Membrane production method

Abstract

A method for producing heat-resistant membranes with high surface area and surface porosity to be used in batteries, fuel cells and electrolysers comprises preparing single and / or more solutions, applying an electrospinning process to the single and / or more solutions, thereby obtaining a nanofiber membrane.

Description

DescriptionTitle: MEMBRANE PRODUCTION METHODCross-reference to related applications

[0001] This application is related to the Turkish national patent application No 2024 / 002003 filed on 20.02.2024, the entire contents of the application are incorporated herein by reference.Technical field

[0002] The invention relates to a production method for membranes and separators.

[0003] The invention particularly relates to a membrane production method used for the manufacture of polymer membranes as separators in fuel cells and batteries, such as lithium ion, lithium sulphide, lithium air, redox flow batteries, and sodium ion batteries. The polymer membrane and can be used as anion exchanger or a cation exchanger.Prior Art

[0004] A separator is a component of a battery that separates the anode and cathode and does not participate in electrochemical reactions in the batteries. The separators have a porous polymer structure and can store electrolyte. The separators allow ions to transfer freely between the anode and cathode.

[0005] The choice of the polymer separators used is based on following properties of polymer materials: chemical stability, separator thickness, porosity, size of pore (preferably less than 1 pm), ion permeability, mechanical strength, electrolyte wettability, and thermal resistance.

[0006] Current production methods and product structures comprise a dry process or a wet process.

[0007] The dry process comprises extrusion, annealing and stretching steps. The final porosity of the polymer membrane depends on the morphology of the precursor polymer film and the properties of each step. The extrusion step is usually performed at a temperaturehigher than the melting point of polymer resin. This is because the polymer resins are melted and converted into a uniaxially oriented tubular film termed the “precursor film”. The structure and orientation of the precursor films depend on processing conditions and properties of the polymer resin. In the annealing step, the precursor film is annealed at a temperature slightly lower than the melting point of the polymer film. The purpose of this annealing step is to improve the crystal structure of the polymer membrane.

[0008] During the stretching step, the annealed film is stretched along the machine direction by a cold stretch followed by a hot stretching step at a lower temperature with a faster stretching rate. The hot stretching step increases pore sizes in the polymer membrane by using a higher temperature and a slower strain rate. The relaxation step reduces internal stress within the polymer membrane.

[0009] The dry process is only suitable for those polymers with a high degree of crystallinity.

[0010] The wet process comprises mixing, heating, extrusion, stretching, and additive removal. The polymer resins are first mixed with paraffin oil, antioxidants, and other additives. The mixture is heated to obtain a homogeneous solution. The heated solution is forced through a sheet die to make a film. The additives are then removed with a volatile solvent to form the microporous film. This microporous film can then be stretched uniaxially (along a machine direction) or biaxially (along both a machine direction and cross directions), allowing for formation of further pores in the microporous film. The wet process is suitable for both crystalline polymers and amorphous polymers. Those separators made from the wet process generally use ultra-high molecular weight polyethylene.

[0011] The separator is one of the components in the batteries. The separator affects the safety, ionic conductivity and electrochemical performance of the battery.

[0012] The characteristics of current commercially available polyolefin-based separators include low porosity, high thermal shrinkage, low electrolyte uptake and retention, poor wettability with liquid electrolyte. There is therefore a need to develop improved polymer materials for use as the separator.

[0013] It will be appreciated that the separator should have good wettability to enable the separator to absorb quickly to prevent electrolyte loss and evaporation during the battery assembly process. It will also be appreciated that there is a need for a uniform distribution of the electrolyte in the separator to increase the Coulombic efficiency of the battery.

[0014] Good wettability means that the separator can not only store sufficient amount of electrolyte but also extend the service life of the battery by smoothly conducting ions. Good wettability also means good compatibility with electrolytes so that the uptake of the electrolytes is good, and the electrolyte is more homogeneously / well distributed throughout the separator.

[0015] As noted above, the separators are porous selectively permeable structures that allow ion flow and prevent electrical contact. The number of pores present in the prior art polyolefin separators are limited and this limits transfer of the ion through the separator.

[0016] In the prior art methods of manufacture, polyolefin separators can be obtained using the dry method and the wet method. The pores in the polyolefin separators are formed by stretching after the polymers are made into thin polymer films with the help of an extruder. It will be appreciated that an “ideal” separator should have zero ionic resistance. These zero ionic resistances can only be achieved with high porosity. The porosity rate in the prior art polyolefin separators is currently between 30% and 55%.

[0017] Cation exchange membrane

[0018] A cation exchange membrane is generally called polymer electrolyte membrane (PEM). The cation exchange membranes are one of the components in polymer electrolyte membrane fuel cells, polymer electrolyte membrane electrolysers as well as redox flow batteries, and should have the following properties: high ionic conductivity, good chemical resistance, high mechanical strength, impermeability to hydrogen and oxygen gases and be electrically insulating.

[0019] Products and manufacturers in the field of cation exchange membrane include, but are not limited to, Nafion (DuPont Co. / Chemours), Aquivion (Solvay-Solexis), Aciplex (Asahi Chemical), Flemion (Asahi Glass), Gore-Select (W.L. Gore & Associates).

[0020] Production processes used for producing cation exchange membranes include melt extrusion, solution casting and expanded polytetrafluoroethylene (e-PTFE) supported membrane process.

[0021] It is also known that perfluorosulfonic acid (PFSA) precursor in the form of sulfonyl fluoride melts above 200 °C and can be made into the cation exchange membranes. DuPont's polymer electrolyte membrane fuel cell (PEMFC) membranes Nafion 117, Nafion 115 and Nafion 112 were prepared by the melt-extrusion process over years ago.

[0022] Typical solution cast membranes from DuPont are: Nafion 212 and Nafion 211. The membranes produced by solution casting can be used to increase the durability of the membranes and are usually combined with e-PTFE reinforcement materials and additives. Currently, the most commercially available Nafion® cation exchange membranes are based on perfluorinated or partially fluorinated materials which was described in two patent applications and filed in 1966 and 1982 and were assigned to the Dow Chemical Company at the time (Connolly and Gresham, 1966, Ezzell et al., 1982). These membranes are classified as perfluorosulphonate ionomer membranes, which are based on fluoropolymer- based sulfonic acid groups bonded to them.

[0023] In 1994, Gore began developing methods to integrate proton-conducting ionomer into e-PTFE, producing ionomer / e-PTFE composites with excellent mechanical strength. Due to their high fuel cell performance, long life, and improved safety even when the membrane is damaged, most PFSA membranes used in automotive fuel cell applications today are produced by the solution casting method reinforced with e-PTFE.

[0024] A different production method for cation exchange membranes uses pellets obtained from PFSA ions. The pellets are mixed with the appropriate amount of additive and a solvent comprising a mixture of ethanol and water. The additives come from the azoles family, such as triazole and benzimidazole. The amount of additive and the solvent volume are calculated based on the ion exchange capacity (IEC) of the ionomer. The pellets are then dried to remove the solvent. The dried pellets are fed to a multilayer melt-blow line for extrusion.

[0025] The resulting membranes are washed with sulfuric acid and deionized (DI) water to remove the additives. The optional step is applied if the additive can be easily removed during fuel cell stack conditioning without compromising its performance. The remaining steps are the same as the e-PTFE (expanded polytetrafluoroethylene) solvent-casting process. The membranes are dried and covered with protective sheets to prevent surface contamination.

[0026] Disadvantages of prior art Cation Exchange Membranes

[0027] The polymers of these prior art cation exchange membranes are fluorinated structures. Perfluoroalkyl and polyfluoroalkyl substances (PFAS) constitute a class of synthetic compounds that have attracted considerable public attention, especially since the early 2000s, when the persistent hazards and widespread occurrence of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were reported and recognized. Sincethen, research and risk management measures have expanded from these two PFAS to a broad spectrum of PFAS. In general, PFASs can be divided into two categories; non- polymeric and polymeric. To date, research has focused largely on understanding the identity, life cycle, hazard, distribution, exposure, and risk of the non-polymeric PFASs, such as perfluoroalkylcarboxylic acids (PFCAs), perfluoroalkanesulfonic acids (PFSAs), and some well-known non-polymeric precursors derived from fluorotelomers.

[0028] The perfluoroalkyl and the polyfluoroalkyl substances (PFASs) have been used as components or intermediates of surfactants and surface protectants for a variety of industrial and consumer applications since the 1950s. Some of the unique physicochemical properties that have popularized the widespread use of the PFASs are also associated with environmental and human health concerns. For example, over the last decade, several long- chain perfluoroalkyl acids have been recognized as persistent, bioaccumulative and toxic. Many have been detected in the environment, biota, food and humans worldwide. This has led to the development of risk reduction approaches to reduce the global impact of these chemicals on the environment and health and to support a global transition towards safer alternatives.

[0029] The proposal to restrict the perfluoroalkyl substances and the polyfluoroalkyl substances (PFASs) to be submitted to ECHA by five European countries is an important pillar of the EU’s Chemicals Strategy. However, a restriction could have disastrous consequences for the EU’s new hydrogen sector if it does not consider the specific profile of the PFAS, especially when adopting a group approach that includes fluoropolymers, and does not adequately assess the necessity of their use, the availability of ready-to-use alternatives, and the socio-economic, industrial and environmental impacts. Clean technologies are essential for the green transition and energy security and therefore require a positive regulatory framework to enable them to develop. High energy consumption is a major disadvantage for the production process.

[0030] Anion Exchange Membranes:The polymer backbone is an important element in determining the mechanical strength and stability of anion exchange membranes (AEMs). Adding a rigid structure, such as aromatic rings or perfluorinated structures, to ensure the mechanical stability of the membrane plays a role in the mechanical stability of the membrane. However, addressing the issue of poor dimensional stability can compromise the overall mechanical strength of the membrane. Avariety of materials have been used as backbones in the AEMs, including oxidation-resistant fluorinated polymers, aromatic polymers derived from hydrocarbons, condensation polymers, and block polymers. The choice of the polymer backbone directly affects a number of membrane properties, such as rigidity, tensile strength, water sorption, OH- conductivity, and chemical stability.

[0031] In the last few years, there has been an increasing interest in aromatic polymers due to their inherent rigidity and impressive thermal stability. However, it should be noted that aromatic polymers can be damaged by reactive oxygen radicals, especially at the benzene carbon sites. To address this sensitivity, a cross-linked structure can be introduced. This cross-linked structure can provide a shield to the polymer chains or head groups by protecting the polymer chains or the head groups from radical attacks. In order to provide a comprehensive overview of the commercial membranes and their properties, a summary of different membranes is presented according to their chemical structure, main chain type, functional groups for OH- transfer, and related properties.

[0032] To date, there is no universally accepted commercial standard within the scientific community for water electrolyser (WE) and fuel cell (FC) applications. However, various commercial membranes are used for these purposes. The AEMs are generally designed for a wide range of applications such as electrolysis, fuel cells, electrodialysis, desalination, and redox batteries. Extensive research and progress in the field of AEMs has been ongoing for over seven decades.

[0033] Avalable Commercial Anion Exchange Membranes;

[0034] a) Fumatech: FAA Series. The FAA series membrane is an anion ion exchange membrane available from independent distributors or directly from Fumatech. It is available in different thicknesses and can be purchased as an unsupported membrane or with polyether ether ketone (PEEK) or (polypropylene) PP reinforcement. This membrane consists of a polyaromatic polymer with four covalently bonded ammonium groups in the main chain and also has ether bonds within the main chain.

[0035] Dioxide Materials: Sustainion® X37-50- Developed by Richard Masel’s research team and manufactured by Dioxide Materials, Sustainion membranes are a commercial product available directly from Dioxide Materials or independent distributors. These membranes use a design based on imidazole functionalized poly(4-vinylbenzyl chloride-co- styrene). The specific product code, Sustainion 37-50, refers to a copolymer compositioncontaining 37% molar ratio of 4-vinylbenzyl chloride and a thickness of 50 gm. Sustainion membranes were first developed and patented in 2015.

[0036] Aemion™ membranes were developed by the Holdcroft group at Simon Fraser University and are based on methylated polybenzimidazole (PBI) chemistry. In the early stages, these membranes were initially referred to as “functionalized-PBI”, meaning that the polybenzimidazole (PBI) was derived from a diacetyl containing a synthesized tetraamine and mesitylene.

[0037] While traditional polybenzimidazole (PBI) membranes are susceptible to hydroxide attack at the C2 position of the imidazolium component, the Aemion™ membranes use a modified structure comprising at least two phenyl rings and are designed to stabilize positive charges of adjacent imidazolium ions. This design improvement gives Aemion™ membranes chemical stability across the entire pH scale (0-14), making them suitable for the efficient recovery and reuse of strong chemicals. These membranes have demonstrated exceptional performance in hot and strongly alkaline environments in a variety of applications, including but not limited to anion exchange membrane fuel cells (AEMFC) and anion exchange membrane water electrolyser (AEMWE).

[0038] Orion TM1. The membrane known as Orion TM1 is referred to in the scientific literature as poly(terphenylene). One of the challenges faced is their mechanical stability when hydrated.

[0039] The membrane set out in this document is inspired by current situations and aims to solve the above-mentioned issues.

[0040] US 2015 / 328631 teaches the manufacture of nanofibers made from polyvinyl alcohol.

[0041] CN114552117A teaches a polymer composite diaphragm modified by an inorganic substance for batteries and also relates to a preparation method of the polymer composite diaphragm. The polymer composite membrane modified by inorganic substances for batteries includes a three-layer composite structure, and the three-layer composite structure is PVDF / PVDF-PAN / PVDF. The inorganic filler is silicon dioxide, aluminium oxide or zinc oxide. The polymer composite is a polyvinylidene fluoride (PVDF) polymer mixed with a polyacrylonitrile (PAN) polymer. It is unclear whether the PAN is a homopolymer or a copolymer.

[0042] WO 2013 / 159752 teaches a lithium-ion battery separator material having a three- layer composite structure. A microporous film enables a thermal stability intermediate layer and an organic network structure - inorganic composites composite outer composite structure can improve the mechanical properties and thermal stability of the nano-fiber battery separator film material. The first and second outer layers, respectively, may be selected from the group comprising polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene (PVDF-HFP), poly sulfone (PES), polyacrylonitrile (PAN), aramid and cellulose material with one or more polymers formed.

[0043] An object of the invention is to develop battery separators, cation exchange membranes and anion exchange membranes that provide improved performance.

[0044] Another object of the invention is to increase the resistance of nanofiber membranes to high temperatures to be used as battery separators by using polymers with high temperature resistance.

[0045] Another object of the invention is to provide a battery production method that is safer, more secure and less affected by temperature changes.Summary of the invention

[0046] A method for producing a heat-resistant nanofiber membrane with a high surface area and surface porosity to be used in batteries, fuel cells and electrolysers is taught in this disclosure. The method comprises preparing at least one solution, applying an electrospinning process to the at least one solution, and obtaining the nanofiber membrane having substantial homogenous content in a single layer, i.e. the nanofiber is distributed substantially in the layer.

[0047] A heat-resistant membrane is one in which the mechanical strength and performance properties of the membrane do not decrease above 80°C, and the properties of the membrane (separator) remain at least the same.

[0048] The term “high surface area and porosity” means that at least 40% on the total surface area is formed by the pores, and up to 70% of the surface area is formed by the pores. It will be appreciated that, as the number of pores on the (unit) surface area increases then there will be an increase in interactions, processing capability and more functionality can be accommodated in the same area. The degree of porosity is determined by the number ofpores (also known as voids) in the internal structure of the material, and this is related to the number of pores that are present on the material’s surface.

[0049] Definition of high ionic conductivity. The ionic conductivity is a measure of a material’s tendency to transport ions and results show that the membranes set out in this document have a conductivity value that is 15% of more compared to the prior art. The results vary heavily depending on the conditions of testing (humidity, heat, equipment, thickness, etc). However, in the same conditions and equipment, under dry testing we achieve an ionic conductivity of 0.306 s / m whereas benchmark product Nafion reaches 0.173 s / m.

[0050] The nanofibers made using the process have a diameter of between 150 nm and 400nm, but this is not limiting of the invention.

[0051] The nanofiber membranes set out in this document can be used as a battery separator. The battery separators have a high surface area and high surface porosity using the electrospinning process, enable shortening of the battery charging time comprising this battery separator, and increasing the service life of the battery. This is achieved by using homogeneous porous separators and used separator production materials which allow electrolyte to spread better on and on the battery separator.

[0052] The nanofiber membrane used as a cation exchange membrane and an anion exchange membrane for fuel cells and electrolysers also has ajarge surface area and a high ionic conductivity value. The nanofiber membranes are produced at a lower cost and have a lower carbon footprint.

[0053] In one aspect, in case of a single solution, the solution is prepared by mixing 8-20% first polymer, 0.1-20% second polymer, 50-92% solvent, 0-5% salt, 0.01-15% strengthenhancing support material and 0.01-20% additive at 18°C-100°C for 15 minutes and 8 hours.

[0054] In another alternative aspect, in case of two solutions, the first solution is prepared by mixing 8-20% first polymer, 0.1-20% second polymer, 50-92% solvent, 0-5% salt, 0.01- 15% strength enhancing support material and 0.01-20% additive at 18°C-100°C for 15 minutes and 8 hours to prepare the first solution. The second solution is prepared by mixing 5-20% strength enhancing material and one or more solvents are mixed at 18°C-100°C for 2 minutes and 8 hours.

[0055] The first polymer includes polyacrylonitrile homopolymer / copolymer (2-20 % polyacrylonitrile-co-methyl acrylate (PAN-MA), polyacrylonitrile-co-vinyl acetate (PAN- VA), polyacrylonitrile-b-polystyrene, methacrylic acid (MAA), acrylamide (AM), methacrylic acid and dimethylaminoethyl ester (DEMA), poly(acrylonitrile-vinyl acetatedimethylaminoethyl ester), poly(AN-VA-DEMA), cellulose, and polymethylmethacrylate.

[0056] The second polymer is SEBS (Styrene Ethylene Butylene Styrene), SBS (Styrene- Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene- Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).

[0057] The solvent / solvents include ethylene carbonate, strongly polar aprotic dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylamylamine (DMAA), dimethylacetamide (DMAc), cyclohexane, tetrahydrofuran (THF) and inorganic solvent(s) nitric acid, concentrated aqueous solution of zinc chloride, sodium thiocyanate, etc.

[0058] The salts include tetraalkylammonium ion, tetraethyl ammonium bromide (TEAB), sodium chloride, magnesium chloride, potassium chloride, lithium chloride, zinc chloride, sodium nitrate, calcium chloride, zinc chloride, and salts that increase electrical solution conductivity, including but not limited to these.

[0059] The strengthening support material is SEBS (Styrene Ethylene Butylene Styrene). In one aspect this is provided at a minimum concentration of 0.1%. In other aspect, the strengthening support material can be SBS (Styrene-Butadiene-Styrene), SIS (Styrene- Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).

[0060] The additive is borax decahydrate and / or borax pentahydrate and / or melamine.

[0061] Another alternative method of the invention includes the following process steps for using the obtained membrane as a cation exchanger: applying chemical processes to the obtained membrane, rinsing the membrane with pure water, drying the membrane, and packaging the membrane.

[0062] Another alternative method of the invention includes the following process steps for using the obtained membrane as an anion exchanger: coating the obtained membrane with ionic conductive polymer coating using solution casting method, applying chemical process, performing drying process, and performing packaging. The cast polymer merges into the nanofiber structure to form a single (substantially) homogenous layer (i.e. the nanofiberbeing distributed substantially throughout the single layer in the pores) and not two separate layers.

[0063] The structural and characteristic features and all advantages of the invention will be understood more clearly thanks to the figures given below and the detailed explanation written by making references to these figures, and therefore the evaluation should be made by taking these figures and detailed explanation into consideration.Figures

[0064] Figure 1 is a block diagram showing the production stages of the membrane(separator) used in batteries and electrolysers.

[0065] Figure 2 is a block diagram showing the production stages of the membrane(separator) used as a cation exchanger.

[0066] Figure 3 is a block diagram showing the production stages of the membrane(separator) used as an anion exchanger.

[0067] Figure 4 is the views of needle (a) and needleless (b) electrospinning techniques.

[0068] Figures 5, 6, 7 and 8 show impedance measurement graphs of the cation exchange membrane.

[0069] Figure 9 shows specific capacities of an ion membrane separator.

[0070] Figure 10 shows examples of reinforced ion exchange membrane.

[0071] Figure 11 shows different fibre combinations.Detailed Description of the Invention

[0072] In this detailed description, the preferred embodiments of the nanofiber membrane (separator) production method are provided below.

[0073] Fig 10 shows two examples of reinforced ion exchange membrane. The top figure shows a two-layer structure with a PAN-based nanofiber network on a support material made of PAN-based fabric including nanofibers. The bottom figure shows a three-layer structure with two PAN-based nanofiber networks located either side of a support material made of PAN-based fabric including nanofibers. The support material is obtained from PAN homopolymer and / or PAN copolymers. Mono and / or multi-filament fibers obtained fromPAN homopolymer and / or PAN copolymers are woven and / or knited to form a fabric structure. The reinforced ion exchange membrane can be used for either cation exchange membranes or anionic exchange membranes.

[0074] The following process is applied to the fabric material to be used as a support material in the cation exchange membrane.

[0075] The fabric for the cation exchange membrane is doped with phosphoric acid and / or phytic acid and / or sulfonic acid and / or sulfuric acid and / or phosphonic acid for a period of 5 minutes to 24 hours at a temperature between 18-120°C in order to be ionically activated.

[0076] The fabric for the anion exchange membrane is subjected to chemical treatment in a solution containing ammonium and / or amine groups, with or without heat, for a period of 5 minutes to 24 hours.

[0077] After this process, the fabric is washed with distilled water. After the washing process, a drying process is applied. The dried fabric material is placed in the collection area of the electrospinning process for the production of PEM membranes to be produced via electrospinning. The electrospinning process is initiated, and the nanofibers produced are collected on one surface of the fabric. When the thickness of the nanofibers reaches the desired level, the electrospinning process is completed. After this process, the fabric coated with nanofibers is removed from the electrospinning device. The obtained fabric and nanofiber composite structure is pressed under a thermal press. Pressure application can be done using cylindrical flow presses as well as non-cylindrical flat presses. After the pressure application process, the composite structure consisting of fabric and nanofibers will be subjected to chemical treatment.

[0078] After the pressure application, the chemical treatment process (step 2004) mentioned below is applied.

[0079] After the chemical treatments, the material is washed with distilled water.

[0080] After the washing process, the water is removed from the structure by squeezing it between pressure rollers or pressing it with a hydraulic press.

[0081] The reinforced membrane is dried for the next process, cutting is performed if necessary, and the packaging process is carried out.

[0082] A block diagram of a method for producing a heat-resistant nanofiber membrane with surface area and surface porosity, high ionic conductivity to be used in batteries, fuel cells and electrolysers, given in Figure 1, and comprises the following steps: preparation ofsingle and / or more solutions (step 1000), application of needle or needleless electrospinning process (step 1001) to the solution / solutions, obtaining nanofiber membrane (step 1002), application of chemical processes (step 2004), and (preferably) packaging of the obtained nanofiber membrane (step 1003).

[0083] In an alternative method of the invention, in case of a single solution, the solution is prepared by mixing 8-20% first polymer, 0.1-20% second polymer, 50-92% solvent, 0- 5% salt, 0.01-15% strength-enhancing support material and 0.01-20% additive at 18°C- 100°C for 15 minutes and 8 hours (1000). In another alternative method of the invention, in case of two solutions, 8-20% first polymer, 0.1-20% second polymer, 50-92% solvent, 0-5% salt, 0.01-15% strength enhancing support material and 0.01-20% additive are mixed at 18°C-100°C for 15 minutes and 8 hours to prepare the first solution (1000) and 5-20% strength enhancing material and one or more solvents are mixed at 18°C-100°C for 2 minutes and 8 hours to prepare the second solution (1000).

[0084] Another alternative method of the invention, the block diagram of which is given in Figure 2, is to use the obtained membrane as a cation exchanger and has the following process steps: applying chemical processes to the obtained membrane (step 2004), rinsing with pure water (step 2005), drying (step 2006), and packaging (step 1003).

[0085] Another alternative method of the invention, the block diagram of which is given in Figure 3, for the obtained membrane to be used as an anion exchanger and has the following process steps: coating the obtained membrane with ionic conductive polymer coating by solution casting method which substantially fills the pores (step 3001), applying chemical processes (step 2004), drying (step 2006), and packaging (step 1003).

[0086] The method set out in this document covers the production of a nanofiber structure (step 1002) by electrospinning process (step 1001) and the subsequent processing of this nanofiber structure by chemical processes (step 2004) to meet the desired properties. The produced nanofiber structure can be used in battery separator applications without being processed. The structure from the produced nanofibers can include nanofibers of the same polymer or nanofibers produced simultaneously from nanofibers produced from different polymers.

[0087] In the alternative embodiment of the invention, there can be a nanofiber content containing a single polymer or nanofibers containing two or more polymers with different compositions can be formed.

[0088] In another alternative embodiment of the invention, the nanofiber content produced from a single polymer may not contain additives or there may be nanofibers containing additives.

[0089] In another alternative embodiment of the invention, a polymer and a different polymer can be dissolved in the same solvent to form a single solution and a nanofiber structure containing two different polymers and additives can be obtained in the same nanofiber. Nanofibers obtained from another polymer containing a single polymer with such a structure can also be found in the same structure. Figure 1, Figure 2 and Figure 3 provide details about the solutions to be prepared for the production of the above-mentioned nanofibers.

[0090] After the polymer solution is prepared (step 1000) and the formation of nanofiber membranes (step 1002) is accomplished with the electrospinning process (step 1001), chemical processes can be applied to the formed membrane structure in order to load appropriate loads or improve its mechanical properties if necessary (step 2004).

[0091] The production of nanofibers can be done with the needle electrospinning process (in step 1001), as well as needleless and electrospinning processes (step 1001). Figures illustrating the electrospinning techniques are given in Figure 4.

[0092] In needle and needleless electrospinning processes (step 1001), the number of polymer feed rods can be increased as desired so that they are parallel to each other. According to the information given in the preparation of polymer solutions section, each polymer feed rod can be fed with the same polymer, or each rod can be fed with a different polymer solution or a certain number of feed rods can be fed with different polymers or polymer solutions. The length of the polymer feed rod can be adjusted according to the width of the membrane to be produced, while the number of needles can also vary in the needle electrospinning technique.

[0093] The nanofiber structure is formed by electrospinning and the nanofiber structure in the same and / or different polymers and / or composite polymers and / or additive contents has different suitable properties and can be used as a battery separator. The nanofibers comprising the same or different polymers are produced entirely by electrospinning and the structure obtained from composite nanofibers is subjected to chemical treatment (step 2004). With this process, it is possible to produce fluorine-free ion conductingmembranes / separators with larger surface areas. The structure is washed with pure water after the chemical treatment (step 2004) and dried (step 2006).

[0094] The production method mentioned above is not used in commercially available membranes. There are some research studies in the literature using the electrospinning method. However, the methods of formation and / or chemical processes of the nanofiber structure specific to the application (2004) differ from method outlined in this document.

[0095] The chemical processes that can be applied for cation exchange membranes are as fol lows AT reatm ent with phosphoric acid (10%-90%) and / or sulfuric acid (0.001N-5N) at certain concentrations at 18-60°C for 2 minutes to 48 hours is applied as a chemical process. In addition, the chemical process can be repeated more than once, first with one acid and then with a second acid.

[0096] The chemical processes to be applied for the nanofiber structure obtained for anion exchange membranes are as follow ADne side and / or both sides of the obtained nanofiber structure can be coated with ionic conductive coating(s) (step 3001) and thereby substantially filling the pores. After the coating process, chemical processes are applied, and the drying process (step 2006) is performed, and the membrane production is carried out without the washing process (step 2005).

[0097] All polymer structures and coatings mentioned in this document are completely fluorine-free structures. Almost all currently available commercial products contain fluorine. In addition, the polymers used in this invention are based on polyacrylonitrile homo polymers and copolymers.

[0098] The membranes produced by this method show the following properties.

[0099] Environmental friendliness: The membranes are fluorine-free and can be produced from environmentally friendly and recyclable materials. This can contribute to a more sustainable energy sector.

[0100] High performance: The materials set out in this document can increase the durability and performance of fluorine-free membranes. In addition, the nanofiber structure obtained by the electrospinning process increases the ion conductivity by providing channels that increase the ion transfer.

[0101] The high compatibility of the polyacrylonitrile-based polymers used with the electrolytes used in the batteries. The wetting of the separators produced with the polymer and the electrolyte is higher than the existing commercial separators. The ion conductionwithin the battery cells is homogeneous and higher, resulting in increased battery life and performance.

[0102] In electrolysers and fuel cells where anion and cation exchange membranes are used, the ion conductivity of the membranes will be increased and the membranes can be used at higher temperatures than existing commercial membranes, thus reducing the amount of expensive catalysts used in electrolysers and fuel cells. This will reduce the costs of electrolysers and fuel cells

[0103] Application diversity: The membranes set out in this document can be used in a variety of applications from energy storage systems to electric vehicles.

[0104] Economic advantages: The costs of materials used in the production of fluorine-free membranes can be optimized for a more economically efficient production method.

[0105] Type membrane content: Production of nanofibers from a single solution

[0106] The membrane produced as a result of the formation of nanofibers (step 1002) by electrospinning process (step 1001) from the solution (step 1000) to be prepared using the polymer, solvent, salt and strength-enhancing support and additive defined below is produced by the solution electrospinning process (step 1001) prepared as a single solution. The first polymer to be used here will be present in the solution at a rate of 8-20%. The second polymer should be present in the solution at a rate of 0.1-20%. As solvents, the specified solvents can be used alone or as a mixture. The total ratio of solvents in the solution is 50-92%. The maximum salt content of the material to be used will be 5% in the total solution content. The ratio of the strength-enhancing material in the solution is between 0.01- 15%.

[0107] Additive materials can be used as a mixture or alone. The amount of additives in the total solution is between 0.01-20%. The materials in the solution content are mixed at 18°C-100°C and added sequentially or all at once. The mixing of the solution may vary between 15 minutes and 8 hours. The prepared solution is transferred to the solution feeding section of the needleless or needle electrospinning device designed for mass production in an appropriate manner. The voltage range selected for charging the polymer with high voltage is determined between the voltage of the electrospinning machine and 15kV-100kV. High voltage is not limited to these values. The distance between the needle or needleless feeding equipment used for polymer feeding in the electrospinning machine and the collectorplate and / or collector carrier material may be between 15 cm-150 cm. It is not, however, limited to these values. The collector carrier material where the produced nanofibers will be collected is placed appropriately in the electrospinning device. The appropriate collector- polymer feeding distance will be adjusted after the polymer solution is placed. For the determined high voltage feeding, the high voltage setting is made from the high voltage source and / or the mass production high voltage source is opened. In the electrospinning system, the solution feed flow rate is determined according to the mass production electrospinning device design and the polymer solution is fed to the system at the determined flow rate. Nanofiber formation occurs and, in this case, the speed of the collector and / or collector carrier is determined according to the desired membrane thickness. The collector carrier, where nanofiber production is made at the determined thickness, is advanced and collected by wrapping it on the collection roll. The obtained nanofiber structure can be used as a battery separator.

[0108] Cation exchange membrane chemical process:

[0109] The obtained nanofiber structure is kept in a mixture of phosphoric acid solution (5-90% concentration) and / or sulfuric acid (0.01N-10N or 0.01-60%) between 2 min and 24 hours at a temperature between 18°C-90°C with or without mixing. Afterwards, the nanofiber structure is washed 1-3 times with pure water (step 2005) and the drying process (step 2006) is applied. The membrane obtained as a result of drying (step 2006) is a cation exchange membrane. The membrane is separated from the carrier and wrapped on a roll with protective layers on the top and bottom.

[0110] Examples of the first polymer are: polyacrylonitrile homopolymer / copolymer (2-20% polyacrylonitrile-co-methyl acrylate (PAN-MA), polyacrylonitrile-co-vinyl acetate (PAN-VA), polyacrylonitrile-b-polystyrene, methacrylic acid (MAA), acrylamide (AM), methacrylic acid and dimethylaminoethyl ester (DEMA), poly(acrylonitrile-vinyl acetatedimethylaminoethyl ester), and poly(AN-VA-DEMA), cellulose, and polymethyl methacrylate. The second polymer is SEBS (Styrene Ethylene Butylene Styrene). This is a non-fluoropolymer and is a type of thermoplastic elastomer. Other polymers that could be used include SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS ( Sty rene-Ethylene-Propylene- Styrene) as well as the Maleic Anhydride (Mah) grafted versions of these polymers such as MAh grafted SEBS (MAh-g-SEBS).

[0111] Examples of the solvent(s) include ethylene carbonate, strongly polar aprotic dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylamylamine (DMAA), dimethylacetamide (DMAc), cyclohexane, tetrahydrofuran (THF) and inorganic solvent(s) nitric acid, concentrated aqueous solution of zinc chloride, sodium thiocyanate etc.

[0112] Examples of the salts include: Tetraalkylammonium ion, tetraethylammonium bromide (TEAB), sodium chloride, magnesium chloride, potassium chloride, lithium chloride, zinc chloride, sodium nitrate, calcium chloride, zinc chloride and salts that increase electrical solution conductivity, including but not limited to these.

[0113] The strengthening support material is SEBS (Styrene Ethylene Butylene Styrene). In other aspects, the strengthening support material can be SBS (Styrene- Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene- Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).

[0114] The additives include borax decahydrate and / or borax pentahydrate and / or melamine.

[0115] Another example is the formation of membrane by producing two different nanofibers

[0116] This membrane content comprises two different nanofiber structures produced from two different polymer solutions. The two solutions, solution- 1 and solution- 2, the composition of which is given below, are also placed in different polymer feeding areas in the electrospinning machine (needle or needleless polymer feeding) and a membrane structure containing nanofibers produced from two different polymer solutions is obtained by simultaneous nanofiber production. The production speed is determined according to the desired membrane thickness.

[0117] Preparation of Solution- 1 :

[0118] The membrane produced as a result of the formation of nanofibers (1002) by electrospinning process (1001) from the solution to be prepared using the polymer, solvent, salt and strength-enhancing support and additives defined below is produced by the solution electrospinning process (1001) prepared as a single solution. The first polymer to be used here will be present in the solution at a rate of 8-20% by weight. The second polymer should be present in the solution at a rate of 0.1-20% by weight. The solvents specified above can be used alone or as a mixture. The total ratio of solvents in the solution is 50-92 % by weight.The maximum amount of the salt material to be used in the total solution content will be 5% by weight. The ratio of the strength-enhancing material in the solution is between 0.01-15% by weight.

[0119] Additive materials can be used as a mixture or alone. The amount of additives in the total solution is between 0.01-20% by weight. The materials in the solution content are mixed at 18°C-100°C and added sequentially or all at once. The mixing of the solution can vary between 15 minutes and 8 hours.

[0120] Preparation of Solution-2:

[0121] A solution is created with SEBS (Styrene Ethylene Butylene Styrene) polymer material to be used as strength-enhancing material and a mixture of the solvents mentioned below as solvents, either alone or together (Sample solvent mixture: 70% cyclohexane, 20% DMF and 10% THF). The amount of SEBS in the solution should be between 5-20%. The prepared solution is mixed for 2 minutes to 8 hours at 18° C-100°C. In other aspects, SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS) can be used.

[0122] In the mass production electrospinning machine, for the simultaneous production of nanofibers from two different solutions and the production of membranes from composite nanofibers, Solution- 1 and Solution-2 are placed separately in the solution feeding sections of the electrospinning machine. The voltage range selected for charging the feeding solutions with high voltage is determined by the voltage of the electrospinning machine between 15kV-100kV. It will be appreciated that the strength of the voltage is not limited to these values.

[0123] The distance between the needle or needleless polymer solution feeding equipment used for polymer feeding in the electrospinning machine and the collector plate and / or collector carrier material can be between 15 cm-150 cm. It will be appreciated that the distance is not limited to these values. The collector carrier material where the produced nanofibers will be collected is placed appropriately in the electrospinning device.

[0124] After the polymer solution is placed, the appropriate collector-polymer feeding distance will be adjusted. For the determined high voltage supply, the high voltage setting is made from the high voltage source and / or the mass production high voltage source is turned on. In the electrospinning system, the solution feeding flow rate is determinedaccording to the mass production electrospinning device design and the polymer solution is fed to the system at the determined flow rate. Nanofiber formation occurs and, in this case, the speed of the collector and / or collector carrier is determined according to the desired membrane thickness. The collector carrier, where the nanofiber production is made at the determined thickness, is advanced and collected by wrapping it on the collection roll. The obtained nanofiber structure can be used as a battery separator.

[0125] Cation exchange membrane chemical process:

[0126] The obtained nanofiber structure is kept for chemical process (step 2004) in a phosphoric acid solution (5-90% concentration) and / or sulfuric acid (0.01N-10N or 0.01- 60% by concentration) mixture for 2 minutes to 48 hours at 18°C-90°C with or without mixing. Afterwards, it is washed with pure water 1-3 times (step 2005) and the drying process (step 2006) is applied. The membrane obtained as a result of drying (2006) is the cation exchange membrane. It is separated from the carrier and wrapped on a roll with protective layers on the top and bottom. The chemical processing step 2004 can be repeated multiple times using different acids.

[0127] Anion exchange membrane chemical process;

[0128] The obtained nanofiber structure is kept in 0.01-10% glutaraldehyde and / or potassium hydroxide and / or sodium hydroxide and / or quaternary ammonium solution / solution mixture for 2 min to 24 hours at 18°C-90°C with or without mixing. In one aspect, the membrane can be left for at least 15 minutes in a potassium hydroxide (1-50%) or sodium hydroxide (1-50%) solution. Afterwards, it is washed with pure water 1-3 times (step 2005) or dried without washing (2006). The membrane obtained as a result of drying (2006) is an anion exchange membrane. It is separated from the carrier and wrapped on a roll with protective layers on the top and bottom.

[0129] The first polymer includes Polyacrylonitrile homopolymer / copolymer (2-20 % polyacrylonitrile-co-methyl acrylate (PAN-MA), polyacrylonitrile-co-vinyl acetate (PAN-VA), polyacrylonitrile-b-polystyrene, methacrylic acid (MAA), acrylamide (AM), methacrylic acid and dimethylaminoethyl ester (DEMA), poly(acrylonitrile-vinyl acetatedimethylaminoethyl ester), poly(AN-VA-DEMA), cellulose, and polymethylmethacrylate.

[0130] The second polymer is SEBS (Styrene Ethylene Butylene Styrene). In other aspect, the second polymer is SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).

[0131] The solvent / solvents include ethylene carbonate, strongly polar aprotic dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylamylamine (DMAA), dimethylacetamide (DMAc), cyclohexane, tetrahydrofuran (THF) and inorganic solvent(s) nitric acid, concentrated aqueous solution of zinc chloride, sodium thiocyanate, etc.

[0132] The salts include tetraalkylammonium ion, tetraethyl ammonium bromide (TEAB), sodium chloride, magnesium chloride, potassium chloride, lithium chloride, zinc chloride, sodium nitrate, calcium chloride, zinc chloride, and salts that increase electrical solution conductivity, including but not limited to these.

[0133] The strengthening support material is SEBS (Styrene Ethylene Butylene Styrene). In one aspect this is provided at a minimum concentration of 0.1%. In other asepcts, the strengthening support material is SBS (Styrene-Butadiene-Styrene), SIS (Styrene- Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).

[0134] The additive is borax decahydrate and / or borax pentahydrate and / or melamine.

[0135] In one example, the first polymer is a polyacrylonitrile-co-methyl acrylate (PAN-MA), or a poly(acrylonitrile-co-vinyl acetate) (PAN-VA).

[0136] Experimental Results

[0137] Cation exchange membrane

[0138] Impedance measurement graphs at different temperatures under 100% relative humidity for PAN-based cation exchange nanofiber membranes with different content ratios are shown in Figs. 5 and 6. These figures show the results of electrochemical impedance spectroscopy measurements performed to determine the ionic conductivity of ion-conductive membranes. In these measurements, a Nyquist plot is generated to determine the resistance to ion transport. The Nyquist plot allows for the identification of the resistance necessary for calculating the ionic conductivity of the membranes. The lower the resistance, the higher the conductivity. In Figures 5 and 6, the Nyquist plots of a membrane at different temperatures and constant humidity are shown. The plots indicate that the resistance values are low.

[0139] Impedance measurement graphs of PAN-based cation exchange membranes with relative humidity at a constant temperature of 80°C and varying relative humidity in Figs. 7 and 8.

[0140] Fig. 9 shows the coin cell discharge performance at different speeds for the ion membrane separator made of PAN chemically treated with sulphuric acid.REFERENCE NUMERALS1000 Solution preparation1001 Electrospinning process 1002 Obtaining nanofiber membrane1003 Packaging2004 Applying chemical processes2005 Rinsing with pure water2006 Drying process 3001 Coating with ionic conductive polymer coating by solution casting method

Claims

Claims1. A method for producing a heat-resistant nanofiber membrane with a high surface area and surface porosity to be used in batteries, fuel cells and electrolysers, comprising:• preparing (1000) at least one solution,• applying an electrospinning process (1001) to the at least one solution, thereby• obtaining (1002) the nanofiber membrane.

2. The method according to claim 1, comprising packaging (1003) the obtained nanofiber membrane.

3. The method according to any one of claims 1 to 2, further comprising• applying chemical processes (2004) to the obtained nanofiber membrane,• rinsing (2005) with pure water the nanofiber membrane,• drying (2006) the nanofiber membrane, followed by• packaging (1003) the nanofiber membrane.

4. The method according to claim 3, wherein the chemical process applying (2004) comprises:• keeping the obtained nanofiber structure in a first solution comprising a phosphoric acid solution, preferably in a concentration between 5 and 90%, and / or a sulfuric acid solution, preferably in a concentration between 0.01 and 70%, preferably between 5% and 70%, and / or a 0.01-10% glutaraldehyde solution / solution mixture, and / or potassium hydroxide and / or sodium hydroxide and / or a quaternary ammonium solution / solution mixture;• optionally mixing the obtained nanofiber membrane with the first solution for 2 min to 24 hours at a temperature comprised between 18°C and 90°C.

5. The method according to any one of claims 1 to 4, further comprising• coating (3001) the obtained nanofiber membrane with an ionic conductive polymer coating using a solution casting method,• applying (2004) a chemical treatment on the nanofiber membrane;• performing a drying process (2006) on the nanofiber membrane;• packaging (1003) the nanofiber membrane.

6. The method according to claim 5, wherein the chemical treatment (2004) further comprises mixing the nanofiber membrane in a 0.01-10% glutaraldehyde and / or potassium hydroxide and / or sodium hydroxide and / or quaternary ammonium solution / solution mixture for 2 min to 24 hours at a temperature comprised between 18°C and 90°C.

7. The method according to any one of claims 1 to 6, comprising applying an electrospinning process (1001).

8. The method according to any one of claims 1 to 7, wherein one solution is prepared (1000), wherein the preparing (1000) comprises mixing8 to 20% of a first polymer with0.1 to 20% of one of styrene ethylene butylene styrene, SBS (Styrene-Butadiene- Styrene), SIS (Styrene-Isoprene-Styrene), SEPS ( Sty rene-Ethylene-Propylene- Styrene) as well as the Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS);50 to 92% of a solvent; at most 5% of a salt;0.01 to 15% of a strength-increasing support material; and0.01 to 20% of an additive; at a temperature between 18°C tolOO°C for a duration between 15 minutes and 8 hours.

9. The method according to any one of claims 1 to 7, wherein two solutions are prepared (1000), wherein the preparing (1000) comprises preparing (a first solution by mixing8 to 20% of a first polymer;0.1% to 20% of one of styrene ethylene butylene styrene, SBS (Styrene-Butadiene- Styrene), SIS (Styrene-Isoprene-Styrene), SEPS ( Sty rene-Ethylene-Propylene- Styrene) as well as the Maleic Anhydride (Mah) grafted versions of these polymers such as MAh grafted SEBS (MAh-g-SEBS);50 to 92% of a solvent; at most 5% of a salt;0.01 to 15% of a strength-enhancing support material comprising styrene ethylene butylene styrene; and0.01-20% of an additive; at a temperature between 18°C and 100°C for a duration between 15 minutes and 8 hours, and preparing a second solution by mixing5 to 20% of a strength-enhancing material comprising styrene ethylene butylene styrene and75 to 95% one or more solvents at a temperature between 18°C and 100°C for a duration between 2 minutes and 8 hours.

10. A nanofiber membrane obtained by the method of claim 3 or 4, to be used as a cation exchanger.

11. A nanofiber membrane obtained by the method of claim 5 or 6, to be used as an anion exchanger.

12. The method according to any one of claims 3 to 9, wherein a) the first polymer is selected from one of a polyacrylonitrile homopolymer / copolymer (2-20 % Polyacrylonitrile-Co-methyl acrylate, (PAN-MA), Polyacrylonitrile-Co Vinyl acetate (PAN-VA),, a polyacrylonitrile-b-polystyrene, a methacrylic acid (MAA), an acrylamide (AM), a methacrylic acid and a dimethylaminoethyl ester (DEMA), a poly(acrylonitrile-vinyl acetate-dimethylaminoethyl ester), a poly(AN-VA-DEMA), cellulose, polymethyl methacrylate, or a combination thereof; and / or b) the second polymer is selected from one of styrene ethylene butylene styrene (SEBS), SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethyl ene-Propylene- Styrene) as well as the Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS); and / or c) the solvent is selected from one of ethylene carbonate, polar aprotic dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylamylamine (DMAA), dimethylacetamide (DMAc), cyclohexane, tetrahydrofuran (THF), and inorganic solvent(s), such as nitric acid, concentrated aqueous solution of zinc chloride, sodium thiocyanate, or a combination thereof; and / or d) the salt is selected from one of tetraalkylammonium ion, tetraethyl ammonium bromide (TEAB), sodium chloride, magnesium chloride, potassium chloride, lithium chloride, zinc chloride, sodium nitrate, calcium chloride, zinc chloride; or a combination thereof; and / or e) the strength-enhancing support material is one of styrene ethylene butylene styrene (SEBS), SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).; and / or; f) the additive is selected from one of borax decahydrate, borax pentahydrate, melamine, or a combination thereof.

13. The method according to any one of claims 6 to 11, or 12, wherein a) the first polymer is selected from one of a polyacrylonitrile homopolymer / copolymer (2-20 % Polyacrylonitrile-Co-methyl acrylate, (PAN-MA),Polyacrylonitrile-Co Vinyl acetate (PAN-VA), a polyacrylonitrile-b-polystyrene, a methacrylic acid (MAA), an acrylamide (AM), a methacrylic acid and a dimethylaminoethyl ester (DEMA), a poly(acrylonitrile-vinyl acetatedimethylaminoethyl ester), a poly(AN-VA-DEMA), cellulose, polymethyl methacrylate, or a combination thereof; and / or b) the second polymer is one of styrene ethylene butylene styrene (SEBS) SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene- Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS).; and / or c) the solvent is selected from one of ethylene carbonate, polar aprotic dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylamylamine (DMAA),dimethylacetamide (DMAc), cyclohexane, tetrahydrofuran (THF), and inorganic solvent(s), such as nitric acid, concentrated aqueous solution of zinc chloride, sodium thiocyanate, or a combination thereof; and / or d) the salt is selected from one of tetraalkylammonium ion, tetraethyl ammonium bromide (TEAB), sodium chloride, magnesium chloride, potassium chloride, lithium chloride, zinc chloride, sodium nitrate, calcium chloride, zinc chloride; or a combination thereof; and / or e) the strength-enhancing support material is one of styrene ethylene butylene styrene (SEBS) SBS (Styrene-Butadiene-Styrene), SIS (Styrene-Isoprene-Styrene), SEPS (Styrene-Ethylene-Propylene-Styrene), or Maleic Anhydride (Mah) grafted versions of these polymers, such as MAh grafted SEBS (MAh-g-SEBS); and / or; f) the additive is selected from one of borax decahydrate, borax pentahydrate, melamine, or a combination thereof.

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