High-temperature-resistant flame-retardant plastic particle and preparation method thereof

Abstract

The invention provides a high-temperature-resistant flame-retardant plastic particle and a preparation method thereof, and belongs to the field of high-molecular organic compounds. The material comprises the following components: polycarbonate, acrylonitrile-butadiene-styrene copolymer resin, microcapsule ammonium polyphosphate, a carbon source, modified halloysite nanotubes, a flexibilizer, an antioxidant, a lubricant and an anti-dripping agent. The modified halloysite nanotube is obtained by carrying out grafting reaction on a halloysite nanotube through a coupling agent with an epoxy group. The composite material provided by the scheme aims to meet the dual requirements of daily use scenes (especially household appliances) on the flame-retardant safety and the structural reliability of the material. And a stable and compact expanded carbon layer can be formed during combustion in the aspect of flame retardance to effectively isolate heat and oxygen, so that UL94V-0-level flame retardance is realized, and the smoke density is remarkably reduced. Good impact strength, rigidity and dimensional stability are kept in the aspect of mechanical properties, and the assembly and use requirements of shells and internal structural parts of household appliances are met.

Description

Technical Field

[0001] This invention belongs to the field of polymer organic compounds, and particularly relates to a high-temperature resistant flame-retardant plastic granule and its preparation method. Background Technology

[0002] In the field of home appliances, the application of flame-retardant plastics is a key materials science and technology. Its core objective is to proactively prevent fire risks through the inherent properties of the materials, while ensuring product functionality and cost control, and meeting increasingly stringent safety regulations and environmental protection requirements. The working environment of home appliances places complex and stringent comprehensive performance requirements on plastics. The primary and most mandatory requirement is flame-retardant safety, which is usually evaluated according to the UL 94 standard. For most plastic parts that come into direct contact with or are adjacent to live components, such as housings, internal supports, and connectors, the highest V-0 rating is usually required. This means that in a vertical burning test, the sample can self-extinguish within 10 seconds after the flame source is removed, without producing burning drips that could ignite the cotton pad below. In addition, for scenarios where overheating sources may be generated due to overload, poor contact, or other faults, such as switches, sockets, and motor peripheral components, it is also necessary to pass the hot wire test specified in IEC 60695-2-11 to simulate the effect of contact between overheated components and materials. The material is required not to ignite or to have a brief flame that extinguishes within a specified time when in contact with a specific high-temperature hot wire (such as 750°C or 850°C).

[0003] Beyond direct flame retardant properties, plastics used in electrical appliances must meet multi-dimensional requirements for long-term reliability. In terms of thermal properties, materials need sufficiently high heat distortion temperature and relative temperature index (RTI) to ensure that components do not deform, soften, or degrade under the temperature rise generated during long-term operation and seasonal environmental temperature fluctuations. In terms of mechanical properties, they must maintain sufficient impact strength, tensile strength, and flexural strength to withstand assembly stress, accidental drops, and vibrations and loads from internal operation. Regarding electrical safety, for materials used to support or insulate live parts, the tracking index (CTI) is a key indicator. It measures the material's resistance to tracking under electric fields and potential contaminants; a high CTI value effectively prevents leakage-induced fires. In recent years, environmental regulations have become a major driving force for material development. The global RoHS directive and market and consumer expectations for environmental protection strongly promote the halogen-free process. Traditional halogenated flame retardants may produce large amounts of smoke and corrosive toxic gases during combustion; therefore, developing halogen-free flame-retardant plastics with low smoke production and minimal toxic gas release during combustion has become the mainstream direction in the industry.

[0004] To address the aforementioned comprehensive performance requirements, flame-retardant plastics technologies have continuously evolved and formed a systematic approach. At the materials chemistry level, the development and application of flame retardants are central. Currently, mainstream halogen-free solutions include phosphorus-based, nitrogen-based, and inorganic hydroxide systems. Phosphorus-based flame retardants (such as various organic phosphate esters and phosphates) are commonly used as flame-retardant plasticizers in engineering plastics. They function in both the gas and condensed phases, promoting char formation on the material surface to insulate against heat and oxygen, and potentially interfering with gas-phase combustion reactions. Nitrogen-based flame retardants (such as melamine and its derivatives) primarily generate large amounts of non-flammable gases through endothermic decomposition, diluting oxygen and combustible concentrations and assisting in char formation. Inorganic hydroxides, especially aluminum hydroxide and magnesium hydroxide, rely on endothermic decomposition reactions at high loading levels (usually requiring over 50%) to lower the material surface temperature and release water vapor to dilute combustible gases. They are non-toxic and have significant smoke-suppressing effects, but they significantly impact the material's mechanical properties and processing flowability, requiring surface modification and other techniques to optimize their compatibility with the plastic matrix. These flame retardant systems are often used in combination, such as the phosphorus-nitrogen synergistic system, which can produce better flame retardant effects than single components.

[0005] At the materials physics and engineering level, balancing performance through plastic alloying and composite technologies is a common strategy. For example, polycarbonate has excellent impact strength and heat resistance, but suffers from poor processing flow and notch sensitivity; acrylonitrile-butadiene-styrene copolymers offer good processability and lower cost; PC / ABS alloys made by blending these two materials, with the addition of suitable halogen-free flame retardants (such as phosphate esters), can yield materials that combine good flame retardancy (UL 94 V-0), heat resistance, impact strength, and processability, and are widely used in electrical appliance housings. For structural components requiring higher heat resistance, higher strength, and dimensional stability, such as connectors and circuit breakers, glass fiber reinforced engineering plastics, such as flame-retardant reinforced nylon, are often used. By adding glass fibers and flame-retardant systems such as red phosphorus masterbatch or metal hypophosphite to nylon, the material's mechanical strength, heat resistance, and flame retardancy rating can be significantly improved simultaneously. In addition, nanocomposite technology disperses layered silicates (such as montmorillonite) in the plastic matrix at the nanoscale, which can effectively suppress heat and mass transfer by forming a dense carbon layer at a low addition amount, thereby improving flame retardant efficiency and reducing the impact on other properties of the material. Summary of the Invention

[0006] The first objective of this invention is to provide a high-temperature resistant, flame-retardant plastic granule, which contains the following components in parts by weight: Polycarbonate 40-50 Acrylonitrile-butadiene-styrene copolymer resin 20-25 Microencapsulated ammonium polyphosphate 13-22 Carbon source 5-6 Modified halloysite nanotubes 3-5 Toughening agent 3-4 Antioxidant 0.3-0.5 Lubricant 0.5-1.0 Anti-dripping agent 0.2-0.5; The modified halloysite nanotubes are obtained by grafting halloysite nanotubes with a coupling agent containing epoxy groups; the amount of the coupling agent used is at least 3% of the mass of the halloysite nanotubes.

[0007] Preferably, the toughening agent is a polymer containing active groups that chemically react with the terminal functional groups of polycarbonate and has flexible elastomeric segments.

[0008] Preferably, the polycarbonate has a melt volume flow rate between 8 and 12 cm³ / 10 min; the acrylonitrile-butadiene-styrene copolymer resin has a butadiene content between 12 and 20 wt%; and the microcapsule ammonium polyphosphate has a degree of polymerization n ≥ 1000.

[0009] Preferably, the carbon source is a polyol or its derivative.

[0010] Preferably, the method for preparing the modified halloysite nanotubes includes the following steps: S1: Dissolve the coupling agent with epoxy groups in an ethanol aqueous solvent, adjust the pH of the system to 4-5; stir to obtain a hydrolyzed coupling agent solution; S2: Disperse the dried halloysite nanotubes in a hydrolytic coupling agent solution, heat to 80-85℃ and stir for at least 6 hours; after the reaction is completed, centrifuge the system solution to separate the precipitate, wash the precipitate with ethanol and then dry it to obtain modified halloysite nanotubes; The amount of coupling agent used is 3-5% of the mass of halloysite nanotubes.

[0011] Preferably, the antioxidant is a combination of hindered phenolic antioxidants and phosphite antioxidants; the anti-dripping agent is polytetrafluoroethylene.

[0012] Preferably, the high-temperature resistant flame-retardant plastic granules are prepared by first melting and blending modified halloysite nanotubes with a portion of toughening agent to carry out a secondary grafting and chain extension reaction to produce secondary grafted modified halloysite nanotubes.

[0013] The second objective of this invention is to provide a method for preparing high-temperature resistant flame-retardant plastic granules, comprising the following steps: S1: Dry halloysite nanotubes are dispersed in a hydrolyzed coupling solution containing epoxy groups for coupling reaction. After the reaction is completed, the solid is separated, dried, and modified halloysite nanotubes are obtained. S2: Modified halloysite nanotubes are melt-blended with toughening agent and then grafted twice to obtain secondary grafted modified halloysite nanotubes. S3: Mix the secondary grafted modified halloysite nanotubes with the remaining ingredients to obtain a premix; S4: The premixed material is melt-reacted, blended, extruded, cooled, and granulated to obtain high-temperature resistant and flame-retardant plastic granules.

[0014] Preferably, the reaction temperature of the melt blending secondary grafting reaction in step S2 is 160-170℃; and the melting temperature of the premix melt reaction blending in step S4 is 240-260℃.

[0015] This invention aims to provide a composite material that combines excellent high-temperature resistance, high-efficiency halogen-free flame retardancy, low smoke characteristics, and good mechanical properties. Its core design principle lies in the organic combination and synergistic effect of an "intumescent flame retardant system" and "nano-reinforcement technology" through interfacial chemistry and multiphase structure design.

[0016] This solution relates to a high-performance flame-retardant plastic suitable for home appliances and other fields. Its core design is based on interfacial chemical regulation and multi-component synergistic effects, aiming to optimize the material's overall mechanical properties while meeting UL 94 V-0 flame retardancy and low smoke requirements. The key technical principles involved will be objectively explained below.

[0017] (1) Halloysite nanotubes are a natural aluminosilicate nanotube material. Its nanotube structure can play a physical barrier effect during combustion, delaying heat and mass transfer; the abundant silanol groups on the surface provide active sites for chemical modification; compared with carbon nanotubes, it has a lower cost and is an inorganic silicate, which helps to form stable char after combustion and has a certain effect on suppressing smoke.

[0018] However, unmodified halloysite nanotubes have poor compatibility with the polymer matrix due to their hydrophilic surface, and their tendency to agglomerate may lead to a decrease in the mechanical properties of the composite material. Surface grafting modification with a silane coupling agent aims to introduce organic functional groups onto their surface, thereby improving their interfacial compatibility and dispersibility with the polymer matrix.

[0019] The selection of silane coupling agents with epoxy groups (such as 3-(2,3-epoxypropoxy)propyltrimethoxysilane, i.e., KH-560) is based on the characteristic that the epoxy groups can undergo ring-opening reactions with the hydroxyl or carboxyl groups that may be present at the end of polycarbonate under heating conditions. This reaction aims to form chemical bonds between the modified halloysite nanotubes and the polycarbonate matrix, thereby enhancing interfacial adhesion rather than relying solely on physical adsorption.

[0020] (2) This invention requires that the modified halloysite nanotubes be melt-blended with the toughening agent first. This step aims to pre-construct a composite structure with halloysite nanotubes as the core and toughening agent polymer chains as the shell. Compared to blending all components at once, this stepwise method is beneficial for allowing the toughening agent segments to fully interact with the functional groups on the nanotube surface under controlled conditions. This pre-formed "core-shell" structure can promote the dispersion of nanoparticles in the final composite matrix and improve the compatibility with the matrix through the toughening agent shell, thus having a positive impact on the interface structure and properties of the final material.

[0021] (3) In addition to glycidyl methacrylate-grafted ethylene-vinyl acetate copolymer, reactive compatibility toughening agents can also be selected from polymers with similar reactivity and toughening mechanisms. For example, methyl methacrylate-butadiene-styrene copolymer grafted with glycidyl methacrylate is also a common reactive toughening agent. Its internal rubber phase can provide toughening, and its external shell structure is compatible with ABS. At the same time, the grafted epoxy functional groups can participate in the reaction.

[0022] (4) Several technical parameters need to be considered when selecting a carbon source: thermal stability needs to match the processing and flame-retardant decomposition temperature; it needs to have sufficient reactive functional groups such as hydroxyl groups, which can effectively dehydrate and crosslink into carbon under acid catalysis; and it needs to have a certain compatibility with the polymer matrix to reduce the negative impact on mechanical properties. Polyols and their derivatives (such as pentaerythritol and dipentaerythritol) are common choices that meet these conditions.

[0023] (5) The flame-retardant effect of this invention is mainly based on the synergistic effect of the intumescent flame-retardant system in the condensed phase. Ammonium polyphosphate decomposes upon heating, and the resulting polyphosphoric acid can act as an acid source to catalyze the carbon source and the dehydration and carbonization of the polymer matrix. Simultaneously, the released gas promotes the expansion of the char layer. The modified halloysite nanotubes in this system play several roles: acting as a physical barrier to delay thermal decomposition; their nanoscale and surface properties may help stabilize the structure of the expanded char layer and reduce cracking; their inorganic components remain after combustion, providing support and reinforcement to the formed char layer, thereby jointly improving the heat insulation and oxygen barrier efficiency of the char layer. A more stable char layer structure typically corresponds to lower smoke release.

[0024] (6) The mechanical property regulation of the present invention focuses on achieving enhancement and toughness through nanofillers and interface modification. Halloysite nanotubes that are uniformly dispersed and well bonded to the matrix can act as stress transfer points and crack anchors, and may simultaneously improve the strength, modulus and toughness of the material.

[0025] (7) This invention does not directly use glass fiber reinforcement, mainly based on considerations of material performance balance in the application scenario. Although glass fiber can significantly improve strength and rigidity, it often leads to a decrease in material impact toughness, significant anisotropy, poor processing fluidity, and increased wear on equipment. The goal of this solution is to achieve flame retardancy while maintaining good comprehensive mechanical properties and processability, therefore the nano-modification path was chosen.

[0026] (8) In the melt blending process of the preparation step of this invention, the following two types of interactions mainly occur between the components: The chemical reactions primarily occur between reactive functional groups. These include: ring-opening esterification reactions that may occur between the epoxy groups on the surface of secondary grafted halloysite nanotubes or the toughening agent segments grafted onto the polycarbonate molecules and the hydroxyl or carboxyl groups at the ends of the polycarbonate molecules; and similar reactions between the epoxy groups carried by the reactive toughening agent itself and the ends of the polycarbonate molecules. These reactions aim to form chemical bonds between the polymer and the filler.

[0027] Physical interactions and thermodynamic processes: These mainly include the decomposition of ammonium polyphosphate at high temperatures and its catalytic esterification, crosslinking, and other char-forming precursor reactions with carbon sources and polymer matrices; the physical entanglement and miscibility of toughening agent segments with good compatibility with acrylonitrile-butadiene-styrene copolymer phases with acrylonitrile-butadiene-styrene copolymer phases; and the dispersion and mixing processes of all components under shear force.

[0028] The combined result of the aforementioned chemical and physical processes is the formation of a multiphase composite system characterized by chemical bonding and physical entanglement, comprising rigid nanofillers, tough elastomers, resin matrices, and flame retardants. This structural design aims to synergistically optimize the flame retardant and mechanical properties of the material.

[0029] The beneficial effects of this invention are as follows: This invention utilizes an intumescent flame-retardant system composed of microencapsulated ammonium polyphosphate and a specific carbon source. Upon contact with a fire source, this system promotes the rapid formation of a dense and robust intumescent char layer on the material's surface. This char layer effectively insulates against heat and oxygen, breaking the combustion chain and enabling the material to achieve a V-0 flame-retardant rating compliant with UL 94 standards. The introduced modified halloysite nanotubes, with their nanotubular structure, act as a physical barrier in the condensed phase, helping to stabilize the intumescent char layer structure and delay its collapse. This positively impacts flame-retardant efficiency and reduces smoke density during combustion. This synergistic flame-retardant mechanism aims to effectively suppress flame spread and reduce smoke generation in the event of abnormal overheating or electrical malfunctions in household appliances, thereby enhancing product safety.

[0030] This invention achieves high flame retardancy while prioritizing the maintenance and optimization of the matrix's mechanical properties. The use of polycarbonate with suitable intrinsic viscosity and acrylonitrile-butadiene-styrene copolymer with a specific rubber content as the matrix provides the material with a fundamental basis for heat resistance, rigidity, and toughness. This invention aims to significantly improve the interfacial compatibility between the inorganic nanofiller and the organic polymer matrix through coupling agent grafting and pre-grafting treatment with reactive toughening agents on halloysite nanotubes. This strong interfacial bonding facilitates stress transfer, allowing the nanotubes to exert their potential nano-reinforcing effect, thereby compensating for any potential loss in material strength and toughness caused by the addition of large amounts of flame retardants. Detailed Implementation

[0031] To better understand the present invention, the present invention will be further described below with reference to specific serial numbers. The terminology used in the serial numbers is for describing specific embodiments and does not constitute a limitation on the scope of protection of the present invention.

[0032] In the specific implementation methods, unless otherwise specified, the experimental methods used are all conventional methods, and the materials and reagents used are all commercially available unless otherwise specified.

[0033] Unless otherwise specified, percentages, %, parts, etc. in the specific implementation method are calculated based on mass.

[0034] The polycarbonate (PC) used in this invention is Covestro TC110.

[0035] The acrylonitrile-butadiene-styrene copolymer resin (ABS) used in this invention is grade PA-757; the rubber content is between 13-17%.

[0036] The ammonium polyphosphate used in this invention is a coated ammonium polyphosphate with a high degree of polymerization (>1000), a thermal decomposition temperature ≥280℃, a density of about 1.9 g / cm3, a phosphorus content of 30%-32%, and a nitrogen content of 14%-16%.

[0037] The glycidyl methacrylate-grafted ethylene-vinyl acetate copolymer used in this invention is (EVA-g-GMA), with the brand name MC329.

[0038] The antioxidant used in this invention is a combination of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris[2,4-di-tert-butylphenyl] phosphite in a mass ratio of 2:1.

[0039] The lubricant used in this invention is pentaerythritol stearate.

[0040] The anti-dripping agent used in this invention is polytetrafluoroethylene powder.

[0041] Example 1: Preparation of plastic granules, including the following steps: S1: Halloysite nanotubes were vacuum dried at 80°C for 12 hours to remove moisture; KH-560, with a mass of 3% halloysite nanotubes, was dissolved in sufficient ethanol / water (9:1, V / V), and the pH was adjusted to 4 with acetic acid. After stirring and hydrolyzing for 30 min, a hydrolysis coupling agent solution was formed. The dried halloysite nanotubes were dispersed in a hydrolytic coupling agent solution, and the water bath temperature was controlled at 85℃. The reaction was stirred for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation and washed three times with anhydrous ethanol. Then, the precipitate was dried in a vacuum oven at 80℃ to constant weight to obtain modified halloysite nanotubes. S2: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Microencapsulated ammonium polyphosphate 13 Carbon source 5 Modified halloysite nanotubes 3 EVA-g-GMA 3 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; S3: 3 parts by mass of modified halloysite nanotubes and 1 part by mass of EVA-g-GMA are melt-blended in an internal mixer at 160-170℃ for 5 min to obtain secondary grafted modified halloysite nanotubes. S4: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add the formulated amount of secondary grafted modified halloysite nanotubes, the remaining mass of EVA-g-GMA, PC, ABS and all other components to a high-speed mixer and mix for 10 min. Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0042] Example 2: Preparation of plastic granules, including the following steps: S1: Halloysite nanotubes were vacuum dried at 80°C for 12 hours to remove moisture; Dissolve 5% KH-560 of halloysite nanotubes in sufficient ethanol / water (9:1, V / V), adjust the pH to 5 with acetic acid, and stir for 30 min to form a hydrolysis coupling agent solution. The dried halloysite nanotubes were dispersed in a hydrolytic coupling agent solution, and the water bath temperature was controlled at 85℃. The reaction was stirred for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation and washed three times with anhydrous ethanol. Then, the precipitate was dried in a vacuum oven at 80℃ to constant weight to obtain modified halloysite nanotubes. S2: Weigh each component according to the mass fractions below for later use; PC 50 ABS 25 Microencapsulated ammonium polyphosphate 22 Carbon source 6 Modified halloysite nanotubes 5 EVA-g-GMA 4 Antioxidant 0.5 Lubricant 1.0 Anti-dripping agent 0.5; S3: 3 parts by mass of modified halloysite nanotubes and 1 part by mass of EVA-g-GMA are melt-blended in an internal mixer at 160-170℃ for 5 min to obtain secondary grafted modified halloysite nanotubes. S4: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add the formulated amount of secondary grafted modified halloysite nanotubes, the remaining mass of EVA-g-GMA, PC, ABS and all other components to a high-speed mixer and mix for 10 min. Using a co-rotating twin-screw extruder, the melting zone temperature is set to 250-260℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0043] Example 3: Preparation of plastic granules, including the following steps: S1: Halloysite nanotubes were vacuum dried at 80°C for 12 hours to remove moisture; KH-560, with a mass of 3% halloysite nanotubes, was dissolved in sufficient ethanol / water (9:1, V / V), and the pH was adjusted to 4 with acetic acid. After stirring and hydrolyzing for 30 min, a hydrolysis coupling agent solution was formed. The dried halloysite nanotubes were dispersed in a hydrolytic coupling agent solution, and the water bath temperature was controlled at 85℃. The reaction was stirred for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation and washed three times with anhydrous ethanol. Then, the precipitate was dried in a vacuum oven at 80℃ to constant weight to obtain modified halloysite nanotubes. S2: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Microencapsulated ammonium polyphosphate 13 Carbon source 5 Modified halloysite nanotubes 3 EVA-g-GMA 3 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; S3: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add all the ingredients in the formula to a high-speed mixer and mix for 10 minutes; Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0044] Example 4: Preparation of plastic granules, including the following steps: S1: Halloysite nanotubes were vacuum dried at 80°C for 12 hours to remove moisture; 3% (by weight) of halloysite nanotubes (vinyltriethoxysilane) was dissolved in sufficient ethanol / water (9:1, V / V), and the pH was adjusted to 4 with acetic acid; after stirring and hydrolyzing for 30 min, a hydrolysis coupling agent solution was formed. The dried halloysite nanotubes were dispersed in a hydrolytic coupling agent solution, and the water bath temperature was controlled at 85℃. The reaction was stirred for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation and washed three times with anhydrous ethanol. Then, the precipitate was dried in a vacuum oven at 80℃ to constant weight to obtain modified halloysite nanotubes. S2: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Microencapsulated ammonium polyphosphate 13 Carbon source 5 Modified halloysite nanotubes 3 EVA-g-GMA 3 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; S3: 3 parts by mass of modified halloysite nanotubes and 1 part by mass of EVA-g-GMA are melt-blended in an internal mixer at 160-170℃ for 5 min to obtain secondary grafted modified halloysite nanotubes. S4: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add the formulated amount of secondary grafted modified halloysite nanotubes, the remaining mass of EVA-g-GMA, PC, ABS and all other components to a high-speed mixer and mix for 10 min. Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0045] Example 5: Preparation of plastic granules, including the following steps: S1: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Microencapsulated ammonium polyphosphate 13 Carbon source 5 Halloysite nanotubes 3 EVA-g-GMA 3 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; S3: 3 parts by mass halloysite nanotubes and 1 part by mass EVA-g-GMA are melt-blended in an internal mixer at 160-170℃ for 5 min to obtain secondary grafted modified halloysite nanotubes. S4: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add the formulated amount of secondary grafted modified halloysite nanotubes, the remaining mass of EVA-g-GMA, PC, ABS and all other components to a high-speed mixer and mix for 10 min. Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0046] Example 6 Preparation of Plastic Particles The difference from Example 1 is that an equal amount of ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA) was used instead of EVA-g-GMA.

[0047] Example 7 Preparation of Plastic Particles The difference from Example 1 is that an equal amount of maleic anhydride-grafted ABS (ABS-g-MAH) was used instead of EVA-g-GMA.

[0048] Example 8: Preparation of plastic granules, comprising the following steps: S2: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; S2: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add all components to a high-speed mixer and mix for 10 minutes; Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0049] Example 9: Preparation of plastic granules, comprising the following steps: S2: Weigh each component according to the mass fractions below for later use; PC 40 ABS 20 Microencapsulated ammonium polyphosphate 13 Carbon source 5 3-Cut Glass Fiber EVA-g-GMA 3 Antioxidant 0.3 Lubricant 1.0 Anti-dripping agent 0.2; S3: Dry PC and ABS separately at 100-120℃ for 4 hours by forced air drying; Add all the ingredients in the formula to a high-speed mixer and mix for 10 minutes; Using a co-rotating twin-screw extruder, the melting zone temperature is set to 240-250℃, and the screw speed is 300rpm. The mixture is then extruded through the die head, water-cooled, and pelletized to obtain plastic granules.

[0050] Example 10: Preparation of plastic granules, comprising the following steps: The difference from Example 1 is that the melting temperature in step S3 is 220-230°C.

[0051] Example 11 Preparation of plastic granules, including the following steps: The difference from Example 1 is that step S2 is modified as follows: Weigh each component according to the mass percentages below and set aside; PC 30 ABS 30 Microencapsulated ammonium polyphosphate 13 Carbon source 5 Modified halloysite nanotubes 3 EVA-g-GMA 3 Antioxidant 0.3 Lubricant 0.5 Anti-dripping agent 0.2; To verify the performance of the foregoing embodiments, the following performance tests were performed on the embodiments, and the results are shown in Table 1.

[0052] Needle flame resistance test: GB / T 5169.5-2020; refer to the test method in Appendix A, the flame application time is 30s.

[0053] UL-94 flame retardant rating: GB / T 2408-2021 (1.2mm thickness).

[0054] Limiting Oxygen Index (LOI): GB / T2406.0-200.

[0055] Notched impact strength: GB / T 1843-2008 (Cantilever beam notched impact) Table 1

[0056] As can be seen from the data in Table 1, the performance differences between different embodiments mainly stem from the integrity of the interfacial chemistry, the efficiency of component synergy, and the control of process parameters.

[0057] (1) The quality of flame retardant performance depends directly on the density, stability and formation rate of the expanded char layer during the combustion process.

[0058] High-performance group (Examples 1, 2, 6, 7, 11, all achieving V-0): These examples collectively construct a highly efficient “condensed phase” flame-retardant barrier.

[0059] The highest LOI value (38.2%) in Example 2 is directly due to the largest total amount of flame retardant (ammonium polyphosphate, carbon source, halloysite nanotubes), which provides the most sufficient material basis for forming a thicker and more stable expanded carbon layer.

[0060] Examples 1, 6, 7, and 11 achieved V-0 even with a lower total amount of flame retardant than in Example 2, primarily due to the excellent interfacial bonding between halloysite nanotubes and the matrix. In particular, the nanotubes modified with KH-560 coupling agent and secondary grafted exhibited uniform dispersion and firm embedding within the polymer matrix. During combustion, these nanotubes effectively stabilized the expanded char layer formed by the APP / PER system as an inorganic framework, preventing its collapse, and also exerted a "maze effect" to delay the escape of thermal decomposition products. Examples 6 (using EGMA) and 7 (using ABS-g-MAH) achieved V-0, indicating that other reactive compatibilizers capable of forming good interfacial bonding with the matrix can also support the effective operation of this flame retardant system.

[0061] In Example 11, the PC / ABS ratio was adjusted to 1:1, and its LOI (34.4%) remained at a high level, indicating that the flame retardant system is adaptable within this ratio range. However, increasing the ABS ratio may cause slight changes in the char formation mechanism.

[0062] The flame retardancy ratings of Examples 3, 4, 5, 9, and 10 are all V-1 or worse.

[0063] Example 3 omitted secondary grafting, resulting in insufficient chemical bonding between halloysite nanotubes and the toughening agent / matrix, leading to insufficient interfacial strength and weakening the stabilizing effect of the nanotubes on the char layer, manifested as a decrease in LOI and the appearance of cracks. Example 4 used non-reactive vinylsilane, which prevented the halloysite nanotubes from forming chemical bonds with the PC matrix, also resulting in a weak interface and reduced synergistic efficiency. Example 5 used unmodified halloysite nanotubes, which, due to their poor compatibility with the polymer matrix, were prone to agglomeration. During combustion, they not only failed to effectively stabilize the char layer but may also become defect points in the char layer.

[0064] Replacing modified halloysite nanotubes with chopped glass fibers significantly reduced the LOI (26.5%) and caused perforation. Glass fibers are inert materials and cannot participate in char formation or stabilize the char layer. Their interface with the matrix is ​​prone to becoming a crack initiation point at high temperatures, disrupting the continuity of the expanded char layer and leading to flame retardant failure.

[0065] A decrease in the melting zone temperature may lead to insufficient reaction between ammonium polyphosphate and the carbon source, as well as insufficient grafting reaction between the toughening agent and the matrix, thus preventing the synergistic efficiency of the entire flame retardant-compressor system from being fully realized.

[0066] Example 8, a pure PC / ABS alloy without any flame-retardant components, has an LOI of only 21.2% and a UL-94 rating of HB. This, in turn, confirms that the flame-retardant system in this invention is the fundamental reason for giving the material a high flame-retardant rating.

[0067] Impact strength reflects a material’s ability to resist crack propagation and is mainly governed by matrix toughness, interfacial strength, and stress concentration effect.

[0068] Example 8 exhibited the highest measured impact strength, verifying that the homogeneous PC / ABS matrix, undisturbed by inorganic fillers, possesses optimal intrinsic toughness. This data provides a quantitative benchmark for assessing toughness loss in other formulations.

[0069] Examples 1, 2, 6, and 7 maintained high impact strength even after the addition of a large amount of rigid flame-retardant filler. The principle behind this is that reactive toughening agents such as EVA-g-GMA or EGMA chemically bond with the PC ends and the surface of the modified halloysite nanotubes through epoxy groups, forming a strong and flexible interface layer between the rigid filler particles and the matrix. This interface layer effectively transfers and disperses impact stress, inducing crazing and shear banding in the matrix to absorb a large amount of energy, thus greatly compensating for the embrittlement effect caused by the introduction of filler. Example 7 uses ABS-g-MAH, which has a similar toughening mechanism, but its impact strength is slightly lower than that of epoxy-based systems due to differences in the reactivity of functional groups.

[0070] The decrease in impact strength in Examples 3, 4, 5, 9, and 10 is directly or indirectly related to interface failure.

[0071] In Example 3, the lack of secondary grafting and in Example 4, the use of a non-reactive coupling agent both resulted in weak interfacial bonding between halloysite nanotubes and the matrix, making them prone to interfacial debonding and crack initiation upon impact.

[0072] In Example 5, the unmodified halloysite nanotubes exhibited severe agglomeration, resulting in a significant stress concentration effect and thus the lowest impact strength.

[0073] The glass fiber in Example 9 is prone to cracking and rapid propagation under impact due to its rigidity, high aspect ratio, and weak interfacial bonding with the matrix, resulting in low impact strength.

[0074] In Example 10, due to insufficient processing temperature, the chemical reaction between the components may be incomplete, affecting the stability of the final phase and the interface strength.

[0075] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A high-temperature resistant and flame-retardant plastic granule, characterized in that, It contains the following components in parts by mass: Polycarbonate 40-50 Acrylonitrile-butadiene-styrene copolymer resin 20-25 Microencapsulated ammonium polyphosphate 13-22 Carbon source 5-6 Modified halloysite nanotubes 3-5 Toughening agent 3-4 Antioxidant 0.3-0.5 Lubricant 0.5-1.0 Anti-dripping agent 0.2-0.5; The modified halloysite nanotubes are obtained by grafting halloysite nanotubes with a coupling agent containing epoxy groups; the amount of the coupling agent used is at least 3% of the mass of the halloysite nanotubes.

2. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The toughening agent is a polymer containing active groups that chemically react with the terminal functional groups of polycarbonate and has flexible elastomeric segments.

3. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The polycarbonate has a melt volume flow rate between 8 and 12 cm³ / 10 min; the acrylonitrile-butadiene-styrene copolymer resin has a butadiene content between 12 and 20 wt%; and the microcapsule ammonium polyphosphate has a degree of polymerization n ≥ 1000.

4. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The carbon source is a polyol and its derivatives.

5. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The preparation method of the modified halloysite nanotubes includes the following steps: S1: Dissolve the coupling agent with epoxy groups in an ethanol aqueous solvent, adjust the pH of the system to 4-5; stir to obtain a hydrolyzed coupling agent solution; S2: Disperse the dried halloysite nanotubes in a hydrolytic coupling agent solution, heat to 80-85℃ and stir for at least 6 hours; after the reaction is completed, centrifuge the system solution to separate the precipitate, wash the precipitate with ethanol and then dry it to obtain modified halloysite nanotubes; The amount of coupling agent used is 3-5% of the mass of halloysite nanotubes.

6. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The antioxidant is a combination of hindered phenolic antioxidants and phosphite antioxidants; the anti-dripping agent is polytetrafluoroethylene.

7. The high-temperature resistant flame-retardant plastic granules according to claim 1, characterized in that, The high-temperature resistant and flame-retardant plastic granules are prepared by first melting and blending modified halloysite nanotubes with a portion of toughening agent to carry out a secondary grafting and chain extension reaction to produce secondary grafted modified halloysite nanotubes.

8. The method for preparing high-temperature resistant flame-retardant plastic granules according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Dry halloysite nanotubes are dispersed in a hydrolyzed coupling solution containing epoxy groups for coupling reaction. After the reaction is completed, the solid is separated, dried, and modified halloysite nanotubes are obtained. S2: Modified halloysite nanotubes are melt-blended with toughening agent and then grafted twice to obtain secondary grafted modified halloysite nanotubes. S3: Mix the secondary grafted modified halloysite nanotubes with the remaining ingredients to obtain a premix; S4: The premixed material is melt-reacted, blended, extruded, cooled, and granulated to obtain high-temperature resistant and flame-retardant plastic granules.

9. The method for preparing high-temperature resistant flame-retardant plastic granules according to claim 8, characterized in that, The reaction temperature of the secondary grafting reaction in step S2 is 160-170℃; the melting temperature of the premix melt reaction blending in step S4 is 240-260℃.

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