CN113957707B - Composite heat-conducting filler, preparation method thereof, heat-conducting plastic material and application - Google Patents
Composite heat-conducting filler, preparation method thereof, heat-conducting plastic material and application Download PDFInfo
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Abstract
The invention provides a composite heat-conducting filler, a preparation method thereof, a heat-conducting plastic material and application. The preparation method of the composite heat-conducting filler comprises the following steps: and (3) coating the organic silica gel on the surface of the raw material carbon fiber, drying, and sintering at 1500-2500 ℃ for 0.5-5 h to obtain the composite heat-conducting filler. The invention also provides the composite heat-conducting filler obtained by the method. The invention provides a heat-conducting plastic material, which comprises a polyolefin resin base material, a heat-conducting filler, a flame retardant and a coupling agent as raw materials, wherein the heat-conducting filler comprises the composite heat-conducting filler. The invention also provides a plastic pipe prepared from the heat-conducting plastic material. The composite heat-conducting filler provided by the invention can be used for preparing heat-conducting plastic materials, and can improve the heat-conducting property and mechanical strength of the heat-conducting plastic materials.
Description
Technical Field
The invention relates to the technical field of high polymer material modification and heat conduction materials, in particular to a composite heat conduction filler, a preparation method thereof, a heat conduction plastic material and application thereof.
Background
In winter, the northern residents generally use metal heat exchange pipes, the pipes are generally buried in concrete after being arranged and then are placed under the floor, so that the pipes are extremely difficult to repair and replace after being damaged after being used, and a lot of inconvenience is brought to the residents and maintenance staff. In addition, the floor heating pipelines are generally required to have durability and life of 40 years or more. Compared with metal pipes, the polymer plastic pipe has the advantages of low price, good chemical corrosion resistance, light dead weight, sanitation and safety, small water flow resistance, long service life, convenient installation and the like. The plastic pipeline industry in China is a product system represented by polyolefin plastic pipelines.
In recent years, with the continuous progress of polyolefin resin synthesis technology and composite material modification technology, various raw materials for polyolefin pipes have been continuously introduced, and the application field of polyolefin pipes has been further expanded. However, due to the nature of the polymer, compared with metal, the heat conductivity coefficient of the polymer is poorer, and only 0.1-0.3W/m.K, which limits the practical application of the polyolefin plastic pipeline in heat conduction to a certain extent. At present, the addition of high thermal conductivity fillers such as graphite, boron nitride, carbon fiber and the like to polymers is a development trend of polyolefin plastic engineering. Graphite and boron nitride are used as large-scale heat conducting fillers, and although the heat conductivity of plastics can be remarkably improved, the mechanical strength of the materials can be reduced. The nano-scale chopped carbon fiber has high thermal conductivity up to 1850W/m.K, high tensile strength and elastic modulus, and is excellent nano-scale heat conducting filler, and carbon fibers mutually contact in a polyolefin matrix to form a series heat conducting net chain inside the matrix. However, the mechanical properties of polyolefin pipe materials directly added with carbon fibers are greatly reduced because it is difficult to effectively bond the carbon fibers and the matrix. At the same time, this poor interface bonding also limits further improvement in the thermal conductivity of the plastic tubing.
In addition, the strength of the existing heat-conducting plastic pipeline at home is generally 15-20MPa, the toughness is poor, the cold and heat change resistance capability is poor, the service life is short, residents need to replace the heat-conducting plastic pipeline after using the heat-conducting plastic pipeline for years, time and labor are wasted, and the waste of resources and the increase of economic cost are greatly caused. By adding the chopped carbon fiber material into the polyolefin system for interfacial fiber reinforcement, when the interface is impacted, the carbon fiber can serve as two parts of a 'tie' connecting material for losing connection, and excellent mechanical properties can be obtained. However, carbon fibers, while possessing excellent strength and properties, are extremely dependent on the small size effects and quantum effects of the nanophase. Because the reinforcing phase is nano-scale, a large number of contact surfaces exist between the nano-phase and the polyolefin matrix, so that the interface-volume ratio of the carbon fiber-polyolefin plastic is higher, the free energy of the interface is obviously increased, and the surface interface effect is serious. This particular surface interface effect tends to affect the service, failure and fracture behavior of the thermally conductive plastic. In order to reduce the interfacial effect of the carbon fiber-polyolefin plastic, the carbon fiber may be subjected to a surface functionalization treatment. The existing method is that gas or liquid with oxidation is chemically reacted with short carbon fiber to make its surface have active reactive functional group or change the physical form of short carbon fiber, and the oxidation modification process is simple, but damages the mechanical property of short carbon fiber itself, and can reduce the whole toughness of heat-conducting plastic.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a composite heat-conducting filler, a preparation method thereof, a heat-conducting plastic material and application thereof. The composite heat conducting filler can improve the heat conductivity and mechanical property of plastic materials with polyolefin resin as a matrix. The heat-conducting plastic material prepared by the composite heat-conducting filler has higher mechanical toughness and heat conductivity, and the preparation method is simple and low in cost.
In order to achieve the above object, the present invention provides a method for preparing a composite heat conductive filler, comprising: and (3) coating the organic silica gel on the surface of the raw material carbon fiber, and drying and sintering at 1500-2500 ℃ for 0.5-5 h to obtain the composite heat-conducting filler.
In a specific embodiment of the invention, the composite heat-conducting filler obtained by the preparation method is a carbon fiber with silicon carbide grown on the surface. Specifically, in the preparation method, the organic silica gel can be used as a silicon source, the organic silica gel and the raw material carbon fiber are used as a carbon source together, the silicon carbide fiber is grown in situ on the surface of the raw material carbon fiber through sintering treatment (belonging to non-oxidation modification), and the silicon carbide fiber forms a coarse structure on the surface of the carbon fiber. The surface roughness structure is helpful for improving the interfacial binding force between the carbon fiber and the plastic matrix. Meanwhile, as the silicon carbide directly grows on the surface of the carbon fiber in situ, the silicon carbide and the carbon fiber are tightly connected, and the heat conduction capability of the composite heat conduction filler is improved.
In particular embodiments of the present invention, too low a sintering temperature (1200 ℃) may result in failure of the surface of the feedstock carbon fiber to grow silicon carbide. The sintering temperature is controlled to 1500 ℃ -2500 ℃ (for example 1700 ℃ -1900 ℃, 2000 ℃ and the like), and the carbon fiber with the silicon carbide grown on the surface can be successfully obtained. The sintering time can be adjusted correspondingly according to the sintering temperature, and is generally controlled to be 0.5h-5h, for example, 2.5h.
In particular embodiments of the present invention, the feedstock carbon fibers generally employ chopped carbon fibers to enhance the mechanical properties of the composite material. The length of the raw material carbon fiber is generally controlled to be 1mm-9mm, and the diameter is 5 mu m-10 mu m.
In a specific embodiment of the invention, the organic silica gel can provide silicon and carbon elements for silicon carbide growth, has certain viscosity and can stay on the surface of the carbon fiber through a coating (particularly, impregnation, brushing and the like) process. The silicone gum may be a siloxane-based compound such as Polydimethylsiloxane (PDMS), cyclomethicone, and a siloxane-based compound similar in structure to PDMS, cyclomethicone, such as aminosilicone, polymethylphenylsiloxane, polyether polysiloxane copolymer, and the like.
In a specific embodiment of the invention, the time the silicone gum stays on the surface of the raw material carbon fiber during the coating process is preferably 0.5h-2.5h, for example 1.5h.
In particular embodiments of the present invention, the preparation method may further include pre-treating the raw carbon fiber before the silicone gum is coated to clean the surface of the carbon fiber. The pretreatment can be to soak the raw material carbon fiber by using an organic solvent, then to carry out surface modification treatment on the raw material carbon fiber by using nitric acid, and then to wash the raw material carbon fiber by using deionized water.
In a specific embodiment of the present invention, the time for soaking the raw material carbon fiber with the organic solvent is generally controlled to be 12 to 24 hours in the pretreatment.
In a specific embodiment of the present invention, in the pretreatment, the organic solvent may be acetone or the like.
The invention also provides a composite heat-conducting filler, which is prepared by the preparation method. In some embodiments, the carbon fiber surface in the composite thermally conductive filler may be grown with silicon carbide, which is generally fibrous in morphology.
In a specific embodiment of the present invention, the composite thermal conductive filler includes carbon fibers with silicon carbide grown on the surface thereof, i.e., a silicon carbide layer is formed on the surface of the carbon fibers (as shown in fig. 1). In some embodiments, the microstructure of the composite thermally conductive filler may be a brush structure with carbon fibers as "brush stems" and silicon carbide as "bristles". When the composite heat-conducting filler is applied to the preparation of heat-conducting plastics, silicon carbide on the surface of the carbon fiber can be used as a bridge to connect two heterostructures of the carbon fiber and the polyolefin resin base material, so that the interface combination condition between the carbon fiber and the polyolefin resin base material is improved, the heat conduction in the plastic material is improved, and the mechanical strength and toughness of the heat-conducting plastics are enhanced.
In the above composite heat conductive filler, the silicon carbide is generally a fibrous structure, and its length is generally 0.1 μm to 0.6 μm and its diameter is generally 10nm to 50nm.
The invention further provides a heat-conducting plastic material, which comprises, by weight, 100 parts of polyolefin resin base stock, 5-20 parts of heat-conducting filler, 0.5-1 part of flame retardant and 0.5-10 parts of coupling agent; wherein the heat conducting filler comprises the composite heat conducting filler.
In the above heat-conducting plastic material, the polyolefin resin base material is generally a special polyolefin material for pipes, and may specifically include one or a combination of more than two of polyethylene resins, polypropylene resins and polybutylene resins. Wherein the polyethylene resin can be polyethylene PE63, polyethylene PE80, polyethylene PE100, heat-resistant polyethylene PE-RT and the like; the polypropylene resin can be homo-polypropylene PP-H, block polypropylene PP-B, random co-polypropylene PP-R and the like; the polybutene resin may be polybutene PB, random copolymer polybutene PB-R, etc.
In the above heat conductive plastic materials, the coupling agent generally includes a silane coupling agent, a titanate coupling agent, and the like.
In the above heat conductive plastic material, the flame retardant may be a commercial flame retardant such as aluminum hypophosphite.
In the above heat conductive plastic material, the weight ratio of the coupling agent to the polyolefin resin base is preferably 0.5 to 5:100. That is, the raw materials of the heat conductive plastic material preferably include 100 parts of polyolefin resin base stock, 5-20 parts of heat conductive filler, 0.5-1 part of flame retardant and 0.5-5 parts of coupling agent in parts by weight.
In the specific embodiment of the invention, the carbon fiber with silicon carbide grown on the surface is used as the heat-conducting filler to be added into the raw material of the heat-conducting plastic, so that on one hand, the heat-conducting plastic material can be toughened, and on the other hand, the heat conduction efficiency between the carbon fiber and the polyolefin resin base material can be improved, and further, the heat conductivity coefficient of the heat-conducting plastic material is improved. In some embodiments, the thermally conductive plastic material generally has a thermal conductivity of 1.25W/mK to 1.5W/mK. The tensile strength of the heat-conducting plastic material is generally 15MPa-30MPa.
The invention also provides a preparation method of the heat-conducting plastic material, which comprises the following steps: melt blending the heat conducting filler, the polyolefin resin base material, the flame retardant and the coupling agent, extruding and granulating to obtain the heat conducting plastic material; wherein the heat conducting filler comprises the composite heat conducting filler.
In the above method for producing a thermally conductive plastic material, preferably, the melt blending temperature is 180 ℃ to 220 ℃.
In the above-described method for producing a heat-conductive plastic material, it is preferable that the temperature of the material subjected to extrusion granulation is 200 ℃ to 220 ℃, for example 210 ℃.
In a specific embodiment of the present invention, the method for preparing a heat conductive plastic material may specifically include a surface dipping process, a baking process, a high temperature sintering process, a melt blending process, an extrusion granulating process, an injection molding process, and the like, and may include the following processes:
1. respectively carrying out surface pretreatment on the carbon fiber by using an organic solvent such as acetone, nitric acid and water;
coating the pretreated carbon fiber surface with organic silica gel, and drying to quickly dry the impregnated carbon fiber surface;
then sintering the carbon fiber at 1500-2500 ℃ for 0.5-5 h (which can be performed in a high-temperature vacuum furnace), and growing silicon carbide on the surface of the carbon fiber in situ during the sintering process to obtain the composite heat-conducting filler;
2. and (3) carrying out melt blending on the composite heat conducting filler, the polyolefin resin base material, the flame retardant and the coupling agent at 180-220 ℃, and carrying out extrusion granulation on the obtained material (generally carried out in a double-screw extruder), wherein the temperature of the extruded material is generally 200-220 ℃, so as to obtain the heat conducting plastic material.
The invention provides a plastic pipe, which is prepared by taking the heat-conducting plastic material as master batch and performing injection molding. The plastic pipe has better heat conduction capability and higher mechanical property.
The invention has the beneficial effects that:
the composite heat-conducting filler provided by the invention contains the carbon fiber with the surface of silicon carbide grown, can strengthen the interface combination between the carbon fiber and the polyolefin resin base material when being used for preparing heat-conducting plastics, plays a role in improving the mechanical property and the heat-conducting property of the heat-conducting plastics, can effectively reduce the using amount of the filler in the heat-conducting plastics, reduces the economic cost and improves the economic benefit. The plastic pipeline manufactured by the heat-conducting plastic has high heat conductivity coefficient and excellent mechanical property, can meet the use requirement of products, is convenient to process, has low cost and is suitable for popularization and use.
Drawings
FIG. 1 is a low magnification SEM photograph of the product of example 7, step 1.
FIG. 2 is a high magnification SEM photograph of the product of example 7, step 1.
Figure 3 is an XRD pattern of the product of step 1 of example 7.
Detailed Description
The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention.
In the following examples and comparative examples, aluminum hypophosphite was used as the commercial flame retardant and gamma-aminopropyl triethoxysilane was used as the silane coupling agent.
Example 1
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 1mm and the diameter of 5 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, and drying after staying for 0.5 h; sintering in a high-temperature furnace at 1700 ℃ for 5 hours to obtain the carbon fiber with the surface of silicon carbide grown, namely the composite heat-conducting filler.
2. Putting 20 parts by weight of carbon fiber (serving as a heat conducting filler) with silicon carbide grown on the surface into a high-speed shearing machine, and then sequentially adding 100 parts by weight of polyethylene resin PE-RT (serving as a polyolefin resin base stock), 0.5 part by weight of commercial flame retardant and 0.5 part by weight of silane coupling agent to perform melt blending (180 ℃) to form a material; and then extruding and granulating the materials (namely the mixture formed by melt blending) by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 200 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 2
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 5mm and the diameter of 6 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, and drying after staying for 1.5 h; sintering in a high-temperature furnace at 2000 ℃ for 2.5 hours to obtain the carbon fiber with the surface of which silicon carbide grows, namely the composite heat-conducting filler.
2. 10 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface is put into a high-speed shearing machine, and then 100 parts by weight of polyethylene resin PE63 (serving as a polyolefin resin base stock), 0.5 part by weight of commercial flame retardant and 0.5 part by weight of silane coupling agent are sequentially added for melt blending (200 ℃) to form a material; and then extruding and granulating the materials by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 210 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 3
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 9mm and the diameter of 8 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, staying for 2.5 hours, and drying; sintering in a high-temperature furnace at 2500 ℃ for 0.5h to obtain the carbon fiber with the surface of which silicon carbide grows, namely the composite heat-conducting filler.
2. Placing 10 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface into a high-speed shearing machine, and then sequentially adding 100 parts by weight of polyethylene resin PE80 (serving as a polyolefin resin base stock), 1 part by weight of commercial flame retardant and 10 parts by weight of silane coupling agent to perform melt blending (220 ℃) to form a material; and then extruding and granulating the materials by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 220 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 4
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 1mm and the diameter of 5 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, and drying after staying for 0.5 h; sintering in a high-temperature furnace at 1500 ℃ for 5 hours to obtain the carbon fiber with the surface of silicon carbide, namely the composite heat-conducting filler.
2. 10 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface is put into a high-speed shearing machine, and then 100 parts by weight of polypropylene resin PP-H (serving as a polyolefin resin base stock), 1 part by weight of commercial flame retardant and 5 parts by weight of silane coupling agent are sequentially added for melt blending (180 ℃) to form a material; and then extruding and granulating the materials by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 200 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 5
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 5mm and the diameter of 6 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, and drying after staying for 1.5 h; sintering in a high-temperature furnace at 2000 ℃ for 2.5 hours to obtain the carbon fiber with the surface of which silicon carbide grows, namely the composite heat-conducting filler.
2. Putting 5 parts by weight of carbon fiber (serving as a heat conducting filler) with silicon carbide grown on the surface into a high-speed shearing machine, and then sequentially adding 100 parts by weight of polypropylene resin PP-B (serving as a polyolefin resin base stock), 0.5 part by weight of commercial flame retardant and 5 parts by weight of silane coupling agent to perform melt blending (200 ℃) to form a material; and then extruding and granulating the materials by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 220 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 6
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 9mm and the diameter of 8 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, staying for 2.5 hours, and drying; sintering in a high-temperature furnace at 2500 ℃ for 0.5h to obtain the carbon fiber with the surface of which silicon carbide grows, namely the composite heat-conducting filler.
2. 10 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface is put into a high-speed shearing machine, and then 100 parts by weight of polypropylene resin PP-R (serving as a polyolefin resin base stock), 1 part by weight of commercial flame retardant and 5 parts by weight of silane coupling agent are sequentially added for melt blending (220 ℃) to form a material; and then extruding and granulating the formed material by using a double-screw extruder, wherein the temperature of the extruder material is controlled at 210 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Example 7
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 24h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 5mm and the diameter of 6 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel PDMS on the surface of the carbon fiber, and drying after staying for 1.5 h; sintering in a high-temperature furnace at 1500 ℃ for 5 hours to obtain the carbon fiber with the surface of silicon carbide, namely the composite heat-conducting filler.
2. Putting 5 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface into a high-speed shearing machine, and then sequentially adding 100 parts by weight of polyethylene resin PE-RT (serving as a polyolefin resin base stock), 1 part by weight of commercial flame retardant and 5 parts by weight of silane coupling agent to perform melt blending (190 ℃) to form a melt mixture; and then extruding and granulating the molten mixture by using a double-screw extruder, wherein the material temperature of the extruder is controlled at 210 ℃, and the heat-conducting plastic material is obtained.
The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Fig. 1 and 2 are SEM photographs of the carbon fiber of the surface-grown silicon carbide prepared in step 1 of the present example. FIG. 1 is an SEM photograph of a sample, and it can be seen that silicon carbide layers are grown on the surfaces of both sides of a carbon fiber; fig. 2 is a further enlargement of the silicon carbide layer in fig. 1, and it can be seen that the silicon carbide of the silicon carbide layer is fibrous, which is a representation of the rough structure on the surface of the carbon fiber, and the structure helps to improve the interfacial bonding force between the carbon fiber and other heterogeneous materials. From the scanning electron microscope results, the preparation method in the step 1 can enable the carbon fiber surface to grow evenly distributed silicon carbide.
XRD analysis was performed on the product of step 1 of this example, and the results are shown in FIG. 3, in which (101) (102) (110) (116) are characteristic peaks of silicon carbide (PDF#29-1131) and (002) are characteristic peaks of carbon fibers. As can be seen from fig. 3, the product in step 1 is a composite material comprising carbon fibers and silicon carbide. As can be seen from a combination of the results of fig. 1 to 3, the product formed in step 1 is a composite structure product in which silicon carbide grows on the surface of carbon fiber.
Example 8
The embodiment provides a heat-conducting plastic material, and the preparation method comprises the following steps:
1. soaking carbon fiber in acetone for 12h, drying, carrying out surface modification treatment on the carbon fiber (with the length of 2mm and the diameter of 10 mu m) by nitric acid, and cleaning by deionized water to complete pretreatment; coating organic silica gel cyclomethicone on the surface of the carbon fiber, and drying after staying for 0.5 h; sintering in a high-temperature furnace at 2500 ℃ for 0.5h to obtain the carbon fiber with the surface of which silicon carbide grows, namely the composite heat-conducting filler.
2. 10 parts by weight of carbon fiber (serving as a heat-conducting filler) with silicon carbide grown on the surface is put into a high-speed shearing machine, and then 100 parts by weight of polybutene (serving as a polyolefin resin base material), 1 part by weight of commercial flame retardant and 5 parts by weight of titanate coupling agent are sequentially added for melt blending (200 ℃) to form a melt mixture; and then extruding and granulating the molten mixture by using a double-screw extruder, wherein the temperature of the extruder material is controlled at 200 ℃, and the heat-conducting plastic material is obtained. The heat-conducting plastic material is used as master batch for injection molding, and a plastic pipeline can be prepared.
Comparative example 1
The present comparative example provides a thermally conductive plastic material prepared by replacing carbon fibers of silicon carbide grown on the surface of a thermally conductive filler used in example 7 with unmodified raw material carbon fibers, the specific preparation method comprising:
putting 5 parts by weight of carbon fiber (serving as a heat conducting filler) into a high-speed shearing machine, and then sequentially adding 100 parts by weight of polyethylene resin PE-RT (serving as a polyolefin resin base material), 1 part by weight of commercial flame retardant and 5 parts by weight of silane coupling agent to perform melt blending (190 ℃) to form a material; and then extruding and granulating the materials by using a double-screw extruder, wherein the temperature of the materials in the extruder is controlled at 210 ℃, and the heat-conducting plastic material is obtained.
Test example 1
The test example provides a test of the thermal conductivity coefficients of the thermal conductive plastic pipes prepared in example 7 and comparative example 1 by a laser flash method at a temperature of 25 ℃ and in a nitrogen atmosphere. The results showed that the thermal conductivity of the thermal conductive plastic material prepared in example 7 was 1.25W/m·k, the thermal conductivity of the thermal conductive plastic material prepared in comparative example 1 was 0.89W/m·k, i.e., the thermal conductivity of the thermal conductive plastic material was improved by 40% by surface modification of the carbon fibers in the thermal conductive filler in example 7, and the thermal conductivity of the thermal conductive plastic material of example 7 was 3.3 times that of the conventional polyolefin pipe. The mechanical property of the heat-conducting plastic material prepared in the test example 7 is tested, the test method is that the material is stretched at a constant speed (10 mm/min) at room temperature, and finally the tensile strength of the material is 22.0MPa, which is obviously improved by 28% compared with the mechanical strength of 17.2MPa of the pure PE-RT matrix material. The thermal conductivity and mechanical properties of the thermal conductive plastic materials of examples 1 to 6 and 8 were measured, and the thermal conductivity of each thermal conductive plastic material was 1.25W/mK-1.5W/mK, and the tensile strength of each thermal conductive plastic material was 18MPa-23MPa, which were improved to different extents.
The results show that the heat-conducting filler formed by growing silicon carbide on the surface of the carbon fiber can keep better processing performance of the resin when being applied to the preparation of heat-conducting plastics, and simultaneously greatly improve the overall heat-conducting performance and mechanical performance of the heat-conducting plastics. The polyolefin plastic pipe prepared from the heat-conducting plastic material has wide application prospects in the fields of cooling water heat exchange pipes, floor heating pipelines and the like.
Claims (11)
1. A method for preparing a composite heat conductive filler, comprising: coating organic silica gel on the surface of raw material carbon fiber, and drying and sintering at 1500-2500 ℃ for 0.5-5 h to obtain the composite heat-conducting filler;
the raw material carbon fiber is a chopped carbon fiber;
the length of the raw material carbon fiber is 1mm-9mm, and the diameter is 5 mu m-10 mu m;
the organic silica gel comprises one or more than two of polydimethylsiloxane, cyclomethicone, aminosilicone, polymethylphenylsiloxane and polyether polysiloxane copolymer;
in the coating process, the retention time of the organic silica gel on the surface of the raw material carbon fiber is 0.5h-2.5h;
the preparation method comprises the steps of pre-treating raw material carbon fibers before coating organic silica gel, wherein the pre-treating comprises the steps of soaking the raw material carbon fibers by using an organic solvent, then carrying out surface modification treatment on the raw material carbon fibers by using nitric acid, and then washing the raw material carbon fibers by using deionized water;
the time for soaking the carbon fiber by the organic solvent is 12-24 hours.
2. The method for preparing a composite heat conductive filler according to claim 1, wherein the organic solvent comprises acetone.
3. A composite heat conductive filler obtained by the method for producing a composite heat conductive filler according to claim 1 or 2.
4. The composite heat-conducting filler according to claim 3, wherein silicon carbide grows on the surface of the carbon fiber in the composite heat-conducting filler, and the morphology of the silicon carbide is fibrous.
5. The composite heat conductive filler according to claim 4, wherein the silicon carbide fiber has a length of 0.1 μm to 0.6 μm and a diameter of 10nm to 50nm.
6. The heat conducting plastic material comprises, by weight, 100 parts of polyolefin resin base stock, 5-20 parts of heat conducting filler, 0.5-1 part of flame retardant and 0.5-10 parts of coupling agent, wherein the heat conducting filler comprises the composite heat conducting filler according to any one of claims 3-5.
7. The thermally conductive plastic material of claim 6, wherein the polyolefin resin base comprises one or a combination of two or more of polyethylene-based resin, polypropylene-based resin, polybutylene-based resin;
and/or the coupling agent comprises a silane coupling agent and/or a titanate coupling agent;
and/or the flame retardant comprises aluminum hypophosphite.
8. A thermally conductive plastics material according to claim 6 or 7, wherein the weight ratio of the coupling agent to the polyolefin resin base is from 0.5 to 5:100.
9. The thermally conductive plastic material according to claim 6 or 7, wherein the thermally conductive plastic material has a thermal conductivity of 1.25W/m-K-1.5W/m-K.
10. The thermally conductive plastic material of claim 6 or 7, wherein the thermally conductive plastic material has a tensile strength of 15MPa-30MPa.
11. A plastic pipe prepared by injection molding a thermally conductive plastic material according to any one of claims 6 to 10 as a masterbatch.
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