PBI crosslinking modified PET composite film and preparation method and application thereof
By adding PBI crosslinking agent and materials such as nano-aluminum phosphate and graphene to PET masterbatch to form a three-dimensional network structure, the corrosion problem of PET material in electrolyte environment is solved, the corrosion resistance and mechanical properties of battery separator are improved, and the service life is extended.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANGZHOU NANOPORE INNOVATIVE MATERIALS TECH LTD
- Filing Date
- 2026-03-16
- Publication Date
- 2026-06-05
AI Technical Summary
PET materials are easily corroded in electrolyte environments, leading to a decline in material performance and affecting the cycle life and safety of batteries.
By adding PBI as a crosslinking agent to PET masterbatch, a three-dimensional network structure is formed, which is then combined with functional materials such as nano-aluminum phosphate and graphene to form a synergistic effect and improve corrosion resistance.
It significantly improves the electrolyte corrosion resistance, mechanical properties and thermal stability of PET film, extends the service life of battery separators, and maintains good melt flowability and processing performance.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of battery separator technology, specifically to a PBI crosslinked modified PET composite film, its preparation method, and its application. Background Technology
[0002] In fields such as new energy batteries and chemical storage and transportation, PET (polyethylene terephthalate) materials are widely used due to their excellent mechanical properties, barrier properties, and processing performance. However, PET materials are prone to corrosion in electrolyte environments, leading to a decline in material performance and even posing safety hazards. For example, in lithium-ion batteries, organic solvents and fluorides in the electrolyte can corrode PET separators or packaging materials, affecting the battery's cycle life and safety.
[0003] Existing technologies improve the electrolyte corrosion resistance of PET by preparing a coating layer or performing composite modification on the PET surface. For example, patent CN115320206B improves corrosion resistance by constructing a multilayer polyester structure, but the effect is still not ideal. Therefore, this invention proposes a PBI crosslinked modified PET composite film, its preparation method, and its application to solve the above-mentioned technical problems. Summary of the Invention
[0004] The purpose of this invention is to provide a PBI crosslinked modified PET composite film, its preparation method, and its application, so as to solve the problems raised in the prior art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a PBI crosslinked modified PET composite film includes the following steps: S1: Mix PET masterbatch and PBI (polybenzimidazole) at 50~80℃ for 5~10min, melt blend at 260~280℃ and 200~400rpm, and extrude at 230~250℃ to obtain PBI crosslinked PET composite material. S2: The PBI crosslinked PET composite material is processed and shaped to obtain a PBI crosslinked modified PET composite film.
[0006] In the above technical solution, the PBI molecular backbone contains benzimidazole repeating units, exhibiting excellent heat resistance and chemical stability. During melt blending, PBI acts as a crosslinking agent, chemically crosslinking to form a three-dimensional network structure. This crosslinked structure effectively prevents corrosive substances in the electrolyte (such as organic solvents and fluorides) from penetrating into the PET material, thereby improving its corrosion resistance.
[0007] Furthermore, the mass ratio of PET masterbatch to PBI is (90~100): (1~10).
[0008] Furthermore, the PBI crosslinked PET composite material also contains 1-2 parts of antioxidant, 2-3 parts of lubricant, 15-20 parts of nano-aluminum phosphate, and 6-10 parts of graphene.
[0009] Furthermore, the antioxidant is 1010.
[0010] Furthermore, the lubricant is pentaerythritol stearate.
[0011] Furthermore, the viscosity of the PET masterbatch is 0.65~0.85 dL / g.
[0012] Furthermore, the molecular weight of the PBI is 50,000~100,000 g / mol.
[0013] Furthermore, in step S2, the specific process of the forming is as follows: by casting film, biaxial stretching, and heat setting, a nascent film is obtained, and then processed to obtain a PBI crosslinked modified PET composite film; the stretching temperature is 110~120℃, the stretching rate is 120~130mm / s, the heat setting temperature is 210~220℃, and the stretching ratio is 3:1.
[0014] Furthermore, the thickness of the PBI crosslinked modified PET composite film is 4.5~5.0μm.
[0015] Furthermore, the nano-aluminum phosphate undergoes surface modification, and the modification process is as follows: Step 1: Add nano-aluminum phosphate to an aminosilane coupling agent solution, disperse, react at 50~60℃ for 4~6h, centrifuge, wash, and dry to obtain aminated nano-aluminum phosphate; Step 2: Add aminated nano-aluminum phosphate to ethanol and disperse at 70~80℃. Then add maleic anhydride and heat to 110~120℃. React for 2~3 hours. After the reaction is complete, centrifuge and dry to obtain maleimide nano-aluminum phosphate. Step 3: Add maleimide nano-aluminum phosphate to DMF (N,N-dimethylformamide), disperse at high speed, add diallyl bisphenol A, stir evenly, react at 70~80℃ for 2~3h, then add diphenylmethane diisocyanate, continue stirring, after the reaction is completed, centrifuge, dry to obtain modified nano-aluminum phosphate.
[0016] Furthermore, in step one, the aminosilane coupling agent solution is a 20-25 vt% ethanol solution, and the ethanol solution is a 75-90 vt% deionized aqueous solution.
[0017] Furthermore, in step one, the aminosilane coupling agent is 3-aminopropyltriethoxysilane.
[0018] Furthermore, the mass ratio of the aminosilane coupling agent solution to nano-aluminum phosphate is (5~10):1.
[0019] Furthermore, the mass ratio of aminated nano-aluminum phosphate, maleic anhydride, and ethanol is 1:(1.2~2):20.
[0020] Furthermore, the mass ratio of diphenylmethane diisocyanate, diallyl bisphenol A, maleimide nano-aluminum phosphate, and DMF is 0.85∶1∶(1~3.5)∶20.
[0021] In the above technical solution, the present invention utilizes the hydrolysis of the methoxy group in the 3-aminopropyltriethoxysilane molecule to generate silanol groups. The silanol groups undergo a dehydration condensation reaction with the hydroxyl groups on the surface of nano-aluminum phosphate to form Si-O-Al or Si-OP covalent bonds. The amino group is grafted onto the surface of nano-aluminum phosphate to form active sites. The amino group undergoes an addition reaction with the anhydride ring in maleic anhydride, and the amino group attacks the carbonyl carbon of the anhydride to generate an imide bond. Then, diallyl bisphenol A is introduced, and its allyl group undergoes an addition reaction with the double bond in maleimide to generate a six-membered ring structure. The hydroxyl groups on the six-membered ring structure further react with isocyanate to form urethane, resulting in a composite nano-aluminum phosphate structure coated with an organic polymer. This significantly improves the thermal stability and flame retardancy of the filler nano-aluminum phosphate. The long chain structure in the polymer molecular chain forms a steric hindrance structure on the surface of the aluminum phosphate particles, which can effectively prevent secondary agglomeration of nanoparticles, improve dispersibility, and improve the compatibility of nano-aluminum phosphate with PET masterbatch during melt blending.
[0022] Furthermore, the graphene undergoes pretreatment before use, and the specific process is as follows: Step (1): Add aluminum oxide to Tris-dopamine hydrochloride solution and stir to react, to obtain polydopamine aluminum oxide; Step (2): Add graphene to tetrahydrofuran and disperse it at a high speed of 1200~2400r / min. Then add 3-aminopropyltriethoxysilane and react at 30~40℃ for 4~6h. Centrifuge, wash, and dry to obtain pretreated graphene. Step (3): Add pretreated graphene and polydopamine alumina to ethanol, stir to react, centrifuge, and dry to obtain Al2O3-graphene.
[0023] In the above technical solution, alumina has good wear resistance and thermal stability. Combining alumina with graphene can enhance the mechanical properties and thermal stability of graphene. Through dopamine self-polymerization, a polydopamine coating layer is formed on the surface of alumina. Then, the graphene is pretreated by grafting amino groups onto the surface of graphene. The amino groups further form hydrogen bonds with the catechol hydroxyl groups or amino groups on the surface of polydopamine, resulting in a composite structure of alumina and graphene. The strong adhesion of polydopamine firmly forms an interface layer on the surfaces of alumina and graphene, which can effectively transfer stress and enhance the mechanical properties of graphene. At high temperatures, polydopamine can carbonize to form a dense carbon layer, which has a synergistic effect with nano-aluminum phosphate, enhancing the flame retardant properties of PET masterbatch and extending the service life of battery separators. The organic composite structure formed by dopamine self-polymerization has a synergistic effect with the modified nano-aluminum phosphate, enhancing the chemical stability of PET masterbatch, while effectively inhibiting the secondary agglomeration of nano-aluminum phosphate, making the filler in PET masterbatch more uniformly dispersed and improving the interfacial bonding force.
[0024] Furthermore, the mass ratio of alumina to Tris-dopamine hydrochloride solution is (1~2):20.
[0025] Furthermore, the mass ratio of graphene, 3-aminopropyltriethoxysilane, and tetrahydrofuran is 1:(0.3~0.5):10.
[0026] Furthermore, the mass ratio of pretreated graphene, polydopamine alumina, and ethanol is (0.1~0.2):1:20.
[0027] Furthermore, the concentration of the Tris-dopamine hydrochloride solution is 10~12 mM.
[0028] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention modifies PET masterbatch by combining crosslinking agent PBI with PET masterbatch, thereby reducing the penetration of electrolyte into polymer chains and inhibiting hydrolysis and swelling. The high thermal stability of PBI may reduce the corrosion rate of electrolyte on PET at high temperatures, reducing the corrosion rate by more than 50% and extending the service life by 2 to 3 times.
[0029] 2. The modified PET material of this invention still maintains good melt flowability and processing performance, and is suitable for existing PET processing equipment.
[0030] 3. No toxic or harmful substances are used in the PET modification process of this invention, which meets environmental protection requirements.
[0031] 4. This invention utilizes 3-aminopropyltriethoxysilane to graft amino groups onto the surface of nano-aluminum phosphate, forming active sites. The amino groups undergo an addition reaction with the anhydride ring in maleic anhydride, and the amino groups attack the carbonyl carbon of the anhydride to generate an imide bond. Then, diallyl bisphenol A is introduced, and its allyl group undergoes an addition reaction with the double bond in maleimide to generate a six-membered ring structure. The hydroxyl groups on the six-membered ring structure further react with isocyanates to form urethane, resulting in a composite nano-aluminum phosphate structure coated with an organic polymer. This significantly improves the thermal stability and flame retardancy of the filler nano-aluminum phosphate. The long-chain structure in the polymer molecular chain forms a steric hindrance structure on the surface of the aluminum phosphate particles, which can effectively prevent secondary agglomeration of nanoparticles, improve dispersibility, and improve the compatibility of nano-aluminum phosphate with PET masterbatch during melt blending.
[0032] 5. This invention combines alumina and graphene. The strong adhesion properties of polydopamine firmly form an interface layer on the surfaces of alumina and graphene, effectively transferring stress and enhancing the mechanical properties of graphene. At high temperatures, polydopamine can carbonize to form a dense carbon layer, which synergistically interacts with nano-aluminum phosphate to enhance the flame retardant properties of PET masterbatch and extend the service life of battery separators. The organic composite structure formed by the self-polymerization of dopamine synergistically interacts with the modified nano-aluminum phosphate to enhance the chemical stability of PET masterbatch, while effectively inhibiting the secondary agglomeration of nano-aluminum phosphate, resulting in more uniform dispersion of fillers in PET masterbatch and improving interfacial bonding. Detailed Implementation
[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0034] In the following specific embodiments, unless otherwise specified, the number of “parts” refers to parts by mass; PET (polyethylene terephthalate) masterbatch, viscosity 0.65~0.85 dL / g, model XY53 from Toray Industries, Japan; Antioxidant, model 1010; The lubricant is pentaerythritol stearate; Nano aluminum phosphate, model JH-101; Alumina, type α-alumina, average particle size 100nm, purity ≥99%. Example 1:
[0035] A method for preparing a PBI crosslinked modified PET composite film includes the following steps: S1: PET masterbatch, PBI (polybenzimidazole), antioxidant, lubricant, nano aluminum phosphate, and graphene are mixed and stirred at 60°C for 8 minutes. The mixture is then melt-blended at 270°C and 300 rpm, and extruded at 230°C to obtain PBI crosslinked PET composite material; PBI molecular weight is 80000 g / mol. S2: PBI crosslinked PET composite material is cast into a film, biaxially stretched, and heat-set to obtain a nascent film. After further processing, a PBI crosslinked modified PET composite film with a thickness of 4.5 μm is obtained. The stretching temperature is 110℃, the stretching rate is 120 mm / s, the heat setting temperature is 210℃, and the stretching ratio is 3:1. PBI crosslinked PET composite material comprises the following components by weight: 90 parts PET masterbatch, 10 parts PBI, 1 part antioxidant, 2 parts lubricant, 15 parts nano aluminum phosphate, and 6 parts graphene. Example 2:
[0036] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The PBI crosslinked PET composite material includes the following components by mass: 93 parts of PET masterbatch, 7 parts of PBI, 1 part of antioxidant, 2 parts of lubricant, 15 parts of nano-aluminum phosphate, and 6 parts of graphene; the remaining methods are the same as in Example 1. Example 3:
[0037] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The PBI crosslinked PET composite material includes the following components by mass: 95 parts of PET masterbatch, 5 parts of PBI, 1 part of antioxidant, 2 parts of lubricant, 15 parts of nano-aluminum phosphate, and 6 parts of graphene; the remaining methods are the same as in Example 1. Example 4:
[0038] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The PBI crosslinked PET composite material includes the following components by mass: 97 parts of PET masterbatch, 3 parts of PBI, 1 part of antioxidant, 2 parts of lubricant, 15 parts of nano-aluminum phosphate, and 6 parts of graphene; the remaining methods are the same as in Example 1. Example 5:
[0039] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The PBI crosslinked PET composite material includes the following components by mass: 99 parts of PET masterbatch, 1 part of PBI, 1 part of antioxidant, 2 parts of lubricant, 15 parts of nano-aluminum phosphate, and 6 parts of graphene; the remaining methods are the same as in Example 1. Example 6:
[0040] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The molecular weight of PBI is 60000 g / mol, and the rest of the method is the same as in Example 3. Example 7:
[0041] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The molecular weight of PBI is 100,000 g / mol, and the rest of the method is the same as in Example 3. Example 8:
[0042] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The nano-aluminum phosphate undergoes surface modification, and the modification process is as follows: Step 1: Add nano-aluminum phosphate to aminosilane coupling agent solution, disperse, react at 50℃ for 4h, centrifuge, wash, and dry to obtain aminated nano-aluminum phosphate; the mass ratio of aminosilane coupling agent solution to nano-aluminum phosphate is 5:1; the aminosilane coupling agent solution is 20 vt% ethanol solution, and the ethanol solution is 80 vt% deionized water solution. Step 2: Add aminated nano-aluminum phosphate to ethanol and disperse at 70°C. Then add maleic anhydride and heat to 110°C. React for 2 hours. After the reaction is complete, centrifuge and dry to obtain maleimide nano-aluminum phosphate. The mass ratio of aminated nano-aluminum phosphate, maleic anhydride and ethanol is 1:1.2:20. Step 3: Add maleimide nano-aluminum phosphate to DMF and disperse at high speed. Add diallyl bisphenol A and stir until homogeneous. React at 70°C for 2 hours. Then add diphenylmethane diisocyanate and continue stirring. After the reaction is complete, centrifuge and dry to obtain modified nano-aluminum phosphate. The mass ratio of diphenylmethane diisocyanate, diallyl bisphenol A, maleimide nano-aluminum phosphate, and DMF is 0.85:1:1:20. Graphene undergoes pretreatment before use; the specific process is as follows: Step (1): Add alumina to Tris-dopamine hydrochloride solution and stir to react, to obtain polydopamine alumina; the mass ratio of alumina to Tris-dopamine hydrochloride solution is 1:20; Step (2): Add graphene to tetrahydrofuran and disperse it at a high speed of 1200 r / min. Then add 3-aminopropyltriethoxysilane and react at 30°C for 4 h. Centrifuge, wash, and dry to obtain pretreated graphene. The mass ratio of graphene, 3-aminopropyltriethoxysilane, and tetrahydrofuran is 1:0.3:10. Step (3): Add pretreated graphene and polydopamine alumina to ethanol, stir to react, centrifuge, and dry to obtain Al2O3-graphene; the mass ratio of pretreated graphene, polydopamine alumina, and ethanol is 0.1:1:20. The concentration of the Tris-dopamine hydrochloride solution was 10 mM; the rest of the methods were the same as in Example 1. Example 9:
[0043] This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The nano-aluminum phosphate undergoes surface modification, and the modification process is as follows: Step 1: Add nano-aluminum phosphate to aminosilane coupling agent solution, disperse, react at 50℃ for 4h, centrifuge, wash, and dry to obtain aminated nano-aluminum phosphate; the mass ratio of aminosilane coupling agent solution to nano-aluminum phosphate is 5:1; the aminosilane coupling agent solution is 20 vt% ethanol solution, and the ethanol solution is 80 vt% deionized water solution. Step 2: Add the aminated nano-aluminum phosphate to ethanol and disperse it at 80°C. Then add maleic anhydride, heat to 120°C, and react for 3 hours. After the reaction is complete, centrifuge and dry to obtain maleimide nano-aluminum phosphate. The mass ratio of aminated nano-aluminum phosphate, maleic anhydride, and ethanol is 1:2:20. Step 3: Add maleimide nano-aluminum phosphate to DMF and disperse at high speed. Add diallyl bisphenol A and stir until homogeneous. React at 80°C for 2 hours. Then add diphenylmethane diisocyanate and continue stirring. After the reaction is complete, centrifuge and dry to obtain modified nano-aluminum phosphate. The mass ratio of diphenylmethane diisocyanate, diallyl bisphenol A, maleimide nano-aluminum phosphate, and DMF is 0.85:1:2:20. Graphene undergoes pretreatment before use; the specific process is as follows: Step (1): Add alumina to Tris-dopamine hydrochloride solution and stir to react, to obtain polydopamine alumina; the mass ratio of alumina to Tris-dopamine hydrochloride solution is 1:20; Step (2): Add graphene to tetrahydrofuran and disperse it at a high speed of 2400 r / min. Then add 3-aminopropyltriethoxysilane and react at 40℃ for 6 h. Centrifuge, wash and dry to obtain pretreated graphene. The mass ratio of graphene, 3-aminopropyltriethoxysilane and tetrahydrofuran is 1:0.5:10. Step (3): Add pretreated graphene and polydopamine alumina to ethanol, stir to react, centrifuge, and dry to obtain Al2O3-graphene; the mass ratio of pretreated graphene, polydopamine alumina, and ethanol is 0.2:1:20. The concentration of the Tris-dopamine hydrochloride solution was 12 mM; the rest of the methods were the same as in Example 1.
[0044] Example 10: This embodiment provides a method for preparing a PBI crosslinked modified PET composite film. The nano-aluminum phosphate undergoes surface modification, and the modification process is as follows: Step 1: Add nano-aluminum phosphate to aminosilane coupling agent solution, disperse, react at 50℃ for 4h, centrifuge, wash, and dry to obtain aminated nano-aluminum phosphate; the mass ratio of aminosilane coupling agent solution to nano-aluminum phosphate is 5:1; the aminosilane coupling agent solution is 20 vt% ethanol solution, and the ethanol solution is 80 vt% deionized water solution. Step 2: Add the aminated nano-aluminum phosphate to ethanol and disperse it at 80°C. Then add maleic anhydride, heat to 120°C, and react for 3 hours. After the reaction is complete, centrifuge and dry to obtain maleimide nano-aluminum phosphate. The mass ratio of aminated nano-aluminum phosphate, maleic anhydride, and ethanol is 1:2:20. Step 3: Add maleimide nano-aluminum phosphate to DMF and disperse at high speed. Add diallyl bisphenol A and stir until homogeneous. React at 80°C for 3 hours. Then add diphenylmethane diisocyanate and continue stirring. After the reaction is complete, centrifuge and dry to obtain modified nano-aluminum phosphate. The mass ratio of diphenylmethane diisocyanate, diallyl bisphenol A, maleimide nano-aluminum phosphate, and DMF is 0.85:1:3.5:20. Graphene undergoes pretreatment before use; the specific process is as follows: Step (1): Add alumina to Tris-dopamine hydrochloride solution and stir to react, to obtain polydopamine alumina; the mass ratio of alumina to Tris-dopamine hydrochloride solution is 2:20; Step (2): Add graphene to tetrahydrofuran and disperse it at a high speed of 2400 r / min. Then add 3-aminopropyltriethoxysilane and react at 40℃ for 6 h. Centrifuge, wash and dry to obtain pretreated graphene. The mass ratio of graphene, 3-aminopropyltriethoxysilane and tetrahydrofuran is 1:0.5:10. Step (3): Add pretreated graphene and polydopamine alumina to ethanol, stir to react, centrifuge, and dry to obtain Al2O3-graphene; the mass ratio of pretreated graphene, polydopamine alumina, and ethanol is 0.2:1:20. The concentration of the Tris-dopamine hydrochloride solution was 12 mM; the rest of the methods were the same as in Example 1.
[0045] Comparative Example 1: This comparative example provides a method for preparing a PET composite film. The PET masterbatch is not modified by PBI crosslinking, and the rest of the method is the same as in Example 1.
[0046] Comparative Example 2: This comparative example provides a method for preparing a PET composite film. The PBI crosslinked PET composite material includes the following components by mass: 90 parts of PET masterbatch, 10 parts of PBI, 1 part of antioxidant, and 2 parts of lubricant. The remaining methods are the same as in Example 1.
[0047] Comparative Example 3: This comparative example provides a method for preparing a PBI crosslinked modified PET composite film, in which the nano-aluminum phosphate is not modified; the remaining methods are the same as in Example 8.
[0048] Comparative Example 4: This comparative example provides a method for preparing a PBI crosslinked modified PET composite film. The graphene is not pretreated, and the rest of the method is the same as in Example 8. experiment:
[0049] Samples were prepared from the PET composite films obtained in Examples 1-10 and Comparative Examples 1-4, and their performance was tested and the test results were recorded.
[0050] Tensile strength and elongation at break: Using ASTM D882 as the reference standard, an electronic universal testing machine was used. The test conditions were: gauge length 10 mm, tensile speed 50 mm / min, width 15 mm. Tensile strength and elongation at break were determined. Flame retardancy test: Using UL94 as the reference standard, ignite the sample, then remove the ignition source, record the flaming burning time, and classify the flame retardancy of the sample according to the burning situation. Electrolyte corrosion resistance test: Weigh the sample and record the data, then immerse the sample in 1M LiPF6 / EC-DEC electrolyte for 24h and take it out to test the sample weight retention rate. Heat shrinkage test: Using ASTM D1204 as the reference standard, the sample was baked at 150°C for 30 minutes, and the change rate of the sample length before and after heating was measured.
[0051] Performance Comparison Table
[0052] Based on the data in the table above, the following conclusions can be clearly drawn: The PBI crosslinked modified PET composite films obtained in Examples 1-10 were compared with the PET composite films obtained in Comparative Examples 1-4. The test results show that: A comparison of Examples 1-10 with Comparative Example 1 shows that the PBI crosslinked modified PET composite film of the present invention has excellent resistance to electrolyte corrosion, mechanical properties and thermal stability, which are far superior to ordinary PET film. The present invention achieves a synergistic effect by crosslinking the molecular chains of PBI and PET and adding functional materials such as nano-aluminum phosphate and graphene, which significantly improves the electrolyte corrosion resistance, mechanical strength and thermal stability of PET film.
[0053] Comparing Example 8 with Comparative Example 2, the PET composite film obtained in Comparative Example 2, without the addition of nano-aluminum phosphate and graphene to the PET masterbatch, showed a significant decrease in mechanical properties and corrosion resistance, demonstrating the advantages of adding nano-aluminum phosphate and graphene in this invention.
[0054] Comparing Example 8 with Comparative Example 3, the PET composite film obtained in Comparative Example 3, without modification of the nano-aluminum phosphate, showed reduced tensile strength, reduced elongation at break, reduced corrosion resistance, and increased thermal shrinkage. This indicates that the PET composite film prepared by the unmodified nano-aluminum phosphate does not have the same mechanical properties as the present invention, demonstrating the technical advantages of the modified nano-aluminum phosphate composite structure.
[0055] Comparing Example 8 with Comparative Example 4, the PET composite film obtained in Comparative Example 4, without pretreatment of graphene, exhibits reduced tensile strength, decreased elongation at break, reduced corrosion resistance, and increased thermal shrinkage. By combining alumina and graphene, the strong adhesion properties of polydopamine firmly form an interface layer on the surfaces of alumina and graphene, effectively transferring stress and enhancing the mechanical properties of graphene. This, in turn, enhances the overall performance of the PET masterbatch and extends the service life of the battery separator, demonstrating the technical advantage of pretreating graphene in this invention.
[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A method for preparing a PBI crosslinked modified PET composite film, characterized in that: Includes the following steps: S1: Mix PET masterbatch and PBI, melt blend, and extrude to obtain PBI crosslinked PET composite material; S2: The PBI crosslinked PET composite material is processed and shaped to obtain a PBI crosslinked modified PET composite film.
2. The method for preparing a PBI crosslinked modified PET composite film according to claim 1, characterized in that: The mass ratio of PET masterbatch to PBI is (90~100): (1~10).
3. The method for preparing a PBI crosslinked modified PET composite film according to claim 1, characterized in that: In step S1, the PBI crosslinked PET composite material also contains 1-2 parts of antioxidant, 2-3 parts of lubricant, 15-20 parts of nano-aluminum phosphate, and 6-10 parts of graphene.
4. The method for preparing a PBI crosslinked modified PET composite film according to claim 1, characterized in that: In step S2, the specific process of the forming is as follows: a nascent film is obtained by casting, biaxial stretching, and heat setting, and then processed to obtain a PBI crosslinked modified PET composite film; the stretching temperature is 110~120℃, the stretching rate is 120~130mm / s, the heat setting temperature is 210~220℃, and the stretching ratio is 3:
1.
5. The method for preparing a PBI crosslinked modified PET composite film according to claim 1, characterized in that: The viscosity of the PET masterbatch is 0.65~0.85 dL / g; the molecular weight of the PBI is 50000~100000 g / mol; the antioxidant is 1010; and the lubricant is pentaerythritol stearate.
6. The method for preparing a PBI crosslinked modified PET composite film according to claim 3, characterized in that: The nano-aluminum phosphate undergoes surface modification, and the modification process is as follows: Step 1: Add nano-aluminum phosphate to an aminosilane coupling agent solution, disperse, heat to react, centrifuge, wash, and dry to obtain aminated nano-aluminum phosphate; Step 2: Add aminated nano-aluminum phosphate to ethanol, disperse, then add maleic anhydride, heat to 110~120℃, react for 2~3 hours, after the reaction is completed, centrifuge and dry to obtain maleimide nano-aluminum phosphate; Step 3: Add maleimide nano-aluminum phosphate to DMF and disperse at high speed. Add diallyl bisphenol A, stir evenly, heat to react, then add diphenylmethane diisocyanate and continue stirring. After the reaction is complete, centrifuge and dry to obtain modified nano-aluminum phosphate.
7. The method for preparing a PBI crosslinked modified PET composite film according to claim 3, characterized in that: The graphene undergoes pretreatment before use, and the specific process is as follows: Step (1): Add aluminum oxide to Tris-dopamine hydrochloride solution and stir to react, to obtain polydopamine aluminum oxide; Step (2): Add graphene to tetrahydrofuran, disperse, then add 3-aminopropyltriethoxysilane, heat to react, centrifuge, wash, and dry to obtain pretreated graphene; Step (3): Add pretreated graphene and polydopamine alumina to ethanol, stir to react, centrifuge, and dry to obtain Al2O3-graphene.
8. The method for preparing a PBI crosslinked modified PET composite film according to claim 6, characterized in that: The mass ratio of aminosilane coupling agent solution to nano-aluminum phosphate is (5~10):1; the mass ratio of aminated nano-aluminum phosphate, maleic anhydride, and ethanol is 1:(1.2~2):20; the mass ratio of diphenylmethane diisocyanate, diallyl bisphenol A, maleimide nano-aluminum phosphate, and DMF is 0.85:1:(1~3.5):
20.
9. The method for preparing a PBI crosslinked modified PET composite film according to claim 7, characterized in that: The mass ratio of alumina to Tris-dopamine hydrochloride solution is (1~2):20; the mass ratio of graphene, 3-aminopropyltriethoxysilane, and tetrahydrofuran is 1:(0.3~0.5):10; the mass ratio of pretreated graphene, polydopamine alumina, and ethanol is (0.1~0.2):1:20; and the concentration of Tris-dopamine hydrochloride solution is 10~12 mM.
10. The application of a PBI crosslinked modified PET composite film prepared by the preparation method according to any one of claims 1-9, characterized in that: The PBI crosslinked modified PET composite film is used in the preparation of lithium batteries.