A polyamide composition, its preparation method and application

Abstract

This invention discloses a polyamide composition, its preparation method, and its applications, relating to the field of polymer materials technology. The polyamide composition provided by this invention comprises the following components in parts by weight: 33-58 parts polyamide resin, 6-16 parts flame retardant, 15-40 parts glass fiber, and 0.5-5 parts radiation crosslinking agent; the average retention length of the glass fiber in the polyamide composition is 30-150 μm. By introducing glass fiber with a specific average retention length into the components, and in conjunction with the use of the radiation crosslinking agent, the polyamide composition can form a three-dimensional interpenetrating network structure in the polyamide matrix, resulting in an IPT (interpenetrating temperature) duration of over 90 min and, after 500 h of double 85 damp heat aging test, only trace amounts of additives precipitate or do not precipitate at all.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polyamide composition, its preparation method, and its application. Background Technology

[0002] In recent years, as electronic and photovoltaic equipment have developed towards miniaturization, more complex application scenarios, and upgraded safety standards, the requirements for materials in terms of electrical resistance and resistance to damp heat aging have also increased significantly.

[0003] Among the many performance requirements for leakage resistance, inclined plane tracking (IPT) is one of the important indicators. Compared with another indicator, the Comparative Tracking Index (CTI), the IPT test requires the sample to be placed at a certain angle, so that the electrolyte flows downward along the slope under the action of gravity. This state is closer to the actual working state of components such as photovoltaic connectors and insulators outdoors. Moreover, the maximum test range of CTI is only 600 V, while the test range of IPT is 1-5 kV. This means that for materials used in high-voltage scenarios, CTI test results are not very meaningful. Therefore, IPT test results are more instructive for practical applications. In addition to the test conditions, the focus of IPT test results is also different from that of CTI. The failure criteria of IPT are that the material trace length exceeds 25 mm or burn through (forming a hole). Therefore, it is more concerned with the ability of the material to block the formation of a continuous carbon layer than with reducing the conductivity of the carbon layer formed by the material (which is the issue that is more important when improving CTI).

[0004] Since polyamide is one of the most commonly used materials in related fields, providing a polyamide material that combines high resistance to inclined surface tracking index and resistance to damp heat aging is extremely important for the development of electronic equipment and photovoltaic equipment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a polyamide composition that utilizes glass fibers of a specific retention length as fillers, in conjunction with the use of an irradiation crosslinking agent, to form a three-dimensional interpenetrating network structure in the polyamide matrix, thereby simultaneously improving the material's IPT performance and resistance to damp heat aging.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: A polyamide composition comprising the following components in parts by weight: 33-58 parts polyamide resin, 6-16 parts flame retardant, 15-40 parts glass fiber, and 0.5-5 parts irradiation crosslinking agent; The average retention length of the glass fiber in the polyamide composition is 30-150 μm; The molecular structure of the irradiation crosslinking agent contains a carbonyl group and two or more carbon-carbon double bonds.

[0007] The process by which a conductive path gradually forms on the surface of a solid insulating material under the combined action of an electric field and an electrolyte is called tracking. The IPT (inclined tracking index) examines the material's ability to withstand the effects of tilting, continuous dripping of contaminated electrolyte, and the application of an electric field. Compared to CTI, IPT has a wider testing range and better meets the current needs of high-voltage applications. Through extensive experimental research, the inventors of this application discovered that introducing glass fibers of a specific length into polyamide and adding an irradiation crosslinking agent increases the degree of crosslinking between polyamide molecular chains. Glass fibers with a specific average retention length, acting as a good thermal insulation material, can hinder internal heat conduction in the polyamide matrix when the material surface faces destructive phenomena such as arcing during electrical discharge, reducing the likelihood of polyamide combustion forming a continuous char layer. Simultaneously, it can strengthen the matrix, preventing premature burn-through failure. Uncrosslinked linear polyamide molecular chains have large gaps, allowing electrolyte solutions to easily penetrate into the material, forming continuous leakage channels along the molecular chain gaps, leading to localized heating and carbonization, forming electrical tracks. After irradiation crosslinking, the three-dimensional network structure formed by the glass fibers of a specific average retention length and the crosslinked polyamide makes the material surface denser, compressing or blocking the electrolyte penetration path. Therefore, this invention can improve the IPT (internal heat transfer) of the polyamide composition by blocking the path of polyamide forming a continuous char layer.

[0008] The combined introduction of glass fiber and irradiation crosslinking agent can also improve the material's resistance to damp heat aging. Damage resistance to damp heat aging examines the material's tolerance to moisture penetration under high temperature and high humidity conditions. Simultaneously introducing glass fiber and irradiation crosslinking agent into the polyamide matrix allows the glass fiber and crosslinked polyamide, with their specific average retention length after irradiation crosslinking, to synergistically form a three-dimensional interpenetrating network. This network firmly fixes the glass fiber filler, the crosslinking agent (a small molecule), and other possible additives within the matrix, preventing migration and precipitation. It also keeps the polyamide molecular chains in situ, preventing chain movement that could lead to material failure.

[0009] It should be noted that the irradiation crosslinking agent used in this invention should contain a carbonyl group and two or more carbon-carbon double bonds. Irradiation crosslinking agents containing a carbonyl group and two or more carbon-carbon double bonds exhibit stronger hydrogen bonding between other structural segments and the polyamide matrix after crosslinking the polyamide molecular chain. This results in stronger migration resistance under high temperature and high humidity conditions. Furthermore, they can form a tighter bond with glass fibers of a specific average retention length, enhancing the ability to block the formation of continuous carbon layers, which is beneficial for improving IPT (Intense Polymerization Time). Other commonly used polyamide irradiation crosslinking agents in this field, such as triallyl cyanurate (TAC), contain only ether bonds and no carbonyl groups in their molecules, leading to reduced hydrogen bonding with the polyamide matrix and consequently, insufficient resistance to humid heat aging and migration, and lower IPT.

[0010] It should be noted that the average retention length of glass fiber in the composition has a significant impact on both the IPT (Integrated Product Test) and the resistance to damp heat aging. If the average retention length of glass fiber is too short, it cannot provide adequate reinforcement, and the three-dimensional interpenetrating network structure formed by it and the cross-linked polyamide is not tight enough. During the IPT test, the material is prone to failure due to burn-through, and the material's resistance to damp heat aging also decreases. If the average retention length of glass fiber is too long, the carbonized cross-linked polyamide resin will coat the surface of the glass fiber. Excessively long glass fibers can easily bridge and form conductive channels, leading to rapid expansion of electrical traces, which also results in a lower IPT.

[0011] It should be noted that in the polyamide composition of this application, the crosslinking agent is dispersed between the polyamide molecular chains before irradiation crosslinking. During irradiation, the irradiation crosslinking agent reacts with the polymerization units in the polyamide backbone through the carbon-carbon double bonds in its molecular structure.

[0012] Preferably, in the polyamide composition, the polyamide resin is in the range of 33 parts, 35 parts, 37 parts, 40 parts, 45 parts, 50 parts, 55 parts, and 58 parts by weight, or any two of these values; the flame retardant is in the range of 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, and 16 parts by weight, or any two of these values; the glass fiber is in the range of 15 parts, 20 parts, 25 parts, 27 parts, 30 parts, 32 parts, 35 parts, and 40 parts by weight, or any two of these values; and the irradiation crosslinking agent is in the range of 0.5 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, and 5 parts by weight, or any two of these values.

[0013] Preferably, the polyamide composition contains ≥30% polyamide resin by mass.

[0014] Preferably, the irradiation crosslinking agent includes isocyanurate crosslinking agents and / or acrylate crosslinking agents.

[0015] More preferably, the irradiation crosslinking agent includes isocyanurate crosslinking agents and acrylate crosslinking agents, wherein the mass ratio of the isocyanurate crosslinking agent to the acrylate crosslinking agent is (0.25-5):1.

[0016] More preferably, the mass ratio of isocyanurate crosslinking agent and acrylate crosslinking agent in the irradiated crosslinking agent is one or any two of the following: 0.25:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1.

[0017] More preferably, the isocyanurate crosslinking agent in the polyamide composition is in the range of one or any two of the following quantities: 0.25 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, and 2.5 parts.

[0018] More preferably, the mass fraction of the acrylate crosslinking agent in the polyamide composition is one or any two of the following values: 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.67 parts, 0.83 parts, 1 part, 1.25 parts, 2 parts, and 2.5 parts.

[0019] More preferably, the mass ratio of isocyanurate crosslinking agent to acrylate crosslinking agent in the irradiation crosslinking agent is (1-3):1.

[0020] When the composition is injection molded and then subjected to irradiation crosslinking, the specific combination of irradiation crosslinking agents in the product can enable the glass fiber and polyamide crosslinking molecular chains to form a more tightly bonded three-dimensional interpenetrating network structure, thereby improving the overall performance.

[0021] More preferably, the isocyanurate crosslinking agent includes at least one of triallyl isocyanurate (TAIC) and methyltriallyl isocyanurate (TMAIC).

[0022] While the intrinsic leakage protection performance of TAIC crosslinking agents is somewhat insufficient, by combining them with glass fibers of a specific average retention length or with acrylate crosslinking agents, polyamides with suitable structure and strength can be formed, which helps to simultaneously improve IPT performance and resistance to humid heat aging and migration.

[0023] More preferably, the acrylate crosslinking agent includes at least one of trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), and propoxylated trihydroxypropane triacrylate (POTMPTA).

[0024] The aforementioned small molecule crosslinking agent is not easily decomposed under high temperature conditions. At the same time, the molecule contains carbonyl groups, which can form stronger hydrogen bonds with the polyamide matrix. Therefore, it is not easy for migration to occur during damp heat aging tests, thus preventing performance degradation.

[0025] Preferably, the average retention length of the glass fiber in the polyamide composition is a value within the range of one or any two of the following: 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 107 μm, 110 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, and 150 μm.

[0026] More preferably, the average retention length of the glass fiber in the polyamide composition is 50-120 μm.

[0027] Shorter average retention lengths of glass fibers result in higher fluidity and improved system uniformity; longer average retention lengths allow glass fibers to form a tighter three-dimensional interpenetrating network structure with cross-linked polyamide molecular chains. When the average retention length of the glass fibers meets the aforementioned preferred range, the performance of the resulting composition can be further enhanced.

[0028] It should be noted that the retained length of the glass fiber described in this invention is not the same as its original length (i.e., the length of the glass fiber raw material). During the processing of the polyamide composition, based on the material stirring and mixing processes, the retained length of the glass fiber in the product differs from its original length. To ensure the performance of the product during use, the present invention uses its retained length as the standard. Those skilled in the art can adjust the final retained length by controlling the original length of the glass fiber through the preparation process. Alternatively, after selecting a glass fiber of a fixed original length, those skilled in the art can also control the retained length of the glass fiber by using different feeding methods during the processing of the polyamide composition, such as feeding the glass fiber through a main feed port or a side feed port, and setting different mixing screw speeds.

[0029] More preferably, the method for testing the average retention length of glass fibers in the polyamide composition includes the following steps: The polyamide composition was burned at 650°C to eliminate the resin. The length of the glass fibers was observed under a two-dimensional microscope, and the average retention length of at least 500 glass fibers was counted and the average value was taken.

[0030] More preferably, the average retained diameter of the glass fiber is 7~15μm.

[0031] More preferably, the method for testing the average retained diameter of the glass fibers in the polyamide composition includes the following steps: The polyamide composition was burned at 650°C to eliminate the resin. The diameter of the glass fibers was observed under a two-dimensional microscope. The average retained diameter of at least 500 glass fibers was counted and the average value was taken.

[0032] It should be noted that the difference between the average retained diameter (diameter after processing) of the glass fiber and the original diameter (diameter before processing) of the glass fiber is no more than 5%. Therefore, it can be considered that the diameter of the glass fiber remains basically unchanged before and after processing, and the average retained diameter of the glass fiber can be based on the original diameter of the glass fiber.

[0033] The technical solution of this application does not have any special limitation on the type of glass fiber. The glass fiber may include at least one of the following conventional glass fibers in the art: E glass fiber (alkali-free glass fiber), A glass fiber, S glass fiber (high-strength glass fiber), D glass fiber, C glass fiber (medium-alkali glass fiber), quartz glass fiber, E-CR glass fiber (corrosion-resistant glass fiber), AR glass fiber (alkali-resistant glass fiber), high silica glass fiber, and R-glass fiber.

[0034] Preferably, the glass fiber includes at least one of E glass fiber, A glass fiber, S glass fiber, D glass fiber, C glass fiber, and quartz glass fiber.

[0035] More preferably, the glass fiber comprises E glass fiber.

[0036] Preferably, the polyamide resin has a relative viscosity of 2.0-3.4 at 25°C.

[0037] Preferably, the relative viscosity of the polyamide resin at 25°C is one or any two of the following: 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, and 3.4.

[0038] More preferably, the method for testing the relative viscosity of the polyamide resin at 25°C includes the following steps: Weigh 0.5g of polyamide resin and transfer it to a 50ml volumetric flask. Add approximately 40ml of 96% concentrated sulfuric acid and sonicate until the polyamide resin is completely dissolved. Cool the solution to 25℃, dilute it to the mark with concentrated sulfuric acid, and mix thoroughly. Measure the flow time of the 0.01g / mL polyamide resin solution at 25℃ through an Ubbelohde viscometer and record it as t1. Measure the flow time of the concentrated sulfuric acid solvent using the same viscometer and record it as t2. t1 / t2 is the relative viscosity.

[0039] This application does not specifically limit the type of polyamide resin. The polyamide resin may include any one or a combination of at least two of the following conventionally available materials: condensation products of dicarboxylic acids and diamines, ring-opening polymerization products of lactams, and condensation products of aminocarboxylic acids. The dicarboxylic acids exemplarily include, but are not limited to, any one or a combination of at least two of adipic acid, sebacic acid, dodecanoic acid, terephthalic acid, and isophthalic acid. The diamines exemplarily include, but are not limited to, any one or a combination of at least two of pentanediamine, hexamethylenediamine, decanediamine, dodecanediamine, butanediamine, p-phenylenediamine, and m-phenylenediamine. The lactams exemplarily include, but are not limited to, any one or a combination of at least two of caprolactam, octanolactam, undecanolactam, and dodecalactam. The aminocarboxylic acids exemplarily include, but are not limited to, any one or a combination of at least two of the aforementioned ω-amino acids formed by ring-opening of lactams and aminobenzoic acid.

[0040] Preferably, the polyamide resin comprises at least one of polyhexamethylene adipamide, polycaprolactam, polyundecanolactam, polydodecanolactam, polypentyl adipamide, polyhexamethylene adipamide, polydecanoyl adipamide, polydecanoyl adipamide, polydodecanoyl adipamide, polydodecanoyl adipamide, polydodecanoyl adipamide, poly(hexamethylene terephthalamide), poly(decanoyl terephthalamide), and poly(p-phenylene terephthalamide).

[0041] More preferably, the polyamide resin includes at least one of polyhexamethylene adipamide and polycaprolactam.

[0042] In the polyamide composition of the present invention, there is no special limitation on the type of flame retardant, as long as the expected flame retardant effect can be achieved in the system and the flame retardant of the product meets the standards.

[0043] Preferably, the flame retardant includes a phosphorus-based flame retardant.

[0044] Phosphorus-based flame retardants achieve flame retardancy through a condensed phase flame retardant mechanism. Although this leads to rapid char formation in the polyamide matrix, the high thermal insulation of the char layer and the synergistic effect of the glass fiber effectively block the continuous char layer formation process.

[0045] More preferably, the phosphorus content of the phosphorus-based flame retardant is ≥45 wt%.

[0046] More preferably, the phosphorus content of the phosphorus-based flame retardant is 45 wt%-100 wt%.

[0047] More preferably, the phosphorus content of the phosphorus-based flame retardant is 48 wt%-80 wt%.

[0048] More preferably, the phosphorus content of the phosphorus-based flame retardant is one or any two of the following: 45 wt%, 50 wt%, 55 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 100 wt%.

[0049] The phosphorus content of the phosphorus-based flame retardant in this invention was obtained by ICP-OES detection.

[0050] More preferably, the phosphorus-based flame retardant includes at least one of red phosphorus flame retardant and organic phosphonates.

[0051] More preferably, the organic phosphonate includes aluminum diethylphosphonate.

[0052] More preferably, the phosphorus-based flame retardant includes red phosphorus flame retardant.

[0053] In a specific embodiment of the present invention, the phosphorus-based flame retardant may be added in the form of masterbatch or in other conventional forms in the art.

[0054] Preferably, the polyamide composition further comprises 5.5-26 parts of processing aids. More preferably, the processing aids include lubricants, antioxidants, toughening agents, etc., which can be added according to actual needs by those skilled in the art, as long as they do not affect the expected technical effect of the product of the present invention. More preferably, the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, cuprous halide composite antioxidants, or antioxidants containing benzophenone functional groups; the lubricant includes at least one of hydrocarbons, esters, alcohols, fatty acids, fatty acid amides, metal soaps, and silicones, and more preferably silicone lubricants; the toughening agent includes at least one of maleic anhydride-grafted ethylene-octene copolymers, maleic anhydride-grafted ethylene-propylene-diene rubber, styrene-ethylene-butadiene copolymers, ethylene-vinyl acetate copolymers, ethylene-butyl acrylate, ethylene-methacrylate-butyl acrylate, ethylene-acrylic acid copolymers, and acrylonitrile-butadiene-styrene copolymers, and more preferably maleic anhydride-grafted ethylene-octene copolymers.

[0055] More preferably, the antioxidant is 0.1-1 parts by weight, the lubricant is 0.5-5 parts by weight, and the toughening agent is 5-20 parts by weight.

[0056] The introduction of toughening agents can improve the toughness of polyamide matrices. When polyamides turn into carbon, their volume expands to a certain extent. The introduction of toughening agents can maintain good interaction between additives such as glass fibers and the polyamide matrix, further reducing the possibility of material failure.

[0057] This invention also protects a method for preparing the above-mentioned polyamide composition, comprising the following steps: After the components are mixed evenly, they are melt-extruded and granulated in a screw extruder, then injection molded and cross-linked by irradiation to obtain the final product.

[0058] Preferably, the mixing is achieved by adding each component to a high-speed mixer and mixing for 3-10 minutes.

[0059] Preferably, the screw extruder is a twin-screw extruder with a screw speed of 300~800 rpm, a length-to-diameter ratio of (36-48):1, a barrel temperature of 60~250℃ in each section of the extruder, and a die head temperature of 240℃~280℃.

[0060] Preferably, the injection molding temperature is 250-290℃.

[0061] Preferably, the irradiation crosslinking uses an electron beam as the radiation source, and the irradiation dose is 15-25 Mrad.

[0062] This invention also protects the application of the above-mentioned polyamide composition in the fields of photovoltaics, energy storage, and new energy.

[0063] The polyamide composition provided by this invention has both excellent resistance to humid heat aging and IPT (intensity per minute), and has broad application prospects in fields and devices with high requirements for IPT and anti-aging performance, such as photovoltaic connectors.

[0064] The present invention also protects a photovoltaic connector comprising the polyamide composition.

[0065] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes glass fibers of a specific retention length as fillers, in conjunction with the use of irradiation crosslinking agents, to form a three-dimensional interpenetrating network structure in a polyamide matrix, thereby obtaining a polyamide composition with an IPT duration of over 90 minutes and no migration or precipitation after 500 hours of double 85 damp heat aging test. Detailed Implementation

[0066] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. The raw material information used in each embodiment and comparative example is as follows: 1) Polyamide resin: PA Resin-1: Polyhexamethylene adipamide, PA66 EPR24, relative viscosity 2.4, manufactured by Pingdingshan Shenma Engineering Plastics Co., Ltd.

[0067] PA Resin-2: Polycaprolactam, PA6 HY-2800A, relative viscosity 2.8, manufactured by Haiyang Chemical Fiber.

[0068] 2) Fiberglass: Glass fiber-1: ECS301CL-1.7-H, manufactured by Chongqing International Composite Materials Co., Ltd., with an initial average length of 1.7 mm and an initial diameter of 10 μm.

[0069] Fiberglass-2: ECS10-03-568H, manufactured by Jushi, with an initial average fiberglass length of 3mm and an initial diameter of 10μm.

[0070] Fiberglass-3: EMG-70, manufactured by Taian Zhongshuo, with an initial average fiberglass length of 70μm and an initial diameter of 10μm.

[0071] Fiberglass-4: EMG9-35, manufactured by Taishan Fiberglass, with an initial average length of 35μm and an initial diameter of 9μm.

[0072] 3) Flame retardant: Flame retardant-1: Red phosphorus flame retardant, FR9950T, phosphorus content 50 wt%, manufactured by Tongcheng Xinde New Materials Co., Ltd.

[0073] Flame retardant-2: Red phosphorus flame retardant, FRP-950X, red phosphorus content is 80 wt%, Guangzhou Yinsu Flame Retardant Materials Co., Ltd.

[0074] 4) Irradiation crosslinking agent: Irradiation crosslinking agent-1: Triallyl isocyanurate (TAIC), manufactured by Fangruida Chemical Co., Ltd.

[0075] Irradiation crosslinking agent-2: Methyltriallyl isocyanurate (TMAIC), manufactured by Fangruida Chemical Co., Ltd.

[0076] Irradiation crosslinking agent-3: Trimethylolpropane trimethacrylate (TMPTMA), manufactured by Fangruida Chemical Co., Ltd.

[0077] Irradiation crosslinking agent-4: Triallyl cyanurate (TAC), manufactured by Fangruida Chemical Co., Ltd.

[0078] 5) Toughening agent: Maleic anhydride-grafted ethylene-octene copolymer: PC-28A, purchased from Foshan Nanhai Baichen Polymer New Materials Co., Ltd.

[0079] 6) Antioxidants: Hindered phenolic antioxidant: RIANOX 1098, manufactured by Rianlong.

[0080] 7) Lubricant: Lubricant: Silicone masterbatch, MB50-002, with a silicone content of 50%, manufactured by Dow Corning.

[0081] Examples 1-14 This embodiment provides a series of polyamide compositions, the components of which are shown in Table 1: The preparation method of the polyamide compositions in Examples 1-14 includes the following steps: Mix each component in a high-speed mixer for 5 minutes, then add it to the main feed hopper of a twin-screw extruder (when feeding glass fiber, mix it with each component and add it to the main feed hopper; when feeding glass fiber from the side, add it from the 6th or 8th section of the screw barrel; unless otherwise specified, the component feeding method is main feeding). After fully plasticizing and melting, extrude, stretch, cool, and pelletize, and injection mold it into a 130*50*6mm rectangular plate at 270℃. Then, irradiate and crosslink it under electron beam radiation with an irradiation dose of 20 Mrad to obtain a polyamide composite material. The twin-screw extruder has a screw speed of 400 rpm, a length-to-diameter ratio of 40:1, and extruder barrel temperatures of 60℃, 160℃, 250℃, 240℃, 240℃, 220℃, 220℃, 230℃, and 230℃, with a die head temperature of 260℃ (in Example 2, the temperatures are 60℃, 160℃, 230℃, 220℃, 220℃, 200℃, 200℃, 200℃, 210℃, and 210℃, with a die head temperature of 240℃).

[0082] Table 1. Continued from Table 1. Comparative Examples 1-4 The only difference between each comparative example and Example 3 is the type and ratio of components, as shown in Table 2.

[0083] Table 2. Performance testing Average retention length test of glass fibers: The polyamide composition was burned at 650°C to eliminate the resin, and the length of the glass fibers was observed under a two-dimensional microscope. The average retention length of at least 500 glass fibers was counted.

[0084] Tracking per slant (IPT) test: The IPT index of the compositions obtained in the examples and comparative examples was tested according to the constant voltage method of ASTM D2303-13. The fixed voltage was 2kV. Each example or comparative example was tested in parallel 5 times. The average time before tracking and failure was recorded. The longer the time, the better the IPT performance.

[0085] Double 85 migration test: The compositions obtained in the examples and comparative examples were placed in a damp heat aging chamber at 85°C and 85% humidity for 500 hours. The precipitation on the surface was observed by visual observation. If more than 5 white spots were visible on each sample, it was considered obvious precipitation. If fewer white spots were visible (1-5), it was considered a small amount of precipitation. If it was not visible to the naked eye, it was considered a trace amount of precipitation when observed under an electron microscope at 500x magnification. If no precipitation was observed under an electron microscope, it was considered no precipitation.

[0086] The performance test data is shown in Table 3 below: Table 3. Continued from Table 3. Continued from Table 3. As can be seen from Table 3 above, the present invention utilizes glass fibers with a specific average retention length as fillers, and in conjunction with the use of irradiation crosslinking agents, can form a three-dimensional interpenetrating network structure in the polyamide matrix, thereby obtaining a polyamide composition with an IPT duration of up to 90 minutes or more and only trace amounts of additives or no precipitation after 500 hours of double 85 damp heat aging test.

[0087] According to Examples 4-9 and Comparative Examples 1-2, the average retention length of glass fiber in the polyamide composition needs to reach 30-150 μm to fully exert its barrier effect. Too low a glass fiber length (Comparative Example 2) or too high a length (Comparative Example 1) will result in an inability to simultaneously achieve the IPT performance and resistance to damp heat aging of the polyamide composition. Among these, the overall effect is better when the average retention length of glass fiber in the polyamide composition meets the preferred 50-120 μm.

[0088] According to Examples 10-14, using different types of irradiation crosslinking agents can enable the glass fiber and polyamide crosslinked molecular chains to form a more tightly bonded three-dimensional interpenetrating network structure (Examples 10-12), thereby improving overall performance. Specifically, when the mass ratio of isocyanurate crosslinking agent to acrylate crosslinking agent in the irradiation crosslinking agent is the preferred ratio of (1-3):1 (Example 10), a longer inclined plate tracking resistance time can be obtained.

[0089] According to Comparative Example 3, if the amount of irradiation crosslinking agent added is too high, the excess crosslinking agent cannot be fixed by the formed three-dimensional interpenetrating network, which leads to easy migration during the damp heat aging test.

[0090] According to Comparative Example 4, when triallyl cyanurate (TAC) was used as a crosslinking agent, the hydrogen bonding between it and the polyamide matrix decreased because its molecule contains only ether bonds and no carbonyl groups, resulting in insufficient resistance to humid heat aging and migration.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyamide composition, characterized in that, The components include the following parts by weight: 33-58 parts polyamide resin, 6-16 parts flame retardant, 15-40 parts glass fiber, and 0.5-5 parts irradiation crosslinking agent; The average retention length of the glass fiber in the polyamide composition is 30-150 μm; The molecular structure of the irradiation crosslinking agent contains a carbonyl group and two or more carbon-carbon double bonds.

2. The polyamide composition according to claim 1, characterized in that, The irradiation crosslinking agent includes isocyanurate crosslinking agents and / or acrylate crosslinking agents.

3. The polyamide composition according to claim 2, characterized in that, The irradiation crosslinking agent includes isocyanurate crosslinking agents and acrylate crosslinking agents. Preferably, the mass ratio of the isocyanurate crosslinking agent to the acrylate crosslinking agent is (0.25-5):

1.

4. The polyamide composition according to claim 1, characterized in that, The average retention length of the glass fiber in the polyamide composition is 50-120 μm; And / or, the average retained diameter of the glass fiber is 7-15 μm.

5. The polyamide composition according to claim 1, characterized in that, The polyamide resin has a relative viscosity of 2.0-3.4 at 25°C.

6. The polyamide composition according to claim 1, characterized in that, The flame retardant includes a phosphorus-based flame retardant, and preferably, the phosphorus-based flame retardant includes a red phosphorus flame retardant.

7. The polyamide composition according to claim 6, characterized in that, The phosphorus content of the phosphorus-based flame retardant is ≥45 wt%.

8. A method for preparing the polyamide composition according to any one of claims 1-7, characterized in that, Includes the following steps: After the components are mixed evenly, they are melt-extruded and granulated in a screw extruder, then injection molded and crosslinked by irradiation to obtain a polyamide composition.

9. The use of the polyamide composition according to any one of claims 1-7 in the preparation of connectors for new energy vehicles and photovoltaic connectors.

10. A connector for manufacturing new energy vehicles and a photovoltaic connector, characterized in that, Includes the polyamide composition according to any one of claims 1-7.

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