Hybrid graphene modified polyethylene composite material as well as preparation method and application thereof

Abstract

The invention relates to the field of new materials, and particularly discloses a hybrid graphene modified polyethylene composite material as well as a preparation method and application thereof. The composite material comprises the following raw materials in parts by weight: 36-40 parts of HDPE particles; 8 to 10 parts of graphene oxide; 5-8 parts of silicon nitride; 7-9 parts of a carbon nanotube; 34-40 parts of an ethylene monomer; 0.6 to 0.8 part of polyethylene wax; 0.6 to 0.8 part of a silane coupling agent KH-550; and 0.4 to 0.8 part of a self-repairing microcapsule. The preparation method comprises the following steps: pretreating graphene oxide; pretreating the HDPE particles; carrying out in-situ polymerization reaction; and melt blending. The composite material can be used for preparing a hybrid graphene modified polyethylene composite material pipe, can be applied to a ground source heat pump system, and has the advantages of excellent heat-conducting property and mechanical property.

Description

Technical Field

[0001] The present application relates to the field of new materials, and more specifically, to a hybrid graphene-modified polyethylene composite material and a preparation method and application thereof. Background Art

[0002] As an efficient and environmentally friendly heating and cooling technology, ground source heat pumps are increasingly used in the field of building energy. Its working principle is to use shallow geothermal resources underground to exchange heat with the soil through underground buried pipe heat exchangers to achieve heating and cooling of buildings. In this system, the performance of the ground source heat pump pipe material directly affects the overall efficiency and service life of the ground source heat pump.

[0003] Polyethylene pipes have become the preferred material for ground-source heat pump buried pipes due to their good corrosion resistance, flexibility, low cost and easy processing. However, with the continuous development of ground-source heat pump technology, the performance requirements for its pipeline system are becoming higher and higher. Traditional polyethylene pipes have certain limitations in thermal conductivity, which to a certain extent limits the heat transfer efficiency of ground-source heat pump systems. Graphene, as a new type of two-dimensional carbon nanomaterial, has excellent mechanical, electrical and thermal properties. Adding graphene to a polyethylene matrix to prepare a graphene / polyethylene composite material is expected to significantly improve the thermal conductivity of the material while maintaining the original advantages of polyethylene, which is of great significance for improving the performance of ground-source heat pump systems.

[0004] However, graphene has poor dispersion in the polyethylene matrix and is prone to agglomeration, which affects the mechanical properties of the composite material. In addition, the interface compatibility between graphene and polyethylene is also poor, which limits the improvement of the thermal conductivity of the composite material. These problems seriously limit the application of graphene / polyethylene composites in ground source heat pumps. Summary of the invention

[0005] In order to simultaneously improve the dispersibility of graphene in a polyethylene matrix and improve the interface compatibility between graphene and polyethylene, thereby improving the thermal conductivity and mechanical properties of graphene / polyethylene composite materials, the present application provides a hybrid graphene-modified polyethylene composite material, a preparation method and application thereof.

[0006] In a first aspect, the present application provides a hybrid graphene-modified polyethylene composite material, which adopts the following technical solution:

[0007] A hybrid graphene-modified polyethylene composite material comprises the following raw materials in parts by weight:

[0008] 36-40 parts of HDPE granules;

[0009] 8-10 parts of graphene oxide;

[0010] 5-8 parts of silicon nitride;

[0011] 7-9 parts of carbon nanotubes;

[0012] 34-40 parts of ethylene monomer;

[0013] 0.6-0.8 parts of polyethylene wax;

[0014] Silane coupling agent KH-550 0.6-0.8 parts;

[0015] 0.4-0.8 parts of self-repairing microcapsules.

[0016] By adopting the above technical solution, graphene oxide, silicon nitride and carbon nanotubes are compounded as the main thermal conductive raw materials, which has an excellent effect of improving thermal conductivity. Graphene oxide has better dispersibility than graphene. Polyethylene wax as a dispersant can effectively reduce the agglomeration of graphene and improve its dispersibility in the polyethylene matrix; silane coupling agent KH-550 is used to improve the interfacial compatibility between graphene and polyethylene and enhance the bonding between the two. The polyethylene matrix consists of two parts. One part is first made into composite particles through in-situ polymerization of ethylene monomer and graphene oxide, which can improve the compatibility of graphene oxide and polyethylene and enhance its bonding. The composite particles are then melt-blended with HDPE particles. The composite particles can be better dispersed in the HDPE matrix and have stronger interfacial compatibility. The self-healing capsules can play a self-repairing role during the preparation process of the composite material and the subsequent application process, continuously improving the performance of the material and compensating for the influence of the residual agglomeration of graphene oxide on the thermal conductivity and mechanical properties of the composite material. Therefore, it is possible to simultaneously improve the dispersion of graphene in the polyethylene matrix and the interface compatibility between graphene and polyethylene, thereby improving the thermal conductivity and mechanical properties of the graphene / polyethylene composite material.

[0017] Optionally, the self-healing microcapsule has wollastonite whiskers as the capsule core, methyl methacrylate as the healing agent, and a polysiloxane / silicon dioxide composite material as the capsule wall.

[0018] By adopting the above technical scheme, wollastonite whiskers are used as capsule cores and can be compounded with graphene oxide to effectively improve the mechanical strength of the composite material; methyl methacrylate is used as a healing agent, and when cracks occur in the composite material, the self-healing microcapsules rupture, and the outflow of the healing agent can quickly solidify the damaged parts of the composite material, reduce secondary damage, and extend the life of the composite material; the polysiloxane / silicon dioxide composite material is used as a capsule wall and has excellent compatibility with the polyethylene matrix, so that the self-healing microcapsules can improve the dispersion of themselves and graphene oxide in the polyethylene matrix, and the capsule wall has good flexibility, which can effectively alleviate the stress concentration problem caused by the addition of graphene oxide.

[0019] Optionally, the preparation method of the self-repairing microcapsule is:

[0020] Take 10 parts by weight of wollastonite whiskers and use 0.2 parts by weight of silane coupling agent KH-570 for surface modification;

[0021] Take 5 parts by weight of tetraethyl orthosilicate and 5 parts by weight of methyltrimethoxysilane, first add hydrochloric acid to anhydrous ethanol to adjust the pH to 3.5, then gradually add tetraethyl orthosilicate and methyltrimethoxysilane to anhydrous ethanol at a concentration of 0.1 M, stir at room temperature until the mixture is uniformly mixed, react for 6 hours to generate capsule wall material, centrifuge, filter, wash and dry;

[0022] 80 parts by weight of methyl methacrylate is dissolved in anhydrous ethanol, 2 parts by weight of initiator benzoyl peroxide is added, and stirred evenly, and then surface-modified wollastonite whiskers are added, and stirred until uniformly dispersed to form a capsule core / healing agent mixture;

[0023] The capsule wall material is added into the capsule core / healing agent mixture, stirred until uniformly dispersed, and then spray-dried to obtain the self-repairing microcapsules.

[0024] Optionally, the composite material further comprises 0.3-0.5 parts by weight of sponge microneedles and 0.2-0.4 parts by weight of triphenyl phosphate.

[0025] By adopting the above technical solution, triphenyl phosphate is used as a nucleating agent in the polyethylene matrix to improve and promote grain refinement during the crystallization process and increase the number of crystals, thereby making the composite material denser. The sponge microneedles have a unique needle-like microstructure, which, when combined with triphenyl phosphate, can further enhance the effect of grain refinement. It can also be effectively connected with graphene oxide to form a high-strength network structure inside the composite material, further enhancing the thermal conductivity and mechanical properties of the composite material.

[0026] In a second aspect, the present application provides a method for preparing a hybrid graphene-modified polyethylene composite material, using the following technical solution:

[0027] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0028] (1) Graphene oxide pretreatment: The graphene oxide is dried at 60° C. for 24 h to remove moisture and impurities, and then the dried graphene oxide is added to anhydrous ethanol and polyethylene wax, and dispersed at a speed of 2000 to 3000 rpm for 30 to 60 min to obtain a uniformly dispersed graphene oxide suspension;

[0029] (2) HDPE particle pretreatment: HDPE particles were dried at 80 °C for 12 h to remove moisture;

[0030] (3) In-situ polymerization: adding initiator benzoyl peroxide and catalyst triethylaluminum to the pretreated graphene oxide suspension, introducing gaseous ethylene monomer, and carrying out in-situ polymerization at 60-80° C. for 3-5 h under nitrogen protection to form graphene oxide / polyethylene composite particles;

[0031] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles. Silicon nitride, carbon nanotubes, silane coupling agent KH-550 and self-healing microcapsules are also added. The mixture is melt blended by a twin-screw extruder and extruded to obtain a hybrid graphene-modified polyethylene composite material.

[0032] By adopting the above technical scheme, through the pretreatment of graphene oxide and HDPE, the dispersibility of graphene oxide in polyethylene can be effectively improved, and the interface compatibility of graphene oxide and polyethylene can be improved. During the in-situ polymerization reaction, graphene oxide acts as the initiation point of the polymerization reaction, causing ethylene monomer to polymerize on its surface to form graphene oxide / polyethylene composite particles. During the melt blending process, the graphene oxide / polyethylene composite particles are further mixed evenly with the polyethylene matrix, and the coupling agent KH550 enhances the interface bonding force between the thermal conductive raw material and polyethylene. The method of combining in-situ polymerization with melt blending effectively improves the interface compatibility between graphene and polyethylene. The prepared composite material has excellent mechanical properties and thermal conductivity.

[0033] Optionally, the screw speed of the extruder is set to 100-150 rpm, and the temperature of each zone from the feeding section to the die section is 160-180°C, 180-200°C, 200-220°C, and 220-240°C, respectively.

[0034] In a third aspect, the present application provides a method for preparing a hybrid graphene-modified polyethylene composite material, using the following technical solution:

[0035] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0036] (1) Graphene oxide pretreatment: The graphene oxide is dried at 60° C. for 24 h to remove moisture and impurities, and then the dried graphene oxide is added to anhydrous ethanol and polyethylene wax, and dispersed at a speed of 2000 to 3000 rpm for 30 to 60 min to obtain a uniformly dispersed graphene oxide suspension;

[0037] (2) HDPE particle pretreatment: HDPE particles were dried at 80 °C for 12 h to remove moisture;

[0038] (3) In-situ polymerization: adding initiator benzoyl peroxide and catalyst triethylaluminum to the pretreated graphene oxide suspension, introducing gaseous ethylene monomer, and carrying out in-situ polymerization at 60-80° C. for 3-5 h under nitrogen protection to form graphene oxide / polyethylene composite particles;

[0039] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles. Silicon nitride, carbon nanotubes, silane coupling agent KH-550, self-healing microcapsules, sponge microneedles and triphenyl phosphate are also added. The mixture is melt blended by a twin-screw extruder and extruded into granules to obtain a hybrid graphene-modified polyethylene composite material.

[0040] Optionally, the screw speed of the extruder is set to 100-150 rpm, and the temperature of each zone from the feeding section to the die section is 160-180°C, 180-200°C, 200-220°C, and 220-240°C, respectively.

[0041] In a fourth aspect, the present application provides an application of a hybrid graphene-modified polyethylene composite material, using the following technical solution:

[0042] The invention discloses an application of a hybrid graphene-modified polyethylene composite material. The hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. Graphene oxide has better dispersibility than graphene. Polyethylene wax as a dispersant can effectively reduce the agglomeration of graphene and improve its dispersibility in the polyethylene matrix; silane coupling agent KH-550 is used to improve the interfacial compatibility between graphene and polyethylene and enhance the bonding between the two. The polyethylene matrix consists of two parts. One part is firstly prepared into composite particles by in-situ polymerization of ethylene monomer and graphene oxide, which can improve the compatibility of graphene oxide and polyethylene and enhance its bonding. Then the composite particles are melt-blended with HDPE particles. The composite particles can be better dispersed in the HDPE matrix and have stronger interfacial compatibility. Self-repairing capsules can play a self-repairing role in the process of composite material preparation and subsequent application, continuously improve the performance of the material, and make up for the influence of the residual agglomeration of graphene oxide on the thermal conductivity and mechanical properties of the composite material. Therefore, the dispersion of graphene oxide in the polyethylene matrix and the interfacial compatibility between graphene oxide and polyethylene are improved at the same time, thereby improving the thermal conductivity and mechanical properties of the composite material.

[0045] 2. In the present application, triphenyl phosphate is preferably used as a nucleating agent. In the polyethylene matrix, it can improve and promote grain refinement during the crystallization process and increase the number of crystals, thereby making the composite material denser. The sponge microneedles have a unique needle-like microstructure. When combined with triphenyl phosphate, it can further enhance the effect of grain refinement. It can also be effectively connected with graphene oxide to form a high-strength network structure inside the composite material, further enhancing the thermal conductivity and mechanical properties of the composite material.

[0046] 3. The method of the present application effectively improves the interfacial compatibility between graphene oxide and polyethylene by combining in-situ polymerization with melt blending. The prepared composite material has excellent mechanical properties and thermal conductivity. DETAILED DESCRIPTION

[0047] The present application is further described in detail with reference to the following examples. It is specially noted that if no specific conditions are specified in the following examples, the conventional conditions or the conditions recommended by the manufacturer are followed, and the raw materials used in the following examples can be obtained from common commercial sources unless otherwise specified.

[0048] HDPE granules, melt flow index (MFI) is 0.5g / 10min, density is 0.96g / cm 3 .

[0049] Graphene oxide, diameter 0.5μm, thickness 1nm, 5 layers.

[0050] Silicon nitride, particle size 800 mesh, active ingredient content 99.5%.

[0051] Carbon nanotubes, single-walled carbon nanotubes, particle size 5μm, active ingredient content 99.9%.

[0052] Ethylene monomer, pure ethylene gas.

[0053] Wollastonite whisker, CAS No. 1344-95-2, particle size 8μm, aspect ratio 32.

[0054] Methyl methacrylate, molecular weight 500,000, 100 mesh.

[0055] Sponge microneedle, first level, needle length 200μm, diameter 10μm.

[0056] Preparation example of self-healing microcapsules

[0057] Preparation Example 1

[0058] The self-healing microcapsules have wollastonite whiskers as the capsule core, methyl methacrylate as the healing agent, and polysiloxane / silicon dioxide composite materials as the capsule wall.

[0059] The preparation method of self-repairing microcapsules is as follows:

[0060] 10 kg of wollastonite whiskers were taken and surface-modified by spray coating using 0.2 kg of silane coupling agent KH-570.

[0061] Take 5 kg of tetraethyl orthosilicate and 5 kg of methyltrimethoxysilane, first add hydrochloric acid to anhydrous ethanol to adjust the pH to 3.5, then gradually add tetraethyl orthosilicate and methyltrimethoxysilane to the anhydrous ethanol at a concentration of 0.1 M, stir at 500 rpm at room temperature until the mixture is uniformly mixed, react for 6 hours to generate capsule wall material, centrifuge and filter, extract the capsule wall material from the reaction system, wash and dry to obtain the capsule wall.

[0062] Take 80 kg of methyl methacrylate and dissolve it in anhydrous ethanol, add 2 kg of initiator benzoyl peroxide, stir evenly, then add surface-modified wollastonite whiskers, stir at a speed of 4000 rpm until evenly dispersed, to form a capsule core / healing agent mixture;

[0063] The capsule wall material is added to the capsule core / healing agent mixture, stirred at 400 rpm until uniformly dispersed, and then spray-dried to obtain self-healing microcapsules. The feed rate during spray drying is 200 ml per hour, the inlet air temperature is 120°C, the outlet air temperature is 60°C, the nozzle is a centrifugal nozzle, and the particle size is controlled to be 20 μm.

[0064] Preparation Example 2

[0065] The difference between this preparation example and preparation example 1 is that there is no wollastonite whisker in this preparation example.

[0066] Preparation Example 3

[0067] The difference between this preparation example and preparation example 1 is that methyl methacrylate is not contained in this preparation example.

[0068] Preparation Example 4

[0069] The difference between this preparation example and preparation example 1 is that the capsule wall in this preparation example is chitosan.

[0070] Example

[0071] Example 1

[0072] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0073] 40 kg of HDPE particles; 8 kg of graphene oxide; 5 kg of silicon nitride; 7 kg of carbon nanotubes; 34 kg of ethylene monomer; 0.6 kg of polyethylene wax; 0.6 kg of silane coupling agent KH-550; and 0.4 kg of the self-healing microcapsules prepared in Preparation Example 1.

[0074] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0075] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 2000 rpm for 60 min to obtain a uniformly dispersed graphene oxide suspension.

[0076] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0077] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 60° C. for 5 h to form graphene oxide / polyethylene composite particles.

[0078] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550 and self-healing microcapsules are added at the same time, and melt blended by a twin-screw extruder, extruded and granulated to obtain a hybrid graphene-modified polyethylene composite material. The screw speed of the extruder is set to 100 rpm, and the temperatures of each zone from the feeding section to the die section are 160°C, 180°C, 200°C, and 220°C, respectively.

[0079] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0080] Example 2

[0081] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0082] 38kg of HDPE particles; 9kg of graphene oxide; 6kg of silicon nitride; 8kg of carbon nanotubes; 37kg of ethylene monomer; 0.7kg of polyethylene wax; 0.7kg of silane coupling agent KH-550; and 0.6kg of the self-healing microcapsules prepared in Preparation Example 1.

[0083] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0084] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 2500 rpm for 45 min to obtain a uniformly dispersed graphene oxide suspension.

[0085] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0086] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 70°C for 4 hours to form graphene oxide / polyethylene composite particles.

[0087] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550 and self-healing microcapsules are added at the same time, and melt blended by a twin-screw extruder, extruded and granulated to obtain a hybrid graphene-modified polyethylene composite material. The screw speed of the extruder is set to 120 rpm, and the temperatures of each zone from the feeding section to the die section are 170°C, 190°C, 210°C, and 230°C, respectively.

[0088] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0089] Example 3

[0090] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0091] 36 kg of HDPE particles; 10 kg of graphene oxide; 8 kg of silicon nitride; 9 kg of carbon nanotubes; 40 kg of ethylene monomer; 0.8 kg of polyethylene wax; 0.8 kg of silane coupling agent KH-550; and 0.8 kg of self-healing microcapsules prepared in Preparation Example 1.

[0092] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0093] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 3000 rpm for 30 min to obtain a uniformly dispersed graphene oxide suspension.

[0094] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0095] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 80° C. for 3 h to form graphene oxide / polyethylene composite particles.

[0096] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550 and self-healing microcapsules are added at the same time, and melt blended by a twin-screw extruder, extruded and granulated to obtain a hybrid graphene-modified polyethylene composite material. The screw speed of the extruder is set to 150 rpm, and the temperatures of each zone from the feeding section to the die section are 180°C, 200°C, 220°C, and 240°C, respectively.

[0097] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0098] Example 4

[0099] The difference between this embodiment and embodiment 2 is that the self-repairing microcapsules are prepared by preparation example 2.

[0100] Example 5

[0101] The difference between this embodiment and embodiment 2 is that the self-repairing microcapsules are prepared by preparation example 3.

[0102] Example 6

[0103] The difference between this embodiment and embodiment 2 is that the self-repairing microcapsules are prepared by preparation example 4.

[0104] Example 7

[0105] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0106] 40kg HDPE particles; 8kg graphene oxide; 5kg silicon nitride; 7kg carbon nanotubes; 34kg ethylene monomer; 0.6kg polyethylene wax; 0.6kg silane coupling agent KH-550; 0.4kg self-healing microcapsules prepared in Preparation Example 1; 0.3kg sponge microneedles; 0.2kg triphenyl phosphate.

[0107] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0108] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 2000 rpm for 60 min to obtain a uniformly dispersed graphene oxide suspension.

[0109] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0110] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 60° C. for 5 h to form graphene oxide / polyethylene composite particles.

[0111] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550, self-healing microcapsules, sponge microneedles and triphenyl phosphate are added at the same time, and melt blended by a twin-screw extruder, extruded and granulated to obtain a hybrid graphene-modified polyethylene composite material. The screw speed of the extruder is set to 100 rpm, and the temperatures of each zone from the feeding section to the die section are 160°C, 180°C, 200°C, and 220°C, respectively.

[0112] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0113] Example 8

[0114] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0115] 38kg HDPE particles; 9kg graphene oxide; 6kg silicon nitride; 8kg carbon nanotubes; 37kg ethylene monomer; 0.7kg polyethylene wax; 0.7kg silane coupling agent KH-550; 0.6kg self-healing microcapsules prepared in Preparation Example 1; 0.4kg sponge microneedles; 0.3kg triphenyl phosphate.

[0116] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0117] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 2500 rpm for 45 min to obtain a uniformly dispersed graphene oxide suspension.

[0118] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0119] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 70°C for 4 hours to form graphene oxide / polyethylene composite particles.

[0120] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550, self-healing microcapsules, sponge microneedles and triphenyl phosphate are added at the same time, and melt blended by a twin-screw extruder, and extruded and granulated to obtain a hybrid graphene-modified polyethylene composite material. The screw speed of the extruder is set to 120 rpm, and the temperatures of each zone from the feeding section to the die section are 170°C, 190°C, 210°C, and 230°C, respectively.

[0121] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0122] Example 9

[0123] A hybrid graphene-modified polyethylene composite material comprises the following raw materials:

[0124] 36kg HDPE particles; 10kg graphene oxide; 8kg silicon nitride; 9kg carbon nanotubes; 40kg ethylene monomer; 0.8kg polyethylene wax; 0.8kg silane coupling agent KH-550; 0.8kg self-healing microcapsules prepared in Preparation Example 1; 0.5kg sponge microneedles; 0.4kg triphenyl phosphate.

[0125] A method for preparing a hybrid graphene-modified polyethylene composite material comprises the following steps:

[0126] (1) Graphene oxide pretreatment: The graphene oxide was dried at 60° C. for 24 h to remove moisture and impurities. Then, the dried graphene oxide was added to anhydrous ethanol, with the ratio of graphene oxide to anhydrous ethanol being 1:5, and polyethylene wax was added at the same time, and the mixture was dispersed at a speed of 3000 rpm for 30 min to obtain a uniformly dispersed graphene oxide suspension.

[0127] (2) HDPE particle pretreatment: HDPE particles were dried at 80°C for 12 h to remove moisture.

[0128] (3) In situ polymerization: 0.1 kg of initiator benzoyl peroxide and 0.02 kg of catalyst triethylaluminum were added to the pretreated graphene oxide suspension, and gaseous ethylene monomer was introduced. Under nitrogen protection, in situ polymerization was carried out at 80° C. for 3 h to form graphene oxide / polyethylene composite particles.

[0129] (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles, and silicon nitride, carbon nanotubes, silane coupling agent KH-550, self-healing microcapsules, sponge microneedles and triphenyl phosphate are added at the same time, and melt blended by a twin-screw extruder, extruded and granulated to obtain a hybrid graphene modified polyethylene composite material. The screw speed of the extruder is set to 150 rpm, and the temperatures of each zone from the feeding section to the die section are 180°C, 200°C, 220°C, and 240°C, respectively.

[0130] An application of a hybrid graphene-modified polyethylene composite material, wherein the hybrid graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0131] Example 10

[0132] The difference between this embodiment and embodiment 8 is that there are no sponge microneedles in this embodiment.

[0133] Embodiment 11

[0134] The difference between this embodiment and embodiment 8 is that there is no triphenyl phosphate in this embodiment.

[0135] Comparative Example

[0136] Comparative Example 1

[0137] A graphene-modified polyethylene composite material comprises 23 kg of graphene and 75 kg of HDPE particles.

[0138] A method for preparing a graphene-modified polyethylene composite material comprises the following steps: adding graphene and HDPE particles into a hopper of a twin-screw extruder, performing melt blending through the twin-screw extruder, and extruding and granulating to obtain the graphene-modified polyethylene composite material. The screw speed of the extruder is set to 120 rpm, and the temperatures of each zone from the feeding section to the die section are 170° C., 190° C., 210° C., and 230° C., respectively.

[0139] An application of a graphene-modified polyethylene composite material, wherein the graphene-modified polyethylene composite material is extruded, water-cooled, drawn and cut to obtain a graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system. The pipe specification is PN1.6MPa, dn32mm*en3.0mm, the pipe extrusion temperature is 200°C, and the extrusion speed is 7m / min.

[0140] Comparative Example 2

[0141] The difference between this comparative example and Example 2 is that HDPE particles are used to replace ethylene monomers, there is no in-situ polymerization reaction, no polyethylene wax, silane coupling agent KH-550 and self-healing microcapsules, and the hybrid graphene-modified polyethylene composite material is prepared only by melt blending.

[0142] Comparative Example 3

[0143] The difference between this comparative example and Example 2 is that this comparative example does not contain polyethylene wax, silane coupling agent KH-550 and self-repairing microcapsules.

[0144] Comparative Example 4

[0145] The difference between this comparative example and Example 2 is that there is no polyethylene wax and silane coupling agent KH-550 in this comparative example.

[0146] Comparative Example 5

[0147] The difference between this comparative example and Example 2 is that there is no polyethylene wax and self-repairing microcapsules in this comparative example.

[0148] Comparative Example 6

[0149] The difference between this comparative example and Example 2 is that there is no silane coupling agent KH-550 and self-repairing microcapsule in this comparative example.

[0150] Comparative Example 7

[0151] The difference between this comparative example and Example 2 is that there is no polyethylene wax in this comparative example.

[0152] Comparative Example 8

[0153] The difference between this comparative example and Example 2 is that there is no silane coupling agent KH-550 in this comparative example.

[0154] Comparative Example 9

[0155] The difference between this comparative example and Example 2 is that there is no self-repairing microcapsule in this comparative example.

[0156] Comparative Example 10

[0157] The difference between this comparative example and Example 2 is that HDPE particles are used to replace ethylene monomers, there is no in-situ polymerization reaction, and the hybrid graphene-modified polyethylene composite material is obtained only by melt blending.

[0158] Comparative Example 11

[0159] The difference between this comparative example and Example 2 is that graphene oxide is used instead of silicon nitride and carbon nanotubes.

[0160] Table 1 Raw material dosage of each embodiment and comparative example

[0161]

[0162]

[0163] Performance testing

[0164] Detection Methods

[0165] With reference to "GB / T 1040.2-2022 Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics", type 1A specimens were used, and the composite materials prepared in each embodiment and comparative example were tested after sample preparation. The tensile strength is shown in Table 2.

[0166] According to "GB / T 9341-2008 Determination of flexural properties of plastics", the sample size is 80mm×10mm×4mm, and the span is set to 64mm. The bending load is applied at a rate of 2mm / min until the sample breaks. The composite materials prepared in each embodiment and comparative example are tested after sample preparation, and the flexural strength is shown in Table 2.

[0167] With reference to "ASTM E1461-13 Standard Test Method for Thermal Diffusivity by Flash Method", the test temperature was 28°C, and the composite materials prepared in each embodiment and comparative example were tested after sample preparation. The thermal conductivity coefficients are shown in Table 2.

[0168] Table 2 Test results of various embodiments and comparative examples

[0169]

[0170] It can be seen from Example 2 and Comparative Example 1 and Table 2 that the hybrid graphene-modified polyethylene composite material prepared in the present application has excellent thermal conductivity and mechanical properties.

[0171] Combining Example 2 and Comparative Examples 1 to 10 and Table 2, it can be seen that polyethylene wax is used as a dispersant to improve the dispersibility of graphene oxide, and then graphene oxide and ethylene monomer are polymerized by in situ polymerization to form composite particles, which are then melt-blended with HDPE particles. During melt blending, silane coupling agent KH-550 and self-healing microcapsules are compounded. During the preparation process, the dispersibility of graphene oxide in polyethylene is improved, and the interface compatibility of graphene oxide and polyethylene is also improved. The hybrid graphene-modified polyethylene composite material finally obtained has excellent thermal conductivity and mechanical properties.

[0172] Combining Example 2 with Example 4, Example 5, Example 6 and Table 2, it can be seen that when the self-healing capsule uses wollastonite whiskers as the capsule core, methyl methacrylate as the healing agent, and a polysiloxane / silicon dioxide composite material as the capsule wall, the obtained hybrid graphene-modified polyethylene composite material has better thermal conductivity and mechanical properties.

[0173] Combining Example 2 and Example 8 with Table 2, it can be seen that when sponge microneedles and triphenyl phosphate are added to the composite material, the thermal conductivity and mechanical properties of the composite material are further improved. And only when the two are added at the same time, the effect is the best.

[0174] It can be seen from Example 2 and Comparative Example 11 and Table 2 that when graphene oxide, silicon nitride and carbon nanotubes are used as thermal conductive raw materials in the composite material, the thermal conductive performance of the composite material is the best.

[0175] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A hybrid graphene-modified polyethylene composite material, characterized in that: The invention comprises the following raw materials in parts by weight: 36-40 parts of HDPE granules; 8-10 parts of graphene oxide; 5-8 parts of silicon nitride; 7-9 parts of carbon nanotubes; 34-40 parts of ethylene monomer; 0.6-0.8 parts of polyethylene wax; Silane coupling agent KH-550 0.6-0.8 parts; 0.4-0.8 parts of self-repairing microcapsules.

2. A hybrid graphene-modified polyethylene composite material according to claim 1, characterized in that: The self-healing microcapsules have wollastonite whiskers as the capsule core, methyl methacrylate as the healing agent, and polysiloxane / silicon dioxide composite materials as the capsule wall.

3. A hybrid graphene-modified polyethylene composite material according to claim 2, characterized in that: The preparation method of self-repairing microcapsules is as follows: Take 10 parts by weight of wollastonite whiskers and use 0.2 parts by weight of silane coupling agent KH-570 for surface modification; Take 5 parts by weight of tetraethyl orthosilicate and 5 parts by weight of methyltrimethoxysilane, first add hydrochloric acid to anhydrous ethanol to adjust the pH to 3.5, then gradually add tetraethyl orthosilicate and methyltrimethoxysilane to anhydrous ethanol at a concentration of 0.1 M, stir at room temperature until the mixture is uniformly mixed, react for 6 hours to generate capsule wall material, centrifuge, filter, wash and dry; 80 parts by weight of methyl methacrylate is dissolved in anhydrous ethanol, 2 parts by weight of initiator benzoyl peroxide is added, and stirred evenly, and then surface-modified wollastonite whiskers are added, and stirred until uniformly dispersed to form a capsule core / healing agent mixture; The capsule wall material is added into the capsule core / healing agent mixture, stirred until uniformly dispersed, and then spray-dried to obtain the self-repairing microcapsules.

4. The hybrid graphene-modified polyethylene composite material according to claim 1, characterized in that: The composite material also includes 0.3-0.5 weight parts of sponge microneedles and 0.2-0.4 weight parts of triphenyl phosphate.

5. The method for preparing a hybrid graphene-modified polyethylene composite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Graphene oxide pretreatment: The graphene oxide is dried at 60° C. for 24 h to remove moisture and impurities, and then the dried graphene oxide is added to anhydrous ethanol and polyethylene wax, and dispersed at a speed of 2000 to 3000 rpm for 30 to 60 min to obtain a uniformly dispersed graphene oxide suspension; (2) HDPE particle pretreatment: HDPE particles were dried at 80 °C for 12 h to remove moisture; (3) In-situ polymerization: adding initiator benzoyl peroxide and catalyst triethylaluminum to the pretreated graphene oxide suspension, introducing gaseous ethylene monomer, and carrying out in-situ polymerization at 60-80° C. for 3-5 h under nitrogen protection to form graphene oxide / polyethylene composite particles; (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles. Silicon nitride, carbon nanotubes, silane coupling agent KH-550 and self-healing microcapsules are also added. The mixture is melt blended by a twin-screw extruder and extruded to obtain a hybrid graphene-modified polyethylene composite material.

6. The method for preparing a hybrid graphene-modified polyethylene composite material according to claim 5, characterized in that: The screw speed of the extruder is set to 100-150 rpm, and the temperature of each zone from the feeding section to the die section is 160-180°C, 180-200°C, 200-220°C, and 220-240°C, respectively.

7. The method for preparing a hybrid graphene-modified polyethylene composite material according to claim 4, characterized in that: The following steps are involved: (1) Graphene oxide pretreatment: The graphene oxide is dried at 60° C. for 24 h to remove moisture and impurities, and then the dried graphene oxide is added to anhydrous ethanol and polyethylene wax, and dispersed at a speed of 2000 to 3000 rpm for 30 to 60 min to obtain a uniformly dispersed graphene oxide suspension; (2) HDPE particle pretreatment: HDPE particles were dried at 80 °C for 12 h to remove moisture; (3) In-situ polymerization: adding initiator benzoyl peroxide and catalyst triethylaluminum to the pretreated graphene oxide suspension, introducing gaseous ethylene monomer, and carrying out in-situ polymerization at 60-80° C. for 3-5 h under nitrogen protection to form graphene oxide / polyethylene composite particles; (4) Melt blending: The graphene oxide / polyethylene composite particles obtained by in-situ polymerization are added to the hopper of a twin-screw extruder together with HDPE particles. Silicon nitride, carbon nanotubes, silane coupling agent KH-550, self-healing microcapsules, sponge microneedles and triphenyl phosphate are also added. The mixture is melt blended by a twin-screw extruder and extruded into granules to obtain a hybrid graphene-modified polyethylene composite material.

8. The method for preparing a hybrid graphene-modified polyethylene composite material according to claim 7, characterized in that: The screw speed of the extruder is set to 100-150 rpm, and the temperature of each zone from the feeding section to the die section is 160-180°C, 180-200°C, 200-220°C, and 220-240°C, respectively.

9. The use of a hybrid graphene-modified polyethylene composite material according to any one of claims 1 to 8, characterized in that: The hybrid graphene-modified polyethylene composite material is subjected to extrusion, water-cooling shaping, pulling and cutting to obtain a hybrid graphene-modified polyethylene composite material pipe, which can be applied to a ground source heat pump system.

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