Halogen-free flame-retardant pp material resistant to extremely cold and its preparation method and application

Abstract

The application relates to the field of flame-retardant materials, in particular to a halogen-free flame-retardant PP material resistant to extremely cold conditions and a preparation method and application thereof. The halogen-free flame-retardant PP material resistant to extremely cold conditions is prepared from raw materials including a polypropylene matrix, a composite flame retardant, a functional combination agent, an interface compatibility and crystallization adjusting agent, a stabilizer, a lubricant and a composite reinforcing agent. The halogen-free flame-retardant polypropylene composite material provided by the application can realize efficient halogen-free flame retardation and solve the problem that traditional flame-retardant polypropylene is prone to brittle cracking in an extremely low-temperature environment. With a unique interface strengthening and toughening mechanism, a firm and elastic microstructure is formed in the material, so that the material can still maintain excellent impact resistance and structural integrity in extremely cold conditions, and the long-term stability and reliability of the material in harsh working conditions are ensured.

Description

Technical Field

[0001] This application relates to the field of flame retardant materials, and more specifically to a halogen-free flame retardant PP material resistant to extreme cold, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP), a general-purpose thermoplastic, is widely used in various fields such as automobiles, electronics, construction, and daily necessities due to its excellent mechanical properties, processing performance, and cost advantages. However, PP material itself is flammable, with a limiting oxygen index of only about 17%. During combustion, it drips heavily, easily causing secondary fires. In recent years, with increasingly stringent environmental regulations and enhanced consumer safety awareness, halogen-free flame-retardant PP materials have become a research hotspot. Compared with traditional halogen-containing flame-retardant systems, they have advantages such as low smoke, low toxicity, and environmental friendliness, and are gradually replacing halogen-containing flame retardants such as bromine-based ones.

[0003] In practical applications, especially in high-latitude or high-altitude regions, PP materials also need to possess excellent cold-weather resistance. For example, automotive exterior parts, outdoor electrical equipment housings, or polar research equipment used in cold regions often require materials to maintain sufficient impact toughness and structural integrity even at temperatures as low as -40°C or even -60°C. However, while conventional halogen-free flame-retardant PP systems can meet UL94 V-0 flame-retardant requirements after introducing a large amount of inorganic flame-retardant fillers, their rigidity increases significantly, while their toughness decreases drastically. Brittleness is particularly pronounced at low temperatures, making them highly susceptible to cracking or breakage. Furthermore, some phosphorus- or nitrogen-based flame retardants may have poor compatibility with the PP matrix, leading to weakened interfacial bonding at low temperatures and further deteriorating their mechanical properties.

[0004] However, achieving the two key requirements of halogen-free flame retardancy and extreme cold toughness in the same polypropylene material system presents significant technical challenges. The addition of large amounts of flame retardants not only reduces melt flow and makes processing difficult, but also significantly deteriorates the material's mechanical properties, particularly low-temperature impact toughness. This is because many flame retardant fillers have poor compatibility with the polypropylene matrix, easily becoming stress concentration points at low temperatures, inducing cracks and accelerating fracture. On the other hand, toughening elastomer components added to improve low-temperature toughness often negatively impact the material's flame retardant properties, potentially reducing the limiting oxygen index or disrupting the integrity of the char layer during combustion, leading to decreased flame retardant efficiency. Summary of the Invention

[0005] In summary, most current solutions on the market struggle to maintain both high-efficiency halogen-free flame retardancy and excellent impact resistance at temperatures as low as -30 degrees Celsius. Therefore, developing a polypropylene composite material that can maintain reliable performance under extreme low temperatures and flame threats—that is, one possessing both excellent cold-weather toughness and high-efficiency halogen-free flame retardancy—has become a critical issue that urgently needs to be addressed in this technological field.

[0006] A cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 70-90 parts polypropylene matrix, 18-25 parts composite flame retardant, 10-16 parts functional compound agent, 3-6 parts interface compatibility and crystallization regulator, 0.3-0.5 parts stabilizer, 0.5-1 part lubricant, 0.7-1 part dispersant, 0.3-0.5 parts UV stabilizer, and 5-10 parts composite reinforcing agent.

[0007] Preferably, the polypropylene matrix is ​​block copolymer polypropylene.

[0008] Preferably, the melt flow rate of the polypropylene matrix is ​​10~12 g / 10 min, 230°C, and 2.16 kg.

[0009] Preferably, the mass ratio of the polypropylene matrix, the composite flame retardant, the functional combination agent, and the interfacial compatibility and crystallization regulator is (7.5~8.5):(2~2.4):(1.2~1.5):(0.4~0.6).

[0010] Preferably, the mass ratio of the polypropylene matrix, composite flame retardant, functional combination agent, and interfacial compatibility and crystallization regulator is (7.8~8.2):(2.1~2.2):(1.3~1.4):(0.4~0.5).

[0011] Preferably, the composite flame retardant is a combination of coated ammonium polyphosphate, diethyl aluminum hypophosphite, and organomontmorillonite.

[0012] Preferably, the mass ratio of the coated ammonium polyphosphate, diethylaluminum hypophosphite and organomontmorillonite is (1~1.5):(0.5~0.7):(0.2~0.4).

[0013] Preferably, the mass ratio of the coated ammonium polyphosphate, diethylaluminum hypophosphite and organomontmorillonite is (1.2~1.3):(0.5~0.6):(0.2~0.3).

[0014] Preferably, the functional combination agent is a combination of polyolefin elastomer and dynamically vulcanized thermoplastic elastomer.

[0015] Preferably, the mass ratio of the polyolefin elastomer to the dynamically vulcanized thermoplastic elastomer is (2~4):(1~3).

[0016] Preferably, the mass ratio of the polyolefin elastomer to the dynamically vulcanized thermoplastic elastomer is (3~4):(1~1.5).

[0017] Preferably, the polyolefin elastomer is Engage 8180, manufactured by Dow Chemical Company, USA.

[0018] Preferably, the dynamically vulcanized thermoplastic elastomer is Santoprene 8211-55, manufactured by Celanese, USA.

[0019] Preferably, the interfacial compatibility and crystallization regulator is a combination of maleic anhydride-grafted polypropylene and β-crystalline TMB-5.

[0020] Preferably, the mass ratio of maleic anhydride-grafted polypropylene to β-crystalline TMB-5 is (2~3):(0.8~1.4).

[0021] Preferably, the mass ratio of maleic anhydride-grafted polypropylene to β-crystalline TMB-5 is (2~2.5):(0.9~1.2).

[0022] The combination of functional agents and interfacial compatibility and crystallization regulators used in this application significantly reduces the probability of brittle fracture and component interface debonding of PP material in extremely cold environments while ensuring the flame retardant efficiency of the material. The toughening system composed of functional agents constructs a flexible network that runs through the polypropylene matrix and remains elastic at ultra-low temperatures. This network can effectively initiate and terminate crazes, absorb and disperse impact energy, and directly endow the material with excellent low-temperature toughness. At the same time, the maleic anhydride functional groups in the system can chemically interact with the surface of the polar halogen-free flame retardant, while the polypropylene segments are physically entangled with the matrix resin, greatly enhancing the interfacial bonding strength. Furthermore, the β-crystal nucleating agent induces the formation of a large number of high-toughness β-crystals in the polypropylene matrix. This crystal structure itself has better energy absorption capacity, improving the material's cold resistance and impact resistance from the intrinsic properties of the matrix.

[0023] Preferably, the stabilizer is a combination of Irganox 1010 and Irgafos 168.

[0024] Preferably, the mass ratio of Irganox 1010 to Irgafos 168 is (2~3):(2~3).

[0025] Preferably, the mass ratio of Irganox 1010 to Irgafos 168 is 2:3.

[0026] Preferably, the lubricant is at least one selected from ethylene bis-stearamide, calcium stearate, zinc stearate, and erucamide.

[0027] Preferably, the lubricant is ethylene bis-stearamide or erucamide.

[0028] Preferably, the lubricant is ethylene bis-stearamide.

[0029] Preferably, the dispersant is oxidized polyethylene wax and / or glyceryl monostearate.

[0030] Preferably, the dispersant is glyceryl monostearate.

[0031] Preferably, the UV stabilizer is at least one of Tinuvin 770, Tinuvin 326, Tinuvin 327 and Tinuvin 460.

[0032] Preferably, the UV stabilizer is Tinuvin 770 or Tinuvin 326.

[0033] Preferably, the UV stabilizer is Tinuvin 770.

[0034] Preferably, the composite reinforcing agent is a combination of sartomer CN104 and maleic anhydride-functionalized polyolefin wax.

[0035] Preferably, the mass ratio of sartomer CN104 to maleic anhydride functionalized polyolefin wax is (3~5):(1~3).

[0036] Preferably, the mass ratio of sartomer CN104 to maleic anhydride-functionalized polyolefin wax is (4~4.5):(1.5~2.2).

[0037] Preferably, the sartomer CN104 is from Sartoma, France.

[0038] Preferably, the maleic anhydride-functionalized polyolefin wax is PP MA 6452, manufactured by Clariant, Germany.

[0039] Preferably, the mass ratio of the polypropylene matrix to the composite reinforcing agent is (7.5~8.5):(0.6~0.9).

[0040] Preferably, the mass ratio of the polypropylene matrix to the composite reinforcing agent is (7.8~8.2):(0.7~0.8).

[0041] The final composite reinforcing agent further enhances the interfacial integrity, intrinsic toughness, and environmental resistance of PP materials under extreme conditions. Maleic anhydride-functionalized polyolefin wax effectively coats and wets the surface of polar halogen-free flame retardants and nanofiller particles during processing. Its maleic anhydride functional groups can react with hydroxyl and other groups on the filler surface to form strong chemical bonding anchors, thereby transforming the originally fragile interface prone to debonding into a robust stress transfer bridge, significantly improving the compatibility and mechanical strength of the composite system.

[0042] On the other hand, Sartomer CN104, as a long-chain flexible liquid polymer containing epoxy groups, can not only undergo grafting reaction with the polypropylene matrix to enhance interfacial adhesion, but also construct a microscopic flexible cross-linked network in the matrix. It can still maintain a certain degree of movement and deformation at extremely low temperatures, directly absorb and disperse impact energy, thereby greatly improving the low-temperature toughness of the material and ensuring the stable comprehensive performance of PP material in extreme environments.

[0043] A method for preparing a cold-resistant halogen-free flame-retardant PP material includes the following steps: S1: Add the composite flame retardant, functional combination agent, and interfacial compatibility and crystallization regulator to a high-speed mixer and premix at 800-1000 rpm for 3-5 min. Then add the remaining raw materials of the polypropylene matrix and mix at 600-800 rpm for 10-15 min to obtain a mixed masterbatch; S2: Add the mixed masterbatch to a co-rotating twin-screw extruder through the main feed port. The extruder temperature is set from the feeding section to the die head as 170℃, 185℃, 195℃, 200℃, 200℃, and 195℃. The screw speed is 240-280 rpm. The vacuum exhaust port is kept open. The melt is extruded, water-cooled, and pelletized; S3: Dry the pellets obtained by pelletizing at 80-90℃ for 3-4 h and then seal and package them to obtain the final product.

[0044] This application further defines the application of the obtained extremely cold-resistant halogen-free flame-retardant PP material in new energy vehicles, outdoor communication and power infrastructure, special industrial equipment and cold chain logistics components.

[0045] Preferably, the halogen-free flame-retardant PP material is used to prepare halogen-free flame-retardant PP sheets for application in new energy vehicles, outdoor communication and power infrastructure, special industrial equipment, and cold chain logistics components.

[0046] Preferably, the preparation method of the halogen-free flame-retardant PP sheet includes the following steps: S1: Drying the halogen-free flame-retardant PP material at 80~90℃ for 3~4h to ensure that the moisture content is <0.03%; S2: Extruding the halogen-free flame-retardant PP material using a single-screw extruder, with the temperature control range from the feed port to the die head being 160~210℃, extruding the melt with a T-die head, pressing it against a 70~75℃ casting roller, calendering it with a precision three-roll calender and cooling it to ensure a thickness of 0.43mm; S3: After cooling, winding the sheet, cutting off the edge material, and placing it at room temperature for 22~24h, then checking that the thickness is qualified to obtain the final product.

[0047] The beneficial effects of this application are: 1. The extreme cold-resistant halogen-free flame-retardant polypropylene composite material provided in this application not only achieves high-efficiency halogen-free flame retardancy but also effectively solves the core problem of traditional flame-retardant polypropylene being prone to brittleness in extreme low-temperature environments. Through a unique interface strengthening and toughening mechanism, a robust and elastic microstructure is formed inside the material, enabling it to maintain excellent impact resistance and structural integrity under extremely cold conditions. It also endows the material with good resistance to environmental aging and moisture penetration, ensuring its long-term stability and reliability under harsh working conditions.

[0048] 2. This application utilizes the synergistic combination of functional agents, interfacial compatibility agents, and crystallization regulators to significantly improve the reliability of materials in extremely cold environments while maintaining high flame retardancy. This system effectively initiates and terminates crazes and absorbs impact energy by constructing an ultra-low temperature elastic network within the matrix; simultaneously, it strengthens interfacial adhesion through functional group reactions and physical entanglement to prevent debonding; and induces the formation of a high-toughness β-crystal structure, fundamentally enhancing the energy absorption capacity of the matrix. These three factors work together to overcome the challenges of low-temperature brittle fracture and interfacial failure.

[0049] 3. The composite reinforcing agent used in this application significantly improves the overall performance of the material through a unique synergistic mechanism. One component constructs strong chemical bonding anchors between the filler and the matrix through a chemical reaction, transforming the fragile interface into a robust stress transfer bridge, greatly enhancing interface integrity and mechanical strength. The other component forms a micro-flexible network, effectively absorbing and dispersing impact energy even at extremely low temperatures, directly improving the intrinsic toughness of the material. The combined effect of these two components ensures the material exhibits excellent and stable reliability and durability in harsh environments such as extreme cold and humidity. Attached Figure Description

[0050] Figure 1 This is a physical image of the halogen-free flame-retardant PP sheet that is resistant to extreme cold, prepared according to Example 1 of this application. Detailed Implementation

[0051] Example 1

[0052] A cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 80 parts polypropylene matrix, 21 parts composite flame retardant, 13.2 parts functional compounding agent, 4.8 parts interface compatibility and crystallization regulator, 0.4 parts stabilizer, 0.8 parts lubricant, 0.7 parts dispersant, 0.3 parts UV stabilizer, and 7.6 parts composite reinforcing agent.

[0053] The polypropylene matrix is ​​block copolymer polypropylene Moplen RP340, with a melt flow rate of 11 g / 10 min, 230℃, and a yield of 2.16 kg. It is manufactured in Daelim, South Korea.

[0054] The composite flame retardant is a combination of coated ammonium polyphosphate, diethylaluminum hypophosphite, and organomontmorillonite, with a mass ratio of 1.2:0.6:0.2. The coated ammonium polyphosphate is Exolit AP422 (Clariant, Switzerland); the organomontmorillonite is Nanomer I.44P (Shanghai Huanyang Chemical, China).

[0055] The functional compound is a combination of polyolefin elastomer and dynamically vulcanizing thermoplastic elastomer in a mass ratio of 3.8:1.2. The polyolefin elastomer is Engage 8180 from Dow Chemical Company, USA; the dynamically vulcanizing thermoplastic elastomer is Santoprene 8211-55 from Celanese Chemical Company, USA.

[0056] The interfacial compatibility and crystallization regulator is a combination of maleic anhydride-grafted polypropylene and β-crystalline TMB-5, with a mass ratio of 2.1:0.9. Maleic anhydride-grafted polypropylene 50E803 is from DuPont, USA; β-crystalline TMB-5 is from Hubei Shuaiyan Ligao Biotechnology Co., Ltd., China.

[0057] The stabilizer is a combination of Irganox 1010 and Irgafos 168 in a mass ratio of 2:3.

[0058] The lubricant is ethylene bis-stearamide; the dispersant is glyceryl monostearate; and the UV stabilizer is Tinuvin 770.

[0059] The composite reinforcing agent is a combination of sartomer CN104 and maleic anhydride-functionalized polyolefin wax, with a mass ratio of 4.2:1.8. The maleic anhydride-functionalized polyolefin wax is PP MA 6452 from Clariant (Germany); and sartomer CN104 is from Sartomer (France).

[0060] A method for preparing a cold-resistant halogen-free flame-retardant PP material includes the following steps: S1: Add the composite flame retardant, functional combination agent, and interfacial compatibility and crystallization regulator to a high-speed mixer and premix at 900 rpm for 5 min. Then add the remaining raw materials of the polypropylene matrix and mix at 800 rpm for 12 min to obtain a mixed masterbatch; S2: Feed the mixed masterbatch into a co-rotating twin-screw extruder through the main feed port. The extruder temperature is set from the feeding section to the die head as 170℃, 185℃, 195℃, 200℃, 200℃, and 195℃. The screw speed is 260 rpm. The vacuum exhaust port is kept open. The melt is extruded, water-cooled, and pelletized; S3: Dry the pellets obtained by pelletizing at 85℃ for 4 h and then seal and package them to obtain the final product.

[0061] The extremely cold-resistant halogen-free flame-retardant PP material prepared in this embodiment can be used to make halogen-free flame-retardant PP sheets for application in new energy vehicles, outdoor communication and power infrastructure, special industrial equipment and cold chain logistics components.

[0062] The preparation method of halogen-free flame-retardant PP sheet includes the following steps: S1: Dry the halogen-free flame-retardant PP material at 90℃ for 4 hours to ensure that the moisture content is <0.03%; S2: Extrude the halogen-free flame-retardant PP material using a single-screw extruder, with the temperature from the feed inlet to the die controlled at 165 / 175 / 185 / 195 / 210℃, extruding the melt with a T-die, pressing it against a 75℃ casting roller, calendering it with a precision three-roll calender and cooling it to ensure a thickness of 0.43mm; S3: After cooling, rewind the sheet, cut off the edge material, and place it at room temperature for 24 hours. After the thickness is found to be qualified, the sheet is obtained.

[0063] The actual product of the extremely cold-resistant halogen-free flame-retardant PP sheet prepared in this embodiment is shown below. Figure 1 As shown.

[0064] Example 2 This embodiment differs from Embodiment 1 only in the following aspects: A cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 85 parts polypropylene matrix, 22 parts composite flame retardant, 14.5 parts functional compound agent, 5.2 parts interface compatibility and crystallization regulator, 0.4 parts stabilizer, 0.8 parts lubricant, 0.7 parts dispersant, 0.3 parts UV stabilizer, and 6.8 parts composite reinforcing agent.

[0065] The remaining implementation methods are the same.

[0066] Example 3 This embodiment differs from Embodiment 1 only in the following aspects: A cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 85 parts polypropylene matrix, 20 parts composite flame retardant, 15 parts functional compound agent, 5.5 parts interface compatibility and crystallization regulator, 0.4 parts stabilizer, 0.8 parts lubricant, 0.7 parts dispersant, 0.3 parts UV stabilizer, and 8 parts composite reinforcing agent.

[0067] The remaining implementation methods are the same.

[0068] Comparative Example 1 This comparative example differs from Example 1 only in the following aspects: an extremely cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 90 parts polypropylene matrix, 24.5 parts composite flame retardant, 15.5 parts functional compound agent, 4.8 parts interface compatibility and crystallization regulator, 0.4 parts stabilizer, 0.8 parts lubricant, 0.7 parts dispersant, 0.3 parts UV stabilizer, and 2.2 parts composite reinforcing agent.

[0069] The remaining implementation methods are the same.

[0070] Comparative Example 2 This comparative example differs from Example 1 only in the following aspects: an extremely cold-resistant halogen-free flame-retardant PP material, by weight, comprises: 90 parts polypropylene matrix, 21 parts composite flame retardant, 6.5 parts functional compound agent, 2.5 parts interface compatibility and crystallization regulator, 0.4 parts stabilizer, 0.8 parts lubricant, 0.7 parts dispersant, 0.3 parts UV stabilizer, and 10 parts composite reinforcing agent.

[0071] The remaining implementation methods are the same.

[0072] Comparative Example 3 The only difference between this comparative example and Example 1 is that the composite flame retardant is a combination of coated ammonium polyphosphate, diethyl aluminum hypophosphite and organomontmorillonite in a mass ratio of 0.6:1.3:0.1.

[0073] The functional compound is a combination of polyolefin elastomer and dynamically vulcanized thermoplastic elastomer in a mass ratio of 4.5:0.5.

[0074] The remaining implementation methods are the same.

[0075] Comparative Example 4 This comparative example differs from Example 1 only in the following way: the functional combination agent is a combination of polyolefin elastomer and dynamically vulcanized thermoplastic elastomer in a mass ratio of 2:3.

[0076] The interfacial compatibility and crystallization regulator is a combination of maleic anhydride-grafted polypropylene and β-crystalline TMB-5 in a mass ratio of 1:2.

[0077] The remaining implementation methods are the same.

[0078] Comparative Example 5 The only difference between this comparative example and Example 1 is that the composite reinforcing agent is a combination of sartomer CN104 and maleic anhydride functionalized polyolefin wax in a mass ratio of 5.5:0.5.

[0079] The remaining implementation methods are the same.

[0080] Comparative Example 6 The only difference between this comparative example and Example 1 is that the composite reinforcing agent is a combination of sartomer CN104 and maleic anhydride functionalized polyolefin wax in a mass ratio of 2.5:3.5.

[0081] The remaining implementation methods are the same.

[0082] Performance testing 1. Flame retardancy: Tested according to UL 94, results are recorded in Table 1.

[0083] 2. Low-temperature impact toughness: A notched injection-molded standard specimen, 80 mm × 10 mm × 4 mm, was used. Before testing, the specimen was pretreated in a low-temperature environment of -40℃ for 4 hours and then quickly transferred to the impact testing machine to ensure that the core temperature of the specimen was maintained at -40℃. The pendulum impacted the back of the notched specimen, and the average value of 10 low-temperature notched impact strength tests was recorded in Table 1.

[0084] 3. Tensile strength: The test was conducted according to ISO 527-2:2025, and the results were the average of 10 tests and recorded in Table 1.

[0085] 4. Bending strength: PP sheet was cut into 15mm×15mm specimens and subjected to a three-point bending loading method with a span of 25mm, a loading head radius and a support radius of 2mm, a loading rate of 1mm / min, and environmental conditions of 25℃ and 50%RH. The average value of 10 bending strength tests was recorded in Table 1.

[0086] 5. Resistance to damp heat aging: The same type of specimen used for tensile strength testing was placed in a constant temperature and humidity chamber at 90℃ and 85% relative humidity for 1500 hours. After removal, it was conditioned in a standard laboratory environment at 25℃ and 50% RH for 24 hours, and then its tensile strength was tested. The tensile strength retention rate was recorded, and the average of 10 tests was recorded in Table 1. 6. Water absorption rate: The test is conducted according to ISO 62:2008, and the result is the average of 10 tests, which is recorded in Table 1.

[0087] Table 1 Performance Test Results

[0088] Examples 1-3 of this application achieve superior performance results compared to Comparative Examples 1-6. This is because the technical solutions specified in this application, adopted in Examples 1-3, through the synergistic compounding of functional agents, interface compatibility agents, and crystallization regulators, significantly improve the reliability of the material in extremely cold environments while maintaining high flame retardancy. Furthermore, the composite reinforcing agent transforms the fragile interface into a robust stress transfer bridge, greatly enhancing interface integrity and mechanical strength, ensuring excellent and stable reliability and durability of the material in harsh environments such as extreme cold and humidity. In contrast, Comparative Examples 1-6, due to the adoption of different non-limited technical solutions, resulted in a significant decrease in their corresponding technical effects within the PP material system of this application, ultimately leading to a decline in the overall comprehensive performance of the final PP sheet.

Claims

1. A halogen-free flame-retardant PP compound resistant to extremely low temperatures, characterized in that: By weight, the raw materials include: 70-90 parts of polypropylene matrix, 18-25 parts of composite flame retardant, 10-16 parts of functional compound agent, 3-6 parts of interfacial compatibility and crystallization regulator, 0.3-0.5 parts of stabilizer, 0.5-1 part of lubricant, 0.7-1 part of dispersant, 0.3-0.5 parts of UV stabilizer, and 5-10 parts of composite reinforcing agent; The polypropylene matrix is ​​block copolymer polypropylene with a melt flow rate of 10~12 g / 10 min at 230℃ and 2.16 kg. The composite flame retardant is a combination of coated ammonium polyphosphate, diethylaluminum hypophosphite and organomontmorillonite, with a mass ratio of (1~1.5):(0.5~0.7):(0.2~0.4). The functional combination agent is a combination of polyolefin elastomer and dynamically vulcanized thermoplastic elastomer in a mass ratio of (2~4):(1~3). The mass ratio of the polypropylene matrix, composite flame retardant, functional combination agent, and interfacial compatibility and crystallization regulator is (7.5~8.5):(2~2.4):(1.2~1.5):(0.4~0.6). The interfacial compatibility and crystallization regulator is a combination of maleic anhydride-grafted polypropylene and β-crystalline TMB-5, with a mass ratio of (2~3):(0.8~1.4). The composite reinforcing agent is a combination of sartomer CN104 and maleic anhydride-functionalized polyolefin wax, with a mass ratio of (3~5):(1~3). The stabilizer is a combination of Irganox 1010 and Irgafos 168 in a mass ratio of (2~3):(2~3).

2. The extremely cold resistant, halogen-free flame retardant PP material according to claim 1, characterized in that The lubricant is at least one of ethylene bis-stearamide, calcium stearate, zinc stearate, and erucamide.

3. The extremely cold resistant, halogen-free flame retardant PP material according to claim 2, characterized in that: The dispersant is oxidized polyethylene wax and / or glyceryl monostearate.

4. The extremely cold resistant, halogen-free flame retardant PP composition according to claim 3, characterized in that: The UV stabilizer is at least one of Tinuvin 770, Tinuvin 326, Tinuvin 327 and Tinuvin 460.

5. A process for the preparation of the halogen-free flame-retardant PP composition according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1: Add the composite flame retardant, functional combination agent, and interfacial compatibility and crystallization regulator to a high-speed mixer and premix at 800~1000 rpm for 3~5 min. Then add the polypropylene matrix and other remaining raw materials and mix at 600~800 rpm for 10~15 min to obtain a mixed masterbatch. S2: Add the mixed masterbatch to a co-rotating twin-screw extruder through the main feed port. Set the extruder temperature from the feeding section to the die head to 170℃, 185℃, 195℃, 200℃, 200℃, and 195℃. The screw speed is 240~280 rpm. Keep the vacuum exhaust port open. The melt is extruded, water-cooled, and pelletized. S3: Dry the pellets obtained from pelleting at 80~90℃ for 3~4 h and then seal and package them to obtain the final product.

6. The application of a cold-resistant halogen-free flame-retardant PP material according to any one of claims 1 to 4 in new energy vehicles, outdoor communication and power infrastructure, special industrial equipment and cold chain logistics components.

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