Creep-resistant polypropylene composite material, preparation method and application

Abstract

The invention provides a creep-resistant polypropylene composite material, a preparation method and application, the creep-resistant polypropylene composite material comprises 60-80 parts of composite polypropylene resin, 10-30 parts of glass fiber, 1-5 parts of an MOF filler, 2-5 parts of a compatilizer, 0.1-1 part of an antioxidant and 0.1-0.5 part of a nucleating agent, and the MOF filler is a silane coupling agent modified MOF filler. MOF with good thermal conductivity and thermal stability is introduced into a glass fiber reinforced polypropylene system and is subjected to silane modification, so that the MOF is uniformly distributed in polypropylene and acts together with glass fibers to form more heat conduction channels and effectively transfer loads; meanwhile, due to interaction of special metal clusters and organic ligands of the MOF, stress mismatching between the polypropylene and the glass fibers can be balanced through microstructure changes, so that the creep resistance of the material is improved; in addition, the MOF filler has a large specific surface area and a porous structure, so that the lightweight characteristic of the material is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a creep-resistant polypropylene composite material, a preparation method and application thereof. Background Art

[0002] In recent years, polymer-based composite materials (such as glass fiber reinforced polypropylene, carbon fiber reinforced plastics, etc.) have gradually become a research hotspot in the field of thermal management due to their low density, strong mechanical properties and good processing performance. In particular, glass fiber reinforced polypropylene (GF-PP), as a plastic material with good strength, rigidity and chemical stability, has a very broad application prospect.

[0003] Polypropylene (PP) itself has excellent chemical corrosion resistance, good processability and low density, but its thermal stability and creep resistance are poor, which limits its application in efficient thermal management systems. Glass fiber, due to its high heat resistance, can significantly increase the heat deformation temperature of the system, thus giving polypropylene good heat resistance, making it more stable under mechanical loads and high temperature environments.

[0004] However, the toughness of the system is significantly reduced after adding glass fiber. This is because in glass fiber reinforced polypropylene, the glass fiber mainly bears most of the tensile stress of the material, and the polypropylene bears relatively less tension. When the tension increases to the critical point where the glass fiber breaks or is pulled out, the glass fiber breaks or is pulled out instantly, and the polypropylene breaks before it can transfer the tension. At the same time, if only relying on glass fiber to improve the creep resistance and thermal stability of polypropylene materials will lead to negative effects. As the glass fiber content increases, the impact performance of the material slows down and even decreases significantly when the glass fiber content exceeds 30%. Therefore, while further improving the creep resistance and thermal stability of polypropylene materials, how to take into account the mechanical properties of the material has become an urgent problem to be solved. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a creep-resistant polypropylene composite material, a preparation method and an application thereof, so as to solve the problem that the glass fiber reinforced polypropylene material in the prior art cannot take into account both creep resistance and mechanical properties.

[0006] In order to achieve the above-mentioned object and other related objects, the present invention provides the following technical solutions: The first aspect of the present invention provides a creep-resistant polypropylene composite material, which comprises the following components in parts by weight: 60 to 80 parts of composite polypropylene resin, 10 to 30 parts of glass fiber, 1 to 5 parts of metal organic framework (MOF) filler, 2 to 5 parts of compatibilizer, 0.1 to 1 part of antioxidant, and 0.1 to 0.5 part of nucleating agent.

[0007] MOF fillers have good thermal conductivity, especially when working with glass fibers, they can form more heat conduction channels; and MOF fillers have high thermal stability, which can effectively improve the thermal stability of composite materials and prevent thermal degradation of polypropylene in high temperature environments. Therefore, the introduction of MOF fillers can improve the creep resistance of composite materials, enabling them to better maintain their shape and performance at high temperatures. At the same time, the interaction between the metal clusters and organic ligands contained in MOF will cause the MOF to undergo microscopic structural changes when subjected to external forces, absorb part of the energy, balance the stress mismatch between polypropylene and glass fibers, and improve the mechanical properties of the material. In addition, MOF fillers can provide a certain porous structure to improve the lightweight characteristics of the material.

[0008] Furthermore, the MOF filler includes at least one of ZIF-8, UiO-66, and MIL-101.

[0009] Furthermore, the glass fiber is chopped glass fiber, and the diameter of the glass fiber is 10-15 microns and the length is 4-5 millimeters.

[0010] In order to improve the toughness of the system, the glass fiber is a modified glass fiber, specifically a silica gel-coated glass fiber; the MOF filler is a modified MOF filler, specifically a silane coupling agent-modified MOF filler.

[0011] Furthermore, the silane coupling agent modified MOF filler is prepared by the following method: dissolving the silane coupling agent in water, soaking the MOF powder in the coupling agent solution, taking it out after a period of reaction, and heat-treating the dried MOF powder to obtain the silane coupling agent modified MOF filler.

[0012] Furthermore, the silane coupling agent includes at least one of 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane or 3-chloropropyltriethoxysilane; The concentration of the silane coupling agent in the coupling agent solution is 1-2% (v / v); A small amount of acidic catalyst may be added to the coupling agent solution; The reaction temperature is 50-80°C and the reaction time is 1-2h; The drying temperature is 60-100°C and the drying time is 30-60min; The heat treatment temperature is 120-150° C., and the heat treatment time is 1-2 hours. The heat treatment helps the silane groups to fully cross-link with the MOF surface, thereby improving the bonding strength between the silane groups and the MOF surface and the polypropylene and the glass fiber.

[0013] The surface modification of MOF introduces silane groups, which enable it to interact well with the polypropylene matrix and the glass fiber surface, enhancing the interfacial bonding force. Good interfacial bonding force can effectively transfer loads, reduce the shedding of glass fibers and the cracking of the polypropylene matrix, thereby improving the toughness of the composite material. The modified MOF can be evenly dispersed in the polypropylene matrix, playing a role similar to that of microfillers, and can hinder the expansion of cracks when tensile fracture occurs.

[0014] Furthermore, the silica gel coated glass fiber is obtained by the following preparation method: fully dissolving silica gel in an organic solvent to obtain a silica gel solution, soaking the cleaned glass fiber in the silica gel solution, taking it out after soaking for a period of time, and obtaining the silica gel coated glass fiber after drying.

[0015] Furthermore, the silica gel includes polydimethylsiloxane; The organic solvent includes at least one of cyclohexane, ethanol, isopropanol, carbon tetrachloride and toluene; An appropriate amount of platinum catalyst or nickel sulfate may be added to the silica gel solution to control the curing time and temperature of the silica gel; The concentration of silica gel in the silica gel solution is 3-10% (v / v); Soaking time is 10~15min; The drying temperature is 100~120℃ and the drying time is 1~2h.

[0016] A flexible and stable film layer is formed on the surface of the glass fiber by coating with silicone, which can act as an intermediary layer to directly reduce the thermal expansion mismatch and stress distribution imbalance between the glass fiber and polypropylene, thereby reducing the brittle fracture or pull-out of the glass fiber and improving the toughness of the material; at the same time, it can also enhance the bonding strength between the glass fiber and components such as polypropylene and MOF, and improve the mechanical properties and thermal stability of the material.

[0017] Furthermore, the composite polypropylene resin includes homopolymer polypropylene and copolymer polypropylene in a mass ratio of 1: (0.2-0.5). Although homopolymer polypropylene has high rigidity, its creep resistance is not ideal, while copolymer polypropylene has better high temperature creep resistance. Therefore, by reasonably compounding the two, the composite material has good rigidity-toughness balance and outstanding high temperature creep resistance.

[0018] Furthermore, the compatibilizer includes maleic anhydride grafted polypropylene.

[0019] Furthermore, the antioxidant includes at least two of phenolic antioxidants, amine antioxidants, and phosphite antioxidants.

[0020] Furthermore, the nucleating agent includes at least one of talc, silicon dioxide and calcium stearate. The addition of the nucleating agent improves the transparency, rigidity and thermal deformation performance of the material.

[0021] A second aspect of the present invention provides a method for preparing a creep-resistant polypropylene composite material, comprising the following steps: S1. Weigh each raw material according to weight ratio; S2, putting composite polypropylene resin, MOF filler, compatibilizer, antioxidant and nucleating agent into a mixer, mixing to obtain a premix; S3, adding the premix to the main feed of the twin-screw extruder, adding the glass fiber to the side feed, and melt-extrude to obtain a molten material; S4, drawing, cooling and pelletizing the molten material to obtain the creep-resistant polypropylene composite material.

[0022] Premixing the materials other than glass fiber first can ensure the uniform dispersion of MOF filler in the polypropylene matrix. During the melt mixing process, adding glass fiber through side feeding can reduce the breakage of glass fiber, better ensure the uniform dispersion and integrity of glass fiber, and ensure its close bonding with the polypropylene matrix.

[0023] Furthermore, in step S2, the mixing time is 8 to 15 minutes.

[0024] Furthermore, in step S3, the temperature of each zone of the screw is 190°C to 230°C, and the screw speed is 250 to 600 rpm.

[0025] A third aspect of the present invention provides an application of a creep-resistant polypropylene composite material, which is used in a thermal management system for new energy vehicles.

[0026] As described above, the creep-resistant polypropylene composite material, preparation method and application of the present invention have the following beneficial effects: 1. The present invention adds a small amount of MOF to the glass fiber reinforced polypropylene system. MOF has good thermal conductivity, especially when it works together with glass fiber, it can form more heat conduction channels, improve the thermal conductivity of the material, and prevent heat accumulation; and MOF also has high thermal stability, effectively improves the thermal stability of the system, and prevents polypropylene from thermal degradation in a high temperature environment. Therefore, the introduction of MOF fillers can improve the creep resistance of the composite material, so that it can better maintain its shape and performance at high temperatures; at the same time, the interaction between the metal clusters and organic ligands contained in MOF will cause the MOF to undergo microscopic structural changes when subjected to external forces, absorb part of the energy, balance the stress mismatch between polypropylene and glass fiber, and improve the mechanical properties of the material. In addition, MOF fillers can provide a certain porous structure to improve the lightweight characteristics of the material.

[0027] 2. The present invention introduces silane groups on the surface of MOF by modifying it, so that it can interact well with the polypropylene matrix and the glass fiber surface, thereby enhancing the interfacial bonding force. The good interfacial bonding force can effectively transfer the load, reduce the shedding of the glass fiber and the cracking of the polypropylene matrix, and improve the comprehensive performance of the material; and the modified MOF can be evenly dispersed in the polypropylene matrix, playing a role similar to that of a microfiller. When tensile fracture occurs, it can reduce the pull-out of the glass fiber and hinder the expansion of the crack.

[0028] 3. The present invention forms a flexible and stable silicone film layer on the surface of the modified glass fiber, which can serve as an intermediate layer to directly reduce the thermal expansion mismatch and stress distribution imbalance between the glass fiber and polypropylene, thereby reducing the brittle fracture or pull-out of the glass fiber and improving the toughness of the material; at the same time, it can also enhance the bonding force between the glass fiber and components such as polypropylene and MOF, and improve the mechanical properties and thermal stability of the material. DETAILED DESCRIPTION

[0029] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0030] Example 1 This embodiment provides a creep-resistant polypropylene composite material, and the raw material formula is shown in Table 1.

[0031] Table 1, raw material formula of embodiment 1

[0032] The preparation method of the creep-resistant polypropylene composite material comprises the following steps: S1. Weigh the raw materials in Table 1 according to the weight ratio; S2, putting the first component polypropylene, the second component polypropylene, MOF filler, compatibilizer, antioxidant and nucleating agent into a mixer and mixing for 10 minutes to obtain a premix; S3, adding the premix to the main feed of the twin-screw extruder, adding the glass fiber to the side feed, and melt extruding, the temperature of each zone of the screw is 190°C~230°C, the screw speed is 350 rpm, and a molten material is obtained; S4. At a water temperature of 30-50° C., the molten material is drawn into strips, cooled, and pelletized to obtain the creep-resistant polypropylene composite material.

[0033] Example 2 This embodiment provides a creep-resistant polypropylene composite material. Compared with Embodiment 1, the only difference is that the raw material formula of this embodiment is shown in Table 2.

[0034] Table 2, raw material formula of Example 2

[0035] The above-mentioned silane coupling agent modified UiO-66 is obtained by the following preparation method: 3-aminopropyltriethoxysilane is dissolved in water to prepare a coupling agent solution with a concentration of 1%, and two drops of hydrochloric acid are added, and UiO-66 powder is immersed in the coupling agent solution, reacted at 50°C for 1 hour, and then vacuum dried at 80°C. The dried UiO-66 powder is heat-treated at 135°C for 1.5 hours to obtain the silane coupling agent modified UiO-66.

[0036] The above-mentioned silica gel-coated chopped glass fibers are obtained by the following preparation method: polydimethylsiloxane is fully dissolved in cyclohexane to prepare a silica gel solution with a concentration of 5%, the cleaned chopped glass fibers are immersed in the silica gel solution, taken out after immersion for 10 minutes, and dried in an oven at 100°C to obtain the silica gel-coated chopped glass fibers.

[0037] Example 3 This embodiment provides a creep-resistant polypropylene composite material. Compared with Embodiment 2, the only difference is that the raw material formula of this embodiment is shown in Table 3.

[0038] Table 3, raw material formula of embodiment 3

[0039] Example 4 This embodiment provides a creep-resistant polypropylene composite material. Compared with Embodiment 2, the only difference is that the raw material formula of this embodiment is shown in Table 4.

[0040] Table 4, raw material formula of Example 4

[0041] Example 5 This embodiment provides a creep-resistant polypropylene composite material. Compared with Embodiment 2, the only difference is that the raw material formula of this embodiment is shown in Table 5.

[0042] Table 5, raw material formula of Example 5

[0043] The silane coupling agent modified MIL-101 is obtained by the following preparation method: 3-(2,3-epoxypropoxy)propyltriethoxysilane is dissolved in water to prepare a coupling agent solution with a concentration of 1%, and two drops of acetic acid are added, and MIL-101 powder is immersed in the coupling agent solution, reacted at 50°C for 1 hour, and then vacuum dried at 80°C. The dried MIL-101 powder is heat-treated at 135°C for 1.5 hours to obtain the silane coupling agent modified MIL-101.

[0044] Comparative Example 1 Comparative Example 1 provides a glass fiber reinforced polypropylene composite material, and the raw material formula is shown in Table 6.

[0045] Table 6, raw material formula of comparative example 1

[0046] The preparation method of the creep-resistant polypropylene composite material comprises the following steps: S1. Weigh the raw materials in Table 6 according to the weight ratio; S2, putting the first component polypropylene, the second component polypropylene, the compatibilizer, the antioxidant and the nucleating agent into a mixer, and mixing for 10 minutes to obtain a premix; S3, adding the premix to the main feed of the twin-screw extruder, adding the glass fiber to the side feed, and melt extruding, the temperature of each zone of the screw is 190°C~230°C, the screw speed is 350 rpm, and a molten material is obtained; S4. At a water temperature of 30-50° C., the molten material is drawn into strips, cooled, and pelletized to obtain the creep-resistant polypropylene composite material.

[0047] The creep-resistant polypropylene composite materials of Examples 1 to 5 and the glass fiber reinforced polypropylene composite material of Comparative Example 1 were sampled and then subjected to comparative experiments. The test items and results are shown in Table 8 below.

[0048] Table 8 Performance test results of Examples 1 to 5 and Comparative Example 1

[0049] According to the comparison between Example 1 and Comparative Example 1, Example 1 significantly increases the heat deformation temperature of the material and reduces the creep rate by adding a small amount of UIO-66 to the glass fiber reinforced polypropylene system. Therefore, the addition of MOF can significantly improve the creep resistance and thermal stability of the material, and also improve other mechanical properties to a certain extent.

[0050] According to the comparison between Example 1 and Example 2, Example 2 improves the compatibility of UIO-66 and glass fiber with the polypropylene matrix by surface modification. The two can be more evenly dispersed in the polypropylene matrix, reducing the pull-out of the glass fiber, and balancing the thermal expansion coefficient and stress transfer between different components, so that the creep resistance, thermal stability and mechanical properties of the material are greatly improved.

[0051] According to the comparison of Examples 2 to 4, the addition amount of MOF filler will affect the overall performance of the material. When the MOF filler is too little, not enough heat conduction channels can be formed, so that the thermal stability and creep resistance of the material are not significantly improved. When the MOF filler is too much, it is easy to cause uneven distribution of MOF, resulting in accumulation in the system, and the mechanical properties will decrease instead of increase, and the improvement of thermal conductivity is not obvious. Therefore, it is necessary to control the appropriate amount of MOF addition.

[0052] In summary, the present invention introduces MOF with good thermal conductivity and thermal stability into the glass fiber reinforced polypropylene system, and silane modifies it so that it is evenly distributed in the polypropylene, and works together with the glass fiber to form more heat conduction channels and effectively transfer the load; at the same time, due to the interaction between the special metal clusters and organic ligands of MOF, the stress mismatch between polypropylene and glass fiber can be balanced through microstructural changes, thereby improving the creep resistance of the material; in addition, the large specific surface area and porous structure of MOF filler effectively improve the lightweight characteristics of the material. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A creep-resistant polypropylene composite material, characterized in that: The composition comprises the following components by weight: 60-80 parts of composite polypropylene resin, 10-30 parts of glass fiber, 1-5 parts of MOF filler, 2-5 parts of compatibilizer, 0.1-1 parts of antioxidant and 0.1-0.5 parts of nucleating agent.

2. The creep-resistant polypropylene composite material according to claim 1, characterized in that: The MOF filler includes at least one of ZIF-8, UiO-66, and MIL-101.

3. The creep-resistant polypropylene composite material according to claim 1 or 2, characterized in that: The MOF filler is a MOF filler modified by a silane coupling agent.

4. The creep-resistant polypropylene composite material according to claim 3, characterized in that: The silane coupling agent modified MOF filler is prepared by the following method: dissolving the silane coupling agent in water, soaking the MOF powder in the coupling agent solution, taking it out after a period of reaction, and heat-treating the dried MOF powder to obtain the silane coupling agent modified MOF filler.

5. The creep-resistant polypropylene composite material according to claim 4, characterized in that: The silane coupling agent includes at least one of 3-(2,3-epoxypropyloxy)propyltriethoxysilane, 3-(2,3-epoxypropyloxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-chloropropyltriethoxysilane.

6. The creep-resistant polypropylene composite material according to claim 4, characterized in that: The heat treatment temperature is 120-150° C., and the heat treatment time is 1-2 hours.

7. The creep-resistant polypropylene composite material according to claim 1, characterized in that: The glass fiber is chopped glass fiber, and the diameter of the glass fiber is 10-15 microns and the length is 4-5 millimeters.

8. The creep-resistant polypropylene composite material according to claim 1 or 7, characterized in that: The glass fiber is glass fiber coated with silica gel, and the silica gel includes polydimethylsiloxane.

9. A method for preparing the creep-resistant polypropylene composite material according to any one of claims 1 to 8, characterized in that: The steps include: S1. Weigh each raw material according to weight ratio; S2, putting composite polypropylene resin, MOF filler, compatibilizer, antioxidant and nucleating agent into a mixer, mixing to obtain a premix; S3, adding the premix to the main feed of the twin-screw extruder, adding the glass fiber to the side feed, and melt-extrude to obtain a molten material; S4, drawing, cooling and pelletizing the molten material to obtain the creep-resistant polypropylene composite material.

10. Use of the creep-resistant polypropylene composite material according to any one of claims 1 to 8, wherein the creep-resistant polypropylene composite material is used in a thermal management system of a new energy vehicle.

Images