A chain-extended modified nylon material, its preparation method and application

Abstract

This application discloses a chain-extended modified nylon material, its preparation method, and its application, specifically relating to the field of battery sealing ring technology. The chain-extended modified nylon material comprises the following raw materials in parts by weight: 60-90 parts nylon resin, 0.5-5 parts chain extender, 0.5-4.8 parts 1-vinyl-3-ethylimidazolium tetrafluoroborate, 0.5-2 parts nano-silica, 0.5-2.67 parts halloysite nanotubes, 0.75-3 parts vinyltrimethoxysilane, 0.1-0.5 parts azobisisobutyronitrile, 5-20 parts maleic anhydride-grafted polyethylene, 1-2 parts antioxidant, and 1-2 parts lubricant. This application significantly improves the mechanical strength, multi-component compatibility, and low-temperature toughness of nylon materials.

Description

Technical Field

[0001] This application relates to the field of battery sealing ring technology, and in particular to a chain-extended modified nylon material, its preparation method, and its application. Background Technology

[0002] Battery sealing rings are key structural components in chemical power sources such as lithium batteries and alkaline batteries. Their main function is to ensure an airtight seal between the battery's interior and the external environment, preventing electrolyte leakage and the entry of external moisture, oxygen, and other contaminants, thereby ensuring the battery's safety, capacity, and cycle life. With the rapid development of new energy vehicles, energy storage systems, and portable electronic devices, higher demands are placed on the reliability, durability, and environmental adaptability of battery sealing rings, especially their sealing performance under low-temperature conditions, which has become a key focus of the industry.

[0003] Currently, nylon is widely used as the base material for battery seals due to its excellent mechanical properties, oil resistance, resistance to electrolyte corrosion, and good processing fluidity. However, when traditional nylon materials are used in battery seals, the movement of its molecular chain segments is restricted in low-temperature environments (such as -20°C and below), resulting in significant brittle behavior. The seals are prone to cracking during pressure assembly or use, leading to sealing failure and severely limiting their reliability in cold regions or low-temperature applications (such as the winter operation of new energy vehicles).

[0004] To improve the low-temperature toughness of nylon, a common technique is to add toughening agents or elastomer components, such as polyether polyols, polyester elastomers, and grafted rubber, to the nylon matrix. However, because these toughening components lack good interfacial affinity with the highly polar nylon matrix, simple blending easily leads to significant phase separation. Phase separation not only reduces the overall mechanical properties of the material (such as decreased tensile strength and elongation at break), but also causes defects such as surface delamination and flow marks during the molding and processing of sealing rings, affecting the sealing effect and long-term stability of the product. Summary of the Invention

[0005] To address the technical problems of insufficient low-temperature toughness and poor multi-component compatibility in nylon-based battery sealing ring materials, this application provides a chain-extended modified nylon material, its preparation method, and its application.

[0006] In a first aspect, this application provides a chain-extended modified nylon material, employing the following technical solution: A chain-extended modified nylon material comprises the following raw materials in parts by weight: 60-90 parts nylon resin, 0.5-5 parts chain extender, 0.5-4.8 parts 1-vinyl-3-ethylimidazolium tetrafluoroborate, 0.5-2 parts nano-silica, 0.5-2.67 parts halloysite nanotubes, 0.75-3 parts vinyltrimethoxysilane, 0.1-0.5 parts azobisisobutyronitrile, 5-20 parts maleic anhydride-grafted polyethylene, 1-2 parts antioxidant, and 1-2 parts lubricant.

[0007] By adopting the above technical solution, this application generates a polyionic liquid through in-situ polymerization of 1-vinyl-3-ethylimidazolium tetrafluoroborate initiated by azobisisobutyronitrile. This polyionic liquid is anchored by a coupling agent and simultaneously inserted into the interlayer domains of halloysite nanotubes and / or coated onto their surface, and uniformly coated with nano-silica, significantly reducing the surface energy of the filler, inhibiting agglomeration, and improving dispersibility and compatibility, thereby ensuring high tensile strength and elongation at break. The chain extender reacts with the terminal amino and carboxyl groups of nylon, reconnecting the molecular chains broken by high-temperature shear, reconstructing a high molecular weight structure, and improving melt strength. The material exhibits good melt flow rate and processing stability. The anhydride groups of maleic anhydride-grafted polyethylene react in situ with the terminal amino groups of nylon to form chemical bonds at the interface, achieving reactive toughening and significantly improving low-temperature notched impact strength. In addition, fibrous halloysite nanotubes and spherical nano-silica form a multi-scale synergistic reinforcement effect. Halloysite nanotubes act as a framework to bridge microcracks and hinder crack propagation, while nano-silica fills the gaps in the framework to enhance rigidity. The two complement each other in morphology and synergize in function, further ensuring the balance between strength and toughness of the material at low temperatures.

[0008] Optionally, the weight ratio of the nano-silica to halloysite nanotubes is 1:(1-2).

[0009] By employing the above-mentioned technical solution, this application utilizes a specific weight ratio of nano-silica and halloysite nanotubes to construct a highly efficient multi-scale synergistic reinforcement network within a nylon matrix. The fibrous halloysite nanotubes serve as the primary reinforcing framework, forming a three-dimensional physical network within the matrix. This network effectively bridges crazing and hinders crack propagation, significantly enhancing the material's toughness and load-bearing capacity. Sufficient spherical nano-silica fully fills the voids in the fibrous framework, inhibiting excessive entanglement and dense agglomeration of halloysite nanotubes during melt processing through a physical barrier effect, promoting uniform dispersion of both. Simultaneously, the filling of nano-silica significantly enhances the system's rigidity, hardness, and dimensional stability, forming a spatial morphological complement to the halloysite nanotubes. This synergistic effect ensures that stress can be efficiently transferred and dissipated through a multi-level path from the matrix to the nanoparticles to the fiber framework, avoiding agglomeration or stress concentration problems caused by excessive single filler, thereby maximizing the overall mechanical properties of the nylon material.

[0010] Optionally, the weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate to nano-silica is (1.5-3):1.

[0011] By employing the above technical solution, this application uses a specific weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate and nano-silica to ensure that the ionic liquid monomer is fully adsorbed on the surface of nano-silica and between its aggregates. During subsequent in-situ polymerization, the polyionic liquid generates a continuous and uniform organic coating layer on the particle surface, which helps to dissociate secondary aggregates into primary particles, realizing the transformation of nano-silica from "partial coating" to "fully uniform coating". This coating layer effectively shields the van der Waals forces between nano-silica particles, inhibiting their self-aggregation tendency, thereby significantly improving the primary particle dispersion level of nano-silica in the nylon matrix. At the same time, the uniform organic coating layer, as an interfacial transition layer, can effectively enhance the compatibility and interfacial bonding force between the filler and the nylon matrix, enabling stress to be transferred efficiently and avoiding early failure caused by interfacial debonding.

[0012] Optionally, the particle size of the nano-silica is 20-50 nm, and the diameter of the halloysite nanotubes is 50-300 nm.

[0013] By employing the above technical solution, limiting the particle size of nano-silica to 20-50 nm and the diameter of halloysite nanotubes to 50-300 nm, a multi-scale reinforcement system with a reasonable size distribution can be constructed in a nylon matrix. Nano-silica within this particle size range possesses extremely high specific surface area and surface energy, allowing it to be uniformly dispersed and embedded in the gaps of the submicron-scale fiber network constructed from halloysite nanotubes. This achieves complementary spatial filling from the nanoscale to the submicron scale, effectively alleviating stress concentration between filler aggregates. The 50-300 nm diameter of the halloysite nanotubes provides a suitable aspect ratio and good structural stability, sufficient to form an effective physical framework to support and bridge microcracks, while avoiding a reduction in interfacial area per unit mass due to excessively large tube diameter, ensuring a sufficient stress transfer interface between the fiber and the matrix. The gradient matching of the two fillers at the geometric scale enables stress to be efficiently transferred via a multi-level path of "matrix-nanoparticle-fiber framework," avoiding premature failure caused by interfacial stress concentration when using only a single-scale filler, thereby synergistically improving the material's stiffness, strength, and impact toughness.

[0014] Optionally, the mass percentage of maleic anhydride in the maleic anhydride-grafted polyethylene is 1-2 wt%.

[0015] By employing the above technical solution, the grafting rate of maleic anhydride in maleic anhydride-grafted polyethylene is controlled at 1-2 wt%. The anhydride group density on its molecular chain is moderate, allowing it to undergo in-situ chemical reactions with the terminal amino groups of nylon during melt blending. This forms strong chemical bonds between the polyethylene chain segments and the nylon matrix, effectively reducing the interfacial tension between the two phases and promoting the refinement of the polyethylene dispersed phase. This results in a smaller, more uniform particle size distribution within the nylon matrix. The reduced particle size shortens the interparticle spacing, which is beneficial for more effectively terminating crack propagation or inducing matrix shear yielding under impact, thereby dissipating more energy and achieving highly efficient toughening of the nylon matrix.

[0016] Optionally, the chain extender includes isophorone diisocyanate and styrene-glycidyl methacrylate.

[0017] Optionally, the weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate is 1:(1.5-3).

[0018] By employing the above-mentioned technical solution, this application utilizes a specific weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate to construct a synergistic chain extension system combining fast and slow reactions, efficiently repairing nylon molecular chains and enhancing melt strength. Specifically, the diisocyanate group of isophorone diisocyanate exhibits extremely high reactivity, rapidly undergoing end-capping and coupling reactions with the terminal amino and carboxyl groups of nylon in the early stages of melt processing, quickly increasing molecular weight and establishing initial melt strength. Meanwhile, the polyepoxy groups of styrene-glycidyl methacrylate continuously undergo chain extension and branching reactions with the nylon end groups and newly generated active end groups during chain extension at a relatively mild rate, achieving further molecular chain growth and topological adjustment.

[0019] Optionally, the nylon resin is at least one of PA6 and PA66; the antioxidant is N-phenyl-α-naphthylamine; and the lubricant is pentaerythritol stearate.

[0020] By adopting the above technical solutions and selecting PA6 or PA66 as the matrix resin, the material is guaranteed to have excellent mechanical strength, heat resistance and processing fluidity, providing a reliable performance basis for the modified system. Using N-phenyl-α-naphthylamine as an antioxidant can effectively capture free radicals and inhibit thermo-oxidative degradation chain reactions during high-temperature melt processing and use, protecting nylon molecular chains from excessive chain breakage and cross-linking, thereby maintaining the chain extension modification effect and the long-term thermal stability of the material. Using pentaerythritol stearate as a lubricant, its polyhydroxy ester structure has both internal and external lubrication functions, which can reduce the friction between the resin melt and the processing equipment, improve the demolding and extrusion surface quality, and promote the uniform dispersion of fillers in the matrix.

[0021] Secondly, this application provides a method for preparing chain-extended modified nylon materials, employing the following technical solution: A method for preparing chain-extended modified nylon material includes the following steps: S1. Mix nano-silica, halloysite nanotubes, vinyltrimethoxysilane and solvent, disperse ultrasonically, heat and stir, add 1-vinyl-3-ethylimidazolium tetrafluoroborate, stir and adsorb, then add azobisisobutyronitrile, heat and stir, filter, wash and dry to obtain pre-modified material; S2. Mix the pre-modified material with nylon resin, chain extender, maleic anhydride grafted polyethylene, antioxidant, and lubricant, stir evenly, and melt-extrude to obtain chain-extended modified nylon material.

[0022] Optionally, the solvent is anhydrous ethanol.

[0023] Optionally, in step S1, the ultrasonic dispersion power is 300-500W, and the drying temperature is 60-80℃.

[0024] Optionally, in step S2, the stirring speed is 300-500 rpm and the melt extrusion temperature is 200-250℃.

[0025] Thirdly, this application provides an application of chain-extended modified nylon material in battery sealing rings.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. This application describes the in-situ polymerization of 1-vinyl-3-ethylimidazolium tetrafluoroborate under the initiation of azobisisobutyronitrile to generate a polyionic liquid. This polyionic liquid is anchored by a coupling agent and simultaneously inserted into the interlayer domains of halloysite nanotubes and / or coated onto their surface, and uniformly coated with nano-silica. This significantly reduces the surface energy of the filler, inhibits agglomeration, and improves dispersibility and compatibility, thereby ensuring high tensile strength and elongation at break. A chain extender reacts with the terminal amino and carboxyl groups of nylon, reconnecting the molecular chains broken by high-temperature shear, reconstructing a high molecular weight structure, and improving melt strength and processing stability. The properties of the material endow it with good melt flow rate; the anhydride groups of maleic anhydride-grafted polyethylene react in situ with the terminal amino groups of nylon to form chemical bonds at the interface, achieving reactive toughening and significantly improving low-temperature notched impact strength; in addition, fibrous halloysite nanotubes and spherical nano-silica form a multi-scale synergistic reinforcement effect. Halloysite nanotubes act as a framework to bridge microcracks and hinder crack propagation, while nano-silica fills the gaps in the framework to enhance rigidity. The two are complementary in morphology and synergistic in function, further ensuring the balance of strength and toughness of the material at low temperatures; 2. This application employs a specific weight ratio of nano-silica and halloysite nanotubes to construct a highly efficient multi-scale synergistic reinforcement network within a nylon matrix. The fibrous halloysite nanotubes serve as the primary reinforcing framework, forming a three-dimensional physical network within the matrix. This network effectively bridges crazing and hinders crack propagation, significantly enhancing the material's toughness and load-bearing capacity. Sufficient spherical nano-silica fully fills the voids in the fibrous framework, inhibiting excessive entanglement and dense agglomeration of halloysite nanotubes during melt processing through a physical barrier effect, promoting uniform dispersion of both. Simultaneously, the filling of nano-silica significantly enhances the system's rigidity, hardness, and dimensional stability, and forms a spatial morphological complement to the halloysite nanotubes. This synergistic effect ensures efficient stress transfer and dissipation through a multi-level path from matrix to nanoparticles to the fibrous framework, avoiding agglomeration or stress concentration problems caused by excessive single filler, thereby maximizing the overall mechanical properties of the nylon material. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] This application discloses a chain-extended modified nylon material, comprising the following raw materials in parts by weight: 60-90 parts nylon resin, 0.5-5 parts chain extender, 0.5-4.8 parts 1-vinyl-3-ethylimidazolium tetrafluoroborate, 0.5-2 parts nano-silica, 0.5-2.67 parts halloysite nanotubes, 0.75-3 parts vinyltrimethoxysilane, 0.1-0.5 parts azobisisobutyronitrile, 5-20 parts maleic anhydride-grafted polyethylene, 1-2 parts antioxidant, and 1-2 parts lubricant.

[0029] This application discloses a method for preparing chain-extended modified nylon material, including the following steps: S1. Mix nano-silica, halloysite nanotubes, vinyltrimethoxysilane and solvent, ultrasonically disperse at 300-500W for 20-40 min, stir at 60-80℃ and 300-500rpm for 2-4 h, add 1-vinyl-3-ethylimidazolium tetrafluoroborate, stir at 300-500rpm for 1-2 h, then add azobisisobutyronitrile, heat at 800-1000rpm and 60-80℃ for 4-6 h, filter, wash with ethanol solution 3-5 times, dry at 60-80℃ for 4-6 h to obtain pre-modified material; S2. Mix the pre-modified material with nylon resin, chain extender, maleic anhydride grafted polyethylene, antioxidant, and lubricant, stir at 300-500 rpm for 10-20 min, melt extrude, and granulate to obtain chain-extended modified nylon material.

[0030] All raw materials used in the embodiments of this application are commercially available, wherein: PA6, BASF, Germany; PA66, BASF, Germany; Isophorone diisocyanate, Shanghai Aladdin Biochemical Technology Co., Ltd.; Styrene-glycidyl methacrylate, Qingdao Dongguang Biotechnology Co., Ltd.; Maleic anhydride-grafted polyethylene, maleic anhydride grafting rate 1-2wt%, Shanghai Aladdin Biochemical Technology Co., Ltd. Vinyltrimethoxysilane, Shanghai Aladdin Biochemical Technology Co., Ltd.; N-Phenylacetylamine, model T-531, Jinzhou Shengda Chemical Co., Ltd.; Nano-silica, particle size 20-50nm, Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Halloysite nanotubes, diameter 50-300nm, Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. 1-Vinyl-3-ethylimidazolium tetrafluoroborate, Shanghai Aladdin Biochemical Technology Co., Ltd.; Azobisisobutyronitrile (AIBN), Shanghai Aladdin Biochemical Technology Co., Ltd. Pentaerythritol stearate, Shanghai Aladdin Biochemical Technology Co., Ltd.; Anhydrous ethanol, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0031] Example 1 0.5 g of nano-silica, 0.5 g of halloysite nanotubes, 0.75 g of vinyltrimethoxysilane, and 200 mL of anhydrous ethanol were mixed and ultrasonically dispersed at 300 W for 20 min, then stirred at 60 °C and 300 rpm for 2 h. 0.5 g of 1-vinyl-3-ethylimidazolium tetrafluoroborate was added, and the mixture was stirred at 300 rpm for 1 h. Subsequently, 0.1 g of azobisisobutyronitrile was added, and the mixture was reacted at 60 °C and 800 rpm for 4 h under nitrogen protection. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 60 °C for 4 h to obtain the pre-modified material. After 60g of PA6 was vacuum dried at 80℃ for 8h, it was mixed with pre-modified material, 0.2g of isophorone diisocyanate, 0.3g of styrene-glycidyl methacrylate, 5g of maleic anhydride-grafted polyethylene, 1g of N-phenyl-α-naphthylamine and 1g of pentaerythritol stearate, stirred at 300rpm for 10min, melt-extruded and granulated to obtain chain-extended modified nylon material.

[0032] Example 2 1g of nano-silica, 1g of halloysite nanotubes, 1.5g of vinyltrimethoxysilane, and 400mL of anhydrous ethanol were mixed and ultrasonically dispersed at 400W for 30min, then stirred at 70℃ and 400rpm for 3h. 1g of 1-vinyl-3-ethylimidazolium tetrafluoroborate was added, and the mixture was stirred at 400rpm for 1.5h. Subsequently, 0.3g of azobisisobutyronitrile was added, and the mixture was reacted at 70℃ and 900rpm for 5h under nitrogen protection. After the reaction was completed, the mixture was filtered, washed four times with anhydrous ethanol, and dried at 70℃ for 5h to obtain the pre-modified material. After vacuum drying 60g PA6 and 20g PA66 at 85℃ for 8h, they were mixed with pre-modified material, 1.2g isophorone diisocyanate, 1.8g styrene-glycidyl methacrylate, 10g maleic anhydride-grafted polyethylene, 1.5g N-phenyl-α-naphthylamine and 1.5g pentaerythritol stearate, stirred at 400rpm for 15min, melt-extruded, and granulated to obtain chain-extended modified nylon material.

[0033] Example 3 2g of nano-silica, 2g of halloysite nanotubes, 3g of vinyltrimethoxysilane, and 600mL of anhydrous ethanol were mixed and ultrasonically dispersed at 500W for 40min, then stirred at 80℃ and 500rpm for 4h. 2g of 1-vinyl-3-ethylimidazolium tetrafluoroborate was added, and the mixture was stirred at 500rpm for 2h. Subsequently, 0.5g of azobisisobutyronitrile was added, and the mixture was reacted at 80℃ and 1000rpm for 6h under nitrogen protection. After the reaction was complete, the mixture was filtered, washed five times with anhydrous ethanol, and dried at 80℃ for 6h to obtain the pre-modified material. 90g of PA66 was vacuum dried at 90℃ for 6h, then mixed with the pre-modified material, 2g of isophorone diisocyanate, 3g of styrene-glycidyl methacrylate, 20g of maleic anhydride-grafted polyethylene, 2g of N-phenyl-α-naphthylamine, and 2g of pentaerythritol stearate. The mixture was stirred at 500rpm for 20min, melt-extruded, and granulated to obtain the chain-extended modified nylon material.

[0034] Comparative Example 1 The difference between this comparative example and Example 3 is that the nano-silica in Example 3 is replaced with halloysite nanotubes.

[0035] Comparative Example 2 The difference between this comparative example and Example 3 is that the halloysite nanotubes in Example 3 are replaced with nano-silica.

[0036] Performance Test 1 The chain-extended modified nylon materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested for tensile strength, elongation at break, notched impact strength at -30℃, and melt flow rate. The results are shown in Table 1. Tensile strength and elongation at break: Tensile strength and elongation at break were tested according to GB / T 1040.2-2006 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics". Notched impact strength: The notched impact strength of the test specimen after being placed at -30℃ for 4 hours according to GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams (Part 1)"; Melt mass flow rate: According to GB / T 3682.1-2018 "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastic plastics - Part 1: Standard method", the test specimen was tested at 235℃ and 2.16kg load.

[0037] Table 1. Properties of chain-extended modified nylon materials in Examples 1-3 and Comparative Examples 1-2

[0038] As shown in Examples 1-3 and Table 1, the chain-extended modified nylon materials prepared in Examples 1-3 of this application have a tensile strength of over 63.2 MPa, an elongation at break of over 78%, and a notched impact strength of 7.4 kJ / m at -30°C. 2 The melt flow rate is above 15.8 g / 10 min. This indicates that this application utilizes in-situ polymerization of 1-vinyl-3-ethylimidazolium tetrafluoroborate to form a polyionic liquid, synergistically constructing a multi-scale reinforcing network with nano-silica and halloysite nanotubes, and combining the toughening effect of chain extenders and maleic anhydride-grafted polyethylene. This significantly improves the room temperature mechanical strength and low temperature toughness of nylon materials while maintaining good melt processing fluidity. The resulting material is particularly suitable for battery sealing rings with stringent low-temperature reliability requirements.

[0039] As shown in Example 3, Comparative Examples 1-2, and Table 1, the chain-extended modified nylon material prepared in Example 3 of this application has a tensile strength of 72.4 MPa, an elongation at break of 83%, a notched impact strength of 8.3 kJ / m² at -30℃, and a melt flow rate of 16.5 g / 10 min, which are significantly better than those of Comparative Examples 1-2. This indicates that the "spherical-fiber" multi-scale synergistic reinforcement network constructed by nano-silica and halloysite nanotubes in this application can simultaneously improve the room temperature mechanical strength and low temperature impact toughness of the material while maintaining good processing fluidity. Compared with Example 3, although adding only halloysite nanotubes in Comparative Example 1 can form a rigid framework, the movement of molecular chains is restricted, and the material is prone to brittle fracture. Compared with Example 3, although adding only nano-silica in Comparative Example 2 can provide rigid filling, the nanoparticles are prone to agglomeration, forming stress concentration points, and debonding from the matrix interface at low temperatures, which cannot effectively prevent crack propagation, resulting in obvious brittleness of the material.

[0040] Examples 4-5 Based on Example 3, except for the weight ratio of nano-silica and halloysite nanotubes, the other components and preparation methods are the same as in Example 3, and the total weight of nano-silica and halloysite nanotubes remains unchanged.

[0041] Example 4 The difference between this embodiment and embodiment 3 is that the weight ratio of nano-silica to halloysite nanotubes in this embodiment is 1:1.5. Specifically, the weight of nano-silica is 1.6g and the weight of halloysite nanotubes is 2.4g.

[0042] Example 5 The difference between this embodiment and embodiment 3 is that the weight ratio of nano-silica to halloysite nanotubes in this embodiment is 1:2. Specifically, the weight of nano-silica is 1.33g and the weight of halloysite nanotubes is 2.67g.

[0043] Examples 6-7 Based on Example 4, except for the weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate and nano silica, the other components and preparation methods are the same as in Example 4.

[0044] Example 6 The difference between this embodiment and Embodiment 4 is that in this embodiment, the weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate and nano-silica is 2:1. Specifically, the weight of 1-vinyl-3-ethylimidazolium tetrafluoroborate is 3.2g and the weight of nano-silica is 1.6g.

[0045] Example 7 The difference between this embodiment and Embodiment 4 is that in this embodiment, the weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate and nano-silica is 3:1. Specifically, the weight of 1-vinyl-3-ethylimidazolium tetrafluoroborate is 4.8g and the weight of nano-silica is 1.6g.

[0046] Examples 8-9 Based on Example 6, except for the weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate, the other components and preparation methods are the same as in Example 6, and the total weight of isophorone diisocyanate and styrene-glycidyl methacrylate remains unchanged.

[0047] Example 8 The difference between this embodiment and Embodiment 6 is that the weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate in this embodiment is 1:2. Specifically, isophorone diisocyanate weighs 1.67g and styrene-glycidyl methacrylate weighs 3.33g.

[0048] Example 9 The difference between this embodiment and Embodiment 6 is that in this embodiment, the weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate is 1:3. Specifically, isophorone diisocyanate weighs 1.25g and styrene-glycidyl methacrylate weighs 3.75g.

[0049] Performance Test 2 The chain-extended modified nylon materials prepared in Examples 4-9 were subjected to tensile strength, elongation at break, -30℃ notched impact strength, and melt flow rate tests. The test methods were the same as those in Performance Test 1, and the test results are shown in Table 2 below.

[0050] Table 2 Properties of chain-extended modified nylon materials in Examples 3-9

[0051] As shown in Examples 3-5 and Table 2, the chain-extended modified nylon material of Example 4 of this application has a tensile strength of 72.9 MPa, an elongation at break of 86%, a notched impact strength at -30℃ of 9.8 kJ / m², and a melt flow rate of 17.9 g / 10 min, which are significantly better than those of Examples 3 and 5. This indicates that the use of a specific weight ratio of nano-silica and halloysite nanotubes in this application can ensure that stress can be efficiently transferred and dissipated through a multi-level path of matrix-nanoparticle-fiber skeleton, maximizing the improvement of the comprehensive mechanical properties of nylon materials. Compared with Example 4, although the high proportion of nano-silica in Example 3 can effectively fill the physical network, excessive nano-silica is prone to self-aggregation, forming local stress concentration points, weakening the bridging and crack-resistant effect of the halloysite nanotube fiber skeleton, resulting in a decrease in low-temperature impact strength and elongation at break. Compared to Example 4, although the high proportion of halloysite nanotubes in Example 5 can increase the fiber skeleton density, excessive halloysite nanotubes are prone to entanglement and dense agglomeration during melt processing, reducing their uniform dispersion in the nylon matrix. At the same time, it weakens the filling and interfacial bonding effect of nano-silica, resulting in a decrease in tensile strength and melt flow rate.

[0052] As shown in Examples 4, 6-7, and Table 2, the chain-extended modified nylon material of Example 6 has a tensile strength of 78.1 MPa, an elongation at break of 88%, a notched impact strength at -30℃ of 11.4 kJ / m², and a melt flow rate of 18.3 g / 10 min, which are significantly better than those of Examples 4 and 7. This indicates that the use of a specific weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate and nano-silica in this application can form a uniform coating layer. This coating layer not only improves dispersibility but also imparts a certain degree of flexible buffering capacity to the interface, avoiding brittle fracture caused by the rigid interface between the rigid filler and the nylon matrix. Compared to Example 6, the proportion of 1-vinyl-3-ethylimidazolium tetrafluoroborate in Example 4 was insufficient. Although it could form a certain coating on the nano-silica, the coating was discontinuous and uneven, failing to fully dissociate the secondary aggregates of the nano-silica. This resulted in some particles being dispersed in the nylon matrix in an agglomerated form, creating stress concentration points. Simultaneously, insufficient interfacial bonding led to a decrease in tensile strength, low-temperature impact toughness, and elongation at break. Compared to Example 6, the proportion of 1-vinyl-3-ethylimidazolium tetrafluoroborate in Example 7 was too high. Although a complete coating layer could be formed, the excessive polyionic liquid formed an overly thick coating layer on the surface of the nano-silica, and may even form free polyionic liquid regions within the matrix. This excessively thick organic interfacial layer weakened the direct stress transfer between the rigid filler and the nylon matrix. Furthermore, the free polyionic liquid may have a plasticizing effect, leading to a decrease in material rigidity, a reduction in tensile strength, an increase in melt viscosity, and a deterioration in fluidity.

[0053] As shown in Examples 6, 8-9, and Table 2, the chain-extended modified nylon material of Example 8 has a tensile strength of 79 MPa, an elongation at break of 91%, a notched impact strength at -30℃ of 12.1 kJ / m², and a melt flow rate of 18.9 g / 10 min, which are significantly better than those of Examples 6 and 9. This indicates that by using a specific weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate, this application can construct a synergistic chain-extending system combining fast and slow growth, achieving further growth of molecular chains and optimization of topology, thereby comprehensively improving the mechanical properties and processing fluidity of the material. Compared with Example 8, the proportion of isophorone diisocyanate in Example 6 is too high. Although it can rapidly extend the chain, it will excessively cap some of the nylon end groups, inhibiting the subsequent continuous chain extension and branching reaction of styrene-glycidyl methacrylate, resulting in limited increase in molecular weight and insufficient regularity of molecular chain topology, leading to a decrease in tensile strength, low-temperature impact toughness, and elongation at break. Compared with Example 8, the proportion of styrene-glycidyl methacrylate in Example 9 is too high. Although it can provide abundant epoxy groups, the excessive amount of this component continuously participating in the chain extension reaction can easily lead to over-branching or even local cross-linking, resulting in uneven molecular chain structure and gel defects. This can reduce the tensile strength and elongation at break of the material and may cause a decrease in melt flowability.

[0054] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A chain-extended modified nylon material, characterized in that, The raw materials include the following parts by weight: 60-90 parts nylon resin, 0.5-5 parts chain extender, 0.5-4.8 parts 1-vinyl-3-ethylimidazolium tetrafluoroborate, 0.5-2 parts nano silica, 0.5-2.67 parts halloysite nanotubes, 0.75-3 parts vinyltrimethoxysilane, 0.1-0.5 parts azobisisobutyronitrile, 5-20 parts maleic anhydride-grafted polyethylene, 1-2 parts antioxidant, and 1-2 parts lubricant.

2. The chain-extended modified nylon material according to claim 1, characterized in that, The weight ratio of the nano-silica to halloysite nanotubes is 1:(1-2).

3. The chain-extended modified nylon material according to claim 1, characterized in that, The weight ratio of 1-vinyl-3-ethylimidazolium tetrafluoroborate to nano-silica is (1.5-3):

1.

4. The chain-extended modified nylon material according to claim 1, characterized in that, The nano-silica has a particle size of 20-50 nm, and the halloysite nanotubes have a diameter of 50-300 nm.

5. The chain-extended modified nylon material according to claim 1, characterized in that, The maleic anhydride in the maleic anhydride-grafted polyethylene is 1-2 wt% by mass.

6. The chain-extended modified nylon material according to claim 1, characterized in that, The chain extenders include isophorone diisocyanate and styrene-glycidyl methacrylate.

7. The chain-extended modified nylon material according to claim 6, characterized in that, The weight ratio of isophorone diisocyanate and styrene-glycidyl methacrylate is 1:(1.5-3).

8. The chain-extended modified nylon material according to claim 1, characterized in that, The nylon resin is at least one of PA6 and PA66; the antioxidant is N-phenyl-α-naphthylamine; and the lubricant is pentaerythritol stearate.

9. A method for preparing the chain-extended modified nylon material according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Mix nano-silica, halloysite nanotubes, vinyltrimethoxysilane and solvent, disperse ultrasonically, heat and stir, add 1-vinyl-3-ethylimidazolium tetrafluoroborate, stir and adsorb, then add azobisisobutyronitrile, heat and stir, filter, wash and dry to obtain pre-modified material; S2. Mix the pre-modified material with nylon resin, chain extender, maleic anhydride grafted polyethylene, antioxidant, and lubricant, stir evenly, and melt-extrude to obtain chain-extended modified nylon material.

10. The application of the chain-extended modified nylon material according to any one of claims 1-8 in battery sealing rings.

Images