Halogen-free flame-retardant polycarbonate composite material and preparation method thereof

Abstract

The present application relates to the technical field of polycarbonate, in particular to a halogen-free flame-retardant polycarbonate composite material and a preparation method thereof.The present application comprises the following steps: step one: polycarbonate particles, modified styrene-butadiene-styrene block copolymer, modified carbon nanotubes, anti-dripping agent and antioxidant are put into a mixer and stirred until uniformly mixed to obtain a composite material; step two: the composite material is put into a twin-screw extruder, melt-blended, cooled and granulated to obtain a halogen-free flame-retardant polycarbonate composite material.The present application has the beneficial effect that the styrene-butadiene-styrene block copolymer of the blend is grafted and modified, and cooperates with the modified carbon nanotubes to effectively enhance the strength and flame-retardant properties of the polycarbonate composite material.

Description

Technical Field

[0001] This invention relates to the field of polycarbonate, specifically to a halogen-free flame-retardant polycarbonate composite material and its preparation method. Background Technology

[0002] Polycarbonate (PC), as a high-performance engineering plastic, is widely used in electronics, automotive, construction, and aerospace fields due to its excellent transparency, impact resistance, heat resistance, and good mechanical properties. However, the high flammability of PC materials limits its application in a wider range of fields, especially in environments with extremely high fire safety requirements. Traditionally, halogenated flame retardants, such as bromine and chlorine compounds, are added to improve the flame retardant properties of PC. While these halogenated flame retardants effectively reduce the flammability of the material, they release harmful halogenated gases during combustion, posing potential threats to the environment and human health. With increasing global awareness of environmental protection and health, the research and development of halogen-free flame-retardant polycarbonate has become a hot topic in materials science.

[0003] Currently, halogen-free flame retardants often fail to achieve the same flame-retardant effect as halogenated flame retardants, and their poor compatibility with polycarbonate leads to a decline in the mechanical and processing properties of the composite material. Therefore, to solve the above problems, this invention prepares a halogen-free flame-retardant polycarbonate composite material. Summary of the Invention

[0004] The purpose of this invention is to provide a halogen-free flame-retardant polycarbonate composite material and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a halogen-free flame-retardant polycarbonate composite material includes the following steps: Step 1: Put polycarbonate particles, modified styrene-butadiene-styrene block copolymer, modified carbon nanotubes, anti-dripping agent, and antioxidant into a mixer and stir until they are mixed evenly to obtain the composite material; Step 2: The composite material is placed in a twin-screw extruder, melt-blended, cooled, and granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0006] A more optimized approach is as follows: The preparation process of the modified styrene-butadiene-thermoplastic styrene is as follows: S1: Dichloromethylphosphorus, 2-amino-4-methoxy-6-methyl-1,3,5-triazine, triethylamine and dimethyl sulfoxide are stirred and mixed, the temperature is raised to 65-80℃ and the reaction is carried out for 4-5 hours to obtain intermediate A; S2: Dissolve 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add terephthalaldehyde and react for 12-15 h, then add intermediate A and react for 10-12 h to obtain the modifier; S3: Mix the modifier, styrene-butadiene-styrene block copolymer, and azobisisobutyronitrile, and react under a protective atmosphere with ultraviolet light for 30-50 minutes to obtain the modified styrene-butadiene-styrene block copolymer.

[0007] More preferably: the intermediate A comprises the following components: by weight, 8-10 parts dichloromethylphosphine, 5-6 parts 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5-1 parts triethylamine, and 10-15 parts dimethyl sulfoxide; the modifier comprises the following components: by weight, 6-8 parts 2-amino-5-mercapto-1,3,4-thiadiazole, 3-4 parts terephthalaldehyde, and 6-8 parts intermediate A; the modified styrene-butadiene-styrene block copolymer comprises the following components: by weight, 10-12 parts modifier, 8-10 parts styrene-butadiene-styrene block copolymer, and 1-2 parts azobisisobutyronitrile.

[0008] In a more optimized manner, the preparation process of the modified carbon nanotubes is as follows: (1) Mix n-pentylamine, itaconic acid, and deionized water, add N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, and react at 85-90℃ for 40-50 min to obtain intermediate B; (2) Mix acidified carbon nanotubes, γ-aminopropyltriethoxysilane, and 1,3-dicyclohexylcarbodiimide, and under a protective atmosphere, heat to 80-85℃ and react for 4-5 h, cool, and dry to obtain silanized carbon nanotubes; (3) Stir and mix silanized carbon nanotubes, intermediate B, 1,3-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine, and react at 70-75℃ for 2-3 h, wash, and dry to obtain modified carbon nanotubes.

[0009] More preferably: the intermediate B comprises the following components by weight: 3-5 parts n-pentane, 6-8 parts itaconic acid, 1.6-1.8 parts N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 1-1.2 parts N-hydroxysuccinimide; the silanized carbon nanotubes comprise the following components by weight: 10-15 parts acidified carbon nanotubes, 5-8 parts γ-aminopropyltriethoxysilane, and 1-2 parts 1,3-dicyclohexylcarbodiimide; the modified carbon nanotubes comprise the following components by weight: 60-80 parts silanized carbon nanotubes, 30-35 parts intermediate B, 5-6 parts 1,3-dicyclohexylcarbodiimide, and 5-6 parts 4-dimethylaminopyridine.

[0010] More preferably, the composite material comprises the following components by weight: 100-150 parts polycarbonate particles, 50-60 parts modified styrene-butadiene-styrene block copolymer, 0.5-0.8 parts modified carbon nanotubes, 0.5-1 parts anti-dripping agent, and 1-2 parts antioxidant.

[0011] More optimally: the anti-dripping agent includes, but is not limited to, polytetrafluoroethylene; the antioxidant includes, but is not limited to, antioxidant 168.

[0012] In a more optimized manner, the processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 235-240℃; Section 2: 240-245℃; Section 3: 245-255℃; Section 4: 255-270℃; Section 5: 270-275℃; Section 6: 260-270℃; Section 7: 250-260℃; Die head: 240-250℃.

[0013] This invention effectively enhances the strength and flame retardant properties of polycarbonate composites by grafting modification of the styrene-butadiene-styrene block copolymer blend, which works synergistically with modified carbon nanotubes. Specifically: Firstly, a modifier was synthesized relatively easily using 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 2-amino-5-mercapto-1,3,4-thiadiazole, terephthalaldehyde, and dichloromethylphosphorus as raw materials. This modifier was then grafted onto styrene-butadiene-styrene block copolymer (SBS) via a click reaction, and subsequently blended with polycarbonate. The modified SBS functions in both the gas and condensed phases. During gas-phase flame retardancy, the grafted chemical molecules generate non-flammable gases of nitrogen and sulfur upon heating. These gases carry away surface heat, reducing the concentration of oxygen and combustible gases, thus enhancing the flame retardant effect. During condensed-phase flame retardancy, the generated acidic substances promote the formation of a carbon layer. This carbon layer has a barrier effect, protecting the internal matrix and inhibiting the release of smoke and combustible gases.

[0014] Secondly, SBS is a thermoplastic elastomer with excellent flexibility and impact absorption capacity. When blended with polycarbonate, it can effectively enhance the toughness and impact resistance of the composite material. Furthermore, the chemical molecules grafted with SBS have a large number of reactive groups, such as thiol groups and secondary amine groups, as well as nitrogen atoms in the thiadiazole ring and phosphenanthrene ring structures, which can form hydrogen bonds and π-π interactions with polycarbonate, further enhancing the physical properties of the composite material.

[0015] Thirdly, the modified carbon nanotubes, with their longer grafted molecular chains, enhance their dispersibility in polycarbonate. Simultaneously, the modified carbon nanotubes possess a silane structure, which synergistically enhances the flame-retardant effect of modified SBS, strengthens the structure of the char layer during heating, and improves its performance as a heat and mass transfer barrier. Furthermore, as a reinforcing matrix material, carbon nanotubes effectively enhance the strength and physical properties of the composite material. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be noted that the following parts are by weight. There are no special restrictions on the manufacturers of any of the raw materials involved in this invention. Exemplary examples include: polycarbonate particles with product number Suoer90010062, manufactured by Covestro (Shanghai); styrene-butadiene-styrene block copolymer with product number 3411, manufactured by Li Changrong (Huizhou); carbon nanotubes with brand name Naco and model number NACODC8; 2-amino-5-mercapto-1,3,4-thiadiazole with CAS number 2349-67-9, manufactured by Alpha; 2-amino-4-methoxy-6-methyl... 1,3,5-Triazine (CAS 1668-54-8, manufacturer: Jacks); N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) (CAS 25952-53-8, manufacturer: Dilu Pharmaceutical); N-hydroxysuccinimide (NHS) (CAS 6066-82-6, manufacturer: Aladdin); 1,3-dicyclohexylcarbodiimide (DCC) (CAS 538-75-0, manufacturer: Anaiji); 4-dimethylaminopyridine (DMAP) (CAS 1122-58-3, manufacturer: Kaisai Chemical).

[0018] Pre-preparation: Carbon nanotubes were placed in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid in 500 ml, with a volume ratio of concentrated nitric acid to concentrated sulfuric acid of 3:1. After ultrasonic treatment at room temperature for 4 h, distilled water was added to the mixed solution for dilution. The solution was then filtered through a filter membrane. After filtration, an appropriate amount of distilled water was added for further dilution. The solution was allowed to stand, and the supernatant was discarded. The solution was then filtered again. The above operation was repeated several times until the pH of the supernatant was about 7. The carbon nanotubes were then filtered out through the filter membrane, dried in an oven, and ground for 0.5–1 h to obtain acidified carbon nanotubes.

[0019] Example 1: A method for preparing a halogen-free flame-retardant polycarbonate composite material, comprising the following steps: Synthesis of modified styrene-butadiene-styrene block copolymer: S1: Mix 8 parts of dichloromethylphosphorus, 5 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5 parts of triethylamine, and 10 parts of dimethyl sulfoxide, raise the temperature to 65°C, and react for 4 hours to obtain intermediate A; S2: Dissolve 6 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 3 parts of terephthalaldehyde and react for 12 hours, then add 6 parts of intermediate A and react for 10 hours to obtain the modifier. S3: Mix 10 parts of modifier, 8 parts of styrene-butadiene-styrene block copolymer, and 1 part of azobisisobutyronitrile, and react under nitrogen atmosphere and ultraviolet light for 30 min to obtain modified styrene-butadiene-styrene block copolymer.

[0020] Synthesis of modified carbon nanotubes: (1) 3 parts of n-pentane, 6 parts of itaconic acid, 1.6 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1 part of N-hydroxysuccinimide were mixed and reacted at 85°C for 40 min to obtain intermediate B; (2) 10 parts of acidified carbon nanotubes, 5 parts of γ-aminopropyltriethoxysilane and 1 part of 1,3-dicyclohexylcarbodiimide were mixed, heated to 80°C under nitrogen, reacted for 4 h, cooled and dried to obtain silanized carbon nanotubes; (3) 60 parts of silanized carbon nanotubes, 30 parts of intermediate B, 5 parts of 1,3-dicyclohexylcarbodiimide and 5 parts of 4-dimethylaminopyridine were stirred and mixed, reacted at 70°C for 2 h, washed and dried to obtain modified carbon nanotubes.

[0021] Step 1: Put 100 parts of polycarbonate granules, 50 parts of modified styrene-butadiene-styrene block copolymer, 0.5 parts of modified carbon nanotubes, 0.5 parts of anti-dripping agent polytetrafluoroethylene, and 1 part of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 235℃; Section 2: 240℃; Section 3: 245℃; Section 4: 255℃; Section 5: 270℃; Section 6: 260℃; Section 7: 250℃; Die head: 240℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0022] Example 2: A method for preparing a halogen-free flame-retardant polycarbonate composite material, comprising the following steps: Synthesis of modified styrene-butadiene-styrene block copolymer: S1: Mix 10 parts of dichloromethylphosphorus, 6 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 1 part of triethylamine, and 15 parts of dimethyl sulfoxide, raise the temperature to 80°C, and react for 5 hours to obtain intermediate A; S2: Dissolve 8 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 4 parts of terephthalaldehyde and react for 15 h, then add 8 parts of intermediate A and react for 12 h to obtain the modifier. S3: Mix 12 parts of modifier, 10 parts of styrene-butadiene-styrene block copolymer, and 2 parts of azobisisobutyronitrile, and react under nitrogen atmosphere and ultraviolet light for 50 min to obtain modified styrene-butadiene-styrene block copolymer.

[0023] Synthesis of modified carbon nanotubes: (1) Mix 5 parts of n-pentane, 8 parts of itaconic acid, 1.8 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.2 parts of N-hydroxysuccinimide and react at 90℃ for 50 min to obtain intermediate B; (2) Mix 15 parts of acidified carbon nanotubes, 8 parts of γ-aminopropyltriethoxysilane and 2 parts of 1,3-dicyclohexylcarbodiimide, heat to 85℃ under nitrogen, react for 5 h, cool and dry to obtain silanized carbon nanotubes; (3) Mix 80 parts of silanized carbon nanotubes, 35 parts of intermediate B, 6 parts of 1,3-dicyclohexylcarbodiimide and 6 parts of 4-dimethylaminopyridine and stir to react at 75℃ for 3 h, wash and dry to obtain modified carbon nanotubes.

[0024] Step 1: Put 150 parts of polycarbonate granules, 60 parts of modified styrene-butadiene-styrene block copolymer, 0.8 parts of modified carbon nanotubes, 1 part of anti-dripping agent polytetrafluoroethylene, and 2 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0025] Example 3: A method for preparing a halogen-free flame-retardant polycarbonate composite material, comprising the following steps: Synthesis of modified styrene-butadiene-styrene block copolymer: S1: 9 parts of dichloromethylphosphorus, 5.5 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.8 parts of triethylamine, and 12 parts of dimethyl sulfoxide were stirred and mixed, and the temperature was raised to 70°C and reacted for 5 hours to obtain intermediate A; S2: Dissolve 7 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 3.5 parts of terephthalaldehyde and react for 13 hours, then add 7 parts of intermediate A and react for 12 hours to obtain the modifier; S3: Mix 11 parts of modifier, 9 parts of styrene-butadiene-styrene block copolymer, and 2 parts of azobisisobutyronitrile, and react under nitrogen atmosphere and ultraviolet light for 50 min to obtain modified styrene-butadiene-styrene block copolymer.

[0026] Synthesis of modified carbon nanotubes: (1) 4 parts of n-pentane, 7 parts of itaconic acid, 1.7 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.1 parts of N-hydroxysuccinimide were mixed and reacted at 90℃ for 45 min to obtain intermediate B; (2) 15 parts of acidified carbon nanotubes, 8 parts of γ-aminopropyltriethoxysilane and 2 parts of 1,3-dicyclohexylcarbodiimide were mixed, heated to 85℃ under nitrogen, reacted for 5 h, cooled and dried to obtain silanized carbon nanotubes; (3) 70 parts of silanized carbon nanotubes, 35 parts of intermediate B, 5.5 parts of 1,3-dicyclohexylcarbodiimide and 5.5 parts of 4-dimethylaminopyridine were stirred and mixed, reacted at 75℃ for 3 h, washed and dried to obtain modified carbon nanotubes.

[0027] Step 1: Put 120 parts of polycarbonate granules, 55 parts of modified styrene-butadiene-styrene block copolymer, 0.6 parts of modified carbon nanotubes, 0.8 parts of anti-dripping agent polytetrafluoroethylene, and 1.5 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0028] Example 4: A method for preparing a halogen-free flame-retardant polycarbonate composite material, comprising the following steps: Synthesis of modified styrene-butadiene-styrene block copolymer: S1: Mix 8 parts of dichloromethylphosphorus, 5 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5 parts of triethylamine, and 10 parts of dimethyl sulfoxide, raise the temperature to 65°C, and react for 4 hours to obtain intermediate A; S2: Dissolve 6 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 3 parts of terephthalaldehyde and react for 12 hours, then add 6 parts of intermediate A and react for 10 hours to obtain the modifier. S3: Mix 10 parts of modifier, 8 parts of styrene-butadiene-styrene block copolymer, and 1 part of azobisisobutyronitrile, and react under nitrogen atmosphere and ultraviolet light for 30 min to obtain modified styrene-butadiene-styrene block copolymer.

[0029] Synthesis of modified carbon nanotubes: (1) Mix 5 parts of n-pentane, 8 parts of itaconic acid, 1.8 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.2 parts of N-hydroxysuccinimide and react at 90℃ for 50 min to obtain intermediate B; (2) Mix 15 parts of acidified carbon nanotubes, 8 parts of γ-aminopropyltriethoxysilane and 2 parts of 1,3-dicyclohexylcarbodiimide, heat to 85℃ under nitrogen, react for 5 h, cool and dry to obtain silanized carbon nanotubes; (3) Mix 80 parts of silanized carbon nanotubes, 35 parts of intermediate B, 6 parts of 1,3-dicyclohexylcarbodiimide and 6 parts of 4-dimethylaminopyridine and stir to react at 75℃ for 3 h, wash and dry to obtain modified carbon nanotubes.

[0030] Step 1: Put 120 parts of polycarbonate granules, 55 parts of modified styrene-butadiene-styrene block copolymer, 0.6 parts of modified carbon nanotubes, 0.8 parts of anti-dripping agent polytetrafluoroethylene, and 1.5 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0031] Comparative Example 1: No modified carbon nanotubes were added; all other aspects were the same as in Example 4, as detailed below: Synthesis of modified styrene-butadiene-styrene block copolymer: S1: Mix 8 parts of dichloromethylphosphorus, 5 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5 parts of triethylamine, and 10 parts of dimethyl sulfoxide, raise the temperature to 65°C, and react for 4 hours to obtain intermediate A; S2: Dissolve 6 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 3 parts of terephthalaldehyde and react for 12 hours, then add 6 parts of intermediate A and react for 10 hours to obtain the modifier. S3: Mix 10 parts of modifier, 8 parts of styrene-butadiene-styrene block copolymer, and 1 part of azobisisobutyronitrile, and react under nitrogen atmosphere and ultraviolet light for 30 min to obtain modified styrene-butadiene-styrene block copolymer.

[0032] Step 1: Put 120 parts of polycarbonate granules, 55 parts of modified styrene-butadiene-styrene block copolymer, 0.8 parts of anti-dripping agent polytetrafluoroethylene, and 1.5 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0033] Comparative Example 2: The prepared modifier was added to the composite material as a separate flame retardant, as follows: Synthesis of modifiers: S1: Mix 8 parts of dichloromethylphosphorus, 5 parts of 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5 parts of triethylamine, and 10 parts of dimethyl sulfoxide, raise the temperature to 65°C, and react for 4 hours to obtain intermediate A; S2: Dissolve 6 parts of 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add 3 parts of terephthalaldehyde and react for 12 hours, then add 6 parts of intermediate A and react for 10 hours to obtain the modifier.

[0034] Synthesis of modified carbon nanotubes: (1) Mix 5 parts of n-pentane, 8 parts of itaconic acid, 1.8 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.2 parts of N-hydroxysuccinimide and react at 90℃ for 50 min to obtain intermediate B; (2) Mix 15 parts of acidified carbon nanotubes, 8 parts of γ-aminopropyltriethoxysilane and 2 parts of 1,3-dicyclohexylcarbodiimide, heat to 85℃ under nitrogen, react for 5 h, cool and dry to obtain silanized carbon nanotubes; (3) Mix 80 parts of silanized carbon nanotubes, 35 parts of intermediate B, 6 parts of 1,3-dicyclohexylcarbodiimide and 6 parts of 4-dimethylaminopyridine and stir to react at 75℃ for 3 h, wash and dry to obtain modified carbon nanotubes.

[0035] Step 1: Put 120 parts of polycarbonate granules, 1-2 parts of modifier, 0.6 parts of modified carbon nanotubes, 0.8 parts of anti-dripping agent polytetrafluoroethylene, and 1.5 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0036] Comparative Example 3: Blending SBS with polycarbonate without introducing modified SBS, as detailed below: Synthesis of modified carbon nanotubes: (1) Mix 5 parts of n-pentane, 8 parts of itaconic acid, 1.8 parts of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1.2 parts of N-hydroxysuccinimide and react at 90℃ for 50 min to obtain intermediate B; (2) Mix 15 parts of acidified carbon nanotubes, 8 parts of γ-aminopropyltriethoxysilane and 2 parts of 1,3-dicyclohexylcarbodiimide, heat to 85℃ under nitrogen, react for 5 h, cool and dry to obtain silanized carbon nanotubes; (3) Mix 80 parts of silanized carbon nanotubes, 35 parts of intermediate B, 6 parts of 1,3-dicyclohexylcarbodiimide and 6 parts of 4-dimethylaminopyridine and stir to react at 75℃ for 3 h, wash and dry to obtain modified carbon nanotubes.

[0037] Step 1: Put 120 parts of polycarbonate granules, 0.6 parts of modified carbon nanotubes, 0.8 parts of anti-dripping agent polytetrafluoroethylene, and 1.5 parts of antioxidant 168 into a mixer and stir until they are mixed evenly to obtain the composite material. Step 2: The composite material is placed in a twin-screw extruder for melt blending. The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 240℃; Section 2: 245℃; Section 3: 255℃; Section 4: 270℃; Section 5: 275℃; Section 6: 270℃; Section 7: 260℃; Die head: 250℃. After cooling, the mixture is granulated to obtain a halogen-free flame-retardant polycarbonate composite material.

[0038] Testing experiments: The polycarbonate composite materials obtained in the above examples and comparative examples were injection molded into standard specimens of corresponding shapes using an injection molding machine. The limiting oxygen index was determined according to national standard GB / T 2406-2008 "Test Method for Burning Performance of Plastics"; the smoke density was determined according to national standard GB / T 8323.2-2008 "Plastics Smoke Generation Part 2: Test Method for Determination of Smoke Density by Single Chamber Method"; the impact resistance was determined according to national standard GB / T 1043.1-2008 "Determination of Impact Properties of Simply Supported Beams of Plastics Part 1: Non-Instrumental Impact Test"; and the flexural properties were determined according to national standard GB / T 9341-2008 "Determination of Flexural Properties of Plastics". The obtained data are shown in the table below:

[0039] Table 1 Conclusion: Example 4, through graft modification of the SBS blend, synergistically enhances the strength and flame retardant properties of the polycarbonate composite material with modified carbon nanotubes. Comparative Example 1, compared to Example 4, lacks modified carbon nanotubes, resulting in decreased performance. This is because the modified carbon nanotubes, possessing a silane structure, synergistically enhance the flame retardant effect with the modified SBS, strengthen the structure of the char layer during heating, improve its role as a heat and mass transfer barrier, and improve the mechanical properties of the composite material. Comparative Example 2, compared to Example 4, does not use a click reaction to bind with SBS; instead, it is added as a separate flame retardant to the composite material. As a thermoplastic elastomer, the mechanical properties of SBS are significantly reduced without SBS in the blend. Furthermore, during combustion, the butadiene portion of SBS may promote the formation of a char layer, which acts as a protective barrier, slowing down the combustion rate of the internal materials; therefore, the flame retardant effect is also reduced. Comparative Example 3, with the addition of modified carbon nanotubes as a separate flame retardant, shows significantly reduced flame retardant effect and physical properties.

[0040] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a halogen-free flame-retardant polycarbonate composite material, characterized in that: Includes the following steps: Step 1: Put polycarbonate particles, modified styrene-butadiene-styrene block copolymer, modified carbon nanotubes, anti-dripping agent, and antioxidant into a mixer and stir until they are mixed evenly to obtain the composite material; Step 2: The composite material is placed in a twin-screw extruder, melt-blended, cooled, and granulated to obtain a halogen-free flame-retardant polycarbonate composite material. The preparation process of the modified styrene-butadiene-styrene block copolymer is as follows: S1: Dichloromethylphosphine, 2-amino-4-methoxy-6-methyl-1,3,5-triazine, triethylamine, and dimethyl sulfoxide are stirred and mixed, and the temperature is raised to 65-80℃ and reacted for 4-5 hours to obtain intermediate A; intermediate A comprises the following components: by weight, 8-10 parts dichloromethylphosphine, 5-6 parts 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 0.5-1 part triethylamine, 10- 15 parts dimethyl sulfoxide; the modifier comprises the following components: by weight, 6-8 parts 2-amino-5-mercapto-1,3,4-thiadiazole, 3-4 parts terephthalaldehyde, and 6-8 parts intermediate A; the modified styrene-butadiene-styrene block copolymer comprises the following components: by weight, 10-12 parts modifier, 8-10 parts styrene-butadiene-styrene block copolymer, and 1-2 parts azobisisobutyronitrile; S2: Dissolve 2-amino-5-mercapto-1,3,4-thiadiazole in anhydrous ethanol, add terephthalaldehyde and react for 12-15 h, then add intermediate A and react for 10-12 h to obtain the modifier; S3: Mix the modifier, styrene-butadiene-styrene block copolymer, and azobisisobutyronitrile, and react under a protective atmosphere with ultraviolet light for 30-50 min to obtain the modified styrene-butadiene-styrene block copolymer. The preparation process of the modified carbon nanotubes is as follows: (1) Mix n-pentylamine, itaconic acid, and deionized water, add N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide and react at 85-90℃ for 40-50 min to obtain intermediate B; (2) Mix acidified carbon nanotubes, γ-aminopropyltriethoxysilane, and 1,3-dicyclohexylcarbodiimide, heat to 80-85℃ under a protective atmosphere, react for 4-5 h, cool, and dry to obtain silanized carbon nanotubes; (3) Stir and mix silanized carbon nanotubes, intermediate B, 1,3-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine, react at 70-75℃ for 2-3 h, wash, and dry to obtain modified carbon nanotubes; The intermediate B comprises the following components by weight: 3-5 parts n-pentane, 6-8 parts itaconic acid, 1.6-1.8 parts N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and 1-1.2 parts N-hydroxysuccinimide; the silanized carbon nanotubes comprise the following components by weight: 10-15 parts acidified carbon nanotubes, 5-8 parts γ-aminopropyltriethoxysilane, and 1-2 parts 1,3-dicyclohexylcarbodiimide; the modified carbon nanotubes comprise the following components by weight: 60-80 parts silanized carbon nanotubes, 30-35 parts intermediate B, 5-6 parts 1,3-dicyclohexylcarbodiimide, and 5-6 parts 4-dimethylaminopyridine.

2. The method for preparing a halogen-free flame-retardant polycarbonate composite material according to claim 1, characterized in that: The composite material comprises the following components by weight: 100-150 parts polycarbonate particles, 50-60 parts modified styrene-butadiene-styrene block copolymer, 0.5-0.8 parts modified carbon nanotubes, 0.5-1 parts anti-dripping agent, and 1-2 parts antioxidant.

3. The method for preparing a halogen-free flame-retardant polycarbonate composite material according to claim 1, characterized in that: The anti-dripping agent includes polytetrafluoroethylene; the antioxidant includes antioxidant 168.

4. The method for preparing a halogen-free flame-retardant polycarbonate composite material according to claim 1, characterized in that: The processing temperatures of each section of the twin-screw extruder are as follows: Section 1: 235-240℃; Section 2: 240-245℃; Section 3: 245-255℃; Section 4: 255-270℃. Level 5: 270-275℃; Level 6: 260-270℃; Seventh stage: 250-260℃; Machine head: 240-250℃.

5. The halogen-free flame-retardant polycarbonate composite material obtained by the preparation method of the halogen-free flame-retardant polycarbonate composite material according to any one of claims 1-4.

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