A method for preparing a high normal thermal conductive polymer nanocomposite sheet and a composite sheet

Abstract

The invention relates to a preparation method of a high normal thermal conductivity polymer nano-composite sheet and the composite sheet, which is implemented by a multi-microporous flow channel head mechanism, wherein the multi-microporous flow channel head mechanism comprises an inlet, a stretching flow channel, a transition flow channel and an outlet, wherein the cross section of the inlet is arched, the top of the inlet is connected to the stretching flow channel, the stretching flow channel is a plurality of channels oriented in a normal direction, a plurality of the channels are connected to the transition flow channel in a vertical direction, the end of the transition flow channel is connected to the outlet, and the diameter of the outlet is smaller than the diameter of the transition flow channel; the preparation method comprises: S1: mixing a polymer, a nano-filler and a coupling agent to obtain a reaction mixture; S2: after the reaction mixture is melt-blended, entering the stretching flow channel from the inlet for stretching and orientation; S3: after the reaction mixture flows into the transition flow channel for convergence and compression, it is extruded from the outlet to obtain the high normal thermal conductivity polymer nano-composite sheet.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a preparation method of a high normal thermal conductive polymer nano composite sheet and the composite sheet. Background Art

[0002] In recent years, two-dimensional or three-dimensional nanofillers such as carbon fiber, graphene microsheets, and carbon nanotubes have been widely used in polymer composites to improve the various properties of composite materials due to their excellent thermal conductivity, electrical conductivity, and mechanical properties. Among them, high thermal conductivity nanofillers with regular lattices and high orientation can effectively improve the thermal conductivity of polymers in a specific direction, and have broad market prospects in the fields of thermal conductive materials and electronic packaging.

[0003] However, due to the large surface free energy of nanofillers and obvious agglomeration, nanofillers in composite materials are often unevenly distributed, making it difficult for the high thermal conductivity of nanofillers to be fully utilized in the polymer matrix with low thermal conductivity. Therefore, how to arrange nanofillers uniformly in a specific direction in the polymer matrix is ​​the key to improving the anisotropic thermal conductivity of polymer matrix composites.

[0004] At present, it is relatively easy to orient nanofillers in polymers in the in-plane direction. However, when making polymer composite sheets, the thermal conductivity of nanofillers in polymers oriented perpendicular to the in-plane direction (normal direction) is more widely used. However, the existing preparation method has a low degree of orientation of the composite sheets in which nanofillers are oriented in the normal direction in the polymer, resulting in poor thermal conductivity of the composite sheets. Summary of the invention

[0005] The present invention provides a method for preparing a high normal thermal conductive polymer nanocomposite sheet and the composite sheet, which are used to solve the technical problem that the composite sheet obtained by the existing preparation method has a low degree of orientation in which nanofillers are oriented in the normal direction in the polymer.

[0006] In view of this, the present invention provides a method for preparing a high normal thermal conductive polymer nanocomposite sheet, which is implemented by a multi-microporous flow channel head mechanism, wherein the multi-microporous flow channel head mechanism comprises an inlet, a stretching flow channel, a transition flow channel and an outlet, wherein the cross section of the inlet is arched, the top of the inlet is connected to the stretching flow channel, the stretching flow channel is a plurality of channels oriented in a normal direction, a plurality of the channels are connected to the transition flow channel in a vertical direction, the end of the transition flow channel is connected to the outlet, and the diameter of the outlet is smaller than the diameter of the transition flow channel;

[0007] The preparation method comprises:

[0008] S1: mixing a polymer, a nanofiller and a coupling agent to obtain a reaction mixture;

[0009] S2: After the reaction mixture is melted and blended, it enters the stretching channel from the inlet for stretching and orientation;

[0010] S3: After the reaction mixture flows into the transition channel and is converged and compressed, it is extruded from the outlet to obtain a high normal thermal conductive polymer nanocomposite sheet.

[0011] Preferably, the mixing temperature is 60° C. to 100° C., and the mixing time is 3 min to 15 min.

[0012] Preferably, the shear stress of the melt blending is 0.14 MPa to 0.2 MPa, and the time of the melt blending is 250 s to 600 s.

[0013] Preferably, the number of the channels is 100 to 200, the channels are tapered channels, the inlet radius of the channels is 1 mm to 1.5 mm, the outlet radius of the channels is 0.5 mm to 0.75 mm, and the depth of the channels is 10 mm to 15 mm.

[0014] Preferably, the length of the transition flow channel is 80 mm to 100 mm, the height of the transition flow channel is 2 mm to 4 mm, and the width of the transition flow channel is 80 mm to 100 mm.

[0015] Preferably, the amount of the polymer is 500-1000 g, the nanofiller accounts for 5%wt-20%wt of the polymer, and the coupling agent accounts for 1%wt-3%wt of the nanofiller.

[0016] Preferably, the polymer is selected from one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyamide, polyoxymethylene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide and polyetherketone.

[0017] Preferably, the nanofiller is selected from one or more of carbon fibers, carbon nanotubes, graphene microplatelets, molybdenum disulfide, montmorillonite and hexagonal boron nitride.

[0018] Preferably, the coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent and a phosphate coupling agent.

[0019] Preferably, the nanofiller is a two-dimensional nanofiller, and the particle size of the two-dimensional nanofiller is 10 μm to 50 μm.

[0020] More preferably, the particle size of the two-dimensional nanofiller is 20 μm.

[0021] Preferably, the nanofiller is a three-dimensional nanofiller, the sheet diameter of the three-dimensional nanofiller is 30 μm to 200 μm, and the sheet thickness of the three-dimensional nanofiller is 5 nm to 400 nm.

[0022] More preferably, the sheet diameter of the three-dimensional nanofiller is 30 μm to 50 μm, and the sheet thickness of the three-dimensional nanofiller is 5 nm to 100 nm.

[0023] A composite sheet is prepared based on the above-mentioned method for preparing a high normal thermal conductive polymer nanocomposite sheet.

[0024] It can be seen from the above technical solutions that the present invention has the following advantages:

[0025] The present application provides a method for preparing a high normal thermal conductive polymer nanocomposite sheet, which is implemented by using a multi-microporous flow channel head mechanism, wherein the multi-microporous flow channel head mechanism comprises an inlet, a stretching flow channel, a transition flow channel and an outlet, wherein the cross section of the inlet is arched, the top of the inlet is connected to the stretching flow channel, the stretching flow channel is a plurality of channels oriented in a normal direction, a plurality of the channels are connected to the transition flow channel in a vertical direction, the end of the transition flow channel is connected to the outlet, and the diameter of the outlet is smaller than the diameter of the transition flow channel;

[0026] The preparation method comprises:

[0027] S1: mixing a polymer, a nanofiller and a coupling agent to obtain a reaction mixture;

[0028] S2: After the reaction mixture is melted and blended, it enters the stretching channel from the inlet for stretching and orientation;

[0029] S3: After the reaction mixture flows into the transition channel and is converged and compressed, it is extruded from the outlet to obtain a high normal thermal conductive polymer nanocomposite sheet.

[0030] The nanofillers in the reaction mixture can build a random or ordered heat-conducting network structure during the melt blending process with the polymer, so that the polymer nanocomposite material can obtain excellent isotropic or anisotropic thermal conductivity. After completing the above melt blending process, the melt blended reaction mixture enters the multi-microporous flow channel head mechanism through an inlet with an arched cross section, and flows into a plurality of connected normal-direction oriented channels from the top of the inlet, so that the nanofillers are arranged in order in the polymer along the direction perpendicular to the plane as much as possible, forming an anisotropic heat-conducting network structure, and the reaction mixture converges and flows into the transition flow channel in the vertical direction connected by the plurality of channels for convergence and compression, and finally extrusion molding is performed from an outlet with a smaller diameter, and the entire extrusion process is carried out under a shear force field, which improves the thermal conductivity of the polymer in the normal direction, thereby obtaining a high normal heat-conducting polymer nanocomposite sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 This is a schematic diagram of the structure of a high normal thermal conductive polymer nanocomposite sheet according to an embodiment of the present invention;

[0033] Figure 2 It is a three-dimensional structural schematic diagram of the multi-microporous flow channel head mechanism according to an embodiment of the present invention;

[0034] Figure 3 It is a schematic cross-sectional structure diagram of the multi-microporous flow channel head mechanism according to an embodiment of the present invention;

[0035] In the figure: 1. Nanofiller; 2. Polymer; 3. Stretching channel; 4. Transition channel; 5. Inlet; 6. Outlet. DETAILED DESCRIPTION

[0036] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Generally, magnetic field induction and ultrasonic vibration methods can be used on the market to make composite sheets with nanofillers oriented in the normal direction in polymers. Since magnetic field induction requires magnetization of the filler, it will destroy the original structure of the filler to a certain extent, resulting in poor thermal conductivity of the filler in the composite material, and the processing process is relatively complicated and costly. However, the ultrasonic vibration method does not allow the filler to be oriented in the normal direction to a high degree, and is difficult to control accurately. It has certain limitations and is difficult to develop and produce on a large scale.

[0038] In view of this, the present invention provides a method for preparing a high normal thermal conductive polymer nanocomposite sheet and a composite sheet, which are used to solve the technical problem that the nanofillers obtained by the existing preparation method are oriented in the normal direction in the polymer. The composite sheet has a low degree of orientation.

[0039] See also Figure 1-3 An embodiment of the present invention provides a high normal thermal conductivity polymer nanocomposite sheet, which is implemented by a multi-microporous channel head mechanism, and the multi-microporous channel head mechanism includes an inlet 5, a stretching channel 3, a transition channel 4 and an outlet 6. The cross section of the inlet 5 is arched, and the top of the inlet 5 is connected to the stretching channel 3. The stretching channel 3 is a plurality of channels oriented in the normal direction, and the plurality of channels are connected to the transition channel 4 in the vertical direction. The end of the transition channel 4 is connected to the outlet 6, and the diameter of the outlet 6 is smaller than the diameter of the transition channel 4.

[0040] The preparation method comprises:

[0041] S1: mixing polymer 2, nanofiller 1 and coupling agent to obtain a reaction mixture;

[0042] S2: After the reaction mixture is melted and blended, it enters the stretching channel 3 from the inlet 5 for stretching and orientation;

[0043] S3: The reaction mixture flows into the transition channel 4 and is converged and compressed, and then is extruded from the outlet 6 to obtain a high normal thermal conductive polymer nanocomposite sheet.

[0044] It should be noted that the multi-microporous flow channel head mechanism in this embodiment can be installed in a common twin-screw (single) extruder on the market as the head device of the extruder. The reaction mixture (a mixture of plastic particles, fillers and additives) enters the extruder through the extruder barrel, and reaches the head mechanism device after being melted and compressed by the screw. The reaction mixture reaches the channel oriented in the normal direction through the inlet 5. After the stretching action of the channel, the nanofiller 1 in the reaction mixture is oriented and distributed along the normal direction of the polymer 2, and then further converges and compresses through the transition channel 4 and the outlet 6 to obtain an extruded sheet with good thermal conductivity in the normal direction. The entire extrusion process is carried out in a shear force field environment. The cross section of the material is subjected to external force, and the phenomenon of relative displacement deformation along the direction of the external force is called shear.

[0045] As a further improvement, the mixing temperature is 60°C to 100°C, and the mixing time is 3 min to 15 min.

[0046] It should be noted that a more preferred mixing temperature is 70° C. to 80° C., and a more preferred mixing time is 5 min to 10 min.

[0047] As a further improvement, the shear stress of melt blending is 0.14 MPa~0.2 MPa, and the melt blending time is 250 s~600 s.

[0048] As a further improvement, the number of the channels is 100 to 200, the channels are tapered channels, the inlet radius of the channels is 1 mm to 1.5 mm, the outlet radius of the channels is 0.5 mm to 0.75 mm, and the depth of the channels is 10 mm to 15 mm.

[0049] It should be noted that the inlet radius of the tapered channel is larger than the outlet radius of the tapered channel, so that the reaction mixture entering the stretching channel 3 (tapered channel) is initially converged and compressed before entering the transition channel 4 .

[0050] As a further improvement, the length of the transition channel 4 is 80 mm to 100 mm, the height of the transition channel 4 is 2 mm to 4 mm, and the width of the transition channel 4 is 80 mm to 100 mm.

[0051] As a further improvement, the amount of polymer 2 is 500 g~1000 g, the nanofiller 1 accounts for 5%wt~20%wt of the amount of polymer 2, and the coupling agent accounts for 1%wt~3%wt of the amount of nanofiller 1.

[0052] As a further improvement, polymer 2 is selected from one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyamide, polyoxymethylene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide and polyether ketone.

[0053] As a further improvement, the nanofiller 1 is selected from one or more of carbon fibers, carbon nanotubes, graphene microsheets, molybdenum disulfide, montmorillonite and hexagonal boron nitride.

[0054] As a further improvement, the coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent and a phosphate coupling agent.

[0055] As a further improvement, the nanofiller 1 is a two-dimensional nanofiller, and the particle size of the two-dimensional nanofiller is 10 μm to 50 μm.

[0056] It should be noted that a more preferred particle size of the two-dimensional nanofiller is 20 μm, and the two-dimensional nanofiller may be carbon fiber.

[0057] As a further improvement, the nanofiller 1 is a three-dimensional nanofiller, the sheet diameter of the three-dimensional nanofiller is 30 μm~200 μm, and the sheet thickness of the three-dimensional nanofiller is 5 nm~400 nm.

[0058] It should be noted that the more preferred three-dimensional nanofiller has a sheet diameter of 30 μm to 50 μm, a sheet thickness of 5 nm to 100 nm, and the three-dimensional nanofiller may be a graphene microsheet;

[0059] Two-dimensional nanofillers and three-dimensional nanofillers can be used simultaneously.

[0060] The high normal thermal conductivity polymer nanocomposite sheet obtained by the preparation method of the present invention. Compared with the prior art, the present invention aims at the technical problem that the uneven dispersion of nanofillers in the polymer leads to limited improvement in the thermal conductivity of the composite material. The specific melt blending conditions are used in conjunction with the multi-microporous flow channel head mechanism designed by the present invention, which effectively promotes the orientation distribution degree of the nanofillers in the normal direction of the polymer and improves the thermal conductivity of the polymer sheet in the normal direction. The equipment used in the exfoliation and dispersion method provided by the present invention is simple and universal, the process steps are simple, easy to operate, the raw material cost is low, and at the same time, it is pollution-free to the environment, which is conducive to large-scale industrialization.

[0061] The present invention has no special restrictions on the source of the coupling agent, and commercially available silane coupling agents, titanate coupling agents and phosphate coupling agents known to those skilled in the art can be used. In the embodiments and comparative examples of the present invention, the coupling agent is a silane coupling agent with a brand of KH560. The raw materials used in the following embodiments of the present invention are all commercially available products; among them, polypropylene (PP) is injection-molding grade polypropylene, and carbon fiber powder is provided by Toray Industries, Ltd.

[0062] Example 1

[0063] 6 g, 9 g, 12 g, and 15 g of carbon fiber powder were mixed with a coupling agent (the content of the coupling agent accounted for 3% of the filler mass), respectively, and then mixed with 1000 g of high-density polypropylene (PP) and 10 g of lubricant in a mixer at 80 °C for 10 min to obtain four reaction mixtures with different carbon fiber contents.

[0064] The four reaction mixtures were accurately fed into the extruder for melt blending using a feeding device. The screw speed was 200 rpm, and the temperature in each zone was between 160°C and 230°C. Finally, they were formed by a multi-microporous flow channel head mechanism to complete the orientation of the nanofiller in the normal direction and obtain a carbon fiber / PP composite material.

[0065] The thermal conductivity analyzer (Netzsch LFA 447, Germany) was used to measure the thermal diffusion coefficient by the flash method, and the measurement standard was ASTM E-1461. The measurement was carried out at room temperature (25°C). The thermal conductivity of the carbon fiber / PP composite material in the normal direction in Example 1 was tested, and the thermal diffusion coefficients (in mm2) of the carbon fiber content of 6%, 9%, 12%, and 15% were obtained. 2 / s) are 1.21, 1.45, 1.96 and 2.23 respectively.

[0066] Comparative Example 1

[0067] 6 g, 9 g, 12 g, and 15 g of carbon fiber powder were mixed with a coupling agent (the content of the coupling agent accounted for 3% of the filler mass), and then mixed with 1000 g of high-density polyethylene and 10 g of lubricant in a mixer at 80 ° C for 10 min to obtain four reaction mixtures with different carbon fiber contents.

[0068] The four reaction mixtures were accurately fed into the extruder for melt blending using a feeding device. The screw speed was 200 rpm, and the temperature of each zone was between 160°C and 230°C. Finally, they were formed through an ordinary sheet die to obtain a carbon fiber / HDPE composite material.

[0069] The thermal conductivity of the carbon fiber / HDPE composite material obtained in Comparative Example 1 was tested using the test method provided in Example 1. The thermal diffusion coefficient (in mm2) of the carbon fiber content of 6%, 9%, 12%, and 15% 2 / s) are 0.31, 0.37, 0.45 and 0.51 respectively.

[0070] It can be seen that compared with Comparative Example 1, the carbon fiber / PP composite material obtained by the multi-microporous flow channel head mechanism provided in Example 1 can improve the degree of orientation of the carbon fiber in the normal direction compared to the existing plate preparation process, so that the thermal conductivity of the polymer nanocomposite material in the normal direction is greatly improved, which plays an important role in improving the thermal conductivity of the composite material.

[0071] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high normal thermal conductive polymer nanocomposite sheet, characterized in that: The multi-microporous flow channel head mechanism is adopted for implementation, and the multi-microporous flow channel head mechanism includes an inlet, a stretching flow channel, a transition flow channel and an outlet. The cross section of the inlet is arched, and the top of the inlet is connected to the stretching flow channel. The stretching flow channel is a plurality of channels oriented in a normal direction, and the plurality of channels are connected to the transition flow channel in a vertical direction. The end of the transition flow channel is connected to the outlet, and the diameter of the outlet is smaller than the diameter of the transition flow channel. The preparation method comprises: S1: mixing a polymer, a nanofiller and a coupling agent to obtain a reaction mixture; S2: After the reaction mixture is melted and blended, it enters the stretching channel from the inlet for stretching and orientation; S3: After the reaction mixture flows into the transition channel and is converged and compressed, it is extruded from the outlet to obtain a high normal thermal conductive polymer nanocomposite sheet.

2. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The mixing temperature is 60° C. to 100° C., and the mixing time is 3 min to 15 min.

3. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The shear stress of the melt blending is 0.14 MPa to 0.2 MPa, and the time of the melt blending is 250 s to 600 s.

4. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The number of the channels is 100 to 200, the channels are tapered channels, the inlet radius of the channels is 1 mm to 1.5 mm, the outlet radius of the channels is 0.5 mm to 0.75 mm, and the depth of the channels is 10 mm to 15 mm.

5. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The length of the transition flow channel is 80 mm to 100 mm, the height of the transition flow channel is 2 mm to 4 mm, and the width of the transition flow channel is 80 mm to 100 mm.

6. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The amount of the polymer is 500 g to 1000 g, the nanofiller accounts for 5%wt to 20%wt of the polymer, and the coupling agent accounts for 1%wt to 3%wt of the nanofiller.

7. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The polymer is selected from one or more of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyamide, polyoxymethylene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide and polyether ketone.

8. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The nanofiller is selected from one or more of carbon fiber, carbon nanotube, graphene microsheet, molybdenum disulfide, montmorillonite and hexagonal boron nitride.

9. The method for preparing a high normal thermal conductive polymer nanocomposite sheet according to claim 1, characterized in that: The coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent and a phosphate coupling agent.

10. A composite sheet, characterized in that: The high normal thermal conductive polymer nanocomposite sheet is prepared based on the preparation method of any one of claims 1 to 9.

Images