High-toughness low-precipitation flame-retardant PC / ABS composite material and preparation method thereof

Abstract

The invention discloses a high-toughness low-precipitation flame-retardant PC / ABS composite material and a preparation method thereof, and belongs to the technical field of polymer composite materials. The composite material comprises the following components in parts by weight: 55-70 parts of PC resin, 20-35 parts of ABS resin, 3-8 parts of phosphorus-silicon surface modified nano cellulose whiskers, 5-10 parts of a phosphorus-nitrogen-silicon ternary synergistic flame retardant, 2-5 parts of a liquid metal coated MBS core-shell elastomer, and a proper amount of a compatilizer and an auxiliary agent. The preparation method comprises the following steps: firstly, respectively preparing the three key functional components, and then carrying out melt blending granulation on all the components. Through the synergistic effect of the three functional components, the material has high toughness, efficient flame retardance, extremely low high-temperature precipitation rate and excellent heat-conducting property at the same time, and is particularly suitable for being applied to high-end electronic and electric appliance shells and automobile parts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composites, in particular to a polycarbonate / acrylonitrile-butadiene-styrene copolymer composite material with high toughness, low precipitation, high flame retardant efficiency and good thermal conductivity performance and a preparation method thereof. BACKGROUND

[0002] PC / ABS alloy is widely used in the fields of electronic appliances, automobile parts, charging pile shell, etc. due to its comprehensive properties of heat resistance, high strength and high impact toughness of PC and good processing fluidity and chemical resistance of ABS. With the expansion of application fields and the improvement of environmental protection requirements, more stringent requirements are put forward for the flame retardancy, mechanical property retention rate, weather resistance, such as anti-precipitation and anti-migration, etc. of PC / ABS material.

[0003] A lot of research has been conducted in the industry to improve the flame retardant performance of PC / ABS alloy. A PC / ABS alloy for charging pile shell is disclosed in Chinese patent CN112724627B, which uses phosgene method and ester exchange method PC compounding as the matrix and adds modified graphene and phosphoric acid ester / phospholipid compound flame retardant system to realize green flame retardant and high mechanical properties of the material. However, the dispersibility of the modified graphene in this technology is difficult to guarantee, and agglomeration is easy to occur, which not only may lead to a decrease in material toughness, but more importantly, the agglomerates may become stress concentration points, accelerating material aging and cracking, and destroying the continuity of the flame retardant coating. Moreover, the flame retardant system still mainly uses traditional small molecule phosphoric acid ester, which is easy to migrate to the surface of the product after long-term use under heat and light, resulting in sticky surface, environmental pollution, and a decrease in electrical properties, and there is a risk of flame retardant failure due to the loss of effective flame retardant components.

[0004] In addition, Chinese patent application CN120944112A also discloses a flame-retardant polymer and its application. The flame-retardant polymer is a phosphorus-silicon polymer with adjustable molecular structure, which is used as a flame retardant for PC and PC / ABS, effectively improving the compatibility with the matrix and reducing precipitation. However, this technical solution is relatively single in function, mainly focusing on solving the compatibility problem, and lacks consideration of material toughness and thermal conductivity path in the molecular structure design, so the improvement of the overall toughness of the material is limited, and the functional requirements such as thermal conductivity are not involved.

[0005] Furthermore, Chinese invention patent application CN111825969A discloses a PC / ABS alloy with electromagnetic shielding function, which endows the material with electromagnetic shielding properties by introducing silicon-coated metal oxide nanomaterials as electromagnetic shielding fillers. However, the interfacial compatibility between the inorganic filler and the polymer matrix introduced in this technology remains a challenge. Weak interfacial bonding leads to low stress transfer efficiency, often at the cost of sacrificing the material's impact strength.

[0006] In summary, there is an urgent need in this field to develop a novel PC / ABS composite material that can simultaneously achieve a balance of multiple excellent properties, such as high toughness, high efficiency flame retardancy, especially low exudation, and good thermal conductivity, in order to meet the stringent requirements of high-end electronic and electrical equipment for the comprehensive performance of materials. Summary of the Invention

[0007] Therefore, it is necessary to provide a high-toughness, low-exudation flame-retardant PC / ABS composite material and its preparation method to overcome the shortcomings of existing technologies.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A high-toughness, low-exudation, flame-retardant PC / ABS composite material, comprising the following components by weight: 55-70 parts of PC resin; 20-35 parts of ABS resin; 3-8 parts of phosphorus-silicon surface-modified nanocellulose whiskers; 5-10 parts of phosphorus-nitrogen-silicon ternary synergistic flame retardant; Liquid metal-coated MBS core-shell elastomer, 2-5 parts; 1-2 parts compatibilizer; Antioxidant 0.3-0.6 parts; Lubricant 0.2-0.5 parts; 0.3-0.8 parts of light stabilizer.

[0009] Preferably, the preparation method of the phosphorus-silicon surface-modified nanocellulose whiskers includes: dispersing nanocellulose whiskers in ethanol, adding 10%-20% of silane coupling agent KH-550 and 5%-15% of DOPO by mass of nanocellulose whiskers, reacting at 75-85°C for 4-6 hours, and obtaining the product after filtration, washing and drying.

[0010] Preferably, the phosphorus-nitrogen-silicon ternary synergistic flame retardant is an oligomer having the structure shown in the following formula: [DOPO-melamine unit]-[phenylsiloxane unit]n- Wherein, n is an integer from 1 to 5; the preparation method of the phosphorus-nitrogen-silicon ternary synergistic flame retardant includes: reacting DOPO with melamine at 150-180℃ under inert gas protection to generate a phosphorus-nitrogen intermediate, and then carrying out a condensation reaction with amino-terminated phenylsiloxane at 100-130℃ in the presence of a catalyst.

[0011] Preferably, the liquid metal-coated MBS core-shell elastomer is a microcapsule structure formed on the surface of MBS core-shell elastomer particles through physical adsorption and coating, using a low-melting-point Ga-In-Sn eutectic alloy as the shell.

[0012] Furthermore, the present invention also provides a method for preparing the PC / ABS composite material, comprising the following steps: 1. Pre-preparation of phosphorus-silicon surface-modified nanocellulose whiskers, phosphorus-nitrogen-silicon ternary synergistic flame retardant and liquid metal-coated MBS core-shell elastomer; 2. Mix the PC resin, ABS resin, and the components obtained in step 1, along with other additives, in a high-speed mixer at room temperature for 10-15 minutes; 3. Add the mixed material to the twin-screw extruder, and then melt-blend, extrude, water-cool, pelletize, and dry. The temperature of the ten zones from the feed port to the die head of the twin-screw extruder is set to 220-265℃, and the screw speed is 350-450rpm.

[0013] Compared with the prior art, the beneficial effects of the present invention include: 1. Synergistic toughening: Phosphorus-silicon surface-modified nanocellulose whiskers act as rigid reinforcements, working synergistically with liquid metal-coated MBS elastomers / flexible tougheners to prevent crack propagation at both the micro / nano and micro scales, respectively, thus significantly improving the impact toughness of the material while maintaining high strength.

[0014] 2. High efficiency in flame retardancy and low exudation: The self-synthesized phosphorus-nitrogen-silicon ternary synergistic flame retardant integrates the three flame retardant elements into the same molecular chain through chemical bonding, exerting a triple synergistic flame retardant effect of phosphorus-nitrogen-silicon in both the gas phase and condensed phase, resulting in high flame retardant efficiency; at the same time, its macromolecular structure and good compatibility with the matrix fundamentally solve the problem of easy exudation of small molecule flame retardants.

[0015] 3. Functional Integration and Synergistic Toughening: The innovative liquid metal-coated MBS core-shell elastomer of this invention possesses multiple functions: First, its MBS core, as a classic elastomer, can effectively induce crazes and shear bands, absorbing impact energy. Second, its liquid metal shell can deform or even rupture under processing shear forces, releasing liquid metal microspheres that disperse in the matrix and form a localized thermally conductive network, significantly improving the thermal conductivity of the composite material—a function not possessed by traditional toughening agents. Finally, this "rigid shell-elastic core" structure, together with nanocellulose whiskers, forms a multi-level toughening system that combines rigidity and flexibility at the microscale, synergistically preventing crack propagation and achieving a balance between high strength and high toughness.

[0016] 4. Excellent interfacial compatibility: Both nanocellulose whiskers and ternary flame retardants have been modified with groups compatible with PC / ABS through surface modification or molecular design, ensuring uniform dispersion and strong bonding of each component in the matrix. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of a high-toughness, low-exudation, flame-retardant PC / ABS composite material according to the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Please see Figure 1 Specifically, the present invention provides a specific embodiment of a high-toughness, low-exudation, flame-retardant PC / ABS composite material and its preparation method, as follows: Example 1

[0020] 1. Raw material preparation and pretreatment PC resin: Grade IR2200, melt index 10g / 10min.

[0021] ABS resin: Grade HH-112, high resin content.

[0022] a. Preparation of phosphorus-silicon surface-modified cellulose nanofibers: Take 5.0 g of nanocellulose whiskers and disperse them in 200 mL of ethanol. Sonicate the mixture for 30 minutes to ensure thorough dispersion. Add 15% DOPO (based on the mass of the nanocellulose whiskers), e.g., 0.75 g of DOPO. DOPO refers to 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Then, add 15% silane coupling agent KH-550 (based on the mass of the nanocellulose whiskers), e.g., 0.75 g of KH-550. KH-550 refers to γ-aminopropyltriethoxysilane. Next, place the mixture in an 80°C oil bath and reflux for 5 hours with mechanical stirring.

[0023] After the reaction was completed, the product was filtered and washed three times with fresh ethanol to remove unreacted raw materials. Subsequently, the filter cake was dried in a vacuum drying oven at 80°C for 12 hours to obtain a white powdery product, which is phosphorus-silicon surface-modified nanocellulose whiskers.

[0024] Fourier transform infrared spectroscopy (FT-IR) analysis showed that the product exhibited a characteristic absorption peak of P=O near 1150 cm⁻¹ and a characteristic absorption peak of Si-OC near 1090 cm⁻¹, confirming that DOPO and silane coupling agent had been successfully grafted onto the surface of nanocellulose whiskers.

[0025] b. Preparation of phosphorus-nitrogen-silicon ternary synergistic flame retardant: Preparation of phosphorus-nitrogen-silicon ternary synergistic flame retardant: Under a nitrogen atmosphere, 21.6 g (0.1 mol) of DOPO and 6.3 g (0.05 mol) of melamine were added to a 500 mL three-necked flask equipped with a stirrer, thermometer, and condenser. The temperature was slowly raised to 160 °C, and the reaction was stirred at this temperature for 3 hours to obtain a pale yellow, viscous phosphorus-nitrogen intermediate.

[0026] The reaction system was cooled to 110°C, and then 18.1 g (0.05 mol) of amino-terminated diphenylsiloxane dimer, specifically APSi-202, was added. The number-average molecular weight of this substance was approximately 360 g / mol. Simultaneously, 0.2 g of tetraisopropyl titanate was added as a catalyst, with the amount of catalyst being approximately 0.7% of the total mass of the reactants DOPO and melamine. The reaction was continued at 110°C with stirring for 4 hours.

[0027] After the reaction was completed and cooled to room temperature, a pale yellow viscous solid was obtained, which is the target phosphorus-nitrogen-silicon ternary synergistic flame retardant.

[0028] Its number-average molecular weight (Mn) was determined to be approximately 1800 by gel permeation chromatography (GPC), and the content of phosphorus, nitrogen, and silicon elements was determined to be basically consistent with the theoretical values ​​by elemental analysis.

[0029] c. Preparation of liquid metal-coated MBS elastomers: Weigh 2.0g of MBS core-shell elastomer particles, such as Paraaloid EXL-2691, disperse them in 50mL of toluene, and sonicate for 20 minutes to ensure full dispersion.

[0030] Alternatively, take 1.0g of a low-melting-point Ga-In-Sn eutectic alloy, whose composition by mass percentage is: gallium (Ga) 62wt%, indium (In) 25wt%, and tin (Sn) 13wt%, i.e., Ga 0.62g, In 0.25g, and Sn 0.13g. Heat the alloy in a 60℃ water bath until it is completely melted.

[0031] In a high-speed shear emulsifier, with the speed set at 10,000 rpm and vigorous stirring, the molten liquid metal alloy was slowly added dropwise to the toluene suspension of MBS. After the addition was complete, emulsification and shearing continued at this speed for 30 minutes to form a uniform coated emulsion.

[0032] The emulsion was then rotary evaporated at 40°C to completely remove the toluene solvent, yielding a dry, metallic-lustered powder product, which is the liquid metal-coated MBS elastomer.

[0033] Scanning electron microscopy (SEM) revealed that the surface of the MBS particles was covered by a dense metal layer; energy dispersive spectroscopy (EDX) analysis confirmed the presence of gallium, indium, and tin.

[0034] 2. Preparation of composite materials Weigh the following components according to the following weight ratio: 65 parts PC resin, 30 parts ABS resin, 5 parts of the modified nanocellulose whiskers prepared above, 8 parts ternary synergistic flame retardant, 3 parts liquid metal-coated MBS elastomer, 1 part compatibilizer SMA, 0.2 parts antioxidant 1076, 0.2 parts antioxidant 168, and 0.3 parts zinc stearate.

[0035] The compatibilizer is a styrene-maleic anhydride copolymer (SMA); the antioxidant is a mixture of primary antioxidant Irganox 1076 (phenolic) and secondary antioxidant Irgafos 168 (phosphite) in a 1:1 mass ratio; the lubricant is zinc stearate; and the light stabilizer is the hindered amine light stabilizer Tinuvin 770. This embodiment illustrates a specific selection of additives, but the scope of protection of this invention is not limited thereto. Those skilled in the art can select other additives with similar functions as needed.

[0036] Place all the above ingredients in a high-speed mixer and mix at 500 rpm for 12 minutes.

[0037] The uniformly mixed material is added to a co-rotating twin-screw extruder for melt blending and granulation. The twin-screw extruder has a screw diameter of 40 mm and a length-to-diameter ratio of 40:1. The extruder temperatures are set as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 250℃, Zone 5 255℃, Zone 6 260℃, Zone 7 265℃, Zone 8 265℃, Zone 9 260℃, and Die Head 255℃. The screw speed is 400 rpm.

[0038] After the extruded strip is cooled with water, granulated, and dried in a forced-air dryer at 80°C for 4 hours, the high-toughness, low-exudation, flame-retardant PC / ABS composite material particles of the present invention are obtained.

[0039] The granules are then dried at 100°C for 4 hours, and then they can be injection molded into standard test strips using an injection molding machine. Example 2

[0040] 1. Raw material preparation: The preparation methods of phosphorus-silicon surface-modified nanocellulose whiskers, phosphorus-nitrogen-silicon ternary synergistic flame retardant, and liquid metal-coated MBS elastomer are the same as in Example 1.

[0041] 2. Preparation of composite materials: Weigh the following components according to the following weight ratio: 70 parts PC resin, 20 parts ABS resin, 3 parts phosphorus-silicon surface-modified nanocellulose whiskers, 10 parts phosphorus-nitrogen-silicon ternary synergistic flame retardant, 2 parts liquid metal-coated MBS elastomer, 1 part compatibilizer SMA, 0.3 parts antioxidant (Irganox 1076 / Irgafos 168, 1:1), 0.2 parts lubricant zinc stearate, and 0.3 parts light stabilizer Tinuvin 770.

[0042] 3. Mixing and Granulation: All raw materials are placed in a high-speed mixer and mixed for 12 minutes, then melt-blended and granulated using a twin-screw extruder. The processing technology is the same as in Example 1.

[0043] Technical effects of Example 2: The obtained material can still meet the UL94 V-0 flame retardant rating while maintaining good processing fluidity, and has a low exudation rate and better toughness and thermal conductivity than pure PC / ABS alloy. Example 3

[0044] 1. Raw material preparation: Preparation of phosphorus-silicon surface-modified nanocellulose whiskers: Replace the silane coupling agent KH-550 in Example 1 with an equal mass of KH-560, i.e. γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the remaining steps are the same as in Example 1.

[0045] The preparation of the phosphorus-nitrogen-silicon ternary synergistic flame retardant and the liquid metal-coated MBS elastomer is the same as in Example 1.

[0046] 2. Preparation of composite materials: Weigh the following components according to the following weight ratio: 60 parts PC resin, 30 parts ABS resin, 6 parts of the above-mentioned KH-560 modified nanocellulose whiskers, 7 parts phosphorus-nitrogen-silicon ternary synergistic flame retardant, 4 parts liquid metal coated MBS elastomer, 1.5 parts compatibilizer SMA, 0.5 parts antioxidant (Irganox 1076 / Irgafos 168, 1:1), 0.4 parts lubricant zinc stearate, and 0.6 parts light stabilizer Tinuvin 770.

[0047] 3. Mixing and granulation: The process is the same as in Example 1.

[0048] Technical effects of Example 3: Nanocellulose whiskers modified with different silane coupling agents also exhibit good compatibility with the matrix. The resulting material achieves a balanced and excellent performance in terms of toughness, flame retardancy, and anti-exudation properties.

[0049] Comparative Example 1 Using a conventional method in the prior art, the formulation is as follows: 65 parts PC, 30 parts ABS, 5 parts modified graphene, 8 parts flame retardant BDP, 1 part compatibilizer SMA, and 1 part antioxidant and lubricant; the preparation process of Comparative Example 1 is the same as that of Example 1.

[0050] Comparative Example 2 Another conventional scheme in the prior art is adopted, with the following proportions: 65 parts PC, 30 parts ABS, 8 parts of silicon phosphate flame retardant prepared in the prior art, 1 part compatibilizer SMA, 1 part antioxidant and lubricant. The preparation process of this comparative example 2 is the same as that of example 1.

[0051] Furthermore, the performance of the samples prepared in Example 1 and Comparative Examples 1 and 2 was tested, and the results are shown in Table 1 below.

[0052]

[0053] As shown in Table 1 above, Embodiment 1 provided by the present invention has the following performance advantages: 1. Excellent overall mechanical properties: Example 1 shows significantly better notched impact strength than the comparative example, demonstrating its high toughness. Example 1 also demonstrates superior tensile and flexural strength, reflecting its high strength characteristics.

[0054] 2. Higher flame retardant efficiency: Although all three achieved UL94 V-0 rating, Example 1 had a limiting oxygen index as high as 33%, significantly higher than the 28.5-29% range of the comparative examples. This indicates that Example 1 provided by the present invention can maintain good flame retardancy even under more demanding conditions. 3. Excellent resistance to precipitation: The high-temperature exudation rate of Example 1 was only 0.07%, which was 72% lower than that of Comparative Example 1 (0.25%) and 53% lower than that of Comparative Example 2 (0.15%). This fundamentally solved the problem of flame retardant migration and ensured the long-term reliability of the product.

[0055] 4. Additional functional advantages: The thermal conductivity of Example 1 is 0.43 W / m·K, which is almost twice that of the comparative example; this thermal conductivity enhancement effect is a beneficial effect that traditional PC / ABS materials do not possess.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-toughness, low-exudation, flame-retardant PC / ABS composite material, characterized in that, By weight, it comprises the following components: 55-70 parts of PC resin; 20-35 parts of ABS resin; 3-8 parts of phosphorus-silicon surface-modified nanocellulose whiskers; 5-10 parts of phosphorus-nitrogen-silicon ternary synergistic flame retardant; Liquid metal-coated MBS core-shell elastomer, 2-5 parts; 1-2 parts compatibilizer; Antioxidant 0.3-0.6 parts; Lubricant 0.2-0.5 parts; 0.3-0.8 parts of light stabilizer.

2. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 1, characterized in that: The phosphorus-silicon surface-modified nanocellulose whiskers are prepared by the following method: nanocellulose whiskers are dispersed in a solvent, a silane coupling agent and DOPO are added to carry out a surface grafting reaction, and after the reaction is completed, they are separated, washed and dried to obtain the product; the silane coupling agent is γ-aminopropyltriethoxysilane or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

3. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 2, characterized in that: The solvent is ethanol or isopropanol; the reaction temperature of the surface grafting reaction is 75-85℃, and the reaction time is 4-6 hours.

4. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 1, characterized in that: The phosphorus-nitrogen-silicon ternary synergistic flame retardant is an oligomer with the following general formula: [DOPO-melamine unit]-[phenylsiloxane unit]_n- Where n is an integer from 1 to 5.

5. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 4, characterized in that, The preparation method of the phosphorus-nitrogen-silicon ternary synergistic flame retardant includes the following steps: a. React DOPO with melamine at 150-180℃ to generate a phosphorus-nitrogen intermediate; b. The intermediate obtained in step a is subjected to a condensation reaction with an amino-terminated phenylsiloxane at 100-130°C in the presence of a catalyst.

6. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 1, characterized in that: The liquid metal-coated MBS core-shell elastomer is a microcapsule structure powder formed by emulsifying and coating MBS core-shell elastomer particles with gallium-indium-tin eutectic alloy as the shell material through high-speed shearing.

7. The high-toughness, low-exudation, flame-retardant PC / ABS composite material according to claim 6, characterized in that: In the gallium-indium-tin eutectic alloy, the mass ratio of gallium, indium and tin is (60-65):(20-30):(10-15).

8. A method for preparing a high-toughness, low-expiration, flame-retardant PC / ABS composite material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Pre-preparation of phosphorus-silicon surface-modified nanocellulose whiskers, phosphorus-nitrogen-silicon ternary synergistic flame retardant and liquid metal-coated MBS core-shell elastomer; S2. Mix the PC resin, ABS resin, and the components and other additives obtained in step 1 in a high-speed mixer until homogeneous; S3. The material mixed in step S2 is melt-blended, extruded, cooled, and granulated using a twin-screw extruder.

9. The method for preparing a high-toughness, low-explosion flame-retardant PC / ABS composite material according to claim 8, characterized in that: The twin-screw extruder has a processing temperature of 220-265℃ and a screw speed of 350-450rpm.

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