Composite material for waterproof breathable film and preparation method of composite material

Abstract

The invention relates to the technical field of composite materials, in particular to a composite material for a waterproof breathable film and a preparation method of the composite material. The composite material for the waterproof breathable film comprises the following raw materials: PTFE resin, zinc oxide, a surfactant, a compatibilizer and a waterproof filler, the waterproof filler is a porous inorganic carrier material treated by a silane modified waterproof agent; the silane modified waterproof agent is a compound containing a perfluoropolyether chain segment and a siloxane chain segment. According to the prepared composite material for the waterproof and breathable film, the porous filler is subjected to surface modification through the perfluoropolyether-silane coupling agent, and the waterproofness, breathability and mechanical property of the PTFE composite material can be synchronously and synergistically improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a composite material for waterproof and breathable membrane and a preparation method thereof. BACKGROUND

[0002] With the development of consumer electronics, wearable devices, 5G communication devices and the like towards miniaturization, high integration and high reliability, the protection requirements for internal components are increasingly improved. As a key functional component for balancing the air pressure inside and outside the device and preventing water vapor from entering, the waterproof and breathable membrane needs to maintain stable performance under extreme humidity, temperature changes and long-term use conditions. At present, although the microporous membrane material represented by PTFE has certain waterproof and breathable ability, it is still difficult to meet the high requirements of high-end electronic products for long-term protection and material stability.

[0003] The existing waterproof and breathable materials for electronic devices mostly use ordinary PTFE membranes or composite inorganic fillers on the basis of modification. However, conventional fillers such as untreated zinc oxide and diatomite have poor compatibility with the polymer matrix, and are prone to aggregation during processing and use, resulting in uneven pore size distribution, decreased mechanical strength, and even local water leakage defects. In addition, although the porous carriers modified by ordinary silane treatment agents can improve the hydrophobicity to a certain extent, their environmental aging resistance and chemical stability are limited, and they are difficult to cope with the complex chemical environment inside the electronic device and the long-term high-humidity and high-temperature working conditions, which restricts the promotion and application of such materials in high-end electronic products.

[0004] In view of the above problems, researchers have been working on developing new composite systems and surface modification technologies in recent years, aiming to optimize the interfacial properties and dispersion state of fillers to improve the comprehensive performance of membrane materials. In this context, the present application proposes to use a compound containing perfluoropolyether chain segments and siloxane chain segments to modify the surface of porous inorganic carriers, and to composite it with PTFE resin and other matrix materials, in order to significantly improve the durability, environmental adaptability and mechanical stability of the waterproof and breathable membrane for electronic devices, and meet the urgent needs of the next generation of electronic products for high-performance protective materials. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a composite material for waterproof and breathable membrane and a preparation method thereof.

[0006] To solve the above technical problems, the technical solution adopted by the present application is:

[0007] A composite material for waterproof and breathable membrane, comprising the following components: PTFE resin, zinc oxide, surfactant, compatibilizer and waterproof filler.

[0008] The waterproof filler is a porous inorganic carrier material treated with a silane-modified waterproof agent.

[0009] The silane-modified waterproof agent is a compound containing a perfluoropolyether chain segment and a siloxane chain segment.

[0010] Preferably, the waterproof and breathable membrane composite material comprises the following raw materials: 45-80 parts by weight of PTFE resin, 15-30 parts by weight of zinc oxide, 10-20 parts by weight of waterproof filler, 2-5 parts by weight of surfactant, and 1-3 parts by weight of solubilizer.

[0011] The surfactant is any one of sodium lauryl sulfate, sodium olefin sulfonate, sodium lauroyl amino acid, Tween 80, and cetyltrimethylammonium bromide.

[0012] The compatibilizer is at least one of styrene-maleic anhydride copolymer, styrene-acrylonitrile-maleic anhydride copolymer, and ethylene-vinyl acetate copolymer.

[0013] Although the conventional PTFE membrane has good air permeability, its micropores are easily wetted by water vapor or blocked by pollutants during long-term use, resulting in waterproof failure and air permeability decline; simply blending inorganic fillers easily causes agglomeration due to poor interfacial compatibility, thereby damaging the uniformity of the membrane structure and the mechanical properties. The surface of the unmodified porous inorganic filler is hydrophilic, which can absorb water and guide the flow through capillary action, seriously damaging the waterproof property. The special silane-modified porous waterproof filler added in the present application is just to solve the above two problems: its super-hydrophobic surface can resist water vapor intrusion and protect the membrane pores from being blocked; and its good compatibility with the PTFE matrix avoids stress defects and even enhances the mechanical durability of the material, finally realizing the synergistic improvement of waterproofness, air permeability, and reliability.

[0014] A preparation method of a waterproof filler for the waterproof and breathable membrane composite material, comprising the following steps:

[0015] S1, preparation of a silane-modified waterproof agent: dissolving perfluoropolyether carboxylic acid in a fluorine-containing solvent, reacting with an acyl chloride reagent, and then reacting with an organic silicon compound containing at least two amino groups in the presence of a dehydrating agent, and after purification, the silane-modified waterproof agent is obtained;

[0016] S2, preparation of a waterproof filler: mixing a porous inorganic carrier material with a treatment liquid containing a surfactant for pretreatment, and then adding the silane-modified waterproof agent obtained in step S1 for reaction, and after treatment, the waterproof filler is obtained.

[0017] Specifically, the reaction mechanism of the waterproof filler is as follows: S1, preparation of silane-modified waterproof agent: using hexafluoroisopropanol as solvent, acyl chloride reaction of terminal carboxyl of perfluoropolyether carboxylic acid with oxalyl chloride to generate high-reactivity perfluoropolyether acyl chloride; using high-reactivity perfluoropolyether acyl chloride and bis-amino organosilicon compound as main raw materials, amidation condensation reaction is carried out in the presence of dehydrating agent dicyclohexyl carbodiimide in N,N-dimethylformamide medium to obtain silane-modified waterproof agent, which not only retains the extremely low surface energy characteristics of perfluoropolyether segment, but also has the reactivity of silane coupling agent; S2, preparation of waterproof filler: porous inorganic carrier material is treated in the treatment liquid to improve the dispersion performance of the porous inorganic carrier material, and then the silane-modified waterproof agent is added, and under the condition of heating and stirring, chemical reaction occurs between the terminal active silane groups -Si-OR' or -NH2 and the silicon hydroxyl groups on the surface of the porous inorganic carrier material diatomite and zeolite powder, and finally the waterproof filler with waterproof performance grafted on the surface is obtained.

[0018] Preferably, the preparation method of the waterproof filler is as follows:

[0019] S1, preparation of silane-modified waterproof agent: 12-20 parts by weight of perfluoropolyether carboxylic acid, 38-60 parts by weight of hexafluoroisopropanol are mixed, stirred at room temperature at 300-500 rpm for 10-30 min; then 1-3 parts by weight of oxalyl chloride is added, reacted at 60-75°C and 300-800 rpm for 4-10 h, and the solvent is removed by reduced pressure distillation; then 6-12 parts by weight of organosilicon compound containing at least two amino groups, 50-100 parts by weight of N,N-dimethylformamide and 2-7 parts by weight of dicyclohexyl carbodiimide are added, stirred at 60-70°C and 400-800 rpm for 3-9 h; the N,N-dimethylformamide solvent is removed by reduced pressure distillation to obtain the silane-modified waterproof agent;

[0020] S2, preparation of waterproof filler: 10-20 parts by weight of porous inorganic carrier material is mixed with 80-140 parts by weight of treatment liquid, stirred at 50-70°C and 300-500 rpm for 20-50 min; then 3-6 parts by weight of the above-mentioned silane-modified waterproof agent is added, and the stirring is continued at 50-70°C and 300-500 rpm for 1-4 h, and then the waterproof filler is obtained by filtration, washing and drying.

[0021] In the step S1, the organosilicon compound containing at least two amino groups is bis-amino alkyl terminated silane or siloxane.

[0022] In the step S2, the treatment liquid comprises organic alcohol aqueous solution, non-ionic surfactant and anionic surfactant; preferably, the treatment liquid is composed of 80-100 parts by weight of 30-50 wt% ethanol aqueous solution, 2-6 parts by weight of dodecyl glycoside and 1-4 parts by weight of sodium dodecyl benzene sulfonate.

[0023] In the step S2, the porous inorganic carrier material is at least one of diatomite, zeolite powder, and titanium dioxide.

[0024] The present application effectively solves the long-term problems of traditional waterproof and breathable materials in durability, stability and multifunctional balance by introducing the modified waterproof filler into the PTFE composite system. First, the modified filler significantly enhances the persistent waterproofness and high breathability of the material: the perfluoropolyether chain segment on its surface forms a super-hydrophobic barrier with extremely low surface energy, which maximizes the water droplet contact angle and makes it difficult to wet and penetrate; more importantly, the modified layer is firmly anchored to the surface of the porous inorganic carrier by covalent bonding, avoiding the problem of easy migration and shedding of the physical coating layer, so that the waterproof performance remains stable under long-term use, thermal mechanical processing and humid heat aging environment. At the same time, this modification strategy only chemically modifies the surface of the filler, and the rich multi-level pore structure inside is completely preserved, not only does not block the original gas diffusion path, but also cooperates with the micropores in the PTFE matrix to build an efficient water vapor transmission channel, achieving the maintenance or even enhancement of breathability. In addition, the organic silane and perfluoropolyether chain segment introduced on the surface of the filler have good chemical compatibility with PTFE resin, effectively improving the interfacial compatibility problem between traditional inorganic filler and polymer matrix, promoting the uniform dispersion of the filler in the resin, and avoiding problems such as local stress concentration, mechanical property degradation and weak waterproof points caused by agglomeration.

[0025] Secondly, the comprehensive mechanical properties and environmental adaptability of the composite material are also significantly improved. The reinforcement of the filler and matrix interface helps to achieve effective stress transfer, making the composite material perform better in terms of tensile strength, tear strength and toughness, prolonging the service life of the material. The inherent excellent chemical inertness, high temperature resistance and aging resistance of the perfluoropolyether chain segment enable the final product to cope with harsh environmental conditions inside electronic devices, such as high temperature operating environment and temperature and humidity cycle changes, ensuring the long-term reliability of the protection function. In summary, the pore structure in the PTFE matrix of the present application gives a piece of persistent, breathable and water-repellent "protective clothing", successfully breaking through the traditional contradiction between waterproofness and breathability, while strengthening the mechanical properties and durability of the material, providing an important solution for the development of high-end electronic device protection materials.

[0026] The preparation method of the waterproof and breathable film composite material comprises the following steps: mixing and stirring zinc oxide, waterproof filler, surfactant, solubilizer and PTFE resin uniformly to obtain a premix, then feeding the premix into a banbury mixer for banburying and extruding and granulating to obtain the waterproof and breathable film composite material.

[0027] Preferably, the banburying conditions are: banburying at a temperature of 140-170℃ for 7-15min.

[0028] The beneficial effects of the present application: 1. The present application provides a composite material for waterproof and breathable membrane and a preparation method thereof. The present application fundamentally solves the technical contradiction that the waterproofness and breathability of the material are difficult to be considered by grafting modification of the surface of the porous inorganic filler with specific compounds containing perfluoropolyether chain segments and siloxane chain segments. A stable super-hydrophobic layer is formed on the surface of the modified filler, and the water contact angle can reach more than 157°, effectively blocking the penetration of liquid water; at the same time, the porous structure inside the filler is completely retained, and the continuous gas channel is formed with the PTFE matrix micropore, so that the oxygen permeability of the composite material is maintained at more than 4000 cm³ / m 2 .24h.atm. The modified layer is anchored on the surface of the filler by covalent bond, which overcomes the problem of easy migration and falling of physical coating, and gives the material durable and reliable waterproof and breathable performance.

[0029] 2. The organic fluorinated layer on the surface of the modified filler of the present application has excellent compatibility with PTFE resin, effectively improves the interfacial bonding of inorganic filler and polymer matrix, avoids the stress concentration defects caused by agglomeration of unmodified filler. The tensile strength of the composite material is significantly improved, so that it can still maintain structural integrity and functionality under long-term use or complex stress environment, greatly prolonging the service life.

[0030] 3. The composite material prepared by the present application shows excellent environmental adaptability and chemical stability, especially suitable for the harsh protection needs of high-end electronic devices. The material system has good process applicability and formula expandability, and the type and amount of filler carrier can be adjusted according to the actual application requirements, providing a new material solution for realizing high-performance protection of electronic devices. DETAILED DESCRIPTION

[0031] The above summary of the present application will be further described in detail in conjunction with the specific embodiments, but it should not be understood that the scope of the above subject matter of the present application is limited to the following examples.

[0032] In this application, some raw materials are introduced, and other materials are not introduced.

[0033] Perfluoropolyether carboxylic acid is purchased from Wuhan Lalanbai Pharmaceutical Chemical Co., Ltd., model number: LLB51798335, molecular weight: 3000 g / mol.

[0034] Styrene-maleic anhydride copolymer is purchased from Wuhan Kangqiong Biological Medicine Technology Co., Ltd., model number: kq-051.

[0035] PTFE resin is purchased from Dongguan Shangjin New Material Technology Co., Ltd., brand EK-3798M21R.

[0036] Zeolite powder was purchased from Hebei Hengguang Mineral Products Co., Ltd., particle size: 325 mesh.

[0037] Titanium dioxide was purchased from Dongguan Tuonuo Titanium Industry Co., Ltd., model: TYR-568.

[0038] Diatomite was purchased from Lingshou County Huanlun Mineral Product Processing Factory, particle size: 325 mesh.

[0039] Example 1

[0040] A composite material for waterproof and breathable membrane was composed of the following raw materials by weight: 25 parts by weight of zinc oxide, 15 parts by weight of waterproof filler, 3 parts by weight of surfactant, 2 parts by weight of solubilizing agent, and 55 parts by weight of PTFE resin.

[0041] The preparation method of the waterproof filler is as follows:

[0042] S1, 16 parts by weight of perfluoropolyether carboxylic acid, 45 parts by weight of hexafluoroisopropanol were mixed, stirred at room temperature at 400 rpm for 20 min; then 2 parts by weight of oxalyl chloride was added, reacted at 65℃, 500 rpm for 6h, and the solvent was removed by reduced pressure distillation; then 9 parts by weight of 1,3-bis(ammonia propane) tetramethyl disiloxane, 60 parts by weight of N,N-dimethylformamide and 5 parts by weight of dicyclohexyl carbodiimide were added, stirred at 65℃, 600 rpm for 6h; N,N-dimethylformamide solvent was removed by reduced pressure distillation to obtain silane modified waterproof agent;

[0043] S2, 15 parts by weight of porous inorganic carrier material was mixed with 100 parts by weight of treatment liquid, stirred at 60℃, 400 rpm for 30 min; then 4 parts by weight of the above silane modified waterproof agent was added, and continued to stir at 60℃, 400 rpm for 2.5h, filtered, washed, dried to obtain waterproof filler; the treatment liquid was composed of 95 parts by weight of 40wt% ethanol aqueous solution, 3 parts by weight of dodecyl glucoside and 2 parts by weight of sodium dodecyl benzene sulfonate; the porous inorganic carrier material was diatomite.

[0044] The surfactant was composed of sodium lauroyl amino acid, Tween 80, cetyltrimethylammonium bromide according to the mass ratio of 1:1:1.

[0045] The solubilizing agent was styrene-maleic anhydride copolymer.

[0046] The preparation method of the waterproof and breathable membrane composite material, zinc oxide, waterproof filler, surfactant, solubilizing agent, PTFE resin were mixed and stirred uniformly to obtain a premix, then it was put into a 160℃ internal mixer for 10 min of internal mixing, extruded and granulated to obtain the waterproof and breathable membrane composite material.

[0047] Example 2

[0048] The difference between the example 1 and the example 2 is that the preparation method of the waterproof filler is as follows:

[0049] S1, 16 parts by weight of perfluoropolyether carboxylic acid, 45 parts by weight of hexafluoroisopropanol were mixed, stirred at room temperature for 20 min at 400 rpm; then 2 parts by weight of oxalyl chloride was added, reacted at 65℃ for 6h at 500 rpm, and the solvent was removed by distillation under reduced pressure; then 9 parts by weight of KH-550, 60 parts by weight of N,N-dimethylformamide and 5 parts by weight of dicyclohexyl carbodiimide were added, and stirred at 65℃ for 6h at 600 rpm; the N,N-dimethylformamide solvent was removed by distillation under reduced pressure to obtain a silane modified waterproof agent;

[0050] S2, 15 parts by weight of diatomite was mixed with 100 parts by weight of treatment liquid, stirred at 60℃ for 30 min at 400 rpm; then 4 parts by weight of the above silane modified waterproof agent was added, and continued to be stirred at 60℃ for 2.5h at 400 rpm, filtered, washed and dried to obtain a waterproof filler; the treatment liquid was composed of 95 parts by weight of 40wt% ethanol aqueous solution, 3 parts by weight of dodecyl glucoside and 2 parts by weight of sodium dodecyl benzene sulfonate. The surfactant was composed of sodium lauroyl amino acid, Tween 80 and cetyltrimethylammonium bromide according to a mass ratio of 1:1:1.

[0051] Example 3

[0052] The difference between the example 1 and the example 2 is that the preparation method of the waterproof filler is as follows:

[0053] S1, 16 parts by weight of perfluoropolyether carboxylic acid, 45 parts by weight of hexafluoroisopropanol were mixed, stirred at room temperature for 20 min at 400 rpm; then 2 parts by weight of oxalyl chloride was added, reacted at 65℃ for 6h at 500 rpm, and the solvent was removed by distillation under reduced pressure; then 9 parts by weight of KH-550, 60 parts by weight of N,N-dimethylformamide and 5 parts by weight of dicyclohexyl carbodiimide were added, and stirred at 65℃ for 6h at 600 rpm; the N,N-dimethylformamide solvent was removed by distillation under reduced pressure to obtain a silane modified waterproof agent;

[0054] S2, 15 parts by weight of diatomite was mixed with 100 parts by weight of treatment liquid, stirred at 60℃ for 30 min at 400 rpm; then 4 parts by weight of the above silane modified waterproof agent was added, and continued to be stirred at 60℃ for 2.5h at 400 rpm, filtered, washed and dried to obtain a waterproof filler; the treatment liquid was composed of 95 parts by weight of 40wt% ethanol aqueous solution, 3 parts by weight of dodecyl glucoside and 2 parts by weight of sodium dodecyl benzene sulfonate.

[0055] Example 4

[0056] The same as example 1, except that the waterproof filler is 10 parts by weight of the waterproof filler.

[0057] The waterproof filler is prepared in the same way as in example 1.

[0058] Example 5

[0059] The same as example 1, except that the waterproof filler is 20 parts by weight of the waterproof filler.

[0060] The waterproof filler is prepared in the same way as in example 1.

[0061] Example 6

[0062] The same as example 1, except that the porous inorganic carrier material is zeolite powder.

[0063] Example 7

[0064] The same as example 1, except that the porous inorganic carrier material is titanium dioxide.

[0065] Example 8

[0066] The same as example 1, except that in the preparation method of the waterproof filler, the dicyclohexyl carbodiimide in S1 is replaced by 1,1'-carbonyldiimidazole.

[0067] Example 9

[0068] The same as example 1, except that in the preparation method of the waterproof filler, the dicyclohexyl carbodiimide in S1 is replaced by diisopropyl carbodiimide.

[0069] Comparative example 1

[0070] The same as example 1, except that the waterproof filler is diatomite.

[0071] Comparative example 2

[0072] A composite material for a waterproof and breathable film, consisting of the following parts by weight of raw materials: 25 parts by weight of zinc oxide, 15 parts by weight of waterproof filler, 3 parts by weight of surfactant, 2 parts by weight of solubilizer, 55 parts by weight of PTFE resin.

[0073] The preparation method of the waterproof filler is as follows:

[0074] Mix 15 parts by weight of diatomite with 100 parts by weight of treatment liquid, stir at 60℃, 400rpm for 30min; then add 4 parts by weight of 1,3-bis(amino propane alkyl) tetramethyl disiloxane, continue to stir at 60℃, 400rpm for 2.5h, filter, wash, dry to obtain waterproof filler; the treatment liquid is composed of 95 parts by weight of 40wt% ethanol aqueous solution, 3 parts by weight of dodecyl glycoside and 2 parts by weight of sodium dodecyl benzene sulfonate.

[0075] The surfactant is composed of sodium lauroyl amino acid, Tween 80 and cetyltrimethylammonium bromide according to a mass ratio of 1:1:1.

[0076] The compatibilizer is styrene-maleic anhydride copolymer.

[0077] The preparation method of the waterproof and breathable film composite material comprises the following steps: mixing and stirring zinc oxide, waterproof filler, surfactant, solubilizer and PTFE resin uniformly to obtain a premix, and then feeding the premix into a 160℃ banbury mixer for banburying for 10min, and then extruding and granulating to obtain the waterproof and breathable film composite material.

[0078] Comparative example 3

[0079] A waterproof and breathable film composite material is composed of the following raw materials in parts by weight: 25 parts by weight of zinc oxide, 15 parts by weight of waterproof filler, 3 parts by weight of surfactant, 2 parts by weight of solubilizer and 55 parts by weight of PTFE resin.

[0080] The preparation method of the waterproof filler is as follows:

[0081] S1, mix 16 parts by weight of perfluoropolyether carboxylic acid and 45 parts by weight of hexafluoroisopropanol, stir at room temperature, 400rpm for 20min; then add 2 parts by weight of oxalyl chloride, react at 65℃, 500rpm for 6h, and remove the solvent by distillation under reduced pressure; then add 9 parts by weight of 1,3-bis(amino propane alkyl) tetramethyl disiloxane, 60 parts by weight of N,N-dimethylformamide and 5 parts by weight of dicyclohexyl carbodiimide, stir at 65℃, 600rpm for 6h; remove the N,N-dimethylformamide solvent by distillation under reduced pressure to obtain a silane modified waterproof agent;

[0082] S2, mix 15 parts by weight of diatomite with 100 parts by weight of 40wt% ethanol aqueous solution, stir at 60℃, 400rpm for 30min; then add 4 parts by weight of the silane modified waterproof agent, continue to stir at 60℃, 400rpm for 2.5h, filter, wash, dry to obtain the waterproof filler.

[0083] The surfactant is composed of sodium lauroyl amino acid, Tween 80 and cetyltrimethylammonium bromide according to a mass ratio of 1:1:1.

[0084] The compatibilizer is a styrene-maleic anhydride copolymer.

[0085] The preparation method of the waterproof and breathable film composite material is as follows: zinc oxide, waterproof filler, surfactant, solubilizer and PTFE resin are uniformly mixed and stirred to obtain a premix, and then the premix is fed into a 160℃ banbury mixer for banburying for 10 minutes, and then extruded and granulated to obtain the waterproof and breathable film composite material.

[0086] Comparative Example 4

[0087] The waterproof filler is 8 parts by weight of waterproof filler, which is substantially the same as Example 1, except that the waterproof filler is 8 parts by weight of waterproof filler.

[0088] The preparation method of the waterproof filler is the same as that of Example 1.

[0089] Comparative Example 5

[0090] The waterproof filler is 25 parts by weight of waterproof filler, which is substantially the same as Example 1, except that the waterproof filler is 25 parts by weight of waterproof filler.

[0091] The preparation method of the waterproof filler is the same as that of Example 1.

[0092] Test Example 1

[0093] Breathability test: The waterproof and breathable film composite material prepared in Examples 1-7 and Comparative Examples 1-5 above is prepared into a test standard film sample, and the obtained standard film sample is tested for breathability, 5 times for each test, and the average value is taken, and the results are shown in Table 1.

[0094] Waterproof performance test: The prepared waterproof and breathable film composite material is fixed on a glass slide by double-sided tape, 5 μL of water is measured on five positions of each sample at room temperature by using a contact angle measuring instrument (Powereach JC2000D1), and the average value is calculated to obtain the water contact angle, 5 times for each test, and the average value is taken, and the results are shown in Table 1.

[0095] Table 1: Test results of waterproof and breathable film composite material

[0096] oxygen transmission, cm 3 / m 2 .24 h. atm Water contact angle Example 1 4012 157.3° Example 2 3862 151.4° Example 3 3729 148.4° Example 4 3924 153.2° Example 5 3868 151.8° Example 6 3973 155.6° Example 7 3892 150.1° Example 8 4368 158.2 Example 9 3924 151.8 Comparative Example 1 2376 89.6° Comparative Example 2 2943 130° Comparative Example 3 3569 145° Comparative Example 4 3053 135° Comparative Example 5 3495 148°

[0097] Test Example 2

[0098] Tensile property test: The test was performed according to the method of national standard GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: test conditions"; the waterproof and breathable film composite material prepared in each of the above examples and comparative examples was injection molded by an injection molding machine for composite materials, the test sample was a dumbbell-shaped 1A type with a thickness of 4 mm, the test speed was 1 mm / min, there were 5 groups in parallel, and the average value was taken, and the results are shown in Table 2.

[0099] Table 2 Mechanical property test of waterproof and breathable film composite material

[0100] Tensile strength (MPa) Example 1 186.4 Example 2 180.1 Example 3 177.9 Example 4 178.5 Example 5 180.6 Example 6 183.6 Example 7 176.8 Example 8 187.3 Example 9 181.4 Comparative Example 1 127.3 Comparative Example 2 161.1 Comparative Example 3 171.3 Comparative Example 4 163.4 Comparative Example 5 173.9

[0101] From the above experimental results, it can be seen that the waterproof and breathable film composite material prepared by the present application can simultaneously and synergistically improve the waterproofness, air permeability and mechanical properties of the PTFE composite material by surface modification of the porous filler with perfluoropolyether-silane coupling agent. The specific analysis is as follows: the performance of Example 1 and Comparative Example 1 using unmodified filler is poor: the former realizes the perfect combination of a super-hydrophobic contact angle of 157.3° and a high air permeability oxygen transmission rate of 4012 cm³ / m²·24h·atm, and the tensile strength of 186.4 MPa is significantly higher than the tensile strength of 127.3 MPa of Comparative Example 1. The reason is that the hydrophilic diatomite filler in Comparative Example 1 not only has poor compatibility with the PTFE matrix, resulting in interface defects and stress concentration, but also the surface hydroxyl group can absorb water molecules, inducing pore blockage through capillary force, thereby simultaneously degrading the waterproofness and air permeability.

[0102] In further comparison of Examples 1-3, Example 1 has the best performance, with a water contact angle of 157.3°, an oxygen transmission rate of 4012 cm³ / m²·24h·atm, and a tensile strength of 186.4 MPa, all of which are higher than the modification effects of Example 2 using KH-550 and Example 3 using 3-(methacryloyloxy)propyltrimethoxysilane. The fundamental reason is that the 1,3-bis(aminopropanol)tetramethyldisiloxane molecular structure contains both amino groups and siloxane bonds, which can form stable multi-point covalent bonds with perfluoropolyether acid chloride and the surface hydroxyl group of the filler, greatly enhancing the durability of the super-hydrophobic layer; the flexible siloxane segment effectively buffers the interface stress, avoiding rigid interface defects, thereby synergistically improving the mechanical strength and waterproofness of the material; at the same time, the structure ensures good compatibility and dispersion of the modified filler with the PTFE matrix, maintaining the integrity and openness of the gas channel, so that the air permeability is maintained, while KH-550 and 3-(methacryloyloxy)propyltrimethoxysilane have limitations in molecular structure, and have deficiencies in tensile strength, flexibility and compatibility, so the modification effect is slightly inferior.

[0103] Comparative Example 1 and Examples 8-9 can be seen that the replacement of dicyclohexyl carbodiimide with 1,1'-carbonyldiimidazole significantly improves the oxygen transmission rate, while the water contact angle and tensile strength are basically maintained. The reason is that the condensation by-product affects the cleanliness of the carrier surface and pore: when dicyclohexyl carbodiimide or diisopropyl carbodiimide is used, insoluble dicyclohexyl urea or N,N'-diisopropyl urea is easily formed on the pore opening and rough surface of diatomite to induce secondary agglomeration of particles, thereby causing uneven grafting density and spatial distribution of perfluoropolyether-silane coupling molecules on the carrier surface, partial pore blockage, and more dense packing of composite particles in the polytetrafluoroethylene matrix, which reduces the effective connected area of the series micro-pore channel, thereby limiting gas diffusion; when 1,1'-carbonyldiimidazole is used, the carboxylic acid first forms an acylimidazole intermediate, and the by-product is imidazole, which can be washed with water, the residual is significantly reduced, the pore opening is cleaner, the grafting is more uniform, and the dispersion of composite particles in the matrix is more loose and ordered, which makes the micro-pore channel more unobstructed, so the oxygen transmission rate increases; at the same time, the surface superhydrophobicity is mainly provided by the perfluoropolyether segment, the chemical composition and surface energy are unchanged, and the water contact angle remains in the superhydrophobic interval; the reduction of interface contamination is also conducive to the consistency of stress transmission, so that the tensile strength is maintained or slightly improved.

[0104] On the contrary, the superior performance of Example 1 is attributed to the perfluoropolyether segment in the modifier providing extremely low interfacial energy for the filler surface, which is the fundamental reason for achieving superhydrophobicity; and the siloxane end forms a firm Si-O-Si covalent bond with the silanol on the filler surface through hydrolysis-condensation reaction, ensuring the durability of the superhydrophobic layer and avoiding the migration and shedding of the physical coating. More importantly, the modification only constructs a monolayer on the surface of the filler, and the multi-level pore structure inside is completely preserved, which is the key to maintaining or even enhancing the gas permeability. Gas molecules can freely pass through these unblocked pores, while liquid water is effectively blocked by the superhydrophobic layer on the surface. In addition, the organic / fluorinated layer on the modified filler surface has good compatibility with the PTFE matrix, which solves the interface incompatibility problem in Comparative Example 1. This enables the filler to disperse uniformly, avoid agglomeration, and form a strong bond with the matrix, thereby achieving effective stress transmission when stressed, significantly improving the macro-mechanical properties of the material.

[0105] Further comparison of Example 1 and Comparative Examples 2-5, Comparative Example 2 uses ordinary silane, and the modified filler has certain hydrophobicity and mechanical enhancement, but due to the lack of perfluoropolyether segment, it cannot achieve extremely low surface energy, so the water resistance is far inferior to the present application. Comparative Example 3 omits the pretreatment liquid, which proves that pretreatment is crucial to ensure the dispersion of the filler and expose more reaction sites to achieve uniform and dense modification, and its performance decreases due to incomplete modification. Comparative Examples 4-5 show that there is an optimal range of filler content, too low cannot form an effective network, and too high may cause filler agglomeration, which actually damages the performance.

Claims

1. A composite material for a waterproof and breathable membrane, characterized in that, Raw materials include the following components: PTFE resin, zinc oxide, surfactant, compatibilizer, and waterproof filler; The waterproof filler is a porous inorganic carrier material treated with a silane-modified waterproofing agent; The silane-modified waterproofing agent is a compound containing perfluoropolyether segments and siloxane segments.

2. The composite material for waterproof and breathable membranes as described in claim 1, characterized in that, By weight, it includes the following raw materials: 45-80 parts by weight of PTFE resin, 15-30 parts by weight of zinc oxide, 10-20 parts by weight of waterproof filler, 2-5 parts by weight of surfactant, and 1-3 parts by weight of solubilizer.

3. The composite material for waterproof and breathable membranes as described in claim 1 or 2, characterized in that, The surfactant is any one of sodium lauryl sulfate, sodium olefin sulfonate, sodium lauroyl sarcosinate, Tween 80, and cetyltrimethylammonium bromide.

4. The composite material for waterproof and breathable membranes as described in claim 1 or 2, characterized in that, The compatibilizer is at least one of styrene-maleic anhydride copolymer, styrene-acrylonitrile-maleic anhydride copolymer, and ethylene-vinyl acetate copolymer.

5. A method for preparing a waterproof filler for a composite material used in a waterproof and breathable membrane as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Preparation of silane-modified waterproofing agent: Perfluorinated polyether carboxylic acid is dissolved in a fluorinated solvent, reacted with an acyl chloride reagent, and then reacted with an organosilicon compound containing at least two amino groups in the presence of a dehydrating agent. After purification, the silane-modified waterproofing agent is obtained. S2. Preparation of waterproof filler: The porous inorganic carrier material is mixed with a treatment liquid containing a surfactant for pretreatment, and then the silane-modified waterproofing agent obtained in step S1 is added for reaction. After post-treatment, the waterproof filler is obtained.

6. The method for preparing the waterproof filler of the composite material for waterproof and breathable membranes as described in claim 5, characterized in that, In step S1, the organosilicon compound containing at least two amino groups is a diaminoalkyl-terminated silane or siloxane.

7. The method for preparing the waterproof filler of the composite material for waterproof and breathable membranes as described in claim 5, characterized in that, In step S2, the treatment solution includes an aqueous solution of organic alcohol, a nonionic surfactant, and an anionic surfactant.

8. The method for preparing the waterproof filler of the composite material for waterproof and breathable membranes as described in claim 5, characterized in that, In step S2, the porous inorganic carrier material is at least one of diatomaceous earth, zeolite powder, and titanium dioxide.

9. The method for preparing the waterproof and breathable membrane composite material according to any one of claims 1-4, characterized in that, The process includes the following steps: mixing zinc oxide, waterproof filler, surfactant, solubilizer, and PTFE resin evenly to obtain a premix; then feeding the premix into an internal mixer for internal mixing; and finally extruding and granulating to obtain a composite material for waterproof and breathable membranes.

10. The method for preparing the waterproof and breathable membrane composite material as described in claim 9, characterized in that, The mixing conditions are: mixing at a temperature of 140-170℃ for 7-15 minutes.