Fiber-reinforced polymer composite membrane and preparation method therefor

Abstract

A fiber-reinforced polymer composite membrane and a preparation method therefor, relating to the technical field of composite materials. The fiber-reinforced polymer composite membrane comprises a modified glass fiber fabric and a polymer matrix coating the surface of the modified glass fiber fabric; the modified glass fiber fabric is a glass fiber fabric of which the fiber surface is coated with a modified layer; the modified layer comprises a rare earth metal salt and a fluorine-containing polymer; and the polymer matrix at least comprises the fluorine-containing polymer. Glass fibers and the fluorine-containing polymer matrix in the fiber-reinforced polymer composite membrane has high interface bonding strength and good interface toughness.

Description

Fiber-reinforced polymer composite film and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of composite materials, in particular to a fiber-reinforced polymer composite film and a preparation method thereof. Background Art

[0002] With the development of society, many applications have put forward higher technical requirements for the dielectric properties, mechanical properties and reliability of fiber-reinforced fluoropolymer membrane materials. For example, in the preparation process of fabric-reinforced fluoropolymer membrane materials, extremely high requirements are placed on the stability of the glass fiber fabric performance during impregnation treatment, the wettability of the emulsion on the glass fiber, drying, sintering and other processes.

[0003] Currently, in the preparation of fiber-reinforced fluoropolymer membranes, the removal of the glass fiber sizing primarily involves high-temperature heat treatment. This results in significant strength loss after the sizing is removed, with strength retention typically below 80%. Furthermore, to improve the interfacial bonding between the glass fiber and the fluoropolymer matrix, existing techniques primarily utilize silane coupling agents to improve the glass fiber fabric. This approach offers limited improvement in interfacial bonding and can also reduce the flexibility of the membrane material.

[0004] Therefore, there is an urgent need to provide a fiber-reinforced polymer composite membrane with excellent interfacial bonding ability between fibers and polymers.

[0005] Summary of the Invention

[0006] In response to one or more technical problems existing in the prior art, the present invention provides a fiber-reinforced polymer composite membrane and a preparation method thereof. The fiber-reinforced polymer composite membrane provided by the present invention has high interface bonding strength and good interface toughness between the glass fiber and the fluorine-containing polymer matrix.

[0007] The present invention provides a fiber-reinforced polymer composite membrane, the composite membrane comprising a fiber reinforcement and a polymer matrix;

[0008] The fiber reinforcement is a modified glass fiber fabric; the modified glass fiber fabric is a glass fiber fabric with a modified layer coated on the fiber surface; the modified layer contains a rare earth metal salt and a fluorine-containing polymer;

[0009] The polymer matrix includes at least a fluorine-containing polymer.

[0010] Preferably, the diameter of the glass fibers in the glass fiber fabric is 2 to 7 μm; and / or

[0011] The mass ratio of the rare earth metal element to the fluorine-containing polymer in the rare earth metal salt is 0.2-5:30-60, preferably 0.2-3:30-60; preferably, the rare earth metal salt is at least one of a lanthanum salt and a cerium salt, preferably one or more of lanthanum nitrate, cerium nitrate, cerium chloride, lanthanum chloride, cerium oxide, and lanthanum oxide; preferably, the fluorine-containing polymer includes at least polytetrafluoroethylene.

[0012] Preferably, the fluorine-containing polymer further comprises one or more of perfluoroalkyl vinyl ether, polyhexafluoropropylene (HFP), fluorinated ethylene-propylene copolymer, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, perfluoropropylene-vinyl ether, perfluoropropylene-vinyl ether, and perfluoromethyl vinyl ether.

[0013] Preferably, the open area percentage of the glass fiber fabric is 20 to 50%;

[0014] The gram weight of the glass fiber fabric is 300 to 1500 g / m 2 and / or

[0015] The thickness of the polymer matrix is ​​not less than 0.05 mm.

[0016] In a second aspect, the present invention provides a method for preparing the fiber-reinforced polymer composite membrane according to the first aspect, the method comprising the following steps:

[0017] S1. The glass fiber fabric is placed in an aqueous amylase solution and washed to obtain a washed glass fiber fabric;

[0018] S2. The washed glass fiber fabric is modified with a modifier to obtain a modified glass fiber fabric; the modifier is an emulsion of a fluoropolymer containing a rare earth metal salt;

[0019] S3. The modified glass fiber fabric is impregnated in a fluoropolymer emulsion and heat-treated to obtain a membrane;

[0020] S4. Repeat step S3 until the weight gain of the membrane material reaches the required value, thereby obtaining the fiber-reinforced polymer composite membrane.

[0021] Preferably, the water washing treatment is performed by ultrasound at 30-80°C; preferably, the frequency of the ultrasound is 5-100 KHz.

[0022] Preferably, the rare earth metal element in the modifier accounts for 0.2 to 5 wt%, preferably 0.2 to 3 wt%, and the fluorine-containing polymer accounts for 30 to 60 wt%.

[0023] Preferably, the concentration of the amylase aqueous solution is 0.1 to 5 wt %, preferably, the amylase is at least one of α-amylase, β-amylase, γ-amylase and isoamylase; and / or

[0024] The content of the fluorine-containing polymer in the fluorine-containing polymer emulsion is 30-50%, preferably 38-45%.

[0025] Preferably, the heat treatment includes drying, baking and sintering;

[0026] Preferably, the drying temperature is 100-200°C;

[0027] Preferably, the baking temperature is 210-330°C;

[0028] Preferably, the sintering temperature is 350-380°C.

[0029] Preferably, the weight gain of the membrane material reaches the requirement that the weight of the membrane material obtained in the last step S4 is not less than 1.5 times the weight of the glass fiber fabric, and preferably the weight of the membrane material obtained in the last step S4 is 1.5 to 2.9 times the weight of the glass fiber fabric.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] The modified glass fiber fabric in the fiber-reinforced polymer composite membrane of the present invention is a glass fiber fabric with a modified layer coated on the fiber surface. A portion of the rare earth metal elements in the modified layer can combine with oxygen in the hydroxyl groups on the glass fiber surface, and another portion can enter the surface layer through defects on the glass fiber surface and remain in the defects, acting as active centers to generate a distortion zone near the glass fiber surface, thereby activating the glass fiber surface. At the same time, the rare earth metal (RE) elements on the glass fiber surface can attract F atoms in the fluoropolymer, exposing C atoms shielded by the F atoms, thereby forming RE-F bonds or RE-C bonds, thereby improving the interfacial bonding between the glass fiber and the fluoropolymer matrix. At the same time, the rare earth compound present at the interface between the glass fiber and the fluoropolymer matrix plays a role similar to "pinning", thereby strengthening the mechanical bonding between the glass fiber and the fluoropolymer matrix, thereby further improving the affinity between the glass fiber and the fluoropolymer matrix. In addition, due to the small size and simple structure of the rare earth metal elements, the rare earth metal elements can relax the main C-C bonds of the fluoropolymer molecular chain, thereby improving the flexibility of the molecular chain and thereby enhancing the interfacial toughness between the glass fiber and the fluoropolymer. The fiber-reinforced polymer composite membrane provided by the present invention has high interface bonding strength and good interface toughness between the glass fiber and the fluorine-containing polymer matrix.

[0032] The present invention firstly uses amylase to perform water washing treatment on glass fiber fabric, so that starch wetting agent is quickly decomposed into soluble dextrin, thereby ensuring that the starch wetting agent in the fiber fabric is removed without damaging the glass fiber fabric, and the method is efficient, high-speed and pollution-free, thereby overcoming the problem that the strength of the glass fiber fabric is damaged when the starch wetting agent in the glass fiber fabric is removed by high-temperature heat treatment in the prior art; and uses a fluoropolymer emulsion containing a rare earth metal salt as a modifier to perform surface modification on the washed glass fiber fabric, thereby improving the interface bonding ability between the glass fiber and the fluoropolymer matrix and the flexibility of the fluoropolymer molecular chain, thereby enhancing the interface toughness between the glass fiber and the fluoropolymer, thereby overcoming the problem that the flexibility of the fluoropolymer molecular chain is reduced due to the polar groups -NH2, -NH-, etc. in the R groups of the silane coupling agent in the prior art method of performing surface modification on the glass fiber fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] FIG1 is a cross-sectional view of a fiber-reinforced polymer composite membrane provided by the present invention;

[0035] FIG2 is a SEM image of a fiber-reinforced polymer composite membrane provided by the present invention;

[0036] FIG3 is a schematic diagram of the interfacial interaction mechanism of rare earth metal elements in the fiber-reinforced polymer composite film provided by the present invention;

[0037] FIG4 is a flow chart of the preparation of a fiber-reinforced polymer composite membrane provided by the present invention;

[0038] Reference numerals: 11 - fluoropolymer; 12 - weft glass fiber; 13 - warp glass fiber. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] In a first aspect, the present invention provides a fiber-reinforced polymer composite membrane, the composite membrane comprising a fiber reinforcement and a polymer matrix;

[0041] The fiber reinforcement is a modified glass fiber fabric; the modified glass fiber fabric is a glass fiber fabric with a modified layer coated on the fiber surface; the modified layer contains a rare earth metal salt and a fluorine-containing polymer;

[0042] The polymer matrix includes at least a fluorine-containing polymer.

[0043] The modified glass fiber fabric in the fiber-reinforced polymer composite membrane of the present invention is a glass fiber fabric with a modified layer coated on the fiber surface. A portion of the rare earth metal elements in the modified layer can combine with oxygen in the hydroxyl groups on the glass fiber surface, and another portion can enter the surface layer through defects on the glass fiber surface and remain in the defects, acting as active centers to generate a distortion zone near the glass fiber surface, thereby activating the glass fiber surface. At the same time, the rare earth metal (RE) elements on the glass fiber surface can attract F atoms in the fluoropolymer, exposing C atoms shielded by the F atoms, thereby forming RE-F bonds or RE-C bonds, thereby improving the interfacial bonding between the glass fiber and the fluoropolymer matrix. At the same time, the rare earth compound present at the interface between the glass fiber and the fluoropolymer matrix plays a role similar to "pinning", thereby strengthening the mechanical bonding between the glass fiber and the fluoropolymer matrix, thereby further improving the affinity between the glass fiber and the fluoropolymer matrix. In addition, due to the small size and simple structure of the rare earth metal elements, the rare earth metal elements can relax the main C-C bonds of the fluoropolymer molecular chain, thereby improving the flexibility of the molecular chain and thereby enhancing the interfacial toughness between the glass fiber and the fluoropolymer. The fiber-reinforced polymer composite membrane provided by the present invention has high interface bonding strength and good interface toughness between the glass fiber and the fluorine-containing polymer matrix.

[0044] It should be noted that the modified glass fiber fabric of the present invention is obtained by washing the glass fiber fabric with an amylase solution and then modifying the glass fiber fabric with an emulsion of a fluorine-containing polymer containing a rare earth metal salt.

[0045] According to some preferred embodiments, the diameter of the glass fibers in the glass fiber fabric is 2 to 7 μm (for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or 7 μm); and / or

[0046] The mass ratio of the rare earth metal element to the fluorine-containing polymer in the rare earth metal salt is 0.2-5:30-60, preferably 0.2-3:30-60 (for example, 0.2:30, 0.2:40, 0.2:50, 0.2:60, 0.5:30, : 0.5:40, 0.5:50, 0.5:60, 1:30, 1:40, 1:50, 1:60, 1.5:30, 15:40, 1.5:50, 1.5:60, 2:30, 2:40, 2:50, 2:60, 2.5:30, 2.5:40, 2:550, 2.5:60, 3:30, 3:40, 3:50 or 3:60); preferably, the rare earth metal salt is at least one of a lanthanum salt and a cerium salt, preferably one or more of lanthanum nitrate, cerium nitrate, cerium chloride, lanthanum chloride, cerium oxide, and lanthanum oxide; preferably, the fluorine-containing polymer comprises at least polytetrafluoroethylene (PTFE).

[0047] According to some preferred embodiments, the fluoropolymer further comprises one or more of perfluoroalkyl vinyl ether (PFA), polyhexafluoropropylene (HFP), fluorinated ethylene-propylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), perfluoropropylene-vinyl ether (PPVE), perfluoropropylene-vinyl ether, and perfluoromethyl vinyl ether (MFA).

[0048] According to some preferred embodiments, the glass fiber fabric has an open area percentage of 20-50% (e.g., 20%, 22%, 25%, 26%, 28%, 30%, 32%, 35%, 36%, 38%, 40%, 42%, 45%, 46%, 48%, or 50%). The glass fiber fabric of the present invention is a mesh fabric, and the mesh holes are generally of uniform size and spacing. It should be noted that the open area percentage refers to the percentage of the area of ​​the glass fiber fabric occupied by the open area of ​​the holes. The inventors have found that when the glass fiber fabric has an open area percentage of less than 20%, the opportunity for interaction between fluoropolymer molecules located on both sides of the glass fiber fabric is reduced; when the glass fiber fabric has an open area percentage of greater than 50%, the strength of the glass fiber fabric is reduced.

[0049] According to some preferred embodiments, the glass fiber fabric has a gram weight of 300 to 1500 g / m 2 (For example, it can be 300g / m 2 , 400g / m 2 , 500g / m 2 , 600g / m 2 , 700g / m 2 , 800g / m 2, 900g / m 2 , 1000g / m 2 , 1100g / m 2 , 1200g / m 2 , 1300g / m 2 , 1400g / m 2 or 1500g / m 2 );

[0050] According to some preferred embodiments, the thickness of the polymer matrix is ​​not less than 0.05 mm.

[0051] In a first aspect, the present invention provides a method for preparing the fiber-reinforced polymer composite membrane according to the first aspect, the method comprising the following steps:

[0052] S1. The glass fiber fabric is placed in an aqueous amylase solution and washed to obtain a washed glass fiber fabric;

[0053] S2. The washed glass fiber fabric is modified with a modifier to obtain a modified glass fiber fabric; the modifier is an emulsion of a fluoropolymer containing a rare earth metal salt;

[0054] S3. The modified glass fiber fabric is impregnated in a fluoropolymer emulsion and heat-treated to obtain a membrane;

[0055] S4. Repeat step S3 until the weight gain of the membrane material reaches the required value, thereby obtaining the fiber-reinforced polymer composite membrane.

[0056] The present invention firstly uses amylase to wash the glass fiber fabric, so that the starch wetting agent is quickly decomposed into soluble dextrin, ensuring that the starch wetting agent in the fiber fabric is removed without damaging the glass fiber fabric, and the method is efficient, high-speed and pollution-free, thereby overcoming the problem that the strength of the glass fiber fabric is damaged when the starch wetting agent in the glass fiber fabric is removed by high-temperature heat treatment in the prior art; a fluoropolymer emulsion containing a rare earth metal salt is used as a modifier to perform surface modification on the washed glass fiber fabric, thereby improving the interface bonding ability between the glass fiber and the fluoropolymer matrix and the flexibility of the fluoropolymer molecular chain, thereby enhancing the interface toughness between the glass fiber and the fluoropolymer, thereby overcoming the problem that the R group of the silane coupling agent containing polar groups such as -NH2 and -NH- in the silane coupling agent causes the flexibility of the fluoropolymer molecular chain to decrease in the prior art method of surface modification of the glass fiber fabric; then, the modified glass fiber fabric is impregnated with the fluoropolymer emulsion and subjected to heat treatment in sequence until the weight gain of the membrane material meets the requirement, thereby obtaining a fiber-reinforced polymer composite membrane.

[0057] In order to determine the effect of washing glass fiber fabric with amylase solution on the performance of glass fiber fabric, the present invention uses a 300g / m 2 A glass fiber fabric with an open area percentage of 40% was placed in a 2t water storage tank, and 25kg of α-amylase was added thereto. After the amylase was fully dissolved, the water temperature was controlled at 45°C, the washing time was 8 minutes, and the ultrasonic frequency applied during the washing process was 25KHz. Five samples of the glass fiber fabric after washing were tested. The results are shown in Table 1. It can be seen that the use of amylase for washing does not cause obvious damage to the strength of the glass fiber fabric, and the performance stability of the glass fiber fabric after washing is good.

[0058] Table 1. Properties of glass fiber fabric after washing

[0059] Furthermore, the present invention also explores the influence of washing time and ultrasonic frequency on the strength loss rate of glass fiber fabric; specifically: the weight of 550g / m 2 A glass fiber fabric with an open area percentage of 30% was placed in a 2-ton water storage tank, and 25 kg of α-amylase was added. After the amylase was fully dissolved, the water temperature was controlled at 60°C. The strength loss rate of the glass fiber fabric under different washing treatment times and ultrasonic frequencies was measured as shown in Table 2. The solid content in the table refers to the residual amount of organic matter in the glass fiber fabric after washing.

[0060] Table 2. Effect of washing time and ultrasonic frequency on the strength loss rate of glass fiber fabric

[0061] To improve the interfacial bonding between glass fiber fabric and fluoropolymer layers, existing techniques primarily utilize silane coupling agents to modify the surface of glass fiber fabric. The specific mechanism is as follows: the silane coupling agent first hydrolyzes to generate silanols, while the glass fiber surface absorbs water, generating hydroxyl groups. The silanols then form hydrogen bonds with the hydrated glass fiber surface. Drying and dehydration at low temperatures causes an etherification reaction between the silanols. Finally, drying and dehydration at high temperatures cause an etherification reaction between the silanols and the hydrated glass fiber, thereby bonding the silane coupling agent to the glass fiber surface. The R groups (groups attached to silicon atoms) in the silane coupling agent and the fluoropolymer (e.g., PTFE) diffuse and intertwine to form a network structure. Under certain conditions, the highly electronegative fluorine atoms form coordination bonds with the lone pairs of electrons in the coupling agent R groups. However, due to the inertness of the fluorine atoms, the formation of coordination bonds is limited, thus limiting the effectiveness of interfacial modification using silane coupling agents.

[0062] In view of the fact that the existing method of using silane coupling agent to modify the interface of glass fiber fabric has the problem of limited improvement of the interface bonding ability of glass fiber fabric and fluoropolymer, the present invention adopts fluoropolymer emulsion containing rare earth metal salt as modifier to carry out surface treatment on glass fiber fabric, to improve the interface bonding ability between glass fiber fabric and fluoropolymer. Because rare earth metal elements have the characteristics of special 4f electron structure and small electronegativity, they have outstanding chemical activity. During surface treatment, rare earth metal elements are first adsorbed on the surface of glass fiber as surface active elements, so that the energy of the system is reduced. As shown in Figure 3, after adsorption, because rare earth metal elements have low electronegativity value, a part of rare earth metal elements adsorbed on the surface of glass fiber will combine with oxygen in hydroxyl group on the surface of glass fiber. At the same time, because there are microcracks of different numbers and sizes on the surface of glass fiber, another part of rare earth metal elements adsorbed on the surface of glass fiber will enter the surface layer through the surface defects of glass fiber and remain in the defects, becoming active centers and generating distortion zone near the surface of glass fiber, thereby activating the surface of glass fiber. Furthermore, the 4f electrons of rare earth metal (RE) elements are not tightly closed to the nucleus, have a large effective nuclear charge, and have a strong attraction to the electrons of the atoms around them. Therefore, the rare earth metal elements on the surface of the glass fiber can attract the F atoms in the fluoropolymer, exposing the C atoms shielded by the F atoms, thereby forming RE-F bonds or RE-C bonds. At the same time, since rare earth metal atoms are typical hard cations, they have strong complexing ability with oxygen, fluorine, etc., and the bonds between their coordinating atoms are mostly ionic bonds. Therefore, it can be considered that at the interface between the rare earth metal elements and the fluoropolymer, the RE-F bonds or RE-C bonds formed by the rare earth metal elements have strong ionic bonds. In addition, the rare earth metal compounds present at the interface play a role similar to "pinning", strengthening the mechanical bonding between the glass fiber and the fluoropolymer, and further improving the affinity between the glass fiber and the fluoropolymer matrix. In summary, the interaction between the rare earth metal elements and the glass fiber and the fluoropolymer is mainly chemical, and they play a good "bridge" role between the glass fiber and the fluoropolymer.

[0063] In the process of glass fiber fabric being carried out surface modification, for fluoropolymer (for example PTFE), the rare earth metal element (RE) in the R group in the silane coupling agent and the modifying agent of the present invention is all as the substituent on the fluoropolymer molecular main chain, and the polarity of substituent, the volume of substituent, the distance that substituent is arranged along the molecular chain and the symmetry of substituent on the main chain etc. all have an impact on the flexibility of macromolecular chain.The contriver has found that after glass fiber is processed by silane coupling agent KH-550, the R group that glass fiber surface is covered with can react with fluoropolymer (for example PTFE) or dissolve mutually with fluoropolymer (for example PTFE), has polar group-NH2,-NH-etc. in the R group, then can cause the flexibility of fluoropolymer (for example PTFE) molecular chain to descend.Compared with silane coupling agent, because rare earth metal element volume is little, structure is simple, and rare earth metal element can make fluoropolymer (for example PTFE) molecular chain main bond CC key slack, improve the flexibility of molecular chain, also can strengthen the interface toughness between glass fiber and the fluoropolymer. It can be seen that the use of the fluoropolymer emulsion containing rare earth metal salt as a modifier in the present invention is better than the silane coupling agent in improving the toughness of the interface between the glass fiber and the fluoropolymer.

[0064] Furthermore, in order to compare the modification effects of using a silane coupling agent and a fluorine-containing polymer emulsion containing a rare earth metal salt as a modifier on glass fiber fabric, the present invention uses a 500 g / m 2 , a glass fiber fabric with an open area percentage of 45% was washed with an amylase solution to obtain a washed glass fiber fabric; the washed glass fiber fabric was surface-modified using a silane coupling agent (KH-550), a first modifier (a PTFE emulsion containing cerium nitrate, wherein the rare earth metal content was 0.3wt%, the PTFE content was 30wt%, and the remainder was water) and a second modifier (a PTFE emulsion containing lanthanum chloride, wherein the rare earth metal content was 0.3wt%, the PTFE content was 30wt%, and the remainder was water). The properties of the modified glass fiber fabric after treatment are shown in Table 3. Compared with the silane coupling agent, the use of a fluoropolymer emulsion containing a rare earth metal salt as a modifier for modification has a better reinforcing effect on the glass fiber fabric.

[0065] Table 3. Reinforcement of glass fiber fabrics after modification with different modifiers

[0066] According to some preferred embodiments, the water washing treatment is performed by ultrasound at 30-80°C (for example, 30°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C); preferably, the frequency of the ultrasound is 5-100KHz (for example, 5KHz, 10KHz, 15KHz, 20KHz, 23KHz, 25KHz, 26KHz, 28KHz, 30KHz, 35KHz, 40KHz, 45KHz, 50KHz, 60KHz, 70KHz, 75KHz, 80KHz, 85KHz, 90KHz, 95KHz or 100KHz).

[0067] To improve the efficiency of removing starch sizing from glass fibers, ultrasonic waves are applied during the washing process to induce cavitation at the interface between the fiber surface and the washing solution. The ultrasonic waves propagate forward in a pattern of alternating positive and negative pressures. During the negative pressure phase, tiny vacuum cavities are created in the washing solution, forming bubbles. During the positive pressure phase, the bubbles are adiabatically compressed and ultimately burst. The instantaneous high pressure and strong vibrations generated by the tiny inward-bursting bubbles can pull the sizing away from the fiber surface, enhancing the cleaning process. The ultrasonic waves also loosen contaminants such as the sizing adhering to the fiber surface, facilitating their removal. They also stir the amylase aqueous solution, accelerating the emulsification of the washing solution, promoting the dispersion of the sizing particles, and reducing their adhesion to the glass fiber fabric. Furthermore, because the reaction between amylase and the starch sizing requires a certain temperature and time, the washing process in this invention is preferably performed at a temperature of 30-80°C and for a duration of 1-30 minutes.

[0068] According to some preferred embodiments, the rare earth metal element in the modifier accounts for 0.2-5wt%, preferably 0.2-3wt% (for example, it can be 0.2wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt% or 3wt%), and the fluoropolymer accounts for 30-60wt% (for example, it can be 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%, 55wt%, 58wt% or 60wt%).

[0069] The inventors have discovered that when the content of rare earth metal elements in the modifier is within the above range, active rare earth metal atoms can form a porous single-layer rare earth active film on the fiber surface, thereby properly chemically bonding with the fluoropolymer (such as PTFE); when the amount of rare earth metal salt used is too small, the active rare earth metal elements on the fiber surface are unevenly distributed, and only a small amount of active rare earth metal elements chemically react with the fluoropolymer resin, which in turn leads to the dispersion of the binding points in the interface area between the active rare earth metal elements and the fluoropolymer resin, and poor bonding between the active rare earth metal elements and the fluoropolymer resin; when the amount of rare earth metal salt used is too large, excessive active rare earth metal elements accumulate, affecting the activity of the active rare earth metal elements, reducing the bonding effect on the fluoropolymer resin, and thus weakening the bonding strength between the active rare earth metal elements and the fluoropolymer resin.

[0070] According to some preferred embodiments, the concentration of the amylase aqueous solution is 0.1-5 wt% (for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 33.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt% or 5 wt%), preferably, the amylase is at least one of α-amylase, β-amylase, γ-amylase and isoamylase;

[0071] According to some preferred embodiments, the content of the fluoropolymer in the fluoropolymer emulsion is 30-50% (for example, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, or 50%), preferably 38-45% (for example, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%). It should be noted that the fluoropolymer emulsion of the present invention also includes a solvent; in addition, other additives such as surfactants and thickeners may be added as appropriate; for example, the flexibility of the composite film may be increased by adding a silicone elastomer; the flexibility and weather resistance of the composite film may be improved by adding silicone oil; or additives that can provide texture may be added.

[0072] According to some preferred embodiments, the heat treatment includes drying, baking and sintering;

[0073] Preferably, the drying temperature is 100-200° C. (for example, 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., or 200° C.);

[0074] Preferably, the baking temperature is 210-330°C (for example, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C or 330°C);

[0075] Preferably, the sintering temperature is 350-380° C. (for example, 350° C., 355° C., 360° C., 365° C., 370° C., 375° C., or 380° C.).

[0076] The fiber-reinforced polymer composite membrane provided by the present invention is mainly obtained by impregnating the washed glass fiber fabric with a fluorine-containing polymer emulsion and then subjecting it to heat treatment methods such as drying, baking, and sintering. The specific process flow is shown in Figure 4. The impregnated fiber fabric is dehydrated in the drying area of ​​a vertical coating tower (also known as a sintering furnace), and then sent to the baking area to remove surfactants, thickeners and other additives in the emulsion. In the sintering area, polytetrafluoroethylene is melted to form a film. After repeated impregnation and heat treatment, a fiber-reinforced polymer composite membrane with a certain gram weight and thickness is achieved.

[0077] According to some preferred embodiments, the weight gain of the membrane material is required to be no less than 1.5 times the weight of the glass fiber fabric obtained in the last step S4, and preferably the weight of the membrane material obtained in the last step S4 is 1.5 to 2.9 times the weight of the glass fiber fabric.

[0078] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and they can be directly purchased or synthesized.

[0079] The testing method for the performance data of the fiber-reinforced polymer composite membranes prepared in the examples and comparative examples of the present invention is as follows:

[0080] Breaking strength test method: refer to GB / T3932.1 standard, clamping length is 200mm, width is 50mm.

[0081] Example 1

[0082] S1. Change the weight to 850g / m 2 A glass fiber fabric with an open area percentage of 45% was placed in a fabric storage tank containing 2 tons of water, 25 kg of α-amylase was added thereto, and after the amylase was fully dissolved, the water temperature was controlled at 60°C, the washing time was 5 minutes, and an ultrasonic wave frequency of 100 kHz was applied during the washing process to obtain a washed glass fiber fabric;

[0083] S2. The washed glass fiber fabric is placed in a modifier, subjected to surface modification treatment, drying in a drying tunnel to obtain a modified glass fiber fabric; wherein the modifier is a PTFE emulsion containing lanthanum chloride, wherein the rare earth metal content is 0.3wt%, the PTFE content is 30wt%, and the remainder is water;

[0084] S3. The modified glass fiber fabric is subjected to four impregnations. The first impregnation is to place the modified glass fiber fabric in a first impregnation liquid for the first impregnation, wherein the first impregnation liquid includes 35wt% PTFE, 3wt% FEP, and the rest is water; after the impregnation is completed, a first heat treatment is performed: drying at 130°C for 120s, baking at 210°C for 60s, and sintering at 360°C for 60s; the second impregnation is to place the modified glass fiber fabric in a second impregnation liquid for the second impregnation, wherein the second impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a second heat treatment is performed: drying at 160°C for 120s, baking at 290°C for 60s, and sintering at 370°C for 60s s; the third impregnation is to place the modified glass fiber fabric in a third impregnation liquid for the third impregnation, wherein the third impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a third heat treatment is performed: drying at 160°C for 120s, baking at 290°C for 60s, and sintering at 370°C for 60s; the fourth impregnation is to place the modified glass fiber fabric in a fourth impregnation liquid for the fourth impregnation, wherein the fourth impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a fourth heat treatment is performed: drying at 160°C for 120s, baking at 290°C for 60s, and sintering at 370°C for 60s to obtain a fiber-reinforced polymer composite membrane (weight 1746g / m 2 ).

[0085] Example 2

[0086] S1. Change the weight to 300g / m 2 A glass fiber fabric with an open area percentage of 40% was placed in a fabric storage tank containing 2 tons of water. 25 kg of α-amylase was added thereto. After the amylase was fully dissolved, the water temperature was controlled at 45°C and the washing time was 8 minutes. During the washing process, an ultrasonic wave with a frequency of 25 kHz was applied to obtain a washed glass fiber fabric.

[0087] S2. The washed glass fiber fabric is placed in a modifier, subjected to surface modification treatment, drying in a drying tunnel to obtain a modified glass fiber fabric; wherein the modifier is a PTFE emulsion comprising lanthanum chloride, wherein the rare earth metal content is 1wt%, the PTFE content is 40wt%, and the remainder is water;

[0088] S3. The modified glass fiber fabric is subjected to four impregnations. The first impregnation is to place the modified glass fiber fabric in a first impregnation liquid for the first impregnation, wherein the first impregnation liquid includes 35wt% PTFE, 3wt% FEP, and the rest is water; after the impregnation is completed, a first heat treatment is performed: drying at 100°C for 120s, baking at 210°C for 60s, and sintering at 350°C for 60s; the second impregnation is to place the modified glass fiber fabric in a second impregnation liquid for the second impregnation, wherein the second impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a second heat treatment is performed: drying at 160°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 6 0s; the third impregnation is to place the modified glass fiber fabric in a third impregnation liquid for the third impregnation, wherein the third impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a third heat treatment is performed: drying at 160°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 60s; the fourth impregnation is to place the modified glass fiber fabric in a fourth impregnation liquid for the fourth impregnation, wherein the fourth impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a fourth heat treatment is performed: drying at 160°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 60s to obtain a fiber-reinforced polymer composite membrane (weight 662g / m 2 ).

[0089] Example 3

[0090] S1. Change the weight to 500g / m 2 A glass fiber fabric with an open area percentage of 30% was placed in a fabric storage tank containing 2 tons of water, 25 kg of α-amylase was added thereto, and after the amylase was fully dissolved, the water temperature was controlled at 80°C, the washing time was 5 minutes, and an ultrasonic wave frequency of 50 kHz was applied during the washing process to obtain a washed glass fiber fabric;

[0091] S2. The washed glass fiber fabric is placed in a modifier, subjected to surface modification treatment, drying in a drying tunnel to obtain a modified glass fiber fabric; wherein the modifier is a PTFE emulsion containing cerium nitrate, wherein the rare earth metal content is 0.3wt%, the PTFE content is 30wt%, and the remainder is water;

[0092] S3. The modified glass fiber fabric is subjected to four impregnations. The first impregnation is to place the modified glass fiber fabric in a first impregnation liquid for the first impregnation, wherein the first impregnation liquid includes 35wt% PTFE, 3wt% FEP, and the rest is water; after the impregnation is completed, a first heat treatment is performed: drying at 130°C for 120s, baking at 190°C for 60s, and sintering at 360°C for 60s; the second impregnation is to place the modified glass fiber fabric in a second impregnation liquid for the second impregnation, wherein the second impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a second heat treatment is performed: drying at 100°C for 120s, baking at 260°C for 60s, and sintering at 350°C for 60s. s; the third impregnation is to place the modified glass fiber fabric in a third impregnation liquid for the third impregnation, wherein the third impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a third heat treatment is performed: drying at 100°C for 120s, baking at 260°C for 60s, and sintering at 350°C for 60s; the fourth impregnation is to place the modified glass fiber fabric in a fourth impregnation liquid for the fourth impregnation, wherein the fourth impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a fourth heat treatment is performed: drying at 100°C for 120s, baking at 260°C for 60s, and sintering at 350°C for 60s to obtain a fiber-reinforced polymer composite membrane (weight 1160g / m 2 ).

[0093] Example 4

[0094] S1. Change the weight to 1500g / m 2 A glass fiber fabric with an open area percentage of 50% was placed in a fabric storage tank containing 2 tons of water, 25 kg of α-amylase was added thereto, and after the amylase was fully dissolved, the water temperature was controlled at 80°C, the washing time was 30 minutes, and an ultrasonic wave frequency of 100 kHz was applied during the washing process to obtain a washed glass fiber fabric;

[0095] S2. The washed glass fiber fabric is placed in a modifier, subjected to surface modification treatment, drying in a drying tunnel to obtain a modified glass fiber fabric; wherein the modifier is a PTFE emulsion containing lanthanum chloride, wherein the rare earth metal content is 3wt%, the PTFE content is 60wt%, and the remainder is water;

[0096] S3. The modified glass fiber fabric is subjected to four impregnations. The first impregnation is to place the modified glass fiber fabric in a first impregnation liquid for the first impregnation, wherein the first impregnation liquid includes 35wt% PTFE, 5wt% FEP, and the rest is water; after the impregnation is completed, a first heat treatment is performed: drying at 130°C for 120s, baking at 190°C for 60s, and sintering at 360°C for 60s; the second impregnation is to place the modified glass fiber fabric in a second impregnation liquid for the second impregnation, wherein the second impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a second heat treatment is performed: drying at 200°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 60s. s; the third impregnation is to place the modified glass fiber fabric in a third impregnation liquid for the third impregnation, wherein the third impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a third heat treatment is performed: drying at 200°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 60s; the fourth impregnation is to place the modified glass fiber fabric in a fourth impregnation liquid for the fourth impregnation, wherein the fourth impregnation liquid includes 45wt% PTFE and the rest is water; after the impregnation is completed, a fourth heat treatment is performed: drying at 200°C for 120s, baking at 330°C for 60s, and sintering at 380°C for 60s to obtain a fiber-reinforced polymer composite membrane (weight 2860g / m 2 ).

[0097] Example 5

[0098] The method is substantially the same as Example 1, except that lanthanum chloride is replaced with cerium nitrate.

[0099] Example 6

[0100] The method is basically the same as Example 1, except that in step S2, the modifier is a PTFE emulsion containing lanthanum chloride, wherein the rare earth lanthanum content is 1 wt%, the PTFE content is 30 wt%, and the rest is water.

[0101] Example 7

[0102] The process is basically the same as Example 1, except that in step S2, the modifier is a PTFE emulsion containing lanthanum chloride, wherein the rare earth lanthanum content is 3 wt %, the PTFE content is 30 wt %, and the rest is water.

[0103] Example 8

[0104] The process is basically the same as Example 1, except that in step S2, the modifier is a PTFE emulsion containing lanthanum chloride, wherein the rare earth lanthanum content is 5 wt%, the PTFE content is 30 wt%, and the rest is water.

[0105] Comparative Example 1

[0106] The method is basically the same as Example 1, except that in S2, the modifier comprises a silane coupling agent KH550, wherein the content of the silane coupling agent is 0.3 wt %, the content of PTFE is 30 wt %, and the rest is water.

[0107] Comparative Example 2

[0108] The process is basically the same as Example 1, except that in step S2, the modifier does not contain lanthanum chloride.

[0109] Table 4. Performance data of fiber-reinforced polymer composite membranes prepared in Examples of the present invention and Comparative Examples

[0110] As shown in Figures 1-2 and Table 4, fiber fabric and fluoropolymer are tightly combined in the fiber reinforced polymer composite film provided by the present invention, and the interface bonding strength of glass fiber and fluoropolymer matrix is ​​large and interface toughness is good, and composite film surface defects are less. As shown in Example 1 and Example 6-8, along with the increase of the content of rare earth metal elements in the modifier, the reinforcement effect on glass fiber fabric is a trend of first increasing and then decreasing. Comparative Example 1 adopts existing silane coupling agent to carry out surface modification on glass fiber fabric, although there is a certain reinforcement effect on fiber fabric, the fracture strength of the modified glass fiber fabric obtained and the composite film finally obtained are all significantly less than the fracture strength of the modified glass fiber fabric obtained by Example 1 and the composite film finally obtained, as can be seen from the comparison that fiber fabric is modified by adopting silane coupling agent, the fluoropolymer emulsion comprising rare earth metal salts of the present invention is adopted to modify glass fiber fabric to have better reinforcement effect on glass fiber fabric, while being more conducive to promoting the interface bonding strength and interface toughness of glass fiber and fluoropolymer matrix. In Comparative Example 2, a fluorine-containing polymer emulsion (without adding rare earth metal salt) was used to modify the surface of the glass fiber fabric. Although the strength of the fiber fabric was increased, the fracture strength of the modified glass fiber fabric and the composite membrane obtained were significantly lower than the fracture strength of the modified glass fiber fabric and the composite membrane obtained in Comparative Example 1 and Example 1.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A fiber-reinforced polymer composite film, characterized in that, The composite film comprises a fiber reinforcement and a polymer matrix; The fiber reinforcement is a modified glass fiber fabric; the modified glass fiber fabric is a glass fiber fabric with a modified layer coated on the fiber surface; the modified layer contains rare earth metal salts and fluoropolymers; The polymer matrix at least comprises a fluoropolymer.

2. The composite film according to claim 1, wherein The diameter of the glass fibers in the glass fiber fabric is 2-7 μm; and / or The mass ratio of the rare earth metal element to the fluoropolymer in the rare earth metal salt is 0.2-5:30-60, preferably 0.2-3:30-60; preferably, the rare earth metal salt is at least one of lanthanum salts and cerium salts, preferably one or more of lanthanum nitrate, cerium nitrate, cerium chloride, lanthanum chloride, cerium oxide, and lanthanum oxide; preferably, the fluoropolymer at least comprises polytetrafluoroethylene.

3. The composite film according to claim 2, wherein The fluoropolymer further comprises one or more of perfluoroalkyl vinyl ether, polyhexafluoropropylene, fluorinated ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, perfluoropropylene-vinyl ether, perfluoropropylene-vinyl ether, and perfluoromethyl vinyl ether.

4. The composite film according to claim 1, wherein The percentage of the open pore area of the glass fiber fabric is 20-50%; The grammage of the glass fiber fabric is 300 to 1500 g / m 2 ; and / or The thickness of the polymer matrix is not less than 0.05 mm.

5. A method for preparing the fiber-reinforced polymer composite film according to any one of claims 1-4, characterized in that, The preparation method comprises the following steps: S1. Placing the glass fiber fabric in an aqueous amylase solution, and performing a water washing treatment to obtain a water-washed glass fiber fabric; S2. Modifying the water-washed glass fiber fabric with a modifier to obtain a modified glass fiber fabric; the modifier is an emulsion of a fluoropolymer containing rare earth metal salts; S3. Immersing the modified glass fiber fabric in a fluoropolymer emulsion, and performing a heat treatment to obtain a film material; S4. Repeating step S3 until the weight gain of the film material meets the requirements to obtain the fiber-reinforced polymer composite film.

6. The preparation method according to claim 5, characterized in that, The water washing treatment is performed by ultrasonic wave at 30-80 °C; preferably, the frequency of the ultrasonic wave is 5-100 KHz.

7. The preparation method according to claim 5, wherein The rare earth metal element in the modifier accounts for 0.2-5 wt%, preferably 0.2-3 wt%, and the fluoropolymer accounts for 30-60 wt%.

8. The preparation method according to claim 5, characterized in that, The concentration of the aqueous amylase solution is 0.1-5 wt%, preferably, the amylase is at least one of α-amylase, β-amylase, γ-amylase, and isoamylase; and / or The content of the fluoropolymer in the fluoropolymer emulsion is 30-50%, preferably 38-45%.

9. The preparation method according to claim 5, characterized in that, The heat treatment includes drying, baking, and sintering; Preferably, the temperature of the drying is 100-200 °C; Preferably, the temperature of the baking is 210-330 °C; Preferably, the temperature of the sintering is 350-380 °C.

10. The preparation method according to claim 5, characterized in that, The weight gain of the film material meeting the requirements means that the weight of the film material obtained in the last step S4 is not less than 1.5 times the weight of the glass fiber fabric, preferably, the weight of the film material obtained in the last step S4 is 1.5-2.9 times the weight of the glass fiber fabric.

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