.3. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average functionality of about 2.25. The second MDI may be methylene diphenyl diisocyanate (e.g. a monomer), an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate. Preferably, the second MDI comprises an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate. When the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI may have an average NCO% of from about 10 to about 40 %. For example, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has an average NCO% of from about 26 to about 32 %. Preferably, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has an average NCO% of from about 28 to about 30 %. When the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI may have a viscosity from about 10 to about 100 mPa.s. For example, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has a viscosity from about 20 to about 80 mPa.s. Preferably, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has a viscosity of from about 30 to about 60 mPa.s. When the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI may have an average functionality of from about 2.0 to about 2.2. For example, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has an average functionality of from about 2.05 to about 2.15. Preferably, when the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the second MDI has an average functionality of about 2.1. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average NCO% of from about average NCO% of from about 13 to about 42 % and / or the second MDI may have an average NCO% of from about 10 to about 40 %. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 23 to about 28 % and / or the second MDI has an average NCO% of from 26 to about 32 %. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 25 to 26 % and / or the second MDI has an average NCO% of from about 28 to about 30 %. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have a viscosity of from about 50 to about 350 mPa.s and / or the second MDI may have a viscosity of from 10 to about 100 mPa.s. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has a viscosity of from about 150 to about 250 mPa.s and / or the second MDI has a viscosity of from about from about 20 to about 80 mPa.s. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has a viscosity of from about 190 to about 210mPa.s and / or the second MDI has a viscosity of from about 30 to about 60 mPa.s. When the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average functionality of from about 2.1 to about 2.3 and / or the second MDI may have an average functionality of from about 2.0 to about 2.2. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average functionality of from about 2.2 to about 2.3 and / or the second MDI has an average functionality of from about 2.05 to about 2.15. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average functionality of about 2.25 and / or the second MDI has an average functionality of about 2.1. In some embodiments, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average NCO% of from about 13 to about 42 %, and / or the second MDI may have an average NCO% of from about 10 to about 40%; and the first MDI may have a viscosity of from about 50 to about 350 mPa.s, and / or the second MDI may have a viscosity of from about 10 to about 100 mPa.s; and the first MDI may have an average functionality of from about 2.1 to about 2.3, and / or the second MDI may have an average functionality of from about 2.0 to about 2.2. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 23 to about 28 % and / or the second MDI has an average NCO% of from about from about 26 to about 32 %; and the first MDI has a viscosity of from 150 to about 250 mPa.s and / or the second MDI has a viscosity of from viscosity from about 20 to about 80 mPa.s; and the first MDI has an average functionality of from about 2.2 to about 2.3 and / or the second MDI has an average functionality of from about 2.05 to about 2.15. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 25 to 26 % and / or the second MDI has an average NCO% of from about from about 28 to about 30 %; and the first MDI has a viscosity of from 190 to about 210 mPa.s and / or the second MDI has a viscosity of from viscosity from about 30 to about 60 mPa.s; and the first MDI has an average functionality of about 2.25 and / or the second MDI has an average functionality of about 2.1. In some embodiments, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI may have an average NCO% of from about 13 to about 42 % and the second MDI may have an average NCO% of from about 10 to about 40%; and the first MDI may have a viscosity of from about 50 to about 350 mPa.s and the second MDI may have a viscosity of from about 10 to about 100 mPa.s; and the first MDI may have an average functionality of from about 2.1 to about 2.3 and the second MDI may have an average functionality of from about 2.0 to about 2.2. For example, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 23 to about 28 % and the second MDI has an average NCO% of from about from about 26 to about 32 %; and the first MDI has a viscosity of from 150 to about 250 mPa.s and the second MDI has a viscosity of from viscosity from about 20 to about 80 mPa.s; and the first MDI has an average functionality of from about 2.2 to about 2.3 and the second MDI has an average functionality of from about 2.05 to about 2.15. Preferably, when the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate, the first MDI has an average NCO% of from about 25 to 26 % and the second MDI has an average NCO% of from about from about 28 to about 30 %; and the first MDI has a viscosity of from 190 to about 210 mPa.s and the second MDI has a viscosity of from viscosity from about 30 to about 60 mPa.s; and the first MDI has an average functionality of about 2.25 and the second MDI has an average functionality of about 2.1. In some embodiments, the ratio of the first MDI to the second MDI is from about 15:1 to about 1:15. For example, the ratio of the first MDI to the second MDI is from about 10:1 to about 1:10. Preferably, the ratio of the first MDI to the second MDI is from about 8:1 to about 1:8. More preferably, the ratio of the first MDI to the second MDI is from about 1:1 to 1:5. More preferably, the ratio of the first MDI to the second MDI is from about 7:9 to 1:4. For example, the ratio of the first MDI to the second MDI is about 1:3. In some embodiments, the first component comprises a mixture or blend of at least two types of methylene diphenyl diisocyanate, optionally wherein one of the at least two types of methylene diphenyl diisocyanate has a molecular weight of more than about 250 g / mol. For example, both of the at least two types of methylene diphenyl diisocyanate has a molecular weight of more than about 250 g / mol. Preferably, the first component comprises a blend of MDI. This means that the reaction product can have specific properties to align with the desired purpose. Preferably, the mixture or blend of MDI comprises a first substance comprising a monomeric MDI and a second substance comprising a polymeric MDI. Preferably the mixture or blend of MDI comprises a first substance comprising a polymeric MDI and a second substance comprising a monomeric MDI. In a particularly preferred embodiment, the first polyol has a viscosity of from about 500 to about 1500 mPa.s, and the second polyol has viscosity of from about 3000 to about 4000 mPa.s; and the first polyol has a molecular weight of from about 3000 to about 7000 g / mol, and the second polyol has a molecular weight of from about 1500 to about 3000 g / mol; and the first polyol has a hydroxyl number of from about 25 to about 60 mg KOH / g, and the second polyol has a hydroxyl number of from about 40 to about 70 mg KOH / g; and the first MDI has an average NCO% of from about 23 to about 28 % and the second MDI has an average NCO% of from about 26 to about 32 %; and the first MDI has a viscosity of from 150 to about 250 mPa.s and the second MDI has a viscosity of from about 20 to about 80 mPa.s; and the first MDI has an average functionality of from about 2.2 to about 2.3 and the second MDI has an average functionality of from about 2.05 to about 2.15. In a particularly preferred embodiment, the first polyol has a viscosity of from about 750 to about 950 mPa.s, and the second polyol has a viscosity of from about 3600 to about 3700 mPa.s; and the first polyol has a molecular weight of from about 4500 to about 5000 g / mol, and the second polyol has a molecular weight of from about 2000 to about 2500 g / mol; and the first polyol has a hydroxyl number of from about 33 to about 37 mg KOH / g, and the second polyol has a hydroxyl number of from about 50 to about 55 mg KOH / g; and the first MDI has an average NCO% of from about 25 to 26 % and the second MDI has an average NCO% of from about 28 to about 30 %; and the first MDI has a viscosity of from 190 to about 210 mPa.s and the second MDI has a viscosity of from about 30 to about 60 mPa.s; and the first MDI has an average functionality of about 2.25 and the second MDI has an average functionality of about 2.1. In some embodiments, the body comprises a foam comprising an open cell structure formed by a foaming agent. For example, the body consists of a foam comprising an open cell structure formed by a foaming agent. The open cell structure allows air to flow through foam, making the body of the insole more breathable and moisture-wicking. The open celled foam also decreases the hardness of the body, allowing the body to more easily mould to the user’s foot, and provide increased shock absorption. The foam is formed by a foaming agent. Preferably, the foaming agent is water. In one aspect, there is provided an insole formed from the sheet defined herein. In one aspect, there is provided an orthopaedic device formed from the sheet defined herein. A further aspect provides, an insole comprising: a body comprising the reaction product of: iii) a first component comprising a methylene diphenyl diisocyanate; and iv) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any second component as described herein in relation to any aspect or embodiment. A further aspect provides an insole comprising: a body comprising a polymer or foam formed by the reaction of: iii) a first component comprising a methylene diphenyl diisocyanate; and iv) a second component comprising a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; optionally wherein at least a portion of the body has a thickness of about 4mm or less The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any second component as described herein in relation to any aspect or embodiment. In some embodiments, a portion of the body has a thickness of 4mm or less in a forefoot portion. This is particularly advantageous for ball sport specific footwear, because the insole is lightweight and more flexible, enabling a more tailored fit in the forefoot portion of the shoe and requiring less space in the forefoot portion of the shoe to ensure that the user is comfortable. In some embodiments, the body comprises at least one raised feature, and optionally wherein the at least one raised feature is located approximately centrally within the body. Preferably, the at least one raised feature may be located in a mid-foot portion. Preferably, the at least one raised feature may be located within a metatarsal area in the mid-foot portion, wherein the metatarsal area supports a metatarsal area of the foot when in use. The position of the at least one raised feature reduces pressure in the metatarsal area of the foot of the user by spreading the load across the forefoot portion. The at least one raised body may have an arcuate structure. Preferably, the body comprises a raised feature. The raised feature may have a length extending in a longitudinal direction and the raised feature may comprise two opposing ends (a first end opposing a second end). As a percentage of the total maximum longitudinal length of the insole or body, and with 0% at a forefoot end and 100% at a heel end, the first end of the raised feature may be located from about 25 to about 45% of the total longitudinal length measured from the forefoot end. For example, the first end of the raised feature is located from about 30 to about 40% of the total longitudinal length measured from the forefoot end. Preferably, the first end is located from about 37 to about 39 % of the total longitudinal length measured from the forefoot end. As a percentage of the total maximum longitudinal length of the insole or body, and with 0% at a forefoot end and 100% at a heel end, a second end of the raised feature may be located from about 46% to about 65% of the total longitudinal length measured from the forefoot end. For example, the second end of the raised feature is located from about 50 to about 60% of the total longitudinal length measured from the forefoot end. Preferably, the second end is located from about 52 to about 54 % of the total longitudinal length measured from the forefoot end. The terms ‘first opposing end’ and ‘second opposing end’ may be used interchangeably with the terms ‘first end’ and ‘second end’ respectively. As a percentage of the total maximum longitudinal length of the insole or body, in some embodiments, the first end of the raised feature may be located from about 25 to about 45% of the total longitudinal length measured from the forefoot end, and the second end of the raised feature is located from about 46% to 65% of the total longitudinal length measured from the forefoot end. For example, the first end of the raised feature is located from about 30 to about 40% of the total longitudinal length measured from the forefoot end, and the second end of the raised feature is located from about 50% to 60% of the total longitudinal length measured from the forefoot end. Preferably, the first end of the raised feature is located from about 37 to about 39% of the total longitudinal length measured from the forefoot end, and the second end of the raised feature is located from about 52% to 54% of the total longitudinal length measured from the forefoot end. By positioning the raised feature further away from the forefoot end, the raised feature is closer to the first metatarsophalangeal joint when in use and therefore the raised feature can provide improved support to the metatarsophalangeal joint and surrounding area of the foot. The raised feature may have a width extending in a lateral direction, the lateral direction extending in a direction perpendicular to the longitudinal direction, and the raised feature may comprise a pair of opposing points (a first point and a second point). The first point and the second point may form the maximum width of the raised feature. As a percentage of the total lateral width of the insole or body measured at a longitudinal location from about 40 to about 45% of the total longitudinal length measured from the forefoot end, with 0% at a forefoot end and 100% at a heel end, the first point may be located from about 20 to about 40 % from the lateral side of the insole or body, with 0% at a lateral side and 100% at a medial side of the insole or body. For example, the first point is located from about 25 to about 35% from the lateral side of the insole or body. Preferably, the first point is located from about 30 to about 34 % from the lateral side of the insole or body. As a percentage of the total lateral width of the insole or body measured at a longitudinal location from about 40 to about 45% of the total longitudinal length measured from the forefoot end, with 0% at a forefoot end and 100% at a heel end, the second point may located from about 55 to about 85 % from the lateral side of the insole or body, with 0% at a lateral side and 100% at a medial side of the insole or body. For example, the second point is located from about 65 to about 83% from the lateral side of the insole or body. Preferably, the second point is located from about 65 to about 80% from the lateral side of the insole or body. In some embodiments, the first point may be located from about 20 to about 40% and / or the second point may be located from about 55 to about 85% from the lateral side of the insole, with 0% at a lateral side and 100% at a medial side of the insole or body, when measured at a longitudinal location from about 40 to about 45% of the total longitudinal length measured from the forefoot end, with 0% at the forefoot end and 100% at a heel end. For example, the first point is located from about 25 to about 35% and the second point is located from about 65 to about 83% from the lateral side of the insole or body. Preferably, the first point is located from about 30 to about 34 % and the second point is located from about 65 to about 80% from the lateral side of the insole or body. The terms ‘first point’ and ‘second point’ may be used interchangeably with the terms ‘first opposing point’ and ‘second opposing point’. The raised feature may have a maximum thickness, measured from an upper surface of the body of the forefoot portion of the insole. The maximum thickness of the raised feature may be about the same as the thickness of the forefoot portion, or the maximum thickness of the raised feature may be greater than the thickness of the forefoot portion, for example the maximum thickness of the raised feature may be approximately double the thickness of the forefoot portion. The raised feature may have a base located on the upper surface of the body and the base may comprise three edges. At least one of the three edges may be curved, preferably two of the three edges are curved. One of the edges may be orientated in a direction substantially perpendicular to a longitudinal direction of the insole. Preferably, a shortest edge of the three edges and / or a curved edge may be orientated in a direction substantially perpendicular to a longitudinal direction of the insole. One of the edges may be substantially straight. Preferably, the substantially straight edge is positioned closest to a medial side of the insole and / or the substantially straight edge extends in a direction parallel to the direction of the medial side of the insole. It is particularly advantageous to have a substantially straight edge closest to a medial side because, in combination with positioning the raised feature further from the forefoot end, this arrangement creates a channel between the raised feature and the arch support. The channel can act as a plantar fascial groove to support the plantar fascia of the foot in use, in particular if the plantar fascia is tight. The plantar fascia is a fibrous tissue which helps maintain a longitudinal arch shape. The base of the raised feature may have a maximum length extending in the longitudinal direction (between the first end and the second end of the raised feature) of from about 10 to about 30% of the total longitudinal length of the body or insole. For example, the base of the raised feature has a maximum length extending in a longitudinal direction of from about 12 to about 20% of the total longitudinal length of the body or insole. Preferably, the base of the raised feature has a maximum length extending in a longitudinal direction of from about 14 to 16% of the total longitudinal length of the body or insole. The base may have a maximum width extending in a lateral direction of from about 25 to about 40% of the maximum width of the body or insole. The maximum width of the body or insole is located longitudinally from about 40 to about 45% of the total longitudinal length measured from the forefoot end. For example, the base has a maximum width extending in a lateral direction of from about 30 to about 35% of the maximum width of the body or insole. Preferably, the base has a maximum width extending in a lateral direction of from about 32 to 34% of the maximum width of the body or insole. The insole may be formed to a specific shoe size or two shoe sizes and the raised feature may be in proportion to the size of the insole. By ensuring that the raised feature is in proportion to the size of the insole, the advantages of the raised feature can be realised. Preferably, the body comprises an arch support. More preferably, the body comprises an arch support in addition to the at least one raised feature. The arch support preferably has a maximum length in the longitudinal direction of the insole that is about 10% to about 30% of the length of the insole in the longitudinal direction. The arch support may have a maximum width in the lateral direction of the insole that is about 40% to about 60% of the width of the insole in the lateral direction. The arch support may comprise a geometric central point positioned at a distance from a forefoot end of the insole that is about 35% to about 45% of the longitudinal length of the insole. Preferably, the at least one raised feature has a maximum length in the longitudinal direction of the insole that is about 5% to about 20% of the total length of the insole in the longitudinal direction. The at least one raised feature may have a maximum width in the lateral direction of the insole that is about 5% to about 20% of the width of the insole in the lateral direction. The at least one raised feature may comprise a geometric central point positioned at a distance from a forefoot end of the insole that is about 25% to about 45% of the longitudinal length of the insole. For example, the geometric central point may be positioned at a distance from the forefoot end of the insole that is about 30%, about 35% or about 40% of the longitudinal length of the insole. By positioning the at least one raised feature closer to the arch support in the longitudinal direction, the toes of the user are positioned in a more natural position, thereby stabilising the foot of the user. In some embodiments, the at least one raised feature is substantially dome-shaped. Preferably, the substantially dome-shaped is hemispherical, segmental, or faceted. The dome shape aids in aligning and stabilising the foot of the user. The at least one raised feature may have a maximum thickness of from about 0.1 mm to about 1mm. For example, the at least one raised feature has a maximum thickness of from about 0.2mm to about 0.6mm. Preferably, the at least one raised feature has a maximum thickness of from about 0.3 to about 0.4 mm. The term ‘thickness’ in this context means the distance from an upper surface of the body to the highest point of the at least one raised feature. In some embodiments, the at least one raised feature is formed from the reaction product of the first component to the second component. That is, the at least one raised feature is integral to the body of the insole. In some embodiments, the average density of the body is between about 150kg / m3 and about 400kg / m3 providing increased support for a user. Optionally, the density is graduated through the thickness of the insole, such that the density at an upper surface of the body is greater than the density within a central part of the thickness of the body. The term ‘graduated’ means that the density varies through one or more dimensions. The term ‘upper surface’ means the surface of the body which is in contact with either a fabric or with the user’s foot when in use. The term ‘lower surface’ means the surface of the body which is in contact with the user’s shoe when in use. The body may comprise an upper part, a central part and a lower part within the thickness of the body, and the upper part comprises an upper surface of the body, the lower part comprises a lower surface of the body and the central part is located between the upper part and the lower part. The upper part and the lower part may have a greater density than the central part. The upper part may form from about 20 to about 35% of the thickness of the insole. Similarly, the lower part may form from about 20 to about 35% of the thickness of the insole. The upper part and the lower part may have a density which is approximately 100% greater, or approximately 200% greater or approximately 300% greater than the density of the central part. The upper part and the lower part may be formed from a reaction injection moulding process. In some embodiments, the body has a material hardness in the range of about 20 to 40 Shore A points, preferably 28 to 38 Shore A points, more preferably about 34, 35 or 36 Shore A points. Thus, the body of the present invention is soft and this is a result of the composition of the body (specifically the ratio of first component and the second component) and the open celled foam structure of the reaction product. In some embodiments, the body has a maximum tensile stress of greater than about 0.8MPa. Preferably, the body has a maximum tensile stress of greater than about 0.8MPa at an elongation of greater than 170%. Preferably, the body has a maximum tensile stress of from about 0.8MPa to about 2MPa, more preferably from about 1.2 to about 2 MPa at an elongation of greater than 170%. Preferably, the maximum tensile stress is greater than about 1.1 MPa, or greater than about 1.2MPa, or greater than about 1.3MPa, or greater than about 1.4MPa. In some embodiments, the insole further comprises a polyester fabric coated with a thermoplastic polyurethane affixed to a surface of the body. The polyester fabric may be double stretched. The coating of thermoplastic polyurethane may be positioned such that it is in contact with the body so that the coating minimises or stops at least the first component and the second component seeping into the fabric. In a further aspect, there is provided a process for producing a sheet, the sheet comprising a body, the process comprising: a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; c) Mixing the first substance and the second substance to form a mixture; d) Applying the mixture to a mould to provide a sheet, optionally wherein at least a portion of the body has a thickness of about 4mm or less; preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any second component as described herein in relation to any aspect or embodiment. In some embodiments, the ratio of the first component and the second component is about 3:5. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. In some embodiments, mixing of the first substance and the second substance may be carried out for a duration of about 1 second to about 60 seconds. For example, mixing of the first substance and the second substance is carried out from about 1 second to about 30 seconds. Preferably, mixing of the first substance and the second substance is carried out from about 1 second to about 5 seconds. In some embodiments, the process further comprises heating the mould to a temperature from about 30°C to about 50°C before the mixture is applied to the mould. For example, the mould is heated to a temperature of from about 35°C to about 45°C. Preferably, the mould is heated to a temperature of about 40°C. Preferably, the moulds are heated with water pipework. In some embodiments, the process further comprises curing the mixture to form the body. Curing advantageously improves the mechanical properties of the body. In some embodiments, curing may be carried out at the temperature of the mould for between about 1 minute and about 120 minutes within the mould. For example, curing is carried out at the temperature of the mould for from about 1 minute and about 60 minutes. Preferably, curing is carried out at the temperature of the mould for from about 1 minute to about 10 minutes. More preferably, curing is carried out at the temperature of the mould for from about 5 minutes to about 10 minutes. Preferably, the mould is maintained at the temperature at which the mixture is applied to the mould. In some embodiments, curing may further comprise removing the body from the mould and maintaining the body at a temperature of between about 15°C and about 60°C. For example, the body is maintained at a temperature of from about 15°C to about 25°C. Preferably, the body is maintained at a temperature of from about 18°C and about 23°C. In some embodiments, curing the body which has been removed from the mould may be carried out for a duration of from about 1 to about 7 days. For example, curing the body which has been removed from the mould may be caried out for a duration of from about 1 to about 6 days. Preferably, curing the body which has been removed from the mould may be carried out for a duration of from about 1 day to about 5 days. In some embodiments, the process further comprises providing a third component, the third component being diethylene glycol (DEG), and providing a fourth component, the fourth component being water. The third and fourth components may be part of the second substance. In some embodiments, the ratio of the third component to the fourth component may be from about 20:1 to about 20:3. For example, the ratio of the third component to the fourth component is from about 40:3 to about 40:6. Preferably, the ratio of the third component to the fourth component is about 8:1. Water and diethylene glycol increase the hardness of the body. Water improves the flow of the combination of the first substance and the second substance, such that the combination can flow within a small cavity in the mould. In some embodiments, the second substance comprises DEG and / or water. Preferably, the second substance comprises DEG and water. In some embodiments, the second substance may comprise from about 1 to about 20 wt% DEG. For example, the second substance comprises from about 4 to about 10 wt% DEG. Preferably, the second substance comprises from about 7 to about 8 wt% DEG. In some embodiments, the second substance may comprise from about 0.1 to about 3 wt% water. For example, the second substance comprises from about 0.5 to about 1 wt% water. Preferably, the second substance comprises from about 0.8 to 1.0 wt% water. In some embodiments, the second substance may comprise from about 0.1 to about 3 w.% water, and from about 1 to about 20 wt% DEG. For example, the second substance comprises from about 0.5 to about 1 wt% water and from about 4 to about 10 wt% DEG. Preferably, the second substance comprises from about 0.8 to 1.0 wt% water and from about 7 to about 8 wt% DEG. In some embodiments, the second substance may comprise from about 0.1 to about 3 wt% water, from about 1 to about 20 wt% DEG, and the ratio of DEG to water is from about 20:1 to about 20:3. For example, the second substance comprises from about 0.5 to about 1 wt% water, from about 4 to about 10 wt% DEG, and the ratio of DEG to water is from about 40:3 to about 40:6. Preferably, the second substance comprises from about 0.8 to 1.0 wt% water, from about 7 to about 8 wt% DEG, and the ratio of DEG to water is about 8:1. In some embodiments, the second substance may comprise at least one catalyst. Preferably, the second substance may comprise a first catalyst and a second catalyst. Each catalyst may comprise or consist of triethylenediamine or TEDA (also known as 1,4-diazabicyclo[2.2.2]octane). In some embodiments, the second substance may comprise from about 0.1 to about 3.0 wt% first catalyst. For example, the second substance comprises from about 0.8 to about 1.5 wt% first catalyst. Preferably, the second substance comprises from about 1 to about 1.15 wt% first catalyst. In some embodiments, the second substance may comprise from about 0.01 wt% to about 2 wt% second catalyst. For example, the second substance comprises 0.25 wt % to about 0.75 wt% second catalyst. Preferably, the second substance comprises from about 0.4 to about 0.6 wt% second catalyst. In some embodiments, the second substance may comprise from about 0.1 to about 0.4 wt% first catalyst and second catalyst. For example, the second substance may comprise from about 1 to about 2 wt % first catalyst and second catalyst. Preferably, the second substance may comprise from about 1.4 to about 1.9 wt% first catalyst and second catalyst. The second substance may comprise a surfactant. Preferably the second substance comprises a first surfactant and a second surfactant. Each surfactant may be selected by the skilled person. For example, the surfactant may be a silicone based surfactant, or a non-silicone based surfactant. Preferably, the surfactant is a silicone based surfactant. In some embodiments, the second substance may comprise from about 0.01 to about 2.0 wt% first surfactant. For example, the second substance comprises from about 1.0 to about 1.9 wt% first surfactant. Preferably, the second substance comprises from about 1.4 to about 1.6 wt% first surfactant. In some embodiments, the second substance may comprise from about 0.01 to about 0.4 wt% second surfactant. For example, the second substance comprises from about 0.03 to about 0.20 wt% second surfactant. Preferably, the second substance comprises from about 0.13 to about 0.17 wt% second surfactant. In some embodiments, the ratio of the first surfactant to the second surfactant may be from about 3:1 to about 20:1. For example, the ratio of the first surfactant to the second surfactant is from about 6:1 to about 15:1. Preferably, the ratio of the first surfactant to the second surfactant is about 10:1. The second substance may comprise a pigment. In some embodiments, the second substance may comprise from about 0.1 to about 10 wt% pigment. For example, the second substance may comprise from about 2 to 6 wt% pigment. Preferably, the second substance may comprise from about 3 to 5 wt% pigment. The pigment may advantageously provide a colour to the body of the insole. In some embodiments, the first substance comprises from about 50 to about 100 wt% of the first component. For example, the first substance comprises from about 70 to about 100 wt% of the first component. Preferably, the first substance comprises from about 80 to about 100 wt% of the first component. In some embodiments, the second substance comprises from about 50 to about 95 wt% of the second component. For example, the second substance comprises from about 70 to about 90 wt% of the second component. Preferably, the second substance comprises from about 80 to about 90 wt% of the second component. In some embodiments, the second substance comprises from about 50 to about 95 wt% of the second component, from about from about 0.1 to about 3 wt% water, from about 1 to about 20 wt% DEG, from about 0.01 to about 2.0 wt% first surfactant, and from about 0.01 to about 0.4 wt% second surfactant, and from about 0.1 to about 3.0 wt% first catalyst, from about 0.01 wt% to about 2 wt% second catalyst. For example, the second substance comprises from about 70 to about 90 wt% of the second component, from about from about 0.5 to about 1 wt% water, from about 4 to about 10 wt% DEG, from about 1.0 to about 1.9 wt% first surfactant, and from about 0.03 to about 0.20 wt% second surfactant, and from about 0.8 to about 1.5 wt% first catalyst, from about 0.25 wt% to about 0.75 wt% second catalyst. Preferably, the second substance comprises from about 80 to about 90 wt% of the second component, from about from about 0.8 to 1.0 wt% water, from about 7 to about 8 wt% DEG, from about 1.4 to about 1.6 wt % first surfactant, and from about 0.13 to about 0.17 wt % second surfactant, and from about 1 to about 1.15 wt% first catalyst, from about 0.4 to about 0.6 wt% second catalyst. In some embodiments, the mould comprises a cavity, wherein at least a portion of the cavity has a thickness of about 4mm. Preferably, the at least a portion of the cavity is a forefoot portion. In some embodiments, the mould comprises at least one fastening positioned within an upper part of the mould, and wherein the process further comprises placing and fastening a fabric comprising a coating of thermoplastic polyurethane within the mould using the at least one fastening prior to the mixture being applied to the mould. Preferably, the at least one fastening is one or more pins. Preferably, the mould comprises a top part and a bottom part and wherein the process comprises placing and fastening the fabric to the top part. Preferably, the mixture is applied to the bottom part of the mould. Preferably, the coating of thermoplastic polyurethane is positioned such that, when the mixture is applied to the mould, the thermoplastic polyurethane is in contact with the mixture. The thermoplastic polyurethane advantageously stops the mixture from wetting the fabric. Preferably, after the body is removed from the mould, the fabric is trimmed to the shape of the body to form the insole. In some embodiments, the process further comprises spraying a release agent to the mould prior to the mixture being applied to the mould, optionally wherein the release agent comprises a wax. The release agent advantageously stops the combination of the first substance and the second substance from sticking to the mould and allows easier removal of the body from the mould after the body is cured. In some embodiments, the mould comprises a left foot mould and a right foot mould, and wherein applying the mixture to the mould comprises applying the mixture to the left foot mould and the right foot mould such that a left foot insole and a right foot insole are formed simultaneously. Forming a left foot insole and a right foot insole simultaneously saves time and space and ensures consistency in each pair of insoles. In a further aspect, there is provided a sheet, the sheet comprising a body, the body being formed by a process comprising: a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; c) Mixing the first substance and the second substance to form a mixture, wherein the ratio of the first component to the second component is from about 1:3 to about 3:1; d) Applying the mixture to a mould to provide an insole, optionally wherein at least a portion of the body has a thickness of about 4mm or less preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. The first substance may be any first substance as described herein in relation to any aspect or embodiment. The second substance may be any second substance as described herein in relation to any aspect or embodiment. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any second component as described herein in relation to any aspect or embodiment. The process may be any process as described herein in relation to any aspect or embodiment. In a further aspect, there is provided a sheet, the sheet comprising a body comprising polyurethane, optionally wherein at least a portion of the body has a thickness of about 4mm or less. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. In a further aspect, there is provided a combination for forming a sheet, the combination comprising: a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; and a second substance, the second substance comprising a second component, wherein the second component comprises a polyol; wherein the ratio of the first component to the second component is from about 1:3 to about 3:1. The first substance may be any first substance as described herein in relation to any aspect or embodiment. The second substance may be any second substance as described herein in relation to any aspect or embodiment. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any first component as described herein in relation to any aspect or embodiment. In a further aspect, there is provided a sheet, the sheet comprising a body, the body being formed by the reaction of: i) a first component comprising a methylene diphenyl diisocyanate; and ii) a second component comprising a polyol; wherein the ratio of (i) to (ii) is from 1:3 to 3:1; and optionally wherein at least a portion of the body has a thickness of 4mm or less, preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm. In some embodiments, at least a portion of the body has a thickness of from about 1mm to about 4mm. The first component may be any first component as described herein in relation to any aspect or embodiment. The second component may be any first component as described herein in relation to any aspect or embodiment. MDI Methylene diphenyl diisocyanate (MDI) is otherwise known as 4,4’- methylene diphenyl diisocyanate, 2,2'- methylene diphenyl diisocyanate or 2,4'- methylene diphenyl diisocyanate. Herein, MDI preferably is 4,4’- methylene diphenyl diisocyanate. MDI is commercially produced in monomeric and (preferably) oligomeric / polymeric forms. There are different grades of MDI and choosing a suitable MDI grade may require knowledge of three properties: NCO% content, viscosity and average functionality. The NCO% content is a measure of the molecular weight of isocyanate groups as a percentage of the total molecular weight of the MDI. Functionality is defined as the number of isocyanate groups per MDI. For a monomeric MDI, the functionality is 2, because there are two isocyanate groups available to react on the MDI molecule. An oligomeric / polymeric MDI has a functionality of between 2 and 3. NCO% is measured according to the DIN EN ISO 14896:2009 standard. Functionality is calculated theoretically based on the raw materials used to make the MDI and is a term of art. The skilled person understands this term and is able to identify MDIs with the relevant functionalities. For the purposes of patent offices in which such a term is deemed not to be permissible, we hereby explicitly state that every aspect and embodiment which includes reference to the term “functionality” can be replaced with the identical aspect or embodiment except that the term “functionality” is removed therefrom. Viscosity is measured at 25°C according to ASTM D4889-21 standard. Different grades of MDI are available under the SUPRASEC® name. Each MDI described herein may be a mixture or blend of similar / different MDIs. For example, the first MDI and second MDI may be a mixture or blend of MDIs. In particular, the first MDI may be a mixture of MDIs such that the mixture has the properties and features as described herein. In particular, the second MDI may be a mixture of MDIs such that the mixture has the properties and features as described herein. For example, each MDI may be an oligomer comprising an MDI and a polyol, and / or a polymer comprising an MDI and a polyol. The MDIs described herein may be substituted or unsubstituted MDIs. When a component is said to comprise an MDI (for example, a first MDI and / or second MDI), it may preferably consist of said MDI. Polyol A polyol is a term of art. Polyols are organic compounds that comprise multiple hydroxyl groups (-OH) and can comprise polyethers, polyesters, polycarbonates and acrylic polyols. Preferably, the polyols described herein are poly ether polyols. They can preferably comprise two, three and four hydroxyl groups. All polyols may be used to produce polyurethane polymers. Hydroxyl number (mg KOH / g) is measured according to the ASTM D4274 standard. The molecular weight of a polyol can be calculated by multiplying the polyol equivalent weight (eq. qt.) by the nominal functionality (fn), and is a term of art. The skilled person understands this term and is able to identify MDIs with the relevant functionalities. For the purposes of patent offices in which such a term is deemed not to be permissible, we hereby explicitly state that every aspect and embodiment which includes reference to the term “functionality” can be replaced with the identical aspect or embodiment except that the term “functionality” is removed therefrom. Viscosity is measured at 25°C according to ASTM D4878-23 standard. Different types of polyols are available under the Puranol name. Each polyol described herein may be a mixture or blend of similar / different polyols. For example, the first polyol, second polyol and third polyol may be a mixture or blend of polyols. In particular, the first polyol may be a mixture of polyols such that the mixture has the properties and features as described herein. In particular, the second polyol may be a mixture of polyols such that the mixture has the properties and features as described herein. In particular, the third polyol may be a mixture of polyols such that the mixture has the properties and features as described herein. When a component is said to comprise a polyol (for example, a first polyol, a second polyol, and / or third polyol), it may preferably consist of said polyol. Reaction Product / Combination The reaction product of the first component and the second component comprises polyurethane. Preferably, the reaction product of the first component and the second component is polyurethane. The combination of the first component and the second component in the ratio of from about 1:3 to about 3:1 results in flow characteristics that can result in a thickness that is far thinner than standard sheets. Specifically, the body comprising the reaction product has a thickness of about 4mm or less. This slim profile is particularly useful for ball sport specific shoes, such as for badminton. Insole An insole of the present invention is shown in Figure 5. The insole shown is for a left foot shoe and it will be understood that the components of the left foot are substantially the same mirror image thereof. Additionally, the size of the insole may vary depending on the associated show size (e.g. length and width) and / or gender of the wearer of the associated shoe and insole. Figure 5 is a top view of the insole showing an upper surface 102 of the insole 100 of the present invention. The upper surface in this context means the surface of the insole which is in contact with the user’s foot when in use. The upper surface 102 is formed from a fabric. The insole also comprises a lower surface 104 (shown in Figures 2, 3 and 4) formed from a polyurethane body. The lower surface in this context means the surface of the insole which is in contact with the user’s shoe when in use. As shown in Figure 5, the insole comprises three portions: a forefoot portion 110 for supporting the toes and ball of a user’s foot, a mid-foot portion 120 for supporting the metatarsal area and the arch of the user’s foot and a heel portion 130 for supporting heel of the user’s foot. The insole is contoured and comprises different thicknesses in the longitudinal (along the line A-B) and lateral (along the line C-D) directions of the insole. The forefoot portion 110 is flat or predominantly flat, whilst the mid-foot portion 120 comprises an arch support 122 and a raised feature 124 which create varying curvatures on the upper surface 102 of the insole. The arch support 122 also extends into the heel portion 130. The arch support 122 is shaped and sized as in conventional in the field. The raised feature 124 is shaped and sized for relieving pressure in the metatarsal area of the foot. The contouring of the insole is shown in Figure 8, which will shortly be discussed in more detail later. The raised feature 124 has a base having a substantially teardrop shape, as shown in Figure 5. The base has a width, W, measured in a lateral direction from a first point E to a second point F of about 30cm, and a length, L, measured in a longitudinal direction from a first end G to a second end H of about 45cm. The width is measured at a longitudinal location from about 40 to about 45% of the longitudinal length from the forefoot end 160 of the insole. These measurements are specifically for a UK men’s shoe size 11 insole, and the size of the raised feature is configured such that with different size insoles, the raised feature is in proportion to the size of the insole. The teardrop shaped base comprises three edges. One of the three edges is a substantially straight edge 126 which is located close to a medial side 128 of the insole. Two of the three edges are curved edges 125, and one of the curved edges extends in a substantially longitudinal direction (along the direction shown by line A-B) and one of the curved edges extends in a substantially lateral direction (along the direction shown by line C-D). The raised feature 124 is positioned substantially central in a lateral direction and substantially central in a longitudinal direction in the insole. Figure 6 is a side view of the insole of Figure 5 from the forefoot end 160 of the insole. Figure 6 shows that the raised feature is dome-shaped (i.e. it has a three-dimensional shape) and has a maximum thickness Ti. The maximum thickness Ti of the raised feature 124 is less than a maximum thickness T2 of the arch support 122. The maximum thickness T2 of the arch support 122 is approximately four to five times the maximum thickness Ti of the raised feature 124. The term ‘maximum thickness’ in this context means the vertical distance from the upper surface 141 of the body at the forefoot end 160 or forefoot portion 110, as shown in Figure 2. Figure 2 also shows the thickness Tf of the forefoot portion 110. The thickness Tf of the forefoot portion 110 is about the same as the maximum thickness Ti of the raised feature 124. The maximum thickness T2 of the arch support 122 is approximately four to five times the thickness Tf of the forefoot portion. Figure 8 shows the difference in thickness across the insole. A brighter region indicates that the region is thicker than the surrounding region, whilst a darker region indicates that the region is thinner than the surrounding region. The raised feature 124 is shown as being brighter (i.e. thicker) than the surrounding region, but not as bright as the arch support 122 which has a greater thickness than the raised feature 124. The forefoot portion 110 is flat, as shown in Figure 8, whilst the heel portion 130 has a concave shape in which the periphery of the heel portion is thicker, by from about 0.05mm to about 0.15mm, compared to the centre of the heel portion. Returning to the mid foot portion 120 and as shown in Figures 5 and 8, the raised feature 124 is separate from the arch support 122 and there is a channel 121 between the raised feature 124 and the arch support 122. For users of the insole who have a prominent plantar fascia in the arch area, the channel 121 accommodates and decreases pressure on the plantar fascia. The channel 121 extends longitudinally along a portion of the mid-portion 120 of the insole. The channel 121 has approximately the same thickness as the thickness of the forefoot portion. Figure 7 is a side view of the insole from a medial side 128 of the insole and shows the flat forefoot portion 110, and the arch support extending across the mid-foot portion 120 and the heel portion 130. The heel portion 130 is thicker than the forefoot portion 110 (known as the heel-to-toe drop). A higher heel-to-toe drop means that the user’s hips and knees absorb more impact, whilst a lower heel-to-toe drop means that the user’s ankles absorb more impact. As shown in Figure 7, the heel portion 130 has a thickness Th approximately twice the thickness Tf of the forefoot portion. As shown in Figures 6 and 7, the insole comprises a body 140 formed from polyurethane, and a fabric layer 150. The body comprises a lower surface 143 and an upper surface 141 and the fabric layer 150 is affixed to the upper surface 141 of the body. The upper surface 141 of the body is shaped to support the user’s foot whilst the lower surface 143 is flat. The body 140 is formed from polyurethane, preferably a polyurethane foam. The raised feature 124 and the arch support 122 are formed from the body of polyurethane. The fabric 150 is flexible so it adapts to the contours of the underlying polyurethane body. The fabric 150 may aid in the comfort of user and provide sweat and odour control or the like. The body 140 has a thickness of approximately 4mm or less in the forefoot portion 110, which may increase to an average thickness of approximately 7.5mm at the mid-foot portion 120 and heel portion 130. The fabric layer 150 has a thickness of approximately 0.7mm. Figure 9 is a micrograph through the thickness of the body 140 insole at the forefoot portion and illustrates the difference in density through the body. The body 140 comprises an upper part 210, a central part 220 and a lower part 230. The thickness of the body 140 shown in Figure 5 is approximately 2.8mm. Figure 9 shows that the upper part 230 extends from the upper surface 141 to approximately 300pm beneath the upper surface 141. Figure 9 also shows that the lower part 230 extends from the lower surface 143 to approximately 300pm above the lower surface 143. The central part 220 is located between the upper part 210 and the lower part 230. Whilst Figure 9 shows that the upper part 210 and the lower part 230 have thickness of approximately 300pm, the upper part and the lower part can have a thickness of approximately 400pm, approximately 500pm, approximately 600pm, approximately 700pm, approximately 800pm, approximately 900pm, approximately 1mm or approximately 1.1mm. Thus, the upper part 210 and the lower part 230 may form approximately 75% of the thickness of the body of the insole, or approximately 65%, or approximately 55%, or approximately 45%, or approximately 25%, or approximately 20% of the thickness of the body 140 of the insole. As shown in Figure 9, the upper part 210 and the lower part 230 have a more densely packed structure compared to the central part 220. For example, the upper part 210 and the lower part 230 may have a density approximately 100% greater than the density of the central part 220, or approximately 200% greater, or approximately 300% greater. The micrograph shown in Figure 9 shows the presence of air bubbles 145 throughout the thickness of the body. Specifically, the body comprises an open cell structure which allows air to flow through the body making it moisture wicking and more breathable. As shown in Figure 9, the upper part 210 and lower part 230 contain fewer air bubbles compared to the central part 220. Whilst not shown in Figure 9, the raised feature 124 in the form of a dome is integral to the body 140 and therefore also comprises a range of densities through the thickness of the dome. Specifically, the raised feature or dome 124 comprises an upper part which extends from the upper part 210 of the rest of the body. The dome also comprises a central part which extends from a portion of the central part 220 of the rest of the body. The upper part of the raised feature or dome 124 may have a density approximately 100% greater than the density of the central part, or approximately 200% greater, or approximately 300% greater. Similarly, the arch support is integral to the body and comprises a range of densities through the thickness of the arch support. Figure 10 is a micrograph of an alternative body 300 formed from EVA, which is not within the scope of the invention. Figure 10 is provided as a comparison to Figure 9 and illustrates that the density of the body of EVA is consistent through the thickness of the body. Specifically, the size of the air bubbles 345 and number of air bubbles 345 is relatively consistent throughout the thickness of the body in contrast to the arrangement and size of the air bubbles 145 of the polyurethane foam body shown in Figure 9. Mechanical Properties of the sheet Despite the reduced material thickness in the sheet of the present invention, the sheet maintains superior shock absorption and cushioning properties, a high tensile strength and remains soft. The shock absorption of the sheet may be from about 20 to about 80g, in some examples from about 40 to about 80g and preferably from about 55 to about 75g. The shock absorption is measured by vertically dropping an impact striker of fixed mass with a domed lower surface from a predetermined height onto the insole according to SATRA standard TM142. The mass of the striker and its height from the sheet are adjusted such that the striker impacts the insole with 4 Joules of energy. During impact the maximum deceleration of the striker and the indentation of the sheet are measured. The lower the maximum deceleration, the better the shock absorption properties of the material. The tensile strength of the body is greater than 1 MPa for an elongation of >170%, as measured by a tensile testing machine. A sample of the body of the sheet having a specified initial length is gripped at each longitudinal end by a tensile testing machine. Then a continually increasing uni-axial load is applied. The ultimate tensile strength, otherwise referred to as the tensile strength is the point at which the body deforms such that a large amount of strain disproportionately localises in a small region of the material, otherwise known as a neck. The tensile testing machine continues to apply the uni-axial load until the body fractures. The ultimate tensile strength, omax, is calculated using the formula: Gmax = Pmax / Ao where Pmax is the maximum load (N), and Ao is the original cross sectional area (m2). The elongation measured during tensile testing is the percentage increase in the sample’s length when the sample is stretched under tension. It gives an indication of the sample’s ability to stretch and deform before breaking. It is calculated by the formula: Elongation = (change in length / original length) xlOO The hardness of the body is between 23 and 40 Shore A points as measured by an off-the-shelf hardness durometer comprising a presser foot. A sample of the body is placed on a hard, flat, horizontal surface and the presser foot of the durometer is pressed down firmly onto the sample, and the durometer provides a reading of the hardness of the material. Generally, the hardness is determined by pressing an indenter, either a spherical or a 4-sided square based pyramid indenter, into the surface of the sample and calculating the hardness H from the formula: H = applied test force (kgf) / surface area of indentation (mm2) Process for forming the insole or sheet The sheet or insole may be formed using the apparatus 400 shown in Figure 11. The apparatus 400 comprises two tanks; a first tank 410 holds the first substance and a second tank 420 holds the second substance. Thus, the first substance and the second substance are stored and dispensed separately. The apparatus further comprises a first filter 412 and a second filter 422 and a first metering pump 414 and a second metering pump 424. The first filter 412 and the first metering pump 414 are connected to the first tank 410. The second filter 422 and the second metering pump 424 are connected to the second tank 420. The first filter 412 and the second filter 422 purify the first substance and the second substance respectively and remove any unwanted particulates from the first substance and the second substance which could reduce the efficiency of the reaction between the first substance and the second substance. After the first substance is filtered using the first filter 412, the filtered first substance is dispensed using the first metering pump 414. Similarly, after the second substance is filtered using the second filter 422, the second filtered substance is dispensed using the second metering pump 424. The metering pumps 414, 424 control release of a precise volume of the liquid in a specified time period. The apparatus 400 further comprises a mixing head 430 into which the first substance and the second substance are released. The mixing head 430 comprises a high-speed rotor such that the first substance and the second substance are subjected to an intense shearing action. The mixture produced from combining the first substance and the second substance in the mixing head 430 is dispensed into the mould 450. The tanks 410, 420, filters 412, 422, metering pumps 414, 424 and mixing head 430 are all controlled by a control unit 440. The user can set at least the filtering time, the release of the first substance and the second substance over a specific time period, the mixing speeds and time using the control unit 440 such that the sheet or insole formed in the mould 450 has the desired properties. Mixing of the first substance and the second substance may be controlled by the user via the control unit 440 such that the mixing time is between about 1 and 60 seconds, preferably between about 1 and 30 seconds, more preferably between about 1 and 20 seconds, most preferably between about 1 and 10 seconds. If mixing occurs for longer than 60 seconds, the first substance and the second substance may polymerise in the mixing head. As shown in Figure 11, the mixing head 430 is positioned directly above the mould 450. Preferably, the mixing head 430 is positioned at about 1 to 20cm from the top of the mould, more preferably about 1 to 10cm from the top of the mould, more preferably between about 3 to 8cm from the top of the mould, more preferably between about 4 to 6cm from the top of the mould, preferably about 5cm from the top of the mould. The mould 450 is heated by water pipework, and the first substance and the second substance are dispensed into the mould when the mould is heated to a desired temperature. Each mould has a top and a bottom part. The top part of the mould comprises pins for fixing a fabric having a coating of thermoplastic polyurethane. The fabric may be affixed to the top part of the mould such that the coating can contact the mixture when it is dispensed into the mould. The mixture of the first substance and the second substance is dispensed into the bottom part of the mould so that gravity can allow the mixture to flow downwards therefore forming the sheet or insole. The cavity of the mould has a thickness of about 4mm or less. Once the first substance and the second substance are dispensed into the mould 450, the top part of the mould and the bottom part of the mould are clamped together. The mixture is then left to cure. The moulds are opened after curing and the sheet or insole is removed from the mould. The fabric is then trimmed to match the specific purpose. Process for forming a pair of insoles The process and apparatus may be used for forming a pair of insoles. As shown in Figure 11, a mould 450 comprises a left foot mould and a right foot mould. Each mould has a top and a bottom part. The top part of the mould comprises pins for fixing a single piece of fabric having a coating of thermoplastic polyurethane. The fabric is affixed to the top part of the mould such that the coating can contact the mixture when it is dispensed into the mould. The mixture of the first substance and the second substance is dispensed into the bottom part of the left foot mould and the right foot mould into a heel cavity so that gravity can allow the mixture to flow downwards towards a forefoot cavity therefore forming the forefoot portion of the insole. The forefoot cavity of the left foot mould and the right foot mould has a thickness of about 4mm or less. Once the first substance and the second substance are dispensed into the left foot mould and the right foot mould, the top part of each mould and the bottom part of each mould are clamped together. The mixture is then left to cure. The moulds are opened after curing and the insoles are removed from the moulds still affixed to the single piece of fabric. The fabric is then cut to separate the left foot insole and the right foot insole, and trimmed to match the shape of the body of the left foot insole and the right foot insole. Definitions wt% means weight percentage. When a component, substance or combination is said to comprise a wt% of a something, it is understood that total wt% of the component, substance or combination does not exceed 100 wt% The term ‘insole’ may also be referred to as an insole assembly, innersole or insert. The term ‘upper surface’ of the body means the surface of the body which is in contact with either a fabric or with the user’s foot when in use. The term ‘lower surface’ of the body means the surface of the body which is in contact with the user’s shoe when in use. Reference to “at least a portion of the body has a thickness of’ may be replaced throughout this application with wording “the body has an average thickness of’. An average thickness of the body refers to the average thickness of the body over a substantial part or the whole part of the body. DEG is diethylene glycol. DABCO is (l,4-diazabicyclo[2.2. 2]octane), also known as triethylenediamine or TEDA, is a bicyclic organic compound with the formula Ni(C2114)3. The term “molecular weight” is understood by the skilled person as a term of art. When any component or substance described herein contains more than one compound / oligomer / polymer, the term molecular weight is meant to refer to “average molecular weight”, as would be understood by the skilled person. Example 1 An example is defined below using the methodology described below. Table 1 shows all the components used to form a sheet, according to the invention. Table 1 Component Name Viscosity (mPa.s) NCO (%) Hydroxyl No. (mg KOH / g) Molecular weight (g / mol) MDI 1 Suprasec 2528 200 25.2 375 MDI2 Suprasec 2020 40 29.5 299 Polyol 1 Puranol F330N 750-950 33-37 4800 Polyol 2 Puranol D 2122 3600-3700 50-55 2200 DEG Dye Gecko Pigment Catalyst Dabco 33LV 120 Catalyst Dabco 1029 60 Surfactant Tegostab B8905 550-850 Surfactant Tegostab B8948 2300 5 Water Suprasec 2528 and Suprasec 2020 (sourced from Huntsman Corporation) form the first substance. Puranol PP3645, Puranol F330, Puranol D 2122, DEG, Gecko Pigment, Dabco 33LV, Dabco 1029, Tegostab B8905, Tegostab B8948 and water form the second substance. Tegostab B8905 and B8948 act as surfactants in the reaction. Dabco is triethylenediamine or TEDA (also known as l,4-diazabicyclo[2.2.2]octane) is a bicyclic organic compound with the formula N2(C2H4)3. Dabco 33LV and Dabco B8905 are used as catalysts for the reaction between MDI and polyol. Gecko pigment provides green colouring for the body of the sheet / insole. DEG is used as a chemical intermediate for the production of thermoplastic polyurethane. The first MDI component and the second MDI component were mixed and stored together in a first tank in the amounts shown in Table 2 below. Table 2 Component Weight (g) Suprasec 2528 12.75 Suprasec 2020 38.50 The remaining components were mixed and stored together in a tank in the amounts shown in Table 3. Table 3 Component Weight (g) Puranol F330N 43.00 Puranol D 2122 41.40 DEG 7.10 Gecko Pigment 4.0 Dabco 33LV 1.05 Dabco 1029 0.85 Tegostab B8905 0.15 Tegostab B8925 1.50 Water 0.95 The apparatus was set up as shown in Figure 11. The mould was cleaned and sprayed with a wax. A polyester fabric coated in thermoplastic polyurethane was fixed to a top part of the mould using pins and such that the thermoplastic polyurethane coating was in contact with the mixture. The mould was heated to approximately 40°C using water pipework. Once the mould reached 40°C, the components shown in Tables 2 and 3 were released from their respective separate tanks and were filtered and pumped by metering pumps into the mixing head of the apparatus where they were mixed together for approximately 1 second. The mixture was dispensed from the mixing head, which was a distance of approximately 5cm from the mould, into the mould. Depending on the size of the sheet to be formed, and therefore the size of the mould, between 100g and 150g of mixture was added to the mould to achieve an average moulded density of the body of about 280kg / m3. The top part and the bottom part of the mould were closed and clamped together and the mixture was cured for 8 minutes whilst in the mould at 40°C. The top part and the bottom part of the mould were then opened and the body and fabric were removed from the mould, the fabric was trimmed to the shape of the moulded body to form the sheet, and the sheet was left to cure at room temperature for at least 5 days. Example 2 Two samples of sheets according to the present application comprising a body without a polyester fabric were made and subjected to mechanical testing. 125 g of mixture (as in Example 1) was added to the mould to achieve a sheet with a length of about 350mm, a width of about 250 mm and a thickness of about 3 mm. The thickness of each sample was measured. The hardness of each sample was measured using a hardness durometer. The average density of each sample was measured over the whole sheet. The tensile strength was measured by pulling apart two opposing ends of each sample at a speed of 500mm / min. The change in length (elongation) of each sample was also measured during the tensile test. The results of the testing of two samples having different thickness are shown in Table 4. Table 4 Sample No. Thickness (mm) Shore AO 10 sec heel Tensile strength (N / mm2) Elongation (%) Average Density (kg / m3) 1 3.05 36 1.47 177 289 2 3.12 34 1.49 186 278 The results show that the sheets of samples 1 and 2 are soft (low Shore A points), strong (high tensile strength), dense and can be stretched to more than three times their sample length without breaking. These are all ideal properties for a sheet according to the present invention. Figure 1 shows a sheet according to the present invention which is uniform in all aspects. This contrasts to the comparative sheets shown in Figures 2-4. The invention described above can be practiced in a variety of embodiments, non-limiting examples of which are described herein. The above examples are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A sheet, the sheet comprising:a body comprising the reaction product of:i) a first component comprising a methylene diphenyl diisocyanate; andii) a second component comprising a polyol;wherein the ratio of the first component to the second component is from about 1:3 to about 3:1;optionally wherein at least a portion of the body has a thickness of about 4mm or less; preferably wherein the sheet has a length of from about 300 to about 600 mm, a width of from about 200 to about 500 mm, and a thickness of from about 0.1 to about 4 mm.

2. A sheet according to claim 1, wherein the ratio of the first component to the second component is about 3:5.

3. A sheet according to claim 1 or claim 2, wherein the second component comprises a first polyol, a second polyol, or any combination of a first polyol and a second polyol.

4. A sheet according to claim 3, wherein the first polyol has a viscosity of from about 300 to about 2000 mPa.s, and / or the second polyol has a viscosity of from about 1000 to about 7000 mPa.s; andthe first polyol has a hydroxyl number of from about 15 to about 80 mg KOH / g, and / or the second polyol has a hydroxyl number of from about 20 to about 90 mg KOH / g; andoptionally the second polyol has a molecular weight of from about 2000 to about 9000 g / mol, and / or optionally the third polyol has a molecular weight of from about 500 to about 5000 g / mol.

5. A sheet according to any preceding claim, wherein the first component comprises a first methylene diphenyl diisocyanate (MDI), a second methylene diphenyl diisocyanate(MDI), or any combination of a first methylene diphenyl diisocyanate and a second methylene diphenyl diisocyanate.

6. A sheet according to claim 5, wherein the first MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate; and the second MDI is an oligomer comprising methylene diphenyl diisocyanate, and / or a polymer comprising methylene diphenyl diisocyanate; andthe first MDI has an average NCO% of from about 13 to about 42 %, and / or the second MDI has an average NCO% of from about 10 to about 40%; andthe first MDI has a viscosity of from about 50 to about 350 mPa.s, and / or the second MDI has a viscosity of from about 10 to about 100 mPa.s; andoptionally the first MDI has an average functionality of from about 2.1 to about 2.3, and / or optionally the second MDI has an average functionality of from about 2.0 to about 2.2.

7. A sheet according to any preceding claim, wherein the body comprises a foam comprising an open cell structure formed by a foaming agent.

8. A sheet according to any preceding claim, wherein the portion of the body has a thickness of 4mm or less.

9. A sheet according to any preceding claim, wherein the average density of the body is from about 150kg / m3 to about 400kg / m3; and / orwherein the body has a material hardness from about 20 to about 40A Shore A points; and / orwherein the body has a maximum tensile stress of greater than about 0.8MPa.

10. A sheet according to any preceding claim wherein at least a portion of the body has a thickness of about 3 mm or less, the tensile strength is from about 1.2 to about 2 MPa atan elongation of greater than 170%, and the density is from about 250 kg / m3 to about 300 kg / m3.

11. An orthopaedic device formed from the sheet according to any preceding claim.

12. An insole formed from the sheet according to any of claims 1 to 10.

13. A process for producing a sheet, the sheet comprising a body, the process comprising:a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate;b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol;c) Mixing the first substance and the second substance to form a mixture; andd) Applying the mixture to a mould to provide a sheet, optionally wherein at least a portion of the body has a thickness of about 4mm or less;wherein the ratio of the first component to the second component is from about 1:3 to about 3:1.

14. A process according to claim 13, wherein the ratio of the first component and the second component is about 3:5.

15. A process according to claim 13 or 14, wherein the process further comprises heating the mould to a temperature from about 30°C to about 50°C before the mixture is applied to the mould.

16. A process according to claim 15, wherein the process further comprises curing the mixture to form the body.

17. A process according to claim 16, wherein curing is carried out from about 1 to about 120 minutes within the mould at the temperature of the mould, optionally wherein curing further comprises removing the body from the mould and maintaining the body at a temperature of from about 15 °C to about 60°C.

18. A process according to any one of claims 13 to 17, wherein the process further comprises providing a third component, the third component being a diethylene glycol, and providing a fourth component, the fourth component being water; wherein the ratio of the third component to the fourth component is from about 20:1 to about 20:3.

19. A process according to any one of claims 13 to 18, wherein the mould comprises a cavity, wherein at least a portion of the cavity has a thickness of about 4mm.

20. A process according to any one of claims 13 to 19, wherein the mould comprises at least one fastening positioned within an upper part of the mould, and wherein the process further comprises placing and fastening a fabric comprising a coating of thermoplastic polyurethane within the mould using the at least one fastening prior to the mixture being applied to the mould.

21. A process according to any one of claims 13 to 20, wherein mixing of the first substance and the second substance is carried out for a duration of from about 1 second to about 60 seconds.

22. A sheet, the sheet comprising a body, the body being formed by a process comprising:a) Providing a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate;b) Providing a second substance, the second substance comprising a second component, wherein the second component comprises a polyol;c) Mixing the first substance and the second substance to form a mixture; andd) Applying the mixture to a mould to provide a sheet, optionally wherein at least a portion of the body has a thickness of about 4mm or lesswherein the ratio of the first component to the second component is from about 1:3 to about 3:1.

23. A sheet, the sheet comprising a body comprising polyurethane, optionally wherein at least a portion of the body has a thickness of about 4mm or less.

24. A combination for forming a sheet, the combination comprising:i) a first substance, the first substance comprising a first component, wherein the first component comprises a methylene diphenyl diisocyanate; andii) a second substance, the second substance comprising a second component, wherein the second component comprises a polyol;wherein the ratio of the first component to the second component is from about 1:3 to about 3:1.

25. Use of a combination according to claim 24, for forming a sheet.

Images