Elastic ultra-high molecular weight polyethylene aerogel fibers, films and sheets

Abstract

The present disclosure relates to elastic and flexible ultra-high molecular weight polyethylene (UHMWPE) aerogel fibers, films, and sheets. These fibers, films and sheets are produced by forming a slurry comprising mineral oil and UHMWPE powder, processing the slurry through gel spinning or casting, and extracting the mineral oil using supercritical carbon dioxide to create a porous aerogel structure. The resulting materials exhibit low density, high elasticity, and excellent thermal insulation properties, making them suitable for various applications, including technical textiles, insulation materials, and filtration systems. Optional impregnation with polymerizable oils or elastic polymers further enhances their mechanical properties.

Description

[0001] ELASTIC ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE AEROGEL FIBERS, FILMS AND SHEETS

[0002] BACKGROUND

[0003] Technical Field

[0004] The present disclosure relates to the field of advanced polymeric materials, and more particularly to the development of elastic and flexible ultra-high molecular weight polyethylene (UHMWPE) aerogel fibers, films, and sheets. These materials exhibit a unique combination of low density, high elasticity, and excellent thermal insulation properties, making them suitable for a wide range of applications, including technical textiles, apparel, insulation materials, and filtration systems.

[0005] Description of the Related Art

[0006] Aerogels are renowned for their unique combination of properties, including extremely low density, high porosity, and superior thermal insulation. Traditionally, aerogels are composed of materials such as silica and have been primarily utilized in applications requiring lightweight and insulating materials, such as thermal insulation and filtration. However, a significant limitation of conventional aerogels is their intrinsic brittleness and lack of flexibility, which restricts their use in applications requiring materials with both mechanical strength and elasticity, such as textiles and flexible insulators.

[0007] Previous attempts to integrate aerogel properties into flexible materials have encountered substantial challenges. Such approaches have included embedding silica- or polymer-based aerogels into fabrics or composites. These methods often yield materials that are rigid, bulky or lack sufficient elasticity. Additionally, they may require complex chemical treatments or the use of additives, which can compromise the desired properties of the aerogel, such as increased density and reduced thermal insulation efficiency.

[0008] Accordingly, there exists a need for innovative materials that combine the exceptional properties of aerogels with mechanical flexibility and resilience necessary for applications in textiles, flexible insulation, and other domains requiring both performance and adaptability. BRIEF SUMMARY

[0009] The present disclosure addresses the limitations of the conventional aerogel materials by utilizing ultra-high molecular weight polyethylene (UHMWPE) to produce aerogel fibers, films, and sheets. The resulting UHMWPE aerogel material retains the lightweight and insulating properties of traditional aerogels while exhibiting significant elasticity and mechanical strength, thereby overcoming the brittleness and lack of flexibility observed in prior art materials.

[0010] In one aspect, provided herein are elastic and flexible ultra-high molecular weight polyethylene (UHMWPE) aerogel fibers, films, and sheets with low thickness and high elasticity. These materials are produced from a specially formulated slurry predominantly consisting of a solvent such as mineral oil (approximately 95% to 99.9%) and a small percentage of UHMWPE powder (approximately 0.1% to 5%), with the UHMWPE having a molecular weight ranging from about 1 x 106to about 6 x 106atomic mass units (amu). The slurry is processed via gel spinning to produce monofilament or multifilament fibers, or via casting to form films or sheets. After forming, the solvent such as mineral oil is extracted using a supercritical fluid such as supercritical carbon dioxide (CO2), resulting in a porous aerogel structure with open or closed cells, which imparts significant elasticity to the material, with stretchability up to 400%.

[0011] In some embodiments, following the extraction of the solvent such as mineral oil, the UHMWPE aerogel is impregnated with a polymerizable oil and an initiator required for subsequent polymerization. This impregnation is achieved by swelling the aerogel with a mixture containing the polymerizable oil and the initiator in a supercritical fluid within a pressure vessel. The infused polymerizable oil is then polymerized via thermal or photo-curing reactions to enhance the material’s properties.

[0012] In other embodiments, the UHMWPE aerogel is impregnated with an elastic polymer, such as polyurethane, elastane, poly(styrene-butadiene-styrene) (SBS), styrene-ethylene- butylene-styrene block copolymer (SEBS), silicone, or a photocurable polymer. The polymer infusion is facilitated by a supercritical fluid such as supercritical CO2, optionally in combination with a co-solvent, to ensure uniform distribution within the aerogel structure.

[0013] Alternatively, the UHMWPE powder can be co-extruded with an elastic polymer such as polyurethane, elastane, SBS, SEBS, or others, to produce fibers, films, or sheets with enhanced elasticity and mechanical properties.

[0014] In yet another embodiment, the UHMWPE powder can be co-extruded with a salt such as sodium chloride. Granulated or powdered salt is mixed with UHMWPE powder and a solvent, for example mineral oil to form a slurry, which is then extruded into monofdament or multifdament fibers. The resulting fibers undergo a series of extraction processes to extract the solvent and salt. In some embodiments, the solvent may be extracted using an alkane solvent (e.g., hexane or heptane) or a supercritical fluid (e.g., supercritical CO2). Salt may be extracted using a water bath, sprayed or directed water, or subcritical water in a pressure vessel. The resulting material has a foam-like open pore structure, which imparts elasticity to the material.

[0015] The resulting polyethylene aerogel fibers, films, and sheets are characterized by their lightweight nature, excellent thermal insulation properties, and high stretchability. These materials are particularly advantageous for textile and insulation applications, offering enhanced performance characteristics compared to traditional fibers and fabrics.

[0016] DETAILED DESCRIPTION

[0017] Traditional aerogels, such as silica aerogels, suffer from brittleness and lack of flexibility, limiting their use in applications requiring mechanical resilience. Polymer-based aerogels have been developed to address some of these issues but often at the expense of increased density or decreased thermal insulation. The present disclosure overcomes these limitations by utilizing UHMWPE to form aerogel fibers, films, and sheets that are both lightweight and highly elastic, while maintaining superior thermal insulation properties. The innovative use of supercritical fluid extraction (e.g., supercritical CO2 extraction) enables removal of the processing solvent while preserving the aerogel’s porous structure, thereby avoiding the drawbacks associated with conventional solvent extraction methods.

[0018] Aerogel Production Process

[0019] According to one aspect of the present disclosure, a slurry comprising UHMWPE powder and a solvent is provided. The slurry enables the UHMWPE to be wet spun into fibers or cast into films or sheets.

[0020] The UHMWPE powder may have a molecular weight ranging from about 1 x 106to about 6 x 106atomic mass units (amu). The selection of UHMWPE with a high molecular weight is crucial, as it provides the necessary structural integrity and mechanical strength for the fibers, films, and sheets. The UHMWPE powder may have an average particle, D50, between about 10 microns (pm) and about 2500 pm, for example, between about 100 pm and about 1500 pm or between about 100 and about 400 pm. The bulk density of the UHMWPE powder may be between about 0.2 g / ml and about 1 g / ml, for example, between about 0.3 g / ml and about 0.6 g / ml or between about 0.8 and about 1 g / ml.

[0021] The solvent may be any hydrocarbon solvent suitable for gel spinning or casting. Examples of hydrocarbon solvents include, but are not limited to, octane, nonane, decane, mineral oil such as paraffin oil, naphthene mineral oil, or white mineral oil, kerosene, toluene, xylene, decalin, and tetraline. In some embodiments, the solvent is mineral oil.

[0022] The slurry may include UHMWPE powder at a concentration of no greater than about 20 wt%, no greater than about 15 wt%, no greater than about 10 wt%, no greater than about 8 wt%, no greater than about 6 wt%, or no greater than about 5 wt%. In some embodiments, a concentration of the UHMWPE powder in the slurry may range from about 0.1 wt% to about 15 wt%, for example, from about 0.1 wt% to about 1 wt%, from about 1 wt% to about 5 wt%, from about 5 wt% to about 10 wt%, from about 10 wt% to about 15 wt%. In some embodiments, the slurry comprises from about 0.1 wt% to about 5 wt% UHMWPE powder. In some other embodiments, the slurry comprises from about 1 wt% to about 15 wt% UHMWPE powder.

[0023] The slurry may include solvent at a concentration of no less than about 80 wt%, no less than 85 wt%, no less than about 90 wt%, or no less than about 95 wt%. In some embodiments, a concentration of the solvent in the slurry may range from about 85 wt% to about 90 wt%, from about 90 wt% to about 95 wt%, from about 95 wt% to about 98 wt%, or from about 98 wt% to about 99.5 wt%. In some embodiments, the slurry comprises from about 95 wt% to about 99.9 wt% solvent. In some embodiments, the slurry comprises from about 85 wt% to about 98 wt% solvent. In some embodiments, the slurry comprises about 95 wt% to about 99.9 wt% mineral oil and about 0.1 wt% to about 5 wt% UHMWPE powder.

[0024] To prepare the slurry, the UHMWPE powder is dispersed in the solvent at an elevated temperature ranging from 60 °C to 140 °C. This temperature range facilitates the swelling or partial dissolution of the UHMWPE within the solvent, resulting in a homogeneous mixture suitable for further processing. Continuous stirring is required to prevent phase separation and ensure uniform distribution of the UHMWPE particles within the oil. In some embodiments, the stirring may have a speed of 1800 rpm to 2000 rpm.

[0025] In some embodiments, the slurry may include a salt such as sodium chloride. In some embodiments, the slurry may include salt at a concentration of no less than about 15 wt%, no less than about 10 wt%, or no less than about 5 wt%. In some embodiments, the concentration of the salt in the slurry may range from about 1 wt% to 15 wt%. When salt is present, the UHMWPE powder and the granulated or powdered salt are dispersed in the solvent at elevated temperatures to prepare the slurry.

[0026] Gel Spinning for Fiber Production

[0027] In another aspect of the present disclosure, a method for preparing aerogel fibers from the slurry of the present disclosure is provided. The homogeneous slurry is extruded through a spinneret to form monofilament or multifilament gel fibers. The spinneret's design and orifice size determine the initial diameter of the fibers, typically ranging from 500 to 1500 microns. The spinneret contains multiple spinholes that determine the number of filaments formed. In some embodiments, the spinneret contains at least 2, at least 5, at least 10, at least 20, or at least 50 spinholes. In some embodiments, the spinneret contains from 2 to 400, 5 to 300, or 20 to 200 spinholes. The resulting fiber may comprise from 5 to 50 filaments, from 50 to 100 filaments, from 100 to 150 filaments, from 150 to 200 filaments, from 200 to 300 filaments, or from 200 to 400 filaments. In some embodiments, the fiber comprises 5, 7, 10, 14, 15, 20, 25, 30, 35, 40, 45, or 50 filaments.

[0028] The extruded gel fibers are then passed through a cooling medium, such as air or a water bath, which solidifies the gel fibers. Subsequent drawing steps reduce the fiber diameter to the desired final size, typically between 10 and 50 pm, and align the polymer chains, enhancing the mechanical properties of the fibers.

[0029] After forming the solidified gel fibers, the gel fibers are subjected to a solvent extraction process where the solvent is removed by an extraction solvent to form the aerogel fibers each with a network of open or closed cells distributed throughout the fiber. In some embodiments, the extraction solvent is a supercritical fluid such as supercritical CO2, supercritical ethanol, or supercritical methanol. In some embodiments, when mineral oil is used in the slurry, the mineral oil may be extracted using supercritical CO2, as described in detail below. In some embodiments, when the granulated or powdered salt is co-extruded with the UHMWPE powder, the extruded monofilament or multifilament fibers may undergo a series of solvent extraction processes to extract the solvent and the salt. For example, in some embodiments, the solvent, such as mineral oil, may be extracted in an initial extraction process using a supercritical fluid (e.g., supercritical CO2) or an alkane solvent (e.g., hexane or heptane). The alkane solvent such as hexane may be removed in a drying process with forced heated air. Subsequently, the salt may be extracted using water, either through a water bath, a spray application, or subcritical water in a pressure vessel. In some embodiments, the water is heated water. In some embodiments, the water is subcritical water.

[0030] The fibers produced exhibit significant flexibility and elasticity due to the porous structure formed after solvent extraction. In some embodiments, the fiber exhibits an elasticity of at least 5%. For example, in some embodiments, the fiber has an elasticity of 5%, 10%, 20%, 30%, 50%, 80%, 100%, 150%, or 200%. In some embodiments, the fiber can have a stretchability of up to 400%. In some embodiments, the stretchability of the fiber may range from 50% to 400%, for example, from 50% to 100%, 100% to 200%, from 200% to 300%, and from 300% to 400%. In some embodiments, the fiber has a stretchability of 50%, 100%, 150%, 200%, 250%, 300%, 350 %, or 400%. The open or closed-cell structure significantly reduces the density of the fibers, enhancing thermal insulation properties and making them suitable for lightweight textile applications.

[0031] Sheet Production

[0032] The slurry can also be processed to form films or sheets by casting or extrusion methods. In another aspect of the present disclosure, a method for preparing an aerogel film or sheet from the slurry of the present disclosure is provided. The heated slurry is first extruded through a film die or cast onto a flat surface to form a thin film or sheet. The extruded material is cooled using a water bath, air cooling, or chilled rollers to solidify the gel. The resulting films or sheets can range in thickness from as thin as 0.1 mm to several millimeters, for example, 10 mm, depending on the application requirements. The solidified gel films or sheets are then subjected to the solvent extraction process described above to form the aerogel films or sheets each with a network of open or closed cells distributed throughout the film or sheet.

[0033] Similar to the fibers, the films and sheets exhibit flexibility, lightweight characteristics, and excellent thermal insulation due to the porous structure formed after mineral oil extraction.

[0034] Supercritical Fluid Extraction

[0035] The solvent such as mineral oil is extracted from the gel fibers or films using a supercritical fluid in a pressure vessel. In some embodiments, supercritical CCfi is used as the extraction solvent for mineral oil. Supercritical CO2 is a non-toxic, non-flammable solvent that effectively removes the mineral oil without collapsing the delicate aerogel structure. Unlike traditional solvents, supercritical CO2 does not induce capillary forces that can damage the porous network, thereby preserving the open or closed-cell structure of the aerogel. The extraction of solvent results in a network of interconnected pores throughout the fibers or films, contributing to the material’s elasticity, low density, and thermal insulation properties. The supercritical fluid extraction ensures that no residual solvents remain in the material, making it safe and environmentally friendly.

[0036] Impregnation with Polymerizable Oil or Elastic Polymer

[0037] A) Polymerizable Oil Infusion

[0038] In some embodiments, after solvent extraction, the aerogel fibers or films are impregnated with a mixture comprising a polymerizable oil and an initiator required for subsequent polymerization. This is achieved by swelling the UHMWPE aerogel with a supercritical fluid such as supercritical CO2 and then infusing the polymerizable oil into the swelled UHMWPE aerogel within a pressure vessel. The polymerizable oil is then polymerized via thermal or photo-curing reactions, which can enhance the mechanical properties and elasticity of the material.

[0039] In some embodiments, the polymerizable oil is a polymerizable plant oil including, but not limited to, algal oil, soybean oil, peanut oil, walnut oil, palm oil, palm kernel oil, sesame oil, sunflower oil, safflower oil, rapeseed oil, linseed oil, flax seed oil, colza oil, coconut oil, corn oil, cottonseed oil, olive oil, castor oil, false flax oil, hemp oil, mustard oil, radish oil, ramtil oil, rice bran oil, salicomia oil, tigernut oil, and tung oil. In some embodiments, the polymerizable oil comprises castor oil, algal oil, soybean oil, linseed oil, com oil, flaxseed oil, or rapeseed oil.

[0040] In some embodiments, the initiator comprises a photoinitiator. In some embodiments, the photoinitiator comprises diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl-(2,4,6- trimethylbenzoyl)phenyl phosphinate or a combination thereof. In some embodiments, the initiator comprises a thermal initiator. In some embodiments, the thermal initiator comprises azobisisobutyronitrile, 2,2'-azodi(2-methylbutyronitrile ) or a combination thereof.

[0041] B) Elastic Polymer Infusion

[0042] Alternatively, the aerogel fibers or films can be impregnated with an elastic polymer, such as polyurethane, elastane, poly(styrene-butadiene-styrene) (SBS), styrene ethylene butylene styrene block copolymer (SEBS), silicone, or photocurable polymers. The infusion process utilizes a supercritical fluid, such as supercritical CO2, optionally with a co-solvent, to ensure uniform distribution of the polymer within the aerogel structure. In some embodiments, the cosolvent may include, but not limited to, hexane, octane, nonane, and decane.

[0043] C) Co-Extrusion with Elastic Polymers

[0044] In other embodiments, the UHMWPE powder is co-extruded with an elastic polymer, such as polyurethane, elastane, SBS, SEBS, or others. This involves combining UHMWPE powder with the elastic polymer in the slurry before gel spinning or casting. The co-extruded fibers or films benefit from the properties of both UHMWPE and elastic polymers, resulting in materials with enhanced elasticity and mechanical strength.

[0045] UHMWPE Aerogel Properties

[0046] A) Novel Material Structure

[0047] The present disclosure uniquely integrates UHMWPE ’s exceptional mechanical properties into an aerogel structure with low density and high thermal insulation. The high molecular weight of UHMWPE provides the material with outstanding strength and durability, while the aerogel’s porous structure contributes to its lightweight and insulating characteristics.

[0048] B) Enhanced Elasticity and Flexibility

[0049] Unlike conventional aerogels, which are brittle and lack flexibility, the UHMWPE aerogel fibers, films, and sheets produced by the methods of the present disclosure exhibit significant elasticity and flexibility, with stretchability up to 400%. The enhanced elasticity and flexibility make UHMWPE aerogels highly suitable for applications requiring dynamic movement and resilience, such as textiles and flexible insulation.

[0050] C) Environmentally Friendly Production Process

[0051] The use of supercritical fluid such as supercritical CO2 for solvent extraction is both efficient and environmentally friendly. Using the supercritical fluid as the extraction solvent avoids the use of harmful organic solvents and ensures that the final material is free from residual contaminants. D) Versatility in Applications

[0052] The aerogel fibers, films, and sheets produced can be tailored for a wide range of applications, including apparel, footwear, medical textiles, industrial filters, and insulation materials. The unique combination of lightweight, insulating, and elastic properties opens new possibilities in material design and engineering.

[0053] E) Consistent Quality and Scalability

[0054] The production processes described in the present disclosure allow for precise control over the material properties, ensuring consistent quality and performance. The methods are compatible with existing manufacturing technologies, facilitating scalability for commercial production.

[0055] The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and / or listed in the Application Data Sheet, including but not limited to, U.S. provisional patent application no. 63 / 696,253 filed September 18, 2024 are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

[0056] These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

CLAIMS1. A method for producing an elastic ultra-high molecular weight polyethylene (UHMWPE) aerogel fiber, comprising: forming a slurry comprising a UHMWPE powder and a solvent; gel spinning the slurry to form a monofilament or multifilament fiber; cooling and drawing the fiber to a target diameter; and extracting the solvent from the fiber using a supercritical fluid to create a network of open or closed cells within the fiber.

2. The method of claim 1, further comprising: impregnating the fiber with a mixture comprising a polymerizable oil, an initiator and a supercritical fluid; and subsequently polymerizing the polymerizable oil within the fiber.

3. The method of any one of claims 1-2, further comprising impregnating the fiber with an elastic polymer in a solution comprising a supercritical fluid and a co-solvent.

4. The method of any one of claims 1-3, wherein the target diameter is from 10 pm to 50 pm.

5. A method for producing an elastic ultra-high molecular weight polyethylene (UHMWPE) aerogel film or sheet, comprising: forming a slurry comprising a UHMWPE powder and a solvent; casting the slurry to form a film or sheet; cooling the film or sheet to solidify; and extracting the solvent from the film or sheet using a supercritical fluid to create a network of open or closed cells within the film or sheet.

6. The method of claim 5, further comprising: impregnating the film or sheet with a mixture comprising a polymerizable oil, an initiator and a supercritical fluid; and subsequently polymerizing the polymerizable oil within the film or sheet.

7. The method of any one of claims 5-6, further comprising impregnating the film or sheet with an elastic polymer in a solution comprising a supercritical fluid and a co-solvent.

8. The method of any one of claims 1-7, wherein the slurry comprises from about 0.1 wt% to about 5 wt % UHMWPE powder and from about 95 wt% to about 99.9 wt% solvent.

9. The method of any one of claims 1-8, wherein the supercritical fluid is supercritical CO2.

10. The method of claim 2 or 6, wherein the polymerizable oil comprises castor oil, algal oil, soybean oil, linseed oil, corn oil, flaxseed oil or rapeseed oil.

11. The method of claim 3 or 7, wherein the co-solvent comprises hexane, octane, nonane or decane.

12. A method for producing an elastic ultra-high molecular weight polyethylene (UHMWPE) aerogel fiber, comprising: forming a slurry comprising a UHMWPE powder, a salt and a solvent; gel spinning the slurry to form a monofilament or multifilament fiber; cooling and drawing the fiber to a target diameter; extracting the solvent from the fiber using a supercritical fluid; and extracting the salt using a subcritical fluid, thereby creating a network of open cells within the fiber.

13. The method of claim 12, wherein the supercritical fluid is supercritical CO2, and the subcritical fluid is subcritical water.

14. A method for producing an elastic ultra-high molecular weight polyethylene (UHMWPE) aerogel fiber, comprising: forming a slurry comprising a UHMWPE powder, a salt and a solvent; gel spinning the slurry to form a monofilament or multifilament fiber; cooling and drawing the fiber to a target diameter; extracting the solvent from the fiber using an alkane solvent;removing the alkane solvent; and extracting the salt using water, thereby creating a network of open cells within the fiber.

15. The method of claim 14, wherein the alkane solvent is removed using a drying process.

16. The method of claim 15, wherein the drying process is performed using forced heated air.

17. The method of any one of claims 14-16, wherein the water is subcritical water or heated water.

18. The method of any one of claims 12-17, wherein the slurry comprises about 85% to about 98% solvent, about 1% to about 15% UHMWPE powder and about 1% to about 15% salt.

19. The method of any one of claims 12-18, wherein the solvent is mineral oil.

20. A method for producing an elastic ultra-high molecular weight polyethylene (UHMWPE) aerogel fiber, comprising: forming a slurry comprising about 85% to about 98% mineral oil, about 1% to about 15% UHMWPE powder, and about 1% to about 15% salt; gel spinning the slurry to form a monofilament or multifilament fiber; cooling and drawing the fiber to a target diameter; extracting the mineral oil from the fiber using hexane; removing the hexane with forced heated air; and extracting the salt by submerging the fiber in heated water or subcritical water.

21. The method of any one of claims 12-20, wherein the salt is sodium chloride.

22. A fiber, comprising:a monofilament or multifilament structure formed from ultra-high molecular weight polyethylene (UHMWPE); and a network of open or closed cells distributed throughout the fiber, wherein the fiber exhibits an elasticity of at least 5%.

23. The fiber of claim 22, wherein the fiber has a stretchability up to 400%.

24. The fiber of any one of claims 22-23, wherein the UHMWPE has a molecular weight of about 1 x 106to about 6 x 106atomic mass units (amu).

25. The fiber of any one of claims 22-24, wherein the fiber is produced by a process comprising: forming a slurry comprising a UHMWPE powder and a solvent; gel spinning the slurry into a monofilament or multifilament fiber; and extracting the solvent using a supercritical fluid to create the network of open or closed cells within the fiber.

26. The fiber of claim 25, wherein the slurry comprises from about 0.1 wt% to about 5 wt % UHMWPE powder and from about 95 wt% to about 99.9 wt% solvent.

27. The fiber of any one of claims 25-26, wherein the solvent comprises mineral oil.

28. The fiber of any one of claims 25-27, wherein the supercritical fluid is supercritical CO2.

29. The fiber of any one of claims 25-28, wherein the process further comprises: impregnating the fiber with a mixture comprising a polymerizable oil, an initiator, and a supercritical fluid, and subsequently polymerizing the polymerizable oil within the fiber.

30. The fiber of claim 29, wherein the polymerizable oil comprises castor oil, algal oil, soybean oil, linseed oil, com oil, flaxseed oil or rapeseed oil.

31. The fiber of any one of claims 22-30, wherein the process further comprises impregnating the fiber with a mixture comprising an elastic polymer, a supercritical fluid and a co-solvent.

32. The fiber of claim 29 or 31, wherein the supercritical fluid is supercritical CO2.

33. The fiber of any one of claims 31-32, wherein the co-solvent comprises hexane, octane, nonane or decane.

34. The fiber of any one of claims 22-33, further comprising an elastic polymer in combination with UHMWPE.

35. The fiber of claim 34, wherein the elastic polymer comprises polyurethane, elastane, poly(styrene-butadiene-styrene) (SBS), styrene ethylene butylene styrene block .copolymer (SEBS), silicone or a photocurable polymer.

36. The fiber of any one of claims 22-35, wherein the network of open or closed cells provides the fiber with reduced density and enhanced thermal insulation.

37. The fiber of any one of claims 22-36, wherein the fiber is incorporated into a textile, wherein the textile is a knit or a woven fabric.

38. A textile comprising the fiber of any one of claims 22-37.

39. The textile of claim 38, wherein the textile is a knit or a woven fabric.

40. A film or sheet, comprising: a continuous structure comprising ultra-high molecular weight polyethylene (UHMWPE); and a network of open or closed cells distributed throughout the film or sheet, wherein the film or sheet exhibits an elasticity of at least 5%.

41. The film or sheet of claim 40, wherein the UHMWPE has a molecular weight of about 1 x 106to about 6 x 106atomic mass units (amu).

42. The film or sheet of any one of claims 40-41, wherein the film or sheet is produced by a process comprising: forming a slurry comprising a UHMWPE powder and a solvent; casting the slurry into a film or sheet; and extracting the solvent using a supercritical fluid to create a network of open or closed cells within the film or sheet.

43. The film or sheet of claim 42, wherein the slurry comprises from about 0.1 wt% to about 5 wt% UHMWPE powder and from about 95 wt% to about 99.9 wt% solvent.

44. The film or sheet of any one of claims 42-43, wherein the solvent comprises mineral oil.

45. The film or sheet of any one of claims 42-44, wherein the supercritical fluid is supercritical CO2.

46. The film or sheet of any one of claims 42-45, wherein the process further comprises: impregnating the film or sheet with a polymerizable oil, an initiator, and a supercritical fluid, and subsequently polymerizing the polymerizable oil within the film or sheet.

47. The film or sheet of claim 46, wherein the polymerizable oil comprises castor oil, algal oil, soybean oil, linseed oil, corn oil, flaxseed oil or rapeseed oil.

48. The film or sheet of any one of claims 42- 47, wherein the process further comprises impregnating the film or sheet with a mixture comprising an elastic polymer, a supercritical fluid and a co-solvent.

49. The film or sheet of claim 48, wherein the co-solvent comprises hexane, octane, nonane or decane.

50. The film or sheet of claim 45 or 48, wherein the supercritical fluid is supercritical CO2.

51. The film or sheet of any one of claims 40-50, wherein the UHMWPE is combined with an elastic copolymer.

52. The film or sheet of any one of claims 40-51, wherein the network of open or closed cells provides the film or sheet with reduced density and enhanced thermal insulation.

53. The film or sheet of any one of claims 40-52, wherein the film or sheet is used in an application requiring a flexible, lightweight, and thermally insulating material.

54. An article comprising the film or sheet of any one of claims 40-53.