High-thermal-conductivity phase-change energy-storage wood-plastic composite material and preparation method thereof

Abstract

The invention discloses a high-thermal-conductivity phase-change energy-storage wood-plastic composite material and a preparation method thereof.The method comprises the following steps that 1, wood fiber powder is treated, specifically, epoxy fatty acid methyl ester, a silane coupling agent and a solvent are evenly mixed and then sprayed to the surface of the wood fiber powder, then stirring treatment and drying treatment are conducted, and the treated wood fiber powder is obtained; (2) granulating; (3) mixing the materials; and (4) adopting a co-extrusion process for extrusion molding, respectively melting and extruding the core layer material and the surface layer material by using two extruders, and shaping by using a three-layer co-extrusion mold to obtain the high-thermal-conductivity phase-change energy-storage wood-plastic composite material. The phase change heat storage microcapsule used in the invention constructs a heat conduction and heat storage link in the wood-plastic composite material, the heat conduction coefficient during heat storage and heat release is improved, and the energy storage efficiency of the material is improved by nearly 200%.

Description

Technical Field

[0001] The present invention relates to the technical field of wood-plastic composite materials, and in particular to a high-thermal-conductivity phase-change energy-storage wood-plastic composite material and a preparation method thereof. Background Art

[0002] Wood-plastic composites (WPCs), a new type of composite material, are made from low-value, waste biomass fibers such as wood waste, bamboo, chestnut shells, and cotton stalks, combined with various plastic products. They combine the advantages of easy molding, excellent dimensional stability, non-toxicity, odorlessness, and resistance to moths and decay, making them environmentally friendly and green materials. With their increasing application in furniture and construction, WPCs hold a promising future.

[0003] However, the functions of wood-plastic composite materials are relatively simple, while green phase change energy storage materials can achieve energy saving and temperature regulation through phase transition. Introducing them can give wood-plastic composite materials new functions, enabling the wood-plastic composite materials to respond to ambient temperature and efficiently store and convert thermal energy, which is of great significance to the development of new bio-based green energy-saving materials.

[0004] The project focused on phase-change thermal storage materials and conducted research on the preparation of microcapsule-type phase-change thermal storage materials, the preparation and performance of polymer phase-change energy storage composite wood-plastic profiles, and designed a core-shell microcapsule-type phase-change thermal storage material with high thermal storage density and excellent thermal properties. It also constructed a functional material that combines phase-change energy storage materials with wood-plastic composite materials. The project addressed the interfacial compatibility issues between biomass materials such as waste wood fiber, recycled polymers, and porous and microcapsule-type phase-change thermal storage materials. Through the exploration and optimization of the extrusion process, a biomass polymer phase-change energy storage composite wood-plastic profile with temperature regulation function was prepared for application in the construction field to regulate indoor building temperatures and achieve energy conservation. Summary of the Invention

[0005] The main purpose of the present invention is to provide a high thermal conductivity phase change energy storage wood-plastic composite material and a preparation method thereof.

[0006] To achieve the above object, the present invention provides a method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material, comprising the following steps:

[0007] (1) Treatment of wood fiber powder

[0008] The epoxy fatty acid methyl ester, the silane coupling agent and the solvent are mixed and sprayed on the surface of the wood fiber powder, followed by stirring and drying to obtain the treated wood fiber powder;

[0009] (2) Granulation

[0010] The treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, crosslinking agent and pigment masterbatch are mixed evenly, and then extruded and granulated to obtain wood plastic particles;

[0011] (3) Mixing

[0012] The phase change heat storage microcapsules and wood plastic particles are mixed evenly to prepare the core layer material;

[0013] The surface material is prepared by uniformly mixing silicon dioxide, sarling resin, high-density polyethylene, a compatibilizer, a lubricant and a pigment masterbatch;

[0014] (4) Extrusion molding

[0015] The co-extrusion process is adopted, and the core layer material and the surface layer material are melt-extruded respectively by two extruders, and are shaped by a three-layer co-extrusion die to obtain the high thermal conductivity phase change energy storage wood-plastic composite material.

[0016] Furthermore, in step (1), the silane coupling agent is KH550, the solvent is methanol or ethanol, the mass ratio of epoxy fatty acid methyl ester, KH550 and solvent is 45:45:10, and the total amount of the three is 2.5-3wt% of the wood fiber powder.

[0017] Furthermore, in step (1), the stirring speed is 10-20 rpm, the time is 30 min, and the drying temperature is 105° C., and the time is 4 h.

[0018] Furthermore, in step (2), the crosslinking agent is TAIC, and the mass ratio of the treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, TAIC and pigment masterbatch is 55:27:3:1:1.

[0019] Furthermore, in step (2), the temperature of extrusion granulation is 170-195°C.

[0020] Furthermore, in step (3), in the core layer material, the mass ratio of phase change heat storage microcapsules to wood plastic particles is 15:85.

[0021] Furthermore, in step (3), in the surface material, the mass ratio of silica, surrin resin, high-density polyethylene, compatibilizer, lubricant and pigment masterbatch is 1:20:70:3:3:3; the compatibilizer is maleic anhydride grafted polyethylene or glycidyl methacrylate grafted polyethylene, and the lubricant is stearic acid metal salt or polyol ester.

[0022] Furthermore, in step (4), the melt extrusion conditions of the core layer material are a barrel temperature of 190 to 210° C. and a screw speed of 80 to 120 r / min.

[0023] Furthermore, in step (4), the melt extrusion conditions of the surface layer material are a barrel temperature of 130 to 180° C. and a screw speed of 15 to 22 r / min.

[0024] The present invention also provides a high thermal conductivity phase change energy storage wood-plastic composite material, which is prepared according to the above method.

[0025] The microstructure of a composite material directly determines its mechanical properties and interface properties. The present invention has made the following innovations in terms of interface compatibility:

[0026] (1) Surface treatment of wood fiber powder: using epoxy fatty acid methyl ester to treat wood powder. On the one hand, the epoxy group can react with the hydroxyl group on the surface of the wood powder to form a chemical bond. On the other hand, the long chain of aliphatic hydrocarbon can be entangled with the polyethylene molecules, thereby effectively improving the compatibility of wood powder and resin matrix. The coupling effect of silane coupling agent KH550 can improve the compatibility of wood powder and plastic.

[0027] (2) In addition to using the compatibilizer maleic anhydride to graft polyethylene, the cross-linking agent TAIC is also used as a compatibilizer. This compatibilizer can not only increase the compatibility of the phase change material with wood / bamboo powder, but also improve the interface bonding between the recycled PE and the phase change material resin.

[0028] (3) The unique honeycomb structure of the phase change heat storage microcapsules improves their dispersibility in the plastic matrix, and their increased surface area strengthens the interfacial adhesion and bonding between the plastic and wood powder. The honeycomb shape of the phase change heat storage microcapsules allows the wood fibers to be embedded in the plastic matrix, forming a cross-linked network structure, which improves the overall compatibility. The hydrogen bonding effect also improves the interfacial adhesion of the material. Good interfacial adhesion enables the composite material to withstand more tensile loads.

[0029] These interfacial compatibility technologies significantly enhance the compatibility between the components of the biomass polymer phase-change energy storage composite wood-plastic profile, overcoming the significant challenge of phase-change material self-aggregation, which can lead to large-scale phase separation and severely impact the material's mechanical properties. During destructive testing, the fracture surface exhibited a denser structure with no extended cracks, and the substrate remained tightly wrapped around the filler, demonstrating excellent interfacial adhesion.

[0030] The beneficial effects of the present invention are embodied in:

[0031] This invention improves the thermal conductivity of composite materials. Because biomass and polymer materials have low thermal conductivity, and the phase change material is encapsulated within the composite profile, heat transfer and removal are difficult. By combining phase change energy storage materials with highly thermally conductive materials, a thermal link is constructed, enhancing thermal conductivity and maximizing the material's energy storage efficiency. This overcomes the problem of phase change thermal storage materials prone to agglomeration, which affects the material's heat transfer and storage. The phase change thermal storage microcapsules used in this invention create a thermal link within the wood-plastic composite material, improving thermal conductivity during both heat storage and release, and increasing the material's energy storage efficiency by nearly 200%. DETAILED DESCRIPTION

[0032] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0033] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art.

[0034] The wood fiber powder is poplar wood powder with a diameter of 20 to 80 meshes and an aspect ratio of 1 to 2:1;

[0035] Polyethylene: purchased from Aladdin, brand P434349.

[0036] High-density polyethylene: purchased from Dow Materials Science Company, DOW TM DMDA-8007NT 7, High Density Polyethylene Resin; Maleic anhydride grafted polyethylene: purchased from DuPont Company, USA, brand 4208.

[0037] Maleic anhydride grafted polyethylene: purchased from DuPont, USA, brand 4208.

[0038] Surlyn resin: brand EM PC-2000, purchased from DuPont, USA;

[0039] Glycidyl methacrylate grafted polyethylene: purchased from Basel, model PX2250, grafting rate 1%.

[0040] The preparation method of phase change heat storage microcapsules is as follows:

[0041] (1) Preparation of melamine formaldehyde prepolymer solution

[0042] Pour PEG (polyethylene glycol) into a three-necked flask, add deionized water (50-60 times the mass of PEG), stir evenly, and adjust the pH to 5 with acetic acid. Place the three-necked flask in a 95°C water bath and slowly add melamine while stirring. After the reaction has proceeded for 2 hours, add formaldehyde, and then adjust the pH of the solution to 9 with triethanolamine. Finally, heat in a 75°C water bath and stir continuously until a transparent melamine-formaldehyde prepolymer solution is obtained. The molar mass ratio of PEG:melamine:formaldehyde is 1.05:1:1.1.

[0043] (2) Preparation of paraffin emulsion

[0044] SMA (octadecyl methacrylate) was added to 50°C deionized water (200-250 times the mass of SMA), and sodium hydroxide (8.5-9 times the mass of SMA) was added to fully hydrolyze it. After the hydrolysis was completed, the pH was adjusted to 5 with acetic acid, and then paraffin (50-55 times the mass of SMA) was added. The mixture was stirred for 20 minutes at a speed of 4000-8000 rpm using a high-speed emulsifying homogenizer to obtain a paraffin emulsion.

[0045] (3) Preparation of MicroPCM (Phase Change Thermal Storage Microcapsules)

[0046] Pour the paraffin emulsion into a three-necked flask, add boron nitride particles with a particle size of 380 mesh, place it in a 60℃ water bath and continue stirring and heating, then slowly add the melamine formaldehyde prepolymer solution drop by drop, continue stirring and react for 2.5 hours after the addition is completed, then increase the water bath temperature to 75℃, continue the reaction for 1.5 hours, finally filter with a sand core funnel and wash twice with deionized water, and after drying (45℃, 24 hours), a white powder is obtained, which is the phase change heat storage microcapsule. The mass ratio of paraffin emulsion to boron nitride particles and melamine formaldehyde prepolymer solution is 1:0.5:2.

[0047] Example 1

[0048] Preparation of high thermal conductivity phase change energy storage wood-plastic composites

[0049] The preparation method is as follows:

[0050] (1) Treatment of wood fiber powder

[0051] Epoxy fatty acid methyl ester, silane coupling agent KH550 and methanol were mixed and sprayed on the surface of wood fiber powder. The mass ratio of epoxy fatty acid methyl ester, KH550 and methanol was 45:45:10, and the total amount of the three was 2.5wt% of the wood fiber powder. Then, the mixture was stirred at a stirring speed of 10 rpm for 30 minutes and then dried at 105°C for 4 hours to obtain the treated wood fiber powder.

[0052] (2) Granulation

[0053] The treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, crosslinking agent TAIC and pigment masterbatch are uniformly mixed, and the mass ratio of the treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, TAIC and pigment masterbatch is 55:27:3:1:1, and then extruded and granulated at 170°C to obtain wood plastic particles;

[0054] (3) Mixing

[0055] Phase change heat storage microcapsules and wood plastic particles are mixed evenly in a mass ratio of 15:85 to prepare a core layer material;

[0056] Silicon dioxide, surlyn resin, high-density polyethylene, maleic anhydride grafted polyethylene as a compatibilizer, zinc stearate as a lubricant, and pigment masterbatch are uniformly mixed in a mass ratio of 1:20:70:3:3:3 to prepare a surface layer material;

[0057] (4) Extrusion molding

[0058] A co-extrusion process is adopted, and two extruders are used to melt and extrude the core layer material and the surface layer material respectively. The melt extrusion conditions of the core layer material are a barrel temperature of 190°C and a screw speed of 120r / min, and the melt extrusion conditions of the surface layer material are a barrel temperature of 130°C and a screw speed of 22r / min. The material is shaped by a three-layer co-extrusion die (the core layer material passes through the middle layer, and the surface layer material is evenly distributed through the remaining two layers). The mass ratio of the core layer to the surface layer is 96:4, thereby obtaining the high thermal conductivity phase change energy storage wood-plastic composite material.

[0059] Example 2

[0060] Preparation of high thermal conductivity phase change energy storage wood-plastic composites

[0061] The preparation method is as follows:

[0062] (1) Treatment of wood fiber powder

[0063] Epoxy fatty acid methyl ester, silane coupling agent KH550 and methanol were mixed and sprayed on the surface of wood fiber powder. The mass ratio of epoxy fatty acid methyl ester, KH550 and methanol was 45:45:10, and the total amount of the three was 2.5wt% of the wood fiber powder. Then, the mixture was stirred at a stirring speed of 15 rpm for 30 minutes and then dried at 105°C for 4 hours to obtain the treated wood fiber powder.

[0064] (2) Granulation

[0065] The treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, crosslinking agent TAIC and pigment masterbatch are uniformly mixed, and the mass ratio of the treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, TAIC and pigment masterbatch is 55:27:3:1:1, and then extruded and granulated at 180°C to obtain wood plastic particles;

[0066] (3) Mixing

[0067] Phase change heat storage microcapsules and wood plastic particles are mixed evenly in a mass ratio of 15:85 to prepare a core layer material;

[0068] Silicon dioxide, surlyn resin, high-density polyethylene, maleic anhydride grafted polyethylene as a compatibilizer, zinc stearate as a lubricant, and pigment masterbatch are uniformly mixed in a mass ratio of 1:20:70:3:3:3 to prepare a surface layer material;

[0069] (4) Extrusion molding

[0070] A co-extrusion process is adopted, and two extruders are used to melt and extrude the core layer material and the surface layer material respectively. The melt extrusion conditions of the core layer material are a barrel temperature of 200°C and a screw speed of 100 r / min, and the melt extrusion conditions of the surface layer material are a barrel temperature of 150°C and a screw speed of 20 r / min. The material is shaped by a three-layer co-extrusion die (the core layer material passes through the middle layer, and the surface layer material is evenly distributed through the remaining two layers). The mass ratio of the core layer to the surface layer is 90:10, thereby obtaining the high thermal conductivity phase change energy storage wood-plastic composite material.

[0071] Example 3

[0072] Preparation of high thermal conductivity phase change energy storage wood-plastic composites

[0073] The preparation method is as follows:

[0074] (1) Treatment of wood fiber powder

[0075] Epoxy fatty acid methyl ester, silane coupling agent KH550 and ethanol were mixed and sprayed on the surface of wood fiber powder. The mass ratio of epoxy fatty acid methyl ester, KH550 and ethanol was 45:45:10, and the total amount of the three was 3wt% of the wood fiber powder. Then, the mixture was stirred at a stirring speed of 20 rpm for 30 minutes and then dried at 105°C for 4 hours to obtain the treated wood fiber powder.

[0076] (2) Granulation

[0077] The treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, crosslinking agent TAIC and pigment masterbatch are uniformly mixed, and the mass ratio of the treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, TAIC and pigment masterbatch is 55:27:3:1:1, and then extruded and granulated at 195°C to obtain wood plastic particles;

[0078] (3) Mixing

[0079] Phase change heat storage microcapsules and wood plastic particles are mixed evenly in a mass ratio of 15:85 to prepare a core layer material;

[0080] Silica, surin resin, high-density polyethylene, a compatibilizer, glycidyl methacrylate grafted polyethylene, a lubricant, pentaerythritol ester, and a pigment masterbatch are uniformly mixed in a mass ratio of 1:20:70:3:3:3 to prepare a surface layer material;

[0081] (4) Extrusion molding

[0082] A co-extrusion process is adopted, and two extruders are used to melt and extrude the core layer material and the surface layer material respectively. The melt extrusion conditions of the core layer material are a barrel temperature of 210°C and a screw speed of 80r / min, and the melt extrusion conditions of the surface layer material are a barrel temperature of 180°C and a screw speed of 15r / min. The materials are shaped through a three-layer co-extrusion die (the core layer material passes through the middle layer, and the surface layer material is evenly distributed through the remaining two layers). The mass ratio of the core layer to the surface layer is 93:7, thereby obtaining the high thermal conductivity phase change energy storage wood-plastic composite material.

[0083] Comparative Example 1

[0084] Comparative preparation of wood-plastic composites

[0085] In this comparative example, a wood-plastic composite material was prepared in the same manner as in Example 1, with the only difference being that the addition of phase-change heat storage microcapsules was omitted.

[0086] Material performance testing

[0087] The mechanical properties of the wood-plastic composite materials prepared in Example 1 and Comparative Example 1 were tested for tensile strength (MPa), elongation at break (%), flexural strength (MPa), and flexural modulus (MPa). The results are shown in Table 1 below:

[0088] Table 1

[0089] type Example 1 Comparative Example 1 Tensile strength (MPa) 16 20 Elongation at break (%) 40 40 Flexural strength (MPa) 12 9 Flexural modulus (MPa) 800 3000

[0090] Wood-plastic composite materials were cut into specimens measuring 21 x 140 mm and placed in a 150°C heat environment. Five samples of each were measured at different time intervals using an infrared thermometer, and the average temperature was calculated. The lower the average temperature, the better the thermal storage performance. This is because the phase-change thermal storage microcapsules within the material absorb some heat during the phase change process, thereby slowing the temperature change on the profile surface. The results are shown in Table 2.

[0091] Table 2

[0092]

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material, characterized in that: The following steps are involved: (1) Treatment of wood fiber powder The epoxy fatty acid methyl ester, the silane coupling agent and the solvent are mixed and sprayed on the surface of the wood fiber powder, followed by stirring and drying to obtain the treated wood fiber powder; (2) Granulation The treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, crosslinking agent and pigment masterbatch are mixed evenly, and then extruded and granulated to obtain wood plastic particles; (3) Mixing The phase change heat storage microcapsules and wood plastic particles are mixed evenly to prepare the core layer material; The surface material is prepared by uniformly mixing silicon dioxide, sarling resin, high-density polyethylene, a compatibilizer, a lubricant and a pigment masterbatch; (4) Extrusion molding The co-extrusion process is adopted, and the core layer material and the surface layer material are melt-extruded respectively by two extruders, and are shaped by a three-layer co-extrusion die to obtain the high thermal conductivity phase change energy storage wood-plastic composite material.

2. The method for preparing the high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (1), the silane coupling agent is KH550, the solvent is methanol or ethanol, the mass ratio of epoxy fatty acid methyl ester, KH550 and solvent is 45:45:10, and the total amount of the three is 2.5-3wt% of the wood fiber powder.

3. The method for preparing the high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (1), the stirring speed is 10-20 rpm, the time is 30 min, and the drying temperature is 105° C., and the time is 4 h.

4. The method for preparing the high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (2), the crosslinking agent is TAIC, and the mass ratio of the treated wood fiber powder, polyethylene, maleic anhydride grafted polyethylene, TAIC and pigment masterbatch is 55:27:3:1:

1.

5. The method for preparing the high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (2), the temperature of extrusion granulation is 170-195°C.

6. The method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (3), in the core layer material, the mass ratio of phase change heat storage microcapsules to wood plastic particles is 15:

85.

7. The method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (3), in the surface material, the mass ratio of silica, surrin resin, high-density polyethylene, compatibilizer, lubricant and pigment masterbatch is 1:20:70:3:3:3; the compatibilizer is maleic anhydride grafted polyethylene or glycidyl methacrylate grafted polyethylene, and the lubricant is stearic acid metal salt or polyol ester.

8. The method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (4), the melt extrusion conditions of the core layer material are a barrel temperature of 190 to 210° C. and a screw speed of 80 to 120 r / min.

9. The method for preparing a high thermal conductivity phase change energy storage wood-plastic composite material according to claim 1, wherein: In step (4), the melt extrusion conditions of the surface material are a barrel temperature of 130 to 180° C. and a screw speed of 15 to 22 r / min.

10. A high thermal conductivity phase change energy storage wood-plastic composite material, characterized in that: Prepared according to the method according to any one of claims 1 to 9.

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