A halogen-free flame-retardant and ablation-resistant polypropylene composite material, its preparation method and application

Abstract

This invention belongs to the field of polymer materials technology; specifically, it relates to a halogen-free flame-retardant and ablation-resistant polypropylene composite material, its preparation method, and its application. The polypropylene composite material comprises: 40-60% flame-retardant modified masterbatch and 40-60% long glass fiber reinforced polypropylene masterbatch. The raw materials for preparing the flame-retardant modified masterbatch, by weight, include: 24-44 parts of polypropylene resin, 5-15 parts of PPE resin, 2-5 parts of compatibilizer, 20-40 parts of piperazine, 10-20 parts of ammonium phosphate, 4-8 parts of surface-modified ultrafine aluminum hydroxide, and 0.3-1.5 parts of processing aids. The long glass fiber content in the long glass fiber reinforced polypropylene masterbatch is 40-60 wt%. By introducing PPE resin into a halogen-free flame retardant system and compounding it with modified ultrafine aluminum hydroxide, and then uniformly compounding the halogen-free flame retardant masterbatch with long glass fiber reinforced polypropylene masterbatch in a certain proportion, a halogen-free flame retardant and ablation-resistant material is obtained. While maintaining the high flame retardancy of the material, the ablation resistance can be greatly improved, and it can withstand continuous burning with a 1300℃ flame torch for 10 minutes without burning through.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology; specifically, it relates to a halogen-free flame-retardant and ablation-resistant polypropylene composite material, its preparation method, and its application. Background Technology

[0002] In recent years, with the development of new energy vehicles, especially the iteration of power battery technology, more and more requirements have been placed on the safety, lightweighting, and cost-effectiveness of battery packs. When battery packs are subjected to extreme conditions such as external collisions and punctures, they need to reserve enough time to ensure that the occupants can leave safely. Therefore, a safe and practical ablation-resistant material has become an unavoidable topic. Ablation-resistant materials usually refer to organic refractory polymer materials, which undergo chemical or physical changes such as decomposition, melting, evaporation, sublimation, and carbonization during combustion to consume heat, prevent flame propagation, and provide thermal protection. They are mainly based on epoxy resin, phenolic resin, EPDM rubber, and silicone rubber, and are mainly used in military, aerospace, and wire and cable industries. With the development of the times, in recent years, there have been clear requirements for the use of ablation-resistant materials for the outer shell of new energy battery packs and air conditioning control boxes. The material requirements are as follows: 1. High flame retardant performance: The material has a flame retardant UL94-V0 and 5VA rating; 2. Ablation resistance: The parts made of the material are tested according to GB .T31467 .3-2015 and do not burn through or collapse or deform.

[0003] Existing technologies have proposed several ablation-resistant material solutions from both halogen-based and halogen-free perspectives. For example, patent 202111503847.8 proposes a bromine-based ablation-resistant flame-retardant polypropylene material and its preparation and application, while patent 202111496655.9 proposes a halogen-free heat-insulating, ablation-resistant, and flame-retardant polypropylene material and its preparation and application. However, these technologies involve numerous raw material systems, complex processes, and high costs. Research on high flame retardant, ablation-resistant, and low-smoke-density polyolefin materials is currently a hot topic. However, overall, there are relatively few halogen-free polyolefin materials that simultaneously possess high flame retardancy, ablation resistance, excellent heat insulation, and low smoke density, and are commercially viable. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a halogen-free flame-retardant and ablation-resistant polypropylene composite material, its preparation method, and its applications. This halogen-free flame-retardant and ablation-resistant polypropylene composite material is produced by compounding PPE resin in a halogen-free flame-retardant system and then blending it with long glass fiber masterbatch. Under the synergistic effect of the halogen-free flame retardant, the flame-retardant, heat-insulating, and ablation-resistant properties of the material are effectively improved. Furthermore, the development process is simple, and the material exhibits high mechanical strength.

[0005] A halogen-free flame-retardant and ablation-resistant polypropylene composite material, wherein the polypropylene composite material comprises, by mass percentage: 40-60% flame-retardant modified masterbatch and 40-60% long glass fiber reinforced polypropylene masterbatch.

[0006] The raw materials for preparing the flame-retardant modified masterbatch include, by weight: 24-44 parts of polypropylene resin, 5-15 parts of PPE resin, 2-5 parts of compatibilizer, 20-40 parts of piperazine, 10-20 parts of ammonium phosphate, 4-8 parts of surface-modified ultrafine aluminum hydroxide, and 0.3-1.5 parts of processing aid.

[0007] The long glass fiber reinforced polypropylene masterbatch contains 40-60 wt% long glass fiber.

[0008] Furthermore, the polypropylene resin is one or more of homopolymer polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, and propylene-1-butene random block copolymer.

[0009] Furthermore, the number-average molecular weight distribution of the PPE resin is 20,000 to 60,000.

[0010] Furthermore, the compatibilizer is at least one of PP, POE, SEBS, and SEPS grafted with maleic anhydride.

[0011] Furthermore, the piperazine is one or more of piperazine phosphate, piperazine pyrophosphate, and piperazine polyphosphate; the ammonium phosphate is one or more of melamine phosphate, melamine pyrophosphate, and melamine polyphosphate.

[0012] Further, the preparation steps of the surface-modified ultrafine aluminum hydroxide are as follows: the coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide powder are placed in a high-speed mixer, the temperature is set to 100°C, and the mixture is mixed at high speed for 20 minutes to obtain surface-coated modified ultrafine aluminum hydroxide powder; the mass ratio of the coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide is (2~5):(3~10):(0.1~0.5):(84.5~94.9).

[0013] Furthermore, the specific surface area of ​​the ultrafine aluminum hydroxide is 3~6 m². 2 / g, wherein the coupling agent is at least one of titanate ester and silane coupling agent; the crosslinking agent is at least one of dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide; and the processing aid is at least one of antioxidant, lubricant and colorant.

[0014] A method for preparing a halogen-free flame-retardant and ablation-resistant polypropylene composite material, the method comprising the following steps:

[0015] S1. Polypropylene resin, PPE resin, compatibilizer, piperazine, ammonium phosphate, surface-modified ultrafine aluminum hydroxide, and processing aids are mixed evenly in proportion, and melt-blended, granulated, and dried using a twin-screw extruder to obtain flame-retardant modified masterbatch.

[0016] S2. The flame-retardant modified masterbatch and the long glass fiber reinforced polypropylene masterbatch are mixed evenly to obtain the halogen-free flame-retardant and ablation-resistant polypropylene composite material.

[0017] Further, the screw temperatures of each section of the twin-screw extruder described in step S1, from the feed port to the die head, are as follows: Zone 1 150-160℃, Zone 2 240-260℃, Zone 3 240-260℃, Zone 4 240-260℃, Zone 5 240-260℃, Zone 6 240-260℃, Zone 7 230-250℃, Zone 8 230-250℃, Zone 9 230-250℃, Zone 10 240-260℃; the feed speed is 250-350 rpm; the die head temperature is 230-250℃; the main extruder speed is 300-500 rpm / min; and the vacuum degree is below -0.1 MPa.

[0018] The above-mentioned halogen-free flame-retardant and ablation-resistant polypropylene composite material is used as a raw material in automotive power battery pack shells and electrical control boxes.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention prepares a halogen-free flame-retardant and ablation-resistant polypropylene composite material. PPE resin is introduced into the halogen-free flame-retardant polypropylene system, and modified ultrafine aluminum hydroxide is compounded. The halogen-free flame-retardant masterbatch is then uniformly compounded with long glass fiber reinforced polypropylene masterbatch in a certain proportion to obtain a halogen-free flame-retardant and ablation-resistant material. This halogen-free flame-retardant and ablation-resistant material can achieve a significant improvement in ablation resistance while maintaining high flame retardancy. It can withstand continuous burning with a 1300°C flame torch for 10 minutes without burning through.

[0021] 2. The introduction of PPE resin and modified ultrafine aluminum hydroxide in this invention makes the expanded carbon layer formed during the burning process more dense and compact. This not only effectively prevents the transmission of flame temperature but also keeps the temperature on the back of the flame below 150°C. Furthermore, it has high strength and can withstand certain external pressures without damaging the carbon layer on the back. This effectively isolates the spread of flame in certain situations. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Raw materials used in the examples and comparative examples:

[0024] Polypropylene, grade K7227H, Wuhan Petrochemical;

[0025] PPE resin, grade PPE LXR045, Nantong Xingchen Synthetic Materials Co., Ltd., number average molecular weight 40,000~45,000;

[0026] PPE resin, grade PPE LXR035, Nantong Xingchen Synthetic Materials Co., Ltd., number average molecular weight 25,000~30,000;

[0027] PP-g-MAH, grade CMG 5701, Jia Yi Rong;

[0028] POE-g-MAH, grade CMG 5805-L, Jia Yi Rong;

[0029] Melamine polyphosphate, MPP, Jiangsu Suli Fine Chemical Co., Ltd.;

[0030] Piperazine pyrophosphate, JNP-2, Sichuan Fine Chemical Research and Design Institute;

[0031] Ultrafine aluminum hydroxide, FR-205, Jinan Hongtu New Materials;

[0032] Titanate coupling agent, GR-201, Nanjing Herun Coupling Agent;

[0033] Melamine, Hubei Changao Pharmaceutical Co., Ltd.;

[0034] Long glass fiber reinforced polypropylene masterbatch, LFPP-1438 (glass fiber content 40wt%, particle length 12mm), Huitong New Materials Co., Ltd.

[0035] Long glass fiber reinforced polypropylene masterbatch, LFPP-14310 (glass fiber content 50wt%, particle length 12mm), Huitong New Materials Co., Ltd.

[0036] Long glass fiber reinforced polypropylene masterbatch, LFPP-14312 (glass fiber content 60wt%, particle length 12mm), Huitong New Materials Co., Ltd.

[0037] Other materials such as crosslinking agents, antioxidants, and lubricants are all commercially available standard materials.

[0038] It should be noted that, for commercially available products, the same raw materials used in the following examples and comparative examples are from the same source.

[0039] Examples 1-5: Preparation of halogen-free flame-retardant and ablation-resistant polypropylene composite materials.

[0040] 1. Preparation of surface-modified aluminum hydroxide;

[0041] The coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide powder were mixed in a mass ratio of 3:6:0.3:90.7 and placed in a high-speed mixer. The temperature was set to 100℃ and the mixture was mixed at high speed for 30 minutes. The surface-coated modified ultrafine aluminum hydroxide powder was then discharged.

[0042] 2. Preparation of flame-retardant modified masterbatch;

[0043] Polypropylene resin, PPE resin, compatibilizer, piperazine derivatives, ammonium phosphate, surface-modified ultrafine aluminum hydroxide, and processing aids are mixed uniformly in a certain proportion. The mixture is then melt-blended, granulated, and dried using a twin-screw extruder to obtain flame-retardant modified masterbatch. The temperatures of each section of the twin-screw extruder, from the feed port to the die head, are as follows: Zone 1: 160℃, Zone 2: 250℃, Zone 3: 250℃, Zone 4: 250℃, Zone 5: 250℃, Zone 6: 250℃, Zone 7: 240℃, Zone 8: 240℃, Zone 9: 240℃, Zone 10: 250℃. The feed speed is 250–350 rpm. The die temperature is 240℃.

[0044] The flame retardant masterbatch formulations for Examples 1-5 are shown in Table 1 below;

[0045] Table 1

[0046]

[0047] A method for preparing a halogen-free flame-retardant and ablation-resistant polypropylene composite material, the method comprising the following steps:

[0048] S1. Preparation of flame-retardant modified masterbatch;

[0049] S2. The flame-retardant modified masterbatch and the long glass fiber reinforced polypropylene masterbatch are mixed evenly to obtain the halogen-free flame-retardant and ablation-resistant polypropylene composite material.

[0050] The specific formula is shown in Table 2.

[0051] Table 2

[0052]

[0053] The preparation methods of the polypropylene modified materials in Comparative Examples 1-5 are as follows;

[0054] 1. Preparation of surface-modified aluminum hydroxide;

[0055] The coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide powder were mixed in a mass ratio of 3:6:0.3:90.7 and placed in a high-speed mixer. The temperature was set to 100℃ and the mixture was mixed at high speed for 30 minutes. The surface-coated modified ultrafine aluminum hydroxide powder was then discharged.

[0056] 2. Preparation of flame-retardant modified masterbatch;

[0057] Polypropylene resin, PPE resin, compatibilizer, piperazine derivatives, ammonium phosphate, surface-modified ultrafine aluminum hydroxide, and processing aids are mixed uniformly in a certain proportion. The mixture is then melt-blended, granulated, and dried using a twin-screw extruder to obtain flame-retardant modified masterbatch. The temperatures of each section of the twin-screw extruder, from the feed port to the die head, are as follows: Zone 1: 160℃, Zone 2: 250℃, Zone 3: 250℃, Zone 4: 250℃, Zone 5: 250℃, Zone 6: 250℃, Zone 7: 240℃, Zone 8: 240℃, Zone 9: 240℃, Zone 10: 250℃. The feed speed is 250–350 rpm. The die temperature is 240℃.

[0058] The formulations of the flame-retardant modified masterbatches for Comparative Examples 1-5 are as follows, see Table 3;

[0059] Table 3

[0060]

[0061] A method for preparing a modified polypropylene material, the method comprising the following steps:

[0062] S1. Preparation of flame-retardant modified masterbatch;

[0063] S2. The flame-retardant modified masterbatch and the long glass fiber reinforced polypropylene masterbatch are mixed evenly to obtain the halogen-free flame-retardant and ablation-resistant polypropylene composite material.

[0064] The specific formula is shown in Table 4.

[0065]

[0066] The halogen-free flame-retardant and ablation-resistant polypropylene composite materials prepared in Examples 1-5 and the polypropylene modified materials prepared in Comparative Examples 1-5 were subjected to UL94 flame retardancy rating, continuous burning at 1300℃ for 10 min, sample burn-through condition, back surface temperature, and char layer strength after combustion tests.

[0067] Performance testing standards:

[0068] (1) Flame retardancy rating test: According to UL94-2016, the test strip size is 125mm×12.5mm×2.0mm.

[0069] (2) Ablation resistance test: According to the test method of ablation materials in GJB323A-96, the oxy-acetylene flame was vertically applied to a square plate with a length*width*thickness of 100mm*100mm*2.0mm. The temperature of the oxy-acetylene flame was as high as 1300℃, which ablated the material and recorded the time it took for the square plate to be burned through.

[0070] (3) Back side temperature: According to the GJB323A-96 test method for ablation materials, an oxy-acetylene flame was vertically applied to a square plate with a length*width*thickness of 100mm*100mm*2.0mm until the square plate could no longer support itself. Then, the back side temperature of the square plate was tested using a FLUKE imaging test device.

[0071] (4) Test the strength of the carbon layer after ablation: Use a 250g iron ball to drop vertically onto the back of the carbon layer from different heights and observe the lowest height of the iron ball when the carbon layer breaks.

[0072] The test results are shown in Table 5;

[0073] Table 5

[0074]

[0075] As can be seen from the results in Table 5, the halogen-free flame-retardant and ablation-resistant polypropylene composite materials prepared in Examples 1-5 of this invention can achieve a significant improvement in the corrosion resistance of the material while maintaining the high flame-retardant properties of polypropylene, and achieve lower back-side temperature thermal conductivity and higher back-side char layer strength; they can withstand ablation at 1300℃ for 10 minutes without being burned through, and the back-side temperature of the material is as low as 136~157℃; the impact fracture height of the back-side char layer after burning reaches 250~300mm.

[0076] The polypropylene modified materials prepared in Comparative Examples 1-6 showed that Comparative Example 1 could not even achieve a V0 flame retardant rating. This was because, when the flame retardant content was insufficient, the lack of PPE resin, as described in Comparative Example 1, failed to effectively provide flame retardant properties. PPE resin not only possesses certain flame retardant properties itself, but also provides a char source during combustion and promotes char formation to block the transmission of the ignition source, thus giving the composite material better flame retardancy. Even though Comparative Example 2 achieved V0 flame retardancy, as described in Example 2, the lack of added ultrafine aluminum hydroxide meant that the burning process could not effectively resist the transmission of the heat source, resulting in the sample being burned through. Comparative Example 3 achieved V0 flame retardant performance, and the sample was not burned through during combustion, but the strength of the char layer after burning was significantly reduced. As described in Example 3, the added ultrafine aluminum hydroxide was not surface-modified, and therefore, it failed to achieve good dispersion in the resin system. The melamine-modified ultrafine aluminum hydroxide, through synergistic and uniform formation of a dense char layer, blocks the fire source. Furthermore, the melamine-modified ultrafine aluminum hydroxide undergoes synergistic decomposition and char formation during combustion, simultaneously blocking heat transfer and promoting the formation of a dense char layer to isolate the fire source and heat. Comparative Examples 4 and 5 show that the content and ratio of piperazine-based substances, ammonium phosphate salts, and surface-modified ultrafine aluminum hydroxide require precise control; otherwise, the desired effect cannot be achieved, and good ablation resistance cannot be realized. Although Comparative Example 6 achieved flame retardant performance V0 and did not burn through during the burning process, compared with Comparative Example 1, it can be seen that the back temperature and char layer strength were reduced. This is because the molecular weight of the PPE resin added in Comparative Example 6 is lower than 35,000, which is relatively low and unfavorable for char formation during the burning process, thus increasing the back temperature and decreasing the char layer strength.

[0077] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0078] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A halogen-free, flame-retardant, and ablation-resistant polypropylene composite material, characterized in that, The polypropylene composite material comprises, by mass percentage: 40-60% flame-retardant modified masterbatch and 40-60% long glass fiber reinforced polypropylene masterbatch. The raw materials for preparing the flame-retardant modified masterbatch include, by weight: 24-44 parts of polypropylene resin, 5-15 parts of PPE resin, 2-5 parts of compatibilizer, 20-40 parts of piperazine, 10-20 parts of ammonium phosphate, 4-8 parts of surface-modified ultrafine aluminum hydroxide, and 0.3-1.5 parts of processing aid. The long glass fiber reinforced polypropylene masterbatch contains 40-60 wt% long glass fiber. The preparation steps of the surface-modified ultrafine aluminum hydroxide are as follows: the coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide powder are placed in a high-speed mixer, the temperature is set to 100℃, and the mixture is mixed at high speed for 20 minutes to obtain surface-coated modified ultrafine aluminum hydroxide powder; the mass ratio of the coupling agent, melamine, crosslinking agent and ultrafine aluminum hydroxide is (2~5):(3~10):(0.1~0.5):(84.5~94.9).

2. The halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is one or more of the following: homopolymer polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, and propylene-1-butene random block copolymer.

3. The halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 2, characterized in that, The number-average molecular weight distribution of the PPE resin is above 35,000.

4. The halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 1, characterized in that, The compatibilizer is at least one of PP, POE, SEBS, and SEPS grafted maleic anhydride.

5. The halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 1, characterized in that, The piperazine is piperazine pyrophosphate; the ammonium phosphate is melamine polyphosphate.

6. The halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 1, characterized in that, The ultrafine aluminum hydroxide has a specific surface area of ​​3~6 m². 2 / g, wherein the coupling agent is at least one of titanate ester and silane coupling agent; the crosslinking agent is at least one of dicumyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide; and the processing aid is at least one of antioxidant, lubricant and colorant.

7. A method for preparing a halogen-free flame-retardant and ablation-resistant polypropylene composite material, characterized in that, The preparation method includes the following steps: S1. Polypropylene resin, PPE resin, compatibilizer, piperazine, ammonium phosphate, surface-modified ultrafine aluminum hydroxide, and processing aids are mixed evenly in proportion, and melt-blended, granulated, and dried using a twin-screw extruder to obtain flame-retardant modified masterbatch. S2. The flame-retardant modified masterbatch and the long glass fiber reinforced polypropylene masterbatch are mixed evenly to obtain the halogen-free flame-retardant and ablation-resistant polypropylene composite material.

8. The method for preparing a halogen-free flame-retardant and ablation-resistant polypropylene composite material according to claim 7, characterized in that, The screw temperatures of each section of the twin-screw extruder described in step S1, from the feed port to the die head, are as follows: Zone 1 150-160℃, Zone 2 240-260℃, Zone 3 240-260℃, Zone 4 240-260℃, Zone 5 240-260℃, Zone 6 240-260℃, Zone 7 230-250℃, Zone 8 230-250℃, Zone 9 230-250℃, Zone 10 240-260℃; the feed speed is 250-350 rpm; the die head temperature is 230-250℃; the main extruder speed is 300-500 rpm / min; and the vacuum degree is below -0.1 MPa.

9. The application of the halogen-free flame-retardant and ablation-resistant polypropylene composite material as described in any one of claims 1-6 as a raw material in automotive power battery pack shells and electrical control box products.

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