Halogen-free burn-through-resistant pc composite material and preparation method thereof

Abstract

The present application relates to the technical field of high polymer materials, and particularly relates to a halogen-free burn-through-resistant PC composite material and a preparation method thereof.The composite material comprises: 82-95 parts of polycarbonate resin, 0.2-1 part of processing aid, 2-6 parts of toughening agent, 0.2-0.5 part of antioxidant, 0.2-0.5 part of lubricant, and silicon flame retardant, phosphorus flame retardant and sulfonate; wherein the weight ratio of the silicon flame retardant, the phosphorus flame retardant and the sulfonate is (1-5):(0.5-3):(0.5-1). The present application forms a dense silicon-oxygen carbon layer, captures free radicals, catalyzes carbon formation and releases non-combustible gas in the combustion process through the ternary synergistic compounding of the silicon flame retardant, the phosphorus flame retardant and the sulfonate, so that the pin flame S.2 burn-through time of the composite material under a 1mm thin wall thickness is greater than 60 seconds, excellent mechanical properties are maintained, and the composite material is halogen-free and environmentally friendly. The preparation process of the present application is simple, and the present application can be widely applied in the fields of electronic appliances, automobile manufacturing and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a halogen-free burn-through resistant PC composite material and its preparation method. Background Technology

[0002] Polycarbonate (PC), a thermoplastic engineering plastic with excellent comprehensive properties, is widely used in electronics, automotive manufacturing, and lighting due to its outstanding impact strength, dimensional stability, electrical insulation, and thermal stability. As electronic products become increasingly thinner and smaller, the wall thickness requirements for plastic components are becoming thinner, while safety requirements are also becoming more stringent.

[0003] For example, current safety standards for information technology equipment have introduced more stringent needle flame test requirements (S.2 level), stipulating that thin-walled (1mm) plastic parts should not be burned through after being subjected to a specified period of needle flame burning. However, while ordinary polycarbonate materials can achieve high ratings in vertical burning tests, their resistance to needle flame burn-through under thin-walled conditions is significantly deficient. This is mainly because the glass transition temperature of PC is much lower than its decomposition temperature. When subjected to localized high-temperature flame burning, the material surface melts rapidly, the melt viscosity drops sharply, and the high-temperature melt drips. Simultaneously, the carbon layer formed during PC combustion is loose and discontinuous, failing to effectively block heat and oxygen, allowing the flame to spread rapidly and burn through the material. Conventional PC raw materials typically burn through in about 15 seconds in a needle flame test at a thickness of 1mm, far from meeting the requirements of the new national standard. Therefore, developing PC materials that combine excellent flame retardancy and burn-through resistance has become a pressing technical challenge for the industry.

[0004] To address the aforementioned issues, existing technologies have proposed various modification schemes. For example, Chinese patent CN119875342A discloses improving the burn-through resistance of PC by adding bromine-based, boron-based, and silicon-based flame retardants. However, the use of bromine-based flame retardants poses environmental and biotoxicity risks and does not comply with increasingly stringent halogen-free environmental regulations. Chinese patent CN115991930B uses silicon-based flame retardants to improve burn-through resistance by forming a carbon layer during combustion. However, a single silicon-based flame retardant is still insufficient to meet the requirements of prolonged flame exposure, and the resulting carbon layer lacks density and cannot completely block heat transfer. Furthermore, Chinese patent CN120966218A significantly improves the heat resistance and burn-through resistance of PC by synthesizing specially end-capped branched polycarbonate and combining it with sulfur-based flame retardants. However, this method involves complex source synthesis technology, has high process barriers, and is expensive, hindering industrial promotion and application. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a halogen-free, burn-through-resistant PC composite material, prepared from raw materials comprising the following components by weight: The mixture comprises 82-95 parts of polycarbonate resin, 0.2-1 parts of processing aid, 2-6 parts of toughening agent, 0.2-0.5 parts of antioxidant, 0.2-0.5 parts of lubricant, and a flame retardant system, wherein the flame retardant system is composed of a silicone flame retardant, a phosphorus flame retardant, and a sulfonate; wherein the weight ratio of the silicone flame retardant, the phosphorus flame retardant, and the sulfonate is (1-5):(0.5-3):(0.5-1).

[0006] Based on the above scheme, the silicon flame retardant is further selected from at least one of polymethylphenyl silsesquioxane, organosilicon resin, and MQ silicone resin.

[0007] Based on the above scheme, the phosphorus flame retardant further includes at least one of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphate, and resorcinol tetraphenyl phosphate.

[0008] Based on the above scheme, the sulfonate is further selected from at least one of potassium benzenesulfonylbenzenesulfonate, sulfonate HES-2, trimethylsilylbenzenesulfonic acid, and perfluorobutyl sulfonate.

[0009] It should be noted that the sulfonate HES-2 is a halogen-free mixed salt of aromatic sulfonates produced by Arichem, and its specific structure is known to those skilled in the art or can be obtained through commercial channels.

[0010] Based on the above scheme, the toughening agent is further selected from at least one of methyl methacrylate-butadiene-styrene copolymer and acrylate impact agent; the lubricant is selected from at least one of pentaerythritol ester, ethylene bis-stearamide and montan wax.

[0011] Based on the above scheme, the processing aid further includes at least one of epoxy resin and fluorinated PPA.

[0012] Based on the above scheme, the weight ratio of the epoxy resin to the fluorinated PPA is further 1:1-3.

[0013] Preferably, the weight ratio of the epoxy resin to the fluorinated PPA is 1:1.

[0014] It should be noted that fluorinated PPA is a well-known additive in the field of polymer processing. It is mainly a mixture of fluorinated polymers and has been widely used in the plastics processing industry. It mainly includes one or more of fluorinated polymers such as polyvinylidene fluoride, fluorinated ethylene-propylene copolymer, and perfluoropolyether. These substances are all existing materials well known to those skilled in the art and can be obtained through various commercial channels.

[0015] Based on the above scheme, the antioxidant further includes a mixture of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant or a thiol antioxidant, and the weight ratio of the primary antioxidant to the secondary antioxidant is 1:1-2.

[0016] Based on the above scheme, the composite material has a needle flame S.2 burn-through time of 1 mm thickness greater than or equal to 60 seconds.

[0017] The present invention also provides a method for preparing the halogen-free burn-through resistant polycarbonate composite material as described above, comprising the following steps: S1. Weigh out polycarbonate resin, processing aid, toughening agent, antioxidant, lubricant, silicone flame retardant, phosphorus flame retardant and sulfonate according to the weight parts, wherein the weight ratio of silicone flame retardant, phosphorus flame retardant and sulfonate is (1-5):(0.5-3):(0.5-1), mix evenly to obtain premix; S2. The premixed material is fed into a twin-screw extruder for melt blending and extrusion, then granulated and dried to obtain the halogen-free burn-through resistant polycarbonate composite material.

[0018] Based on the above scheme, the processing temperature of the twin-screw extruder is 230-280℃, and the screw speed is 50-600 rpm.

[0019] Compared with existing technologies, the halogen-free burn-through resistant PC composite material provided by this invention has the following beneficial effects: This invention constructs a ternary synergistic flame retardant system by compounding silicon flame retardants, phosphorus flame retardants, and sulfonates, enabling each component to exert a significant synergistic effect during combustion. Specifically, the silicon flame retardant migrates to the material surface during combustion and forms a dense silicon-oxygen-carbon layer, effectively blocking the transfer of heat and oxygen, while simultaneously increasing the viscosity of the PC melt at high temperatures to suppress dripping. The phosphorus flame retardant releases phosphoric acid, pyrophosphate, and other phosphorus derivatives during thermal decomposition, promoting PC dehydration and carbonization, increasing coke residue, and simultaneously releasing PO· and HPO· free radicals to capture combustion. The H· and OH· free radicals in the atmosphere block the gas-phase combustion chain reaction; the sulfonate catalyzes the reconstruction of the PC molecular chain skeleton under combustion conditions, accelerating the formation of a dense protective carbon layer, while releasing a large amount of non-combustible gases such as CO2 and H2O to dilute the concentration of combustible gases. The three work together to block the combustion process, increase the melt strength, and form a dense and continuous carbon layer on the surface to isolate the flame, thereby achieving the performance of burn-through resistance. Together, they achieve the three major requirements of "flame suppression, anti-dripping, and short afterflame". This allows the composite material of the present invention to achieve a needle flame S.2 burn-through time of more than 60 seconds with a thin wall thickness of 1 mm, while the vertical burning rating of 1.6 mm thickness reaches UL94 V-0 level. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0021] Example 1 This embodiment provides a halogen-free, burn-through resistant PC composite material, whose raw material composition by weight is as follows: 83 parts polycarbonate resin, 5 parts silicone flame retardant, 3 parts phosphorus flame retardant, 1 part sulfonate, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant; The preparation method of this embodiment includes the following steps: (1) Weigh each raw material according to the above weight proportions, mix them evenly, and obtain a premix; (2) The premixed material is fed into a twin-screw extruder for melt blending and extrusion. The extruder processing temperature is 230-280℃, the screw speed is 300rpm, the material is drawn into strips and granulated, and dried until the moisture content is less than 0.02% to obtain the halogen-free burn-through resistant PC composite material.

[0022] Example 2 This embodiment provides a halogen-free, burn-through resistant PC composite material, whose raw material composition by weight is as follows: 85 parts polycarbonate resin, 5 parts silicone flame retardant, 1 part phosphorus flame retardant, 1 part sulfonate, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant; The preparation method in this embodiment is the same as that in Example 1.

[0023] Example 3 This embodiment provides a halogen-free, burn-through resistant PC composite material, whose raw material composition by weight is as follows: 85.5 parts polycarbonate resin, 5 parts silicone flame retardant, 1 part phosphorus flame retardant, 0.5 parts sulfonate, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant; The preparation method in this embodiment is the same as that in Example 1.

[0024] Comparative Example 1 This comparative example provides a PC composite material that differs from Example 1 in that no silicone flame retardant is added, while other components and amounts remain unchanged.

[0025] The raw material composition, by weight, is as follows: 88 parts polycarbonate resin, 3 parts phosphorus flame retardant, 1 part sulfonate, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant. The preparation method of this comparative example is the same as that of Example 1.

[0026] Comparative Example 2 This comparative example provides a PC composite material that differs from Example 1 in that no silicon flame retardant or phosphorus flame retardant is added, while other components and amounts remain unchanged.

[0027] The raw material composition, by weight, is as follows: 91 parts polycarbonate resin, 1 part sulfonate, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant. The preparation method of this comparative example is the same as that of Example 1.

[0028] Comparative Example 3 This comparative example provides a PC composite material that differs from Example 1 in that it does not contain silicone flame retardants, phosphorus flame retardants, and sulfonates, while other components and amounts remain unchanged.

[0029] The raw material composition, by weight, is as follows: 92 parts polycarbonate resin, 6 parts toughening agent, 1 part processing aid, 0.5 parts antioxidant, and 0.5 parts lubricant. The preparation method of this comparative example is the same as that of Example 1.

[0030] Description of raw materials used in the examples: Polycarbonate resin: Covestro 2800; Silicone flame retardant: organosilicon resin; Phosphorus flame retardant: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO); Sulfonate: Trimethylsilylbenzenesulfonic acid; Processing aids: Epoxy resin and fluorinated PPA are mixed in a weight ratio of 1:1; Toughening agent: acrylate impact modifier; Antioxidant: The primary antioxidant AT-76 and the secondary antioxidant AT-168 are mixed at a weight ratio of 1:2; Lubricant: Pentaerythritol ester.

[0031] Performance testing The PC composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were processed into standard test strips on an injection molding machine for performance testing. The test methods are as follows: Needle flame burn-through time test: According to the requirements of needle flame S.2 in GB 4943.1-2022 standard, the burn-through time (unit: seconds) of a 1mm thick sample was tested. Vertical flammability rating test: The vertical flammability rating of a 1.6mm thick sample was tested according to UL94 standard. Tensile strength test: Tested in accordance with GB / T 1040.1-2018 standard (unit: MPa); Bending strength test: Tested in accordance with GB / T 9341-2008 standard (unit: MPa); Flexural modulus test: Tested according to GB / T 9341-2008 standard (unit: MPa); Notched impact strength test of cantilever beam: Tested in accordance with GB / T 1843-2008 standard (unit: kJ / m²).

[0032] The test results are shown in Tables 1 and 2.

[0033] Table 1. Burn-through time of needle flame S.2 for 1 mm thickness in Examples 1-3 and Comparative Examples 1-3.

[0034] Table 2. Physical properties of Examples 1-3 and Comparative Examples 1-3

[0035] The test results in Tables 1 and 2 show that: Burn-through resistance: The burn-through time of the 1mm thick needle flame S.2 in Examples 1-3 was greater than 60 seconds, with Example 1 achieving a burn-through time of 132 seconds, significantly better than Examples 2 and 3. In contrast, the burn-through times of Comparative Examples 1-3 were all less than 60 seconds, failing to meet the standard requirements. This indicates that the present invention, through the synergistic compounding of silicon flame retardant, phosphorus flame retardant, and sulfonate, can significantly improve the burn-through resistance of PC composite materials, and the effect is most excellent when the ratio of the three components is within the preferred range.

[0036] Flame retardant performance: Examples 1-3 all achieved UL94 V-0 rating at a thickness of 1.6 mm, while Comparative Examples 1-3 only achieved V-2 rating. This indicates that the silicon-phosphorus-sulfonate ternary synergistic system is the key to achieving a high flame retardant rating, and the absence of any component will lead to a significant decrease in flame retardant performance.

[0037] Mechanical properties: The tensile strength, flexural strength, flexural modulus and impact strength of Examples 1-3 did not decrease significantly compared with Comparative Example 3, indicating that the flame retardant system of the present invention has little impact on the mechanical properties of polycarbonate resin and maintains the original excellent mechanical properties of the material.

[0038] In summary, based on the thermal decomposition behavior of PC, this invention considers two approaches to enhance its burn-through resistance and flame retardancy during combustion: ① Enhancing charring ability: The carbon layer is strengthened by the polysiloxane network of organosilicon itself, and sulfonates catalyze the reconstruction of the polycarbonate skeleton during PC thermal decomposition, accelerating the formation of a protective carbon layer to achieve the effect of forming a dense carbon layer to insulate against heat; ② Increasing the generation of non-flammable gases in the gas phase: Sulfonates release CO2 and H2O non-flammable gases during the catalytic reconstruction of the polycarbonate skeleton; DOPO, during thermal decomposition, not only releases phosphoric acid, pyrophosphate, and other phosphorus derivatives, but also releases PO· and HPO· free radicals while promoting the dehydration and carbonization of polycarbonate, capturing H· and OH· free radicals during combustion and thus blocking the combustion process; Furthermore, this invention is a halogen-free solution, fully compliant with halogen-free environmental regulations, free of halogen elements such as bromine and chlorine, and meets RoHS 2.0, REACH, and UL standards. It is halogen-free, free of heavy metals, polycyclic aromatic hydrocarbons and other harmful impurities, and can also meet the requirements of needle flame S.2 with a thin wall of 1 mm.

[0039] Although terms such as polycarbonate resin, silicone flame retardant, phosphorus flame retardant, and sulfonate are frequently used herein, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A halogen-free, burn-through resistant PC composite material, characterized in that: It is prepared from raw materials comprising the following components in parts by weight: The mixture comprises 82-95 parts of polycarbonate resin, 0.2-1 parts of processing aid, 2-6 parts of toughening agent, 0.2-0.5 parts of antioxidant, 0.2-0.5 parts of lubricant, and a flame retardant system, wherein the flame retardant system is composed of a silicone flame retardant, a phosphorus flame retardant, and a sulfonate; wherein the weight ratio of the silicone flame retardant, the phosphorus flame retardant, and the sulfonate is (1-5):(0.5-3):(0.5-1).

2. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The silicon flame retardant is selected from at least one of polymethylphenylsilsesquioxane, organosilicon resin, and MQ silicone resin.

3. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The phosphorus flame retardant includes at least one of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphate, and resorcinol tetraphenyl phosphate.

4. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The sulfonate is selected from at least one of potassium benzenesulfonylbenzenesulfonate, sulfonate HES-2, trimethylsilylbenzenesulfonic acid, and perfluorobutyl sulfonate.

5. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The toughening agent is selected from at least one of methyl methacrylate-butadiene-styrene copolymer and acrylate impact modifier; the lubricant is selected from at least one of pentaerythritol ester, ethylene bis-stearamide and montan wax.

6. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The processing aids include at least one of epoxy resin and fluorinated PPA.

7. The halogen-free burn-through resistant PC composite material according to claim 6, characterized in that: The weight ratio of the epoxy resin to the fluorinated PPA is 1:1-3.

8. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The antioxidant comprises a mixture of a primary antioxidant and a secondary antioxidant. The primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant or a thiol antioxidant. The weight ratio of the primary antioxidant to the secondary antioxidant is 1:1-2.

9. The halogen-free burn-through resistant PC composite material according to claim 1, characterized in that: The composite material has a needle flame S.2 burn-through time of ≥60 seconds at a thickness of 1 mm.

10. A method for preparing the halogen-free burn-through resistant polycarbonate composite material as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Weigh out polycarbonate resin, processing aid, toughening agent, antioxidant, lubricant, silicone flame retardant, phosphorus flame retardant and sulfonate according to the weight parts, wherein the weight ratio of silicone flame retardant, phosphorus flame retardant and sulfonate is (1-5):(0.5-3):(0.5-1), mix evenly to obtain premix; S2. The premixed material is fed into a twin-screw extruder for melt blending and extrusion, then granulated and dried to obtain the halogen-free burn-through resistant polycarbonate composite material.

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