Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention belongs to the field of plastic materials, and particularly discloses a polypropylene composite material and a preparation method and application thereof. The polypropylene composite material is prepared from the following components in parts by weight: 38.5 to 95.5 parts of polypropylene resin, 4 to 16 parts of maleic anhydride grafted polypropylene, 4 to 16 parts of maleic anhydride grafted linear low-density polyethylene and 14 to 42 parts of glass fiber. The polypropylene resin comprises a first type of polypropylene resin and a second type of polypropylene resin, the branching degree of the first type of polypropylene resin is less than 5 / 1000C, and the branching degree of the second type of polypropylene resin is more than or equal to 5 / 1000C. In the polypropylene composite material disclosed by the invention, the maleic anhydride grafted polypropylene MAH-g-PP and the maleic anhydride grafted linear low density polyethylene MAH-g-LLDPE synergistically improve the adhesive property and the creep resistance of the composite material; meanwhile, two types of polypropylene resin with different branching degrees are adopted, so that the creep property and the adhesive property of the composite material can be further improved, and the composite material is more suitable for automobile parts which have higher requirements on interlayer adhesion and need to resist creep.

Description

Technical Field

[0001] This invention belongs to the field of plastics, specifically relating to a polypropylene composite material, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP) materials are widely used in various fields such as automobiles and home appliances due to their excellent mechanical properties, environmental friendliness, recyclability, and high cost-effectiveness. However, PP materials have a significant disadvantage in creep resistance compared to engineering plastics such as nylon, making it difficult to meet the high creep resistance requirements of components around batteries in new energy vehicles. Blending PP and nylon in the manufacture of automotive parts is one effective way to improve their creep resistance. Multi-layer co-extrusion processes are commonly used to produce tubing with a multi-layer structure consisting of a PP inner layer, an intermediate adhesive layer (PVC, EPDM, or PA), and an outer nylon layer (PA6 or PA66) for automotive cooling systems. Because of the significant polarity difference between the PP inner layer and the nylon outer layer, the adhesion performance of the intermediate adhesive layer is crucial; however, current adhesive layers cannot simultaneously guarantee adhesion to both the PP inner layer and the nylon outer layer.

[0003] Therefore, it is still necessary to continue developing a type of intermediate layer material that has good adhesion to both the nylon outer layer and the polypropylene inner layer, as well as high creep resistance, to meet the requirements of pipeline materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the prior art. This invention will provide a polypropylene composite material, its preparation method, and its application.

[0005] To achieve the above objectives, the following technical solutions are specifically included: In a first aspect, the present invention provides a polypropylene composite material comprising the following components in parts by weight: 38.5-95.5 parts of polypropylene resin (PP), 4-16 parts of maleic anhydride-grafted polypropylene (MAH-g-PP), 4-16 parts of maleic anhydride-grafted linear low-density polyethylene (MAH-g-LLDPE), and 14-42 parts of glass fiber; wherein the polypropylene resin comprises a first type of polypropylene resin and a second type of polypropylene resin, wherein the branching degree of the first type of polypropylene is <5 / 1000C, and the branching degree of the second type of polypropylene resin is ≥5 / 1000C.

[0006] In the polypropylene composite material of the present invention, on the one hand, MAH-g-PP and MAH-g-LLDPE synergistically improve the bonding performance and creep resistance of the composite material; on the other hand, the use of two types of polypropylene resins with different degrees of branching in the polypropylene matrix resin of the present invention can further improve the creep resistance and bonding performance of the composite material.

[0007] In the polypropylene composite material of the present invention, on the one hand, both MAH-g-PP and MAH-g-LLDPE contain maleic anhydride groups, which make it easier for them to synergistically improve the complexity and tightness of the overall physical winding structure of the material with the polypropylene resin matrix, thereby improving the material's creep resistance. Simultaneously, compared to conventional nonlinear polyethylene or high-density polyethylene grafted with maleic anhydride, MAH-g-LLDPE, with its linear low-density polyethylene matrix, has a lower density and a linear structure, resulting in better compatibility with polypropylene resin or MAH-g-PP. This allows it to more easily penetrate or migrate to the molecular chains of polypropylene resin or MAH-g-PP, leading to a greater improvement in the creep resistance and adhesion properties of the composite material. On the other hand, both MAH-g-PP and MAH-g-LLDPE contain polar maleic anhydride groups, whose polarity is closer to that of nylon, which can improve the compatibility of the composite material with nylon, thereby increasing the adhesion strength of the composite material to the nylon outer layer. Therefore, the polypropylene composite material of the present invention can possess both high creep resistance and high adhesion properties.

[0008] In the composite material of this invention, a first type of polypropylene resin with low branching degree is used as the main matrix skeleton, and a second type of polypropylene with high branching degree is added to increase the branching degree of the polypropylene resin in the overall composite material. This increases the complexity and tightness of the molecular chain entanglement between the various resins, thereby improving the creep performance of the composite material. At the same time, the inventors of this invention have discovered that the combined use of two types of polypropylene resins with different branching degrees not only improves the creep resistance of the composite material, but also improves the adhesive performance of the composite material to a certain extent.

[0009] Preferably, the polypropylene composite material comprises the following components in parts by weight: 39-95 parts polypropylene resin, 5-15 parts maleic anhydride-grafted polypropylene, 5-15 parts maleic anhydride-grafted linear low-density polyethylene, 15-40 parts glass fiber, and 0-1.5 parts additives.

[0010] Preferably, in the polypropylene composite material, the mass percentage of polypropylene resin (PP) is not less than 40%, more preferably not less than 45%, and even more preferably not less than 50%.

[0011] Preferably, the melt flow rate of the first type of polypropylene resin, according to ISO 1133-2022, at 230°C and a load of 2.16 kg, is 0.5-5 g / 10 min, more preferably 1-3 g / 10 min. More specifically, the melt flow rate of the first type of polypropylene resin can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 g / 10 min, etc., and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range. The preferred first type of polypropylene has low fluidity, which meets the requirements for material extrusion molding.

[0012] Preferably, the branching degree of the first type of polypropylene resin is 0 / 1000C-4 / 1000C, more preferably 0. More specifically, the branching degree of the first type of polypropylene resin is 0 / 1000C, 1 / 1000C, 2 / 1000C, 3 / 1000C, 4 / 1000C, etc., as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0013] Preferably, the melt flow rate of the second type of polypropylene, according to ISO 1133-2022, at 230°C and a load of 2.16 kg, is 0.5-5 g / 10 min, more preferably 1-3 g / 10 min. More specifically, the melt flow rate of the first type of polypropylene resin can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 g / 10 min, etc., and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range. The preferred second type of polypropylene has low fluidity, which meets the requirements of material extrusion molding.

[0014] Preferably, the branching degree of the second type of polypropylene resin is ≥8 / 1000C, more preferably 8 / 1000C-15 / 1000C, and even more preferably 10 / 1000C-13 / 1000C. More specifically, the branching degree of the second type of polypropylene resin is 8 / 1000C, 9 / 1000C, 10 / 1000C, 11 / 1000C, 12 / 1000C, 12 / 1000C, 13 / 1000C, 14 / 1000C, 15 / 1000C, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0015] The degree of branching of both type I and type II polypropylene resins was tested using nuclear magnetic resonance (NMR) analysis.

[0016] Preferably, the polypropylene composite material comprises 20-30 parts by weight of the first type of polypropylene resin and 20-30 parts by weight of the second type of polypropylene resin.

[0017] Preferably, in the polypropylene composite material, the mass percentage content of the first type of polypropylene resin is 19%-31%, more specifically, it can be 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0018] Preferably, in the polypropylene composite material, the mass percentage of the second type of polypropylene resin is 19%-31%, more specifically, it can be 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0019] Preferably, the mass ratio of the first type of polypropylene resin to the second type of polypropylene resin is (0.6-1.5):1. More specifically, it can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc., as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0020] Preferably, in the polypropylene composite material, the total mass of the polypropylene resin is M1, and the total mass of the maleic anhydride-grafted polypropylene and maleic anhydride-grafted linear low-density polyethylene is M2, with the ratio of M1 to M2 being (40-94):(10-30). More preferably, the ratio of M1 to M2 is (45-55):(15-25). More specifically, it can be 40:10, 40:15, 40:20, 40:25, 40:30, 50:10, 50:15, 50:20, 50:25, 50:30, or 60:10. The specific point values ​​included in the range are as follows: 60:15, 60:20, 60:25, 60:30, 70:10, 70:15, 70:20, 70:25, 70:30, 80:10, 80:15, 80:20, 80:25, 80:30, 90:10, 90:15, 90:20, 90:25, 90:30, 94:10, 40:15, 94:20, 94:25, 94:30, etc., as well as the specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0021] Preferably, the grafting rate of the maleic anhydride-grafted polypropylene is 0.9%-2%, and more specifically, it can be 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0022] Preferably, the melt flow rate of the maleic anhydride-grafted polypropylene at 230°C and 2.16 kg load, according to ISO 1133-2022, is 1-5 g / 10 min. More specifically, the melt flow rate of the maleic anhydride-grafted polypropylene can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 g / 10 min, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0023] Preferably, the melt flow rate of the maleic anhydride-grafted linear low-density polyethylene at 190°C and 2.16 kg load, according to ISO 1133-2022, is 1-5 g / 10 min. More specifically, the melt flow rate of the maleic anhydride-grafted linear low-density polyethylene can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 g / 10 min, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0024] Preferably, the grafting rate of the maleic anhydride-grafted linear low-density polyethylene is 0.6%-2%, and more specifically, it can be 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0025] Preferably, based on the total mass of maleic anhydride-grafted polypropylene and maleic anhydride-grafted linear low-density polyethylene, the mass percentage of maleic anhydride-grafted linear low-density polyethylene is 25%-75%, more specifically, it can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] Preferably, the average diameter of the glass fiber is 2-10 μm, more specifically, it can be 2, 3, 4, 5, 6, 7, 8, 9, 10 μm, etc., and specific values ​​between the above values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range. The average length of the glass fiber is 0.5-5 mm, more specifically, it can be 0.5, 1, 2, 3, 4, 5 mm, etc., and specific values ​​between the above values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range. The average diameter and average length of the glass fiber are obtained by testing as follows: the glass fiber sample is observed using a scanning electron microscope, the dimensions of 300 glass fibers are measured, and the average value is taken.

[0027] More preferably, the glass fiber can be chopped glass fiber.

[0028] Preferably, in the polypropylene composite material, the mass percentage of glass fiber is 23%-30%, more specifically, it can be 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, the polypropylene composite material further includes 0.01-2 parts by weight of an additive, specifically, which can be 0.01 parts, 0.1 parts, 0.25 parts, 0.5 parts, 0.75 parts, 1 part, 1.25 parts, 1.5 parts, 1.75 parts, 2 parts, etc., as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0030] More preferably, the adjuvant includes at least one of an antioxidant or a light stabilizer.

[0031] More preferably, the antioxidant is present in an amount of 0.1-1 parts by weight, and the light stabilizer is present in an amount of 0.1-1 parts by weight.

[0032] More preferably, the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants, and more specifically, it may include one or a mixture of two or more of antioxidants 1010, 1076, 3114, 168, PEP-36, and 412S.

[0033] More preferably, the light stabilizer includes hindered amine light stabilizers, and more specifically may include one or a mixture of two or more of the light stabilizers UV-3808, LA-402XP, and LA-402AF.

[0034] Secondly, the present invention provides a method for preparing the polypropylene composite material, comprising the following steps: mixing, melt-blending, extruding and granulating the raw materials in sequence to obtain the polypropylene composite material.

[0035] Preferably, the temperature of the melt mixing is 200~220℃.

[0036] Preferably, the rotation speed of the melt mixing is 350~450 rpm.

[0037] Thirdly, the present invention provides a multilayer composite pipe, comprising, in sequence, a first layer containing polypropylene, a second layer containing the aforementioned polypropylene composite material, and a third layer containing nylon resin.

[0038] Preferably, the multilayer composite pipe is produced by multilayer co-extrusion.

[0039] The polypropylene composite material of this invention possesses high adhesion and creep resistance to the polypropylene-containing inner layer and the nylon resin outer layer, enabling the multilayer composite pipe to exhibit high structural stability and creep resistance, significantly improving its service life. The multilayer composite pipe can be applied to the manufacture of peripheral components for new energy vehicle batteries; more specifically, it can be used to manufacture automotive cooling pipes.

[0040] Compared with the prior art, the present invention has the following beneficial effects: In the polypropylene composite material of the present invention, MAH-g-PP and MAH-g-LLDPE synergistically improve the bonding performance and creep resistance of the composite material; at the same time, the use of two types of polypropylene resins with different degrees of branching can further improve the creep performance and bonding performance of the composite material, making it more suitable for automotive parts that have high requirements for interlayer bonding and creep resistance. Detailed Implementation

[0041] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the experimental methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available. Unless otherwise specified, the raw materials used in each embodiment and comparative example of this invention are the same in each parallel experiment.

[0042] Raw material information involved in the following examples and comparative examples: (1) Type I polypropylene: PP1-A: PP 3010, Formosa Plastics, melt flow rate approximately 1.3 g / 10 min, branching degree 0 / 1000°C; PP1-B: PP PPB-M02D (EPS30R Maoming), Maoming Petrochemical, melt flow rate approximately 1.6 g / 10 min, branching degree 0 / 1000C; PP1-C: PP K8003 (ZHEJIANG), Zhejiang Petrochemical, melt flow rate approximately 2 g / 10 min, branching degree 0 / 1000C; (2) Type II polypropylene: PP2-A: PP CIRCULEN 12X, ExxonMobil, melt flow rate 1.5 g / 10 min, degree of branching approximately 8 / 1000°C; PP2-B: PP CIRCULEN 15G, ExxonMobil, melt flow rate 1.5 g / 10 min, degree of branching approximately 10 / 1000C; PP2-C: PP CIRCULEN 17M, ExxonMobil, melt flow rate 1.5 g / 10 min, degree of branching approximately 13 / 1000C.

[0043] (3) MAH-g-PP: MAH-g-PP-1: SCONA TPPP 2003 FB, manufactured by BYK Chemicals, with a grafting rate of 0.9%; MAH-g-PP-2: SCONA TPPP 2003 GB, manufactured by BYK Chemicals, with a grafting rate of 1.2%; MAH-g-PP-3: SCONA TSPP 10213GB, manufactured by BYK Chemical, with a grafting rate of 2%.

[0044] (4) MAH-g-LLDPE: MAH-g-LLDPE-1: Bondyram TL4110, Shanghai Zhuangjing Chemical, grafting rate 1.0%; MAH-g-LLDPE-2: Bondyram TL4108N, Shanghai Zhuangjing Chemical, grafting rate 0.8%; MAH-g-LLDPE-3: Bondyram TL4112N, Shanghai Zhuangjing Chemical, grafting rate 1.2%.

[0045] (5) Maleic anhydride grafted high-density polyethylene (MAH-g-HDPE): EPA-830C, Haifei New Materials, grafting rate 0.8%.

[0046] (6) Maleic anhydride-grafted low-density polyethylene (MAH-g-LDPE): Bondyram TLF42, Shanghai Zhuangjing Chemical, grafting rate 0.6%.

[0047] The MAH grafting rate in MAH-g-PP, MAH-g-LLDPE, MAH-g-HDPE and MAH-g-LDPE involved in this invention was measured by titration. The melt flow rate of MAH-g-LLDPE, MAH-g-HDPE and MAH-g-LDPE was obtained by testing at 190°C and 2.16 kg load according to ISO 1133-2022 standard. The melt flow rate of MAH-g-PP was obtained by testing at 230°C and 2.16 kg load according to ISO 1133-2022 standard.

[0048] (7) Glass fiber: ECS07-03-508A, average diameter 7μm, average length 3mm, produced by Jushi Glass Fiber.

[0049] (8) Antioxidant 1010, antioxidant 168 and light stabilizer 3808PP5 are all commercially available products.

[0050] Examples 1-16 and Comparative Examples 1-7 A method for preparing a polypropylene composite material includes the following steps: According to the formula in Table 1-2, after the raw material components are mixed evenly, they are added to a twin-screw extruder for melt mixing. The melt mixing temperature is 210℃ and the screw speed is 400 rpm. After extrusion and granulation, polypropylene composite material is obtained.

[0051] A multilayer composite pipe is prepared by means of the following steps: using the polypropylene composite material of the example or comparative example as the middle layer of the multilayer composite pipe, and co-extruding multiple layers with the inner layer being polypropylene material and the outer layer being nylon (PA6 material) material to produce the multilayer composite pipe.

[0052] Performance testing: Pull-out force test: The multi-layer composite pipe is fixed on both sides of the outer and inner layers on a universal testing machine according to ISO527-2012 standard, and the pull-out force is tested to determine the pull-out force required after the inner or outer layer is separated (generally the outer nylon layer is separated). The length of the multi-layer composite pipe sample is 60cm.

[0053] High-temperature creep performance test: 1. Sample preparation: The polypropylene composite material prepared in the examples or comparative examples is injection molded into tensile specimens of 150×10×4.0mm size according to the ISO899-1-2017 standard.

[0054] 2. Place a tensile specimen with dimensions of 150×10×4.0mm in a creep testing machine for high-temperature creep testing until the specimen breaks. Record the time of specimen breakage. The creep test temperature is 120℃ and the creep stress is set to 14MPa.

[0055] The test results are shown in Tables 1 and 2.

[0056] Table 1 (parts by weight) Table 2 (parts by weight) As can be seen from Example 1 and Comparative Examples 1-3, compared with Example 1, Comparative Example 1 lacks MAH-g-PP and is replaced by an equal amount of MAH-g-LLDPE; Comparative Example 2 lacks MAH-g-LLDPE and is replaced by an equal amount of MAH-g-PP; Comparative Example 3 lacks both MAH-g-PP and MAH-g-LLDPE. MAH-g-LLDPE and MAH-g-PP can synergistically improve the bonding performance and creep resistance of the composite material. At the same time, combined with the analysis of Comparative Examples 4 and 7, it can be seen that compared with MAH-g-HDPE and MAH-g-LDPE, MAH-g-HDPE has high crystallinity and it is difficult to achieve molecular entanglement. MAH-LDPE has a non-linear structure and it is relatively difficult to achieve good molecular entanglement with polypropylene resins. However, the MAH-g-LLDPE used in this invention has low density and belongs to a linear structure, which is easy to migrate and entangle, and thus improves the bonding performance and creep resistance of the composite material more significantly.

[0057] As the grafting rate in MAH-g-PP gradually increases in Examples 1, 2, and 3, there are more grafts on MAH-g-PP, and the degree of entanglement between MAH-g-PP and other resin molecular chains increases, thus increasing creep resistance. Furthermore, the increased grafting rate leads to increased polarity, making the polarity of the composite material closer to that of nylon resin, thereby improving the adhesive properties of the composite material.

[0058] As the grafting rate in MAH-g-LLDPE gradually increases in Examples 4, 1, and 5, there are more grafts on MAH-g-LLDPE, which increases the degree of entanglement between the polarity of the composite material and the molecular chains of other resins, thus increasing the creep resistance. In addition, the increased grafting rate increases the polarity, making the polarity of the composite material closer to that of nylon resin, and improving the adhesive properties of the composite material.

[0059] With the same total weight proportions of MAH-g-LLDPE and MAH-g-PP, the creep resistance and adhesive properties of the composite material increased as the proportion of MAH-g-LLDPE gradually increased in Examples 7, 1, and 8. However, analysis of Comparative Examples 1-3 shows that using MAH-g-LLDPE or MAH-g-PP alone cannot significantly improve the creep resistance and adhesive properties of the composite material. This indicates that MAH-g-LLDPE and MAH-g-PP exhibit a synergistic effect in improving the creep resistance and adhesive properties of the composite.

[0060] Comparative analysis of Example 1 and Comparative Examples 5-6 shows that, with the same total weight of polypropylene matrix resin, Comparative Example 5 uses only the first type of polypropylene resin with a branching degree of 0, resulting in virtually unbranched matrix resin molecules. This leads to poor entanglement between the matrix resin molecules and MAH-g-LLDPE and MAH-g-PP, resulting in poor creep resistance of the composite material. Comparative Example 6 uses only the second type of polypropylene resin with a higher branching degree, which cannot effectively limit the slippage between the molecular structures of the composite material, resulting in still poor creep resistance. In the composite material of this invention, the first type of polypropylene resin with a low branching degree is used as the main matrix skeleton, supplemented by the second type of polypropylene with a high branching degree. This increases the branching degree of the polypropylene resin in the overall composite material, making the molecular chain entanglement between various resins more complex and compact, thereby improving the creep resistance of the composite material. At the same time, the inventors of this invention have found that the combined use of two types of polypropylene resins with different branching degrees not only improves the creep resistance of the composite material but also improves its adhesive properties to a certain extent.

[0061] Meanwhile, with the total weight of the two types of polypropylene resin remaining unchanged, as the proportion of the second type of polypropylene resin with a higher degree of branching decreases in Examples 1, 10 and 9, the creep resistance decreases slightly, while the adhesion remains basically unchanged. When the weight of the second type of polypropylene resin is within 20-30 parts, the composite material can maintain high creep resistance and good adhesion.

[0062] As the melt flow rate of the first type of polypropylene resin in Examples 1, 11 and 12 increases, the creep resistance and bonding properties of the composite material remain essentially unchanged.

[0063] As the branching degree of the second type of polypropylene resin increased in Examples 1, 13, and 14, the creep resistance of the composite material increased, while the adhesive properties remained essentially unchanged. It can be seen that in the above examples, when the branching degree of the second type of polypropylene resin is between 8 / 1000°C and 13 / 1000°C, the creep resistance of the composite material, measured by the high-temperature creep time, is greater than 60 hours; its adhesive properties, measured by the pull-out force, are greater than 800 N, thus achieving excellent adhesive and creep resistance properties.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polypropylene composite, characterized in that, The polypropylene composite material comprises the following components by weight: polypropylene resin 38.5-95.5 parts, maleic anhydride grafted polypropylene 4-16 parts, maleic anhydride grafted linear low density polyethylene 4-16 parts, and glass fiber 14-42 parts; the polypropylene resin comprises a first type of polypropylene resin and a second type of polypropylene resin, the first type of polypropylene resin has a branching degree < 5 / 1000C, and the second type of polypropylene resin has a branching degree ≥ 5 / 1000C.

2. The polypropylene composite of claim 1, wherein, The maleic anhydride grafted linear low density polyethylene has a grafting rate of 0.6%-2%.

3. The polypropylene composite of claim 1, wherein the polypropylene is a homopolymer of propylene. The maleic anhydride grafted polypropylene has a grafting rate of 0.9%-2%.

4. The polypropylene composite of claim 1, wherein, The maleic anhydride grafted linear low density polyethylene has a mass percentage of 25%-75% based on the total mass of the maleic anhydride grafted polypropylene and the maleic anhydride grafted linear low density polyethylene.

5. The polypropylene composite of claim 1, wherein the polypropylene is a homopolymer of propylene. The first type of polypropylene resin has a branching degree of 0 / 1000C-4 / 1000C.

6. The polypropylene composite of claim 1, wherein, The second type of polypropylene resin has a branching degree of 5 / 1000C-15 / 1000C.

7. The polypropylene composite of claim 1, wherein the polypropylene is a homopolymer of propylene. The mass ratio of the first type of polypropylene resin to the second type of polypropylene resin is (0.6-1.5):

1.

8. The polypropylene composite of claim 1, wherein, 0.01-2 parts by weight of an auxiliary agent comprising at least one of an antioxidant or a light stabilizer are further included.

9. A process for the production of a polypropylene composite material according to any one of claims 1 to 8, characterized in that The polypropylene composite material is obtained by sequentially mixing, melt-kneading, extruding, and granulating the raw materials.

10. A multilayer composite pipe, characterized by The polypropylene composite material comprises a first layer containing polypropylene, a second layer containing the polypropylene composite material according to any one of claims 1-8, and a third layer containing a nylon resin.

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