Fluoride-free flame-retardant PC / ABS composite material and preparation method thereof

Abstract

The invention discloses a fluoride-free flame-retardant PC / ABS composite material and a preparation method thereof, and relates to the technical field of PC / ABS composites.The preparation method comprises the following steps that PC resin, ABS resin, flame-retardant modified nanocellulose and bisphenol A-bis (diphenyl phosphate) are sequentially added into a double-screw extruder, extrusion granulation is conducted, and the fluoride-free flame-retardant PC / ABS composite material is obtained; the fluoride-free flame-retardant PC / ABS composite material is prepared from the following components in parts by mass: 48 to 64 parts of PC resin, 12 to 16 parts of ABS resin, 0.5 to 2 parts of flame-retardant modified nano cellulose and 13 to 14 parts of bisphenol A-bis (diphenyl phosphate).

Description

Technical Field

[0001] The present invention relates to the technical field of PC / ABS composite materials, and specifically to a fluorine-free flame-retardant PC / ABS composite material and a preparation method thereof. Background Art

[0002] In the field of modern material applications, PC / ABS composite materials have been widely used in many industries such as electronics and electrical appliances, automotive manufacturing, and construction due to their excellent comprehensive properties, such as good mechanical properties, processing properties, and appearance characteristics. However, with the increasing requirements for material safety and environmental protection in various industries, the limitations of PC / ABS composite materials in flame retardancy and environmental protection have gradually emerged.

[0003] Traditional methods for flame-retarding PC / ABS composite materials often rely on fluorine-containing flame retardants. Although fluorine-containing flame retardants can effectively improve the flame-retardant performance of materials, they will release toxic and harmful fluorine-containing gases during material combustion, posing a serious threat to the environment and human health, and not meeting the current development concept of green environmental protection. At the same time, the dispersibility of these traditional flame retardants in composite materials is poor, which easily leads to a decline in the mechanical properties of materials and affects their performance in practical applications.

[0004] In addition, with the continuous upgrading of industry standards, the requirements for the flame-retardant performance of PC / ABS composite materials are becoming increasingly strict, and traditional flame-retardant technologies have been difficult to meet the growing high-performance requirements. Developing a fluorine-free flame-retardant PC / ABS composite material and a preparation method thereof that not only have excellent flame-retardant performance, meet environmental protection requirements, but also do not reduce the mechanical properties of materials has become an urgent problem to be solved in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a fluorine-free flame-retardant PC / ABS composite material and a preparation method thereof to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add nanocellulose to deionized water, ultrasonically disperse it, add sodium periodate, stir for 48 h under dark conditions at room temperature, wash the product with deionized water to obtain pre-oxidized nanocellulose; add the pre-oxidized nanocellulose to deionized water, ultrasonically disperse it, add hexamethylenediamine, heat to 30 - 32 °C and react for 6 - 6.5 h, cool to room temperature, add sodium borohydride and stir at room temperature for 1 - 3 h, wash the product with deionized water to obtain amino-functionalized nanocellulose; Further, in the preparation process of the pre-oxidized nanocellulose, 1.6 - 2 g of sodium periodate is added per 1 g of nanocellulose; in the preparation process of the amino-functionalized nanocellulose, 0.9 - 1 g of hexamethylenediamine and 0.58 - 0.6 g of sodium borohydride are added per 1 g of the pre-oxidized nanocellulose; S2: Add the amino-functionalized nanofibers into N,N-dimethylformamide, ultrasonically disperse them, preheat the reaction system to 90 - 95 °C, add the N,N-dimethylformamide solution containing styrene-maleic anhydride copolymer, keep the temperature for reaction for 12 - 12.5 h, centrifuge, wash the product with N,N-dimethylformamide and ethanol, and dry it under vacuum to obtain the copolymer-modified nanocellulose; Further, in the preparation process of the copolymer-modified nanocellulose, the mass ratio of the amino-functionalized nanofibers to the styrene-maleic anhydride copolymer is (2 - 4):(1 - 2); S3: Add the copolymer-modified nanocellulose into the citric acid / sodium citrate buffer solution with a pH of 5, ultrasonically disperse it, add dopamine hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-hydroxysuccinimide, stir and react at room temperature for 6 - 6.5 h under a nitrogen atmosphere, dialyze with ultrapure water, and freeze-dry to obtain the dopamine-modified nanocellulose; Further, in the preparation process of the dopamine-modified nanocellulose, the mass ratio of the copolymer-modified nanocellulose to dopamine hydrochloride to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to N-hydroxysuccinimide is 5:(0.664 - 0.678):(0.38 - 0.41):(0.22 - 0.23); S4: Add polyoxyethylene polyoxypropylene ether into the ethanol aqueous solution, stir evenly, add triethanolamine, stir evenly, add cetyltrimethylammonium bromide, stir evenly, add tetraethyl orthosilicate, stir and react at room temperature for 30 - 45 min, stand for aging, centrifuge, wash the product with deionized water and ethanol, dry it under vacuum, and calcine it at 550 - 555 °C for 6 - 6.5 h to obtain the silica nanoparticles; Further, in the preparation process of the silica nanoparticles, the mass ratio of polyoxyethylene polyoxypropylene ether to triethanolamine to cetyltrimethylammonium bromide to tetraethyl orthosilicate is (2.68 - 2.84):(15.64 - 17.58):(0.664 - 0.672):(0.20 - 0.21); S5: Add the silica nanoparticles into deionized water, ultrasonically disperse them, add tris(trimethylsilyl) borate, stir for 1 - 3 h, centrifuge, wash the product with deionized water, and freeze-dry to obtain the coated and modified silica nanoparticles; Furthermore, in the preparation process of the coated modified silica nanoparticles, the mass ratio of silica nanoparticles: tris(trimethylsilyl)borate is (0.5-1):(0.278-0.282); S6: adding dopamine-modified nanocellulose, coated modified silica nanoparticles, and dopamine to a Tris-HCl buffer solution in sequence, dispersing by ultrasonication, reacting by stirring at room temperature for 4-5 hours, dialyzing with ultrapure water, and freeze-drying to obtain flame-retardant modified nanocellulose; Furthermore, in the preparation process of the flame-retardant modified nanocellulose, the mass ratio of dopamine-modified nanocellulose: coated modified silica nanoparticles: dopamine is (0.1-1):0.1:0.1; S7: PC resin, ABS resin, flame-retardant modified nanocellulose, and bisphenol A-bis(diphenyl phosphate) are sequentially added into a twin-screw extruder, and extruded into granules to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0007] Furthermore, the components in the fluorine-free flame-retardant PC / ABS composite material include 48-64 parts of PC resin, 12-16 parts of ABS resin, 0.5-2 parts of flame-retardant modified nanocellulose, and 13-14 parts of bisphenol A-bis(diphenyl phosphate) in terms of mass fraction.

[0008] Furthermore, the extrusion granulation temperature is 180-200°C.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention prepares amino-functionalized nanocellulose by Schiff base reaction, then grafts styrene-maleic anhydride copolymer to amino-functionalized nanocellulose to prepare copolymer-modified nanocellulose, and finally modifies the surface of copolymer-modified nanocellulose with a homemade inorganic silica-based flame retardant to prepare flame-retardant modified nanocellulose. The flame-retardant modified nanocellulose is added as a fluorine-free flame retardant and toughening filler to PC resin and ABS resin for extrusion granulation to prepare fluorine-free flame-retardant PC / ABS resin.

[0010] 2. Due to the presence of styrene-maleic anhydride copolymer in flame-retardant modified nanocellulose, flame-retardant modified nanocellulose is more inclined to be distributed on the interface of PC / ABS in PC / ABS composite materials. On the one hand, the compatibility of PC and ABS is improved, the dispersibility of bisphenol A-bis(diphenyl phosphate) flame retardant in the composite material is improved, and the mechanical properties of the composite material are improved; on the other hand, the surface-modified inorganic silica-based flame retardant is introduced into the interface of PC and ABS, and a dense flame-retardant shell can be formed at the interface during the thermal combustion process, which reduces the peak heat release rate and total smoke production of the PC / ABS composite material, and greatly improves the flame retardant properties of the composite material.

[0011] 3. The flame-retardant modified nanocellulose prepared by the present invention from renewable resources combines strong toughness and high flame retardancy, can greatly reinforce the PC / ABS composite material, shows great potential for flame-retardant applications, and does not emit toxic by-products after combustion, greatly expanding the application scope of the fluorine-free flame-retardant PC / ABS composite material. Detailed implementation manners

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0013] In the following embodiments, the specifications of the nanocellulose are a diameter of 10 - 70 nm and a length of 1 - 3 µm; the specifications of the styrene-maleic anhydride copolymer are Mn = 28000; the specifications of the polyoxyethylene polyoxypropylene ether are Mn = 12500; the PC resin model is 2505, MFR 15; the ABS resin model is 0215A; and the rest of the substances are all commercially available.

[0014] Embodiment 1: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add 1 g of nanocellulose to deionized water, ultrasonically disperse it, add 1.6 g of sodium periodate, and stir for 48 h under dark conditions at room temperature. Wash the product with deionized water to obtain pre-oxidized nanocellulose; add 1 g of pre-oxidized nanocellulose to deionized water, ultrasonically disperse it, add 0.9 g of hexamethylenediamine, heat to 30 °C and react for 6 h, cool to room temperature, add 0.58 g of sodium borohydride and stir at room temperature for 1 h. Wash the product with deionized water to obtain amino-functionalized nanocellulose; S2: Add 2 g of amino-functionalized nanofibers to N,N-dimethylformamide, ultrasonically disperse it, preheat the reaction system to 90 °C, add an N,N-dimethylformamide solution containing 1 g of styrene-maleic anhydride copolymer, keep the temperature and react for 12 h, centrifuge, wash the product with N,N-dimethylformamide and ethanol, and dry it under vacuum to obtain copolymer-modified nanocellulose; S3: Add 5 g of copolymer-modified nanocellulose to a citric acid / sodium citrate buffer solution with a pH of 5, ultrasonically disperse it, add 0.664 g of hydrochloric acid dopamine, 0.38 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.22 g of N-hydroxysuccinimide. Stir and react at room temperature for 6 - 6.5 h under a nitrogen atmosphere, dialyze with ultrapure water, and freeze-dry to obtain dopamine-modified nanocellulose; S4: Add 2.68 g of polyoxyethylene polyoxypropylene ether into an ethanol aqueous solution, stir evenly, add 15.64 g of triethanolamine, stir evenly, add 0.664 g of cetyltrimethylammonium bromide, stir evenly, add 0.20 g of tetraethyl orthosilicate, stir and react at room temperature for 30 min, stand for aging, centrifuge, wash the product with deionized water and ethanol, dry in vacuum, and calcine at 550 °C for 6 h to obtain silicon dioxide nanoparticles; S5: Add 0.5 g of silicon dioxide nanoparticles into deionized water, disperse ultrasonically, add 0.278 g of tris(trimethylsilyl) borate, stir for 1 h, centrifuge, wash the product with deionized water, and freeze-dry to obtain coated and modified silicon dioxide nanoparticles; S6: Add 0.1 g of dopamine-modified nanocellulose, 0.1 g of coated and modified silicon dioxide nanoparticles, and 0.1 g of dopamine into a Tris-HCl buffer solution in sequence, disperse ultrasonically, stir and react at room temperature for 4 h, dialyze with ultrapure water, and freeze-dry to obtain flame-retardant modified nanocellulose; S7: Add 64 parts of PC resin, 16 parts of ABS resin, 0.5 part of flame-retardant modified nanocellulose, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0015] Example 2: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add 1 g of nanocellulose into deionized water, disperse ultrasonically, add 1.6 g of sodium periodate, stir in the dark at room temperature for 48 h, wash the product with deionized water to obtain pre-oxidized nanocellulose; Add 1 g of pre-oxidized nanocellulose into deionized water, disperse ultrasonically, add 0.9 g of hexamethylenediamine, heat to 30 °C and react for 6 h, cool to room temperature, add 0.58 g of sodium borohydride and stir at room temperature for 1 h, wash the product with deionized water to obtain amino-functionalized nanocellulose; S2: Add 2 g of amino-functionalized nanofibers into N,N-dimethylformamide, disperse ultrasonically, preheat the reaction system to 90 °C, add an N,N-dimethylformamide solution containing 1 g of styrene-maleic anhydride copolymer, keep the temperature and react for 12 h, centrifuge, wash the product with N,N-dimethylformamide and ethanol, and dry in vacuum to obtain copolymer-modified nanocellulose; S3: Add 5 g of copolymer-modified nanocellulose into a citric acid / sodium citrate buffer solution with a pH of 5, disperse ultrasonically, add 0.664 g of hydrochloric acid dopamine, 0.38 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.22 g of N-hydroxysuccinimide, stir and react at room temperature for 6 - 6.5 h under a nitrogen atmosphere, dialyze with ultrapure water, and freeze-dry to obtain dopamine-modified nanocellulose; S4: Add 2.68 g of polyoxyethylene polyoxypropylene ether into the ethanol aqueous solution, stir evenly, add 15.64 g of triethanolamine, stir evenly, add 0.664 g of cetyltrimethylammonium bromide, stir evenly, add 0.20 g of tetraethyl orthosilicate, stir and react at room temperature for 30 min, stand for aging, centrifuge, wash the product with deionized water and ethanol, dry in vacuum, and calcine at 550 °C for 6 h to obtain silicon dioxide nanoparticles; S5: Add 0.5 g of silicon dioxide nanoparticles into deionized water, disperse by ultrasonic wave, add 0.278 g of tris(trimethylsilyl) borate, stir for 1 h, centrifuge, wash the product with deionized water, and freeze-dry to obtain coated and modified silicon dioxide nanoparticles; S6: Add 0.5 g of dopamine-modified nanocellulose, 0.1 g of coated and modified silicon dioxide nanoparticles, and 0.1 g of dopamine into Tris-HCl buffer solution in sequence, disperse by ultrasonic wave, stir and react at room temperature for 4 h, dialyze with ultrapure water, and freeze-dry to obtain flame-retardant modified nanocellulose; S7: Add 64 parts of PC resin, 16 parts of ABS resin, 1 part of flame-retardant modified nanocellulose, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0016] Example 3: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add 1 g of nanocellulose into deionized water, disperse by ultrasonic wave, add 1.6 g of sodium periodate, stir in the dark at room temperature for 48 h, wash the product with deionized water to obtain pre-oxidized nanocellulose; Add 1 g of pre-oxidized nanocellulose into deionized water, disperse by ultrasonic wave, add 0.9 g of hexamethylenediamine, heat to 30 °C and react for 6 h, cool to room temperature, add 0.58 g of sodium borohydride and stir at room temperature for 1 h, wash the product with deionized water to obtain amino-functionalized nanocellulose; S2: Add 2 g of amino-functionalized nanofibers into N,N-dimethylformamide, disperse by ultrasonic wave, preheat the reaction system to 90 °C, add the N,N-dimethylformamide solution containing 1 g of styrene-maleic anhydride copolymer, keep the temperature and react for 12 h, centrifuge, wash the product with N,N-dimethylformamide and ethanol, and dry in vacuum to obtain copolymer-modified nanocellulose; S3: Add 5 g of copolymer-modified nanocellulose into a citric acid / sodium citrate buffer solution with a pH of 5, disperse by ultrasonic wave, add 0.664 g of hydrochloric acid dopamine, 0.38 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.22 g of N-hydroxysuccinimide, stir and react at room temperature for 6 - 6.5 h under a nitrogen atmosphere, dialyze with ultrapure water, and freeze-dry to obtain dopamine-modified nanocellulose; S4: Add 2.68 g of polyoxyethylene polyoxypropylene ether into an ethanol aqueous solution, stir evenly, add 15.64 g of triethanolamine, stir evenly, add 0.664 g of cetyltrimethylammonium bromide, stir evenly, add 0.20 g of tetraethyl orthosilicate, stir and react at room temperature for 30 min, let stand for aging, centrifuge, wash the product with deionized water and ethanol, dry in vacuum, and calcine at 550 °C for 6 h to obtain silica nanoparticles; S5: Add 1 g of silica nanoparticles into deionized water, disperse by ultrasonic wave, add 0.278 g of tris(trimethylsilyl) borate, stir for 1 h, centrifuge, wash the product with deionized water, and freeze-dry to obtain coated and modified silica nanoparticles; S6: Add 1 g of dopamine-modified nanocellulose, 0.1 g of coated and modified silica nanoparticles, and 0.1 g of dopamine into Tris-HCl buffer solution in sequence, disperse by ultrasonic wave, stir and react at room temperature for 4 h, dialyze with ultrapure water, and freeze-dry to obtain flame-retardant modified nanocellulose; S7: Add 64 parts of PC resin, 16 parts of ABS resin, 2 parts of flame-retardant modified nanocellulose, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0017] Comparative Example 1: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add 1 g of nanocellulose into deionized water, disperse by ultrasonic wave, add 1.6 g of sodium periodate, stir in the dark at room temperature for 48 h, wash the product with deionized water to obtain pre-oxidized nanocellulose; Add 1 g of pre-oxidized nanocellulose into deionized water, disperse by ultrasonic wave, add 0.9 g of hexamethylenediamine, heat to 30 °C and react for 6 h, cool to room temperature, add 0.58 g of sodium borohydride and stir at room temperature for 1 h, wash the product with deionized water to obtain amino-functionalized nanocellulose; S2: Add 2 g of amino-functionalized nanofibers into N,N-dimethylformamide, disperse by ultrasonic wave, preheat the reaction system to 90 °C, add an N,N-dimethylformamide solution containing 1 g of styrene-maleic anhydride copolymer, keep the temperature and react for 12 h, centrifuge, wash the product with N,N-dimethylformamide and ethanol, and dry in vacuum to obtain copolymer-modified nanocellulose; S3: Add 5 g of copolymer-modified nanocellulose into a citric acid / sodium citrate buffer solution with a pH of 5, disperse by ultrasonic wave, add 0.664 g of hydrochloric acid dopamine, 0.38 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 0.22 g of N-hydroxysuccinimide, stir and react at room temperature for 6 - 6.5 h under a nitrogen atmosphere, dialyze with ultrapure water, and freeze-dry to obtain dopamine-modified nanocellulose; S4: Add 64 parts of PC resin, 16 parts of ABS resin, 0.5 part of dopamine-modified nanocellulose, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0018] Comparative Example 2: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: S1: Add 2.68 g of polyoxyethylene polyoxypropylene ether into an ethanol aqueous solution, stir evenly, add 15.64 g of triethanolamine, stir evenly, add 0.664 g of cetyltrimethylammonium bromide, stir evenly, add 0.20 g of tetraethyl orthosilicate, stir and react at room temperature for 30 min, stand for aging, centrifuge, wash the product with deionized water and ethanol, dry in vacuum, and calcine at 550 °C for 6 h to obtain silica nanoparticles; S2: Add 0.5 g of silica nanoparticles into deionized water, ultrasonically disperse, add 0.278 g of tris(trimethylsilyl) borate, stir for 1 h, centrifuge, wash the product with deionized water, and freeze-dry to obtain coated and modified silica nanoparticles; S3: Add 64 parts of PC resin, 16 parts of ABS resin, 0.5 part of coated and modified silica nanoparticles, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0019] Comparative Example 3: A preparation method of a fluorine-free flame-retardant PC / ABS composite material, comprising the following steps: Add 64 parts of PC resin, 16 parts of ABS resin, and 13 parts of bisphenol A-bis(diphenyl phosphate) into a twin-screw extruder in sequence, extrude and pelletize to obtain a fluorine-free flame-retardant PC / ABS composite material.

[0020] Experiment: UL-94 vertical burning test: According to the ASTM D3801-2010 standard, use a vertical burning instrument to prepare the composite materials of the examples and comparative examples into samples with dimensions of 130.0×13.0×3.2 mm 3 to evaluate the flame-retardant grade by recording the two burning times (t1 / t2) and whether there is a dripping phenomenon.

[0021] Limiting oxygen index (LOI) test: According to the ASTM D2863 standard, use an oxygen index analyzer to prepare the composite materials of the examples and comparative examples into samples with dimensions of 100.0×6.5×3 mm 3 to evaluate the flame-retardant performance by measuring the lowest oxygen concentration required to maintain the combustion of the material.

[0022] Tensile test: Using a universal testing machine, the tensile rate was set at 10 mm / min. Five specimens were tested for each sample, and the average value was finally taken as the tensile property data of the sample. The recorded indexes were tensile strength and elongation at break.

[0023] The experimental results are shown in Table 1 below.

[0024] Table 1 Performance test data table of fluorine-free flame-retardant PC / ABS composite Conclusion: The fluorine-free flame-retardant PC / ABS composite prepared by the present invention has excellent mechanical properties and flame-retardant properties.

[0025] In Comparative Example 1, dopamine-modified nanocellulose was directly added, resulting in a decrease in flame-retardant properties and mechanical properties; in Comparative Example 2, coated modified silica nanoparticles were directly added, resulting in a decrease in flame-retardant properties and mechanical properties; in Comparative Example 3, flame-retardant modified nanocellulose was missing, resulting in a decrease in flame-retardant properties and mechanical properties.

[0026] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A method for preparing a fluorine-free flame-retardant PC / ABS composite material, characterized in that: The following steps are involved: S1: dopamine-modified nanocellulose, coated modified silica nanoparticles, and dopamine are sequentially added to a Tris-HCl buffer solution, dispersed by ultrasonication, stirred at room temperature for 4-5 hours, dialyzed with ultrapure water, and freeze-dried to obtain flame-retardant modified nanocellulose; S2: PC resin, ABS resin, flame-retardant modified nanocellulose, and bisphenol A-bis(diphenyl phosphate) are sequentially added into a twin-screw extruder, and extruded into granules to obtain a fluorine-free flame-retardant PC / ABS composite material.

2. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 1, characterized in that: During the preparation of flame-retardant modified nanocellulose, the mass ratio of dopamine-modified nanocellulose: coated modified silica nanoparticles: dopamine is (0.1-1):0.1:0.

1.

3. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 1, characterized in that: The components in the fluorine-free flame-retardant PC / ABS composite material include 48-64 parts of PC resin, 12-16 parts of ABS resin, 0.5-2 parts of flame-retardant modified nanocellulose, and 13-14 parts of bisphenol A-bis(diphenyl phosphate) by weight.

4. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 1, characterized in that: The method for preparing coated modified silica nanoparticles comprises the following steps: adding silica nanoparticles into deionized water, ultrasonically dispersing, adding tris(trimethylsilyl)borate, stirring for 1-3 hours, centrifuging, washing the product with deionized water, and freeze-drying to obtain coated modified silica nanoparticles; In the preparation process of coated modified silica nanoparticles, the mass ratio of silica nanoparticles: tris(trimethylsilyl)borate is (0.5-1):(0.278-0.282).

5. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 4, characterized in that: The preparation method of silicon dioxide nanoparticles comprises the following steps: adding polyoxyethylene polyoxypropylene ether to an ethanol aqueous solution, stirring evenly, adding triethanolamine, stirring evenly, adding hexadecyltrimethylammonium bromide, stirring evenly, adding tetraethyl orthosilicate, stirring and reacting for 30-45 minutes at room temperature, standing for aging, centrifuging, washing the product with deionized water and ethanol, vacuum drying, and calcining at 550-555° C. for 6-6.5 hours to obtain silicon dioxide nanoparticles; During the preparation of silica nanoparticles, the mass ratio of polyoxyethylene polyoxypropylene ether: triethanolamine: hexadecyltrimethylammonium bromide: tetraethyl orthosilicate is (2.68-2.84):(15.64-17.58):(0.664-0.672):(0.20-0.21).

6. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 1, characterized in that: The preparation method of dopamine-modified nanocellulose comprises the following steps: adding copolymer-modified nanocellulose to a citric acid / sodium citrate buffer solution with a pH of 5, performing ultrasonic dispersion, adding dopamine hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-hydroxysuccinimide, stirring at room temperature for 6-6.5 hours under a nitrogen atmosphere, dialyzing with ultrapure water, and freeze-drying to obtain dopamine-modified nanocellulose; In the preparation process of dopamine-modified nanocellulose, the mass ratio of copolymer-modified nanocellulose: dopamine hydrochloride: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride: N-hydroxysuccinimide is 5: (0.664-0.678): (0.38-0.41): (0.22-0.23).

7. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 6, characterized in that: The method for preparing the copolymer-modified nanocellulose comprises the following steps: adding amino-functionalized nanofibers to N,N-dimethylformamide, ultrasonically dispersing, preheating the reaction system to 90-95° C., adding an N,N-dimethylformamide solution containing a styrene-maleic anhydride copolymer, keeping the temperature for reaction for 12-12.5 hours, centrifuging, washing the product with N,N-dimethylformamide and ethanol, and vacuum drying to obtain the copolymer-modified nanocellulose; During the preparation of copolymer-modified nanocellulose, the mass ratio of amino-functionalized nanofibers to styrene-maleic anhydride copolymer is (2-4):(1-2).

8. The method for preparing a fluorine-free flame-retardant PC / ABS composite material according to claim 7, characterized in that: The preparation method of amino-functionalized nanocellulose comprises the following steps: adding nanocellulose to deionized water, ultrasonically dispersing, adding sodium periodate, stirring at room temperature and in the dark for 48 hours, washing the product with deionized water to obtain pre-oxidized nanocellulose; adding pre-oxidized nanocellulose to deionized water, ultrasonically dispersing, adding hexamethylenediamine, heating to 30-32° C. for reaction for 6-6.5 hours, cooling to room temperature, adding sodium borohydride and stirring at room temperature for 1-3 hours, washing the product with deionized water to obtain amino-functionalized nanocellulose; During the preparation of pre-oxidized nanocellulose, 1.6-2g of sodium periodate is added to every 1g of nanocellulose; during the preparation of amino-functionalized nanocellulose, 0.9-1g of hexamethylenediamine and 0.58-0.6g of sodium borohydride are added to every 1g of pre-oxidized nanocellulose.

9. A fluorine-free flame-retardant PC / ABS composite material prepared according to the method for preparing a fluorine-free flame-retardant PC / ABS composite material according to any one of claims 1 to 8.

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