Preparation method of multifunctional phase-change transparent wood-based composite material

Abstract

The invention relates to the technical field of wood manufacturing, in particular to a preparation method of a multifunctional phase-change transparent wood-based composite material, which comprises the following steps: delignification of wood through acidic sodium chlorite, modification with silica sol to obtain a porous template, dipping in a PEG / MMA / AIBN / acetone mixed solution, and hot press molding to obtain a phase-change transparent base material; and finally, coating a PDMS solution containing cesium tungsten bronze and strontium aluminate, and performing low-temperature drying twice to obtain the multifunctional composite material. Silica sol pretreatment is combined with a PEG / MMA impregnation and compression technology, the preparation process is simple and easy to implement, leakage of the phase change material can be effectively prevented, meanwhile, the stability and performance consistency of the composite material are improved, the material is suitable for large-scale production, meanwhile, cesium tungsten bronze and strontium aluminate are introduced, the material is endowed with hydrophobicity, light-emitting characteristics and heat shielding capacity, and the material is suitable for large-scale production. And the intelligent building has the functions of photo-thermal management, self-cleaning and decoration, so that diversified application requirements are met.

Description

Technical Field

[0001] This invention relates to the field of wood manufacturing technology, and in particular to a method for preparing a multifunctional phase change transparent wood-based composite material. Background Technology

[0002] With rapid economic development and accelerated urbanization, building energy consumption has become one of the main sources of global energy consumption. Simultaneously, increasing demands for thermal comfort further exacerbate building energy consumption issues, posing greater challenges to energy supply and environmental protection. To address this problem, people have begun to actively explore thermal energy storage technology as a viable solution. Thermal energy storage technology can store and recover excess heat collected during periods of high solar radiation. This technology plays a significant role in improving energy efficiency and provides advantages to different sectors of the energy industry. Among various thermal energy storage technologies, latent heat storage technology based on phase change materials has received widespread attention due to its ease of operation, long cycle life, and high energy density. It has been widely applied in solar energy devices, buildings, temperature control equipment, and industrial waste heat recovery. Phase change materials have the ability to effectively absorb and release large amounts of heat energy in the form of latent heat through a phase change process. By incorporating phase change materials into building components, the energy consumption of building operation can be reduced, providing a new approach to building energy conservation.

[0003] Wood, with its renewable nature, excellent mechanical strength, and good durability, can effectively compete with petroleum-based products and provide a viable solution to environmental sustainability issues. Furthermore, wood's unique porous layered structure makes it highly suitable as a support material for encapsulating phase change materials (PCMs), offering an effective way to address PCM leakage problems. Currently, emerging transparent wood-based composites offer new opportunities in the PCM field. These materials can effectively regulate indoor temperature using photothermal management functions, improving indoor thermal comfort and reducing building energy consumption. Moreover, research on multifunctional transparent wood-based PCMs that combine hydrophobicity, luminescence, and thermal shielding is still relatively limited. Hydrophobicity directly affects the material's stability and durability in humid environments; luminescence can be used to create special lighting environments; and thermal shielding helps reduce energy consumption. These functions collectively form an important foundation for the development of smart building materials. To fully explore the application potential of transparent wood-based PCMs and meet the diverse development needs of smart building materials, functional modification is of great significance. This can help improve their existing performance and endow them with new functional properties, thereby promoting the development of this field towards high performance and wider application.

[0004] The invention patent with patent application number CN201510522111.3 discloses wood-based composite materials and their manufacturing methods, including epoxy resin-infiltrated veneer, epoxy resin-infiltrated thin wood, glue-injected veneer and glue-impregnated thin wood aging, assembly, hot pressing and molding and surface and edge finishing treatment. However, this invention only focuses on structural reinforcement and does not combine energy storage or light transmission. Patent application CN202311383251.8 discloses a translucent opaque wood-based composite material and its preparation method. Specifically, it involves removing lignin and modifying chromophores, and then impregnating and curing pretreated wood materials in titanium dioxide dispersion and methyl methacrylate impregnation solution to obtain a translucent opaque wood-based composite material. However, this invention does not involve phase change materials or multifunctional coatings. In addition, similar research results (such as Yu Ziya, Preparation and Performance Regulation of Transparent Wood-based Composite Materials [D], Shanghai University, 2018) use alkali solution combined with hydrogen peroxide to remove lignin from wood, and then use epoxy resin with matching refractive index to fill the pores of wood to prepare a high light transmittance composite material (visible light transmittance >86%). Cesium tungsten bronze nanoparticles with infrared blocking function are selected as additives for application in energy-saving buildings. However, these studies also do not mention the hydrophobic modification of wood or the introduction of phase change materials, making them unsuitable for thermal management in complex intelligent buildings. Research findings (He Linhan, Ling Kaili, Ren Ruiqing, et al. Study on the performance of wood-based composite phase change thermal storage material with Cu particle-enhanced thermal conductivity [J]. Journal of Beijing Forestry University, 2022, 44(12):132-141.) used acidic sodium chlorite solution to treat balsa wood to improve the encapsulation efficiency of phase change material. Through the solution reduction method of CuSO4 and ascorbic acid solution, monodisperse Cu particles were generated in the wood matrix through multiple cycles. Paraffin (PW) was used as the phase change material to prepare wood-based composite phase change thermal storage material with Cu particle-enhanced thermal conductivity. However, it did not combine other functional materials, nor did it involve the light transmission, hydrophobicity, luminescence and heat shielding functions of wood-based composite materials.

[0005] Therefore, in response to the aforementioned problems, this invention proposes a method for preparing a multifunctional phase change transparent wood-based composite material. The method involves pretreating the wood by soaking delignified wood in a silica sol solution, then impregnating the pretreated wood with a phase change material mixture solution and combining this with a compression process to prepare the phase change transparent wood-based composite material. Finally, a coating modification technique is used to prepare the multifunctional phase change transparent wood-based composite material. This material possesses excellent heat storage, hydrophobic, luminescent, and thermal shielding capabilities, providing a forward-looking solution for the development of advanced thermal management materials in intelligent buildings. Summary of the Invention

[0006] To overcome the problem that existing wood-based phase change composite materials cannot simultaneously possess transparency, hydrophobicity, luminescence, and heat shielding properties, this invention proposes a method for preparing a multifunctional transparent wood-based phase change composite material.

[0007] The technical solution of this invention is: a method for preparing a multifunctional phase change transparent wood-based composite material, comprising: S1, wood is soaked in an acidic sodium chlorite aqueous solution to remove lignin and form a porous skeleton. After washing and drying, it is soaked in a silica sol aqueous solution on the surface of cellulose microfiber to generate a nano silica layer in situ. Then it is washed and freeze-dried to prepare silica sol modified wood template. S2, the silica sol modified wood template obtained in step S1 is impregnated with a mixed solution formed by polyethylene glycol phase change material, methyl methacrylate, 2,2-azobisisobutyronitrile and acetone solvent, then taken out and placed in an oven for a period of time, and then compressed by a hot press to obtain a phase change transparent wood-based composite material. S3, a polydimethylsiloxane solution containing cesium tungsten bronze alcohol solution and strontium aluminate alcohol solution is coated onto the phase change transparent wood matrix composite material obtained in step S2. After drying at low temperature for a period of time, a layer of PDMS is coated on the surface of the phase change transparent wood matrix composite material. After continuing to dry at low temperature, a multifunctional phase change transparent wood matrix composite material is obtained.

[0008] Preferably, the wood in step S1 is balsa wood, and the sodium chlorite aqueous solution has a mass fraction of 2%.

[0009] Preferably, the silica sol aqueous solution in step S1 has a mass fraction of 0-15%.

[0010] Preferably, the polyethylene glycol phase change material in the mixed solution of step S2 is: methyl methacrylate: 2,2-azobisisobutyronitrile: acetone = (30-80): (20-70): (0.05-0.25): 100.

[0011] Preferably, the oven heating temperature in step S2 is 70°C, and the heating time is 5-8 hours.

[0012] Preferably, the compression method in step S2 is either compression of a single-layer impregnated wood template or compression of two impregnated wood pieces stacked alternately.

[0013] Preferably, the hot pressing pressure in step S2 is 10 MPa and the compression time is 10 min.

[0014] Preferably, the concentration of the cesium tungsten bronze alcohol solution in step S3 is 0.04-0.06 g / mL, and the concentration of the strontium aluminate alcohol solution is 2-4 g / mL; the mass ratio of PDMS, cesium tungsten bronze and strontium aluminate in the PDMS solution containing the cesium tungsten bronze alcohol solution and the strontium aluminate alcohol solution is 100:(0.8-1.2):(60-120).

[0015] Preferably, the low-temperature drying temperature in step S3 is 30-40℃, and the drying time is 20-30h.

[0016] The beneficial effects of this invention are: 1. This invention employs silica sol pretreatment combined with PEG / MMA impregnation and compression technology, resulting in a simple and easy preparation process that effectively prevents leakage of phase change materials while improving the stability and performance consistency of composite materials, making it suitable for large-scale production.

[0017] 2. By adopting a multifunctional coating technology to introduce cesium tungsten bronze and strontium aluminate components, the material is endowed with hydrophobicity, luminescent properties and thermal shielding capabilities, enabling it to have photothermal management, self-cleaning and decorative functions in smart buildings, thereby meeting diverse application needs.

[0018] 3. This composite material combines energy storage, optical regulation, and multifunctional coating properties, making it suitable for energy-saving windows, building exteriors, interior decoration, and temperature control equipment, providing innovative solutions for smart buildings and energy-saving technologies.

[0019] 4. The material maintains high light transmittance in the visible light region, while the near-infrared light transmittance can be significantly reduced through the cesium tungsten bronze coating, thereby achieving a balance between natural lighting and heat insulation performance and reducing air conditioning energy consumption. Attached Figure Description

[0020] Figure 1 The diagram shown is a schematic representation of the preparation process of this invention; Figure 2 The diagram shows the water contact angle results of the multifunctional phase change transparent wood-based composite material of the present invention; Figure 3 The image shown is a schematic diagram of the luminescence of the multifunctional phase change transparent wood-based composite material of the present invention; Figure 4 The diagram shows a comparison of the transmittance of the multifunctional phase change transparent wood-based composite material and the phase change transparent wood-based composite material in the visible and near-infrared wavelength regions. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 This invention provides an embodiment: a method for preparing a multifunctional phase change transparent wood-based composite material, comprising: S1. Wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution to remove lignin and form a porous skeleton. Then, it is washed and dried to remove residual chemicals. Next, the wood is soaked in a 0-15% (w / w) silica sol aqueous solution to fill the pores of the wood. Then, it is washed and freeze-dried to prepare a silica sol modified wood template. The template has a uniform porous structure, which provides an ideal carrier for subsequent phase change material loading. S2, polyethylene glycol (PEG), methyl methacrylate (MMA), 2,2-azobisisobutyronitrile (AIBN) and acetone solvent are mixed in a mass ratio of (30-80):(20-70):(0.05-0.25):100 to form a mixed solution. The silica sol-modified wood template obtained in step S1 is impregnated with this solution. Then, the impregnated wood is placed in a 70°C oven and heated for 5-8 hours. Finally, it is compressed at 10MPa pressure for 10 minutes using a hot press to obtain a phase change transparent wood-based composite material. This material has excellent light transmittance and high phase change enthalpy, which can realize efficient thermal energy storage and release. S3. A polydimethylsiloxane (PDMS) solution containing 0.04-0.06 g / mL of cesium tungsten bronze alcohol solution and 2-4 g / mL of strontium aluminate alcohol solution is coated onto the phase change transparent wood-based composite material obtained in step S2. The composite material is then dried at a low temperature of 30-40°C for 20-30 hours. A layer of PDMS is then applied to the surface of the composite material, and the material is dried at a low temperature under the same conditions to obtain a multifunctional phase change transparent wood-based composite material. The mass ratio of PDMS, cesium tungsten bronze, and strontium aluminate in the PDMS solution containing cesium tungsten bronze alcohol solution and strontium aluminate alcohol solution is 100:(0.8-1.2):(60-120). This material has hydrophobicity, luminescence properties, and near-infrared shielding function, and can be widely used in smart windows, energy-saving buildings, and decoration.

[0023] Example 1 First, balsa wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution, washed and dried, then soaked in a 7.5% (w / w) silica sol aqueous solution, washed and freeze-dried to prepare silica sol modified wood template; Pretreated silica sol-modified wood templates were impregnated with a mixed solution of PEG / MMA / AIBN / acetone, wherein the mass ratio of PEG / MMA / AIBN / acetone in the mixed solution was 65:35:0.11:100. The templates were then removed and heated in an oven at 70°C for 5 hours. Two impregnated wood templates were then stacked alternately and compressed under a hot-pressing pressure of 10 MPa for 10 minutes to prepare a phase change transparent wood-based composite material.

[0024] The phase change transparent wood-based composite material prepared in this embodiment has a transmittance of 50.1% at a wavelength of 800 nm and a maximum phase change enthalpy of 75.0 J / g.

[0025] Example 2 First, balsa wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution, washed and dried, then soaked in a 7.5% (w / w) silica sol aqueous solution, washed and freeze-dried to prepare silica sol modified wood template; Pretreated silica sol-modified wood templates were impregnated with a mixed solution of PEG / MMA / AIBN / acetone, wherein the mass ratio of PEG / MMA / AIBN / acetone in the mixed solution was 55:45:0.14:100; then the templates were removed and heated in an oven at 70°C for 6 hours; then two impregnated wood templates were stacked alternately and compressed under a hot-pressing pressure of 10 MPa for 10 minutes to prepare a phase change transparent wood-based composite material.

[0026] The phase change transparent wood-based composite material prepared in this example has a transmittance of 54.5% at a wavelength of 800 nm and a maximum phase change enthalpy of 57.5 J / g.

[0027] Example 3 First, balsa wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution, washed and dried, then soaked in a 7.5% (w / w) silica sol aqueous solution, washed and freeze-dried to prepare silica sol modified wood template; Pretreated silica sol-modified wood templates were impregnated with a mixed solution of PEG / MMA / AIBN / acetone, wherein the mass ratio of PEG / MMA / AIBN / acetone in the mixed solution was 65:35:0.11:100. Then, the templates were removed and placed in an oven at 70°C for 5 hours. Two impregnated wood templates were then stacked alternately and compressed under a hot-pressing pressure of 10 MPa for 10 minutes to prepare a phase change transparent wood-based composite material. PDMS containing a cesium tungsten bronze alcohol solution (0.05 g / mL) and a strontium aluminate alcohol solution (3 g / mL) was coated onto the surface of the aforementioned phase change transparent wood-based composite material. The mass ratio of PDMS, cesium tungsten bronze, and strontium aluminate in the PDMS solution containing the cesium tungsten bronze alcohol solution and the strontium aluminate alcohol solution was 100:1:90. The material was then dried at 35°C for 25 hours. After drying at 35°C for another 25 hours, a layer of PDMS was applied to the surface of the phase change transparent wood-based composite material, and the material was further dried at 35°C for another 25 hours to obtain a multifunctional phase change transparent wood-based composite material.

[0028] The multifunctional phase change transparent wood-based composite material prepared in this example has a transmittance of 38.4% at a wavelength of 800 nm and a maximum phase change enthalpy of 67.8 J / g.

[0029] Please see Figure 2-4Compared to the ordinary phase change transparent wood-based composite material of Example 1, this material further achieves hydrophobicity (water contact angle up to 107.5°), luminescence properties, and heat shielding function by coating the surface with a PDMS functional coating containing cesium tungsten bronze and strontium aluminate. The infrared transmittance is significantly lower than that of Example 1, indicating that it can effectively block heat radiation. The improvement in overall performance makes it more widely applicable in the field of intelligent energy-saving buildings, and can simultaneously meet multiple needs such as light transmission, temperature regulation, moisture protection, and optical decoration.

[0030] Comparative Example 1: First, balsa wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution, washed and dried, then soaked in a 7.5% (w / w) silica sol aqueous solution, washed and freeze-dried to prepare silica sol modified wood template; Pretreated silica sol-modified wood templates were impregnated with a mixed solution of PEG / MMA / AIBN / acetone, wherein the mass ratio of PEG / MMA / AIBN / acetone in the mixed solution was 65:35:0.11:100. The templates were then removed and heated in an oven at 70°C for 5 hours to obtain wood-based composite materials.

[0031] PDMS containing a 0.05 g / mL cesium tungsten bronze alcohol solution and a 3 g / mL strontium aluminate alcohol solution was coated onto the surface of the aforementioned wood-based composite material. The mass ratio of PDMS, cesium tungsten bronze, and strontium aluminate in the PDMS solution containing the cesium tungsten bronze alcohol solution and the strontium aluminate alcohol solution was 100:1:90. The material was then dried at 35°C for 25 hours. After drying at 35°C for another 25 hours, a layer of PDMS was applied to the surface of the wood-based composite material, and the material was dried at 35°C for another 25 hours to obtain a multifunctional phase change wood-based composite material.

[0032] The multifunctional phase change wood-based composite material prepared in this comparative example does not have a transparent effect.

[0033] Comparative Example 2: First, balsa wood is soaked in a 2% (w / w) acidic sodium chlorite aqueous solution, washed and dried, then soaked in a 7.5% (w / w) silica sol aqueous solution, washed and freeze-dried to prepare silica sol modified wood template; Pretreated silica sol-modified wood templates were impregnated with a mixed solution of PEG / MMA / AIBN / acetone, wherein the mass ratio of PEG / MMA / AIBN / acetone in the mixed solution was 90:10:0.03:100; then the templates were removed and heated in an oven at 70°C for 5 hours; then two impregnated wood templates were stacked alternately and compressed under a hot-pressing pressure of 10 MPa for 10 minutes to obtain a phase change wood-based composite material.

[0034] PDMS containing a 0.05 g / mL cesium tungsten bronze alcohol solution and a 3 g / mL strontium aluminate alcohol solution was coated onto the surface of the aforementioned wood-based composite material. The mass ratio of PDMS, cesium tungsten bronze, and strontium aluminate in the PDMS solution containing the cesium tungsten bronze alcohol solution and the strontium aluminate alcohol solution was 100:1:90. The material was then dried at 35°C for 25 hours. After drying at 35°C for another 25 hours, a layer of PDMS was applied to the surface of the wood-based composite material, and the material was dried at 35°C for another 25 hours to obtain a multifunctional phase change wood-based composite material.

[0035] The multifunctional phase change wood-based composite material prepared in this comparative example has poor transparency, with a light transmittance of less than 20%.

[0036] Examples 1-3 demonstrate that the method of this invention can produce high-performance phase-change transparent wood, and by adding a functional coating, it can achieve multifunctional properties such as hydrophobicity, luminescence, and heat shielding. However, unlike Comparative Examples 1-2, which did not achieve the desired transparency, the advantage of this invention lies in using a mixed solution of PEG and MMA in a certain mass ratio to impregnate pretreated wood, combined with compression processes and coating modification techniques, to prepare a wood-based composite material that possesses excellent transparency, heat storage, hydrophobicity, luminescence, and heat shielding capabilities.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a multifunctional phase change transparent wood-based composite material, characterized in that, Including: S1, the wood is soaked in an acidic sodium chlorite aqueous solution to remove lignin and form a porous skeleton. Then it is washed and dried to remove residual chemicals. The wood is then soaked in a silica sol aqueous solution to fill the pores of the wood. Finally, it is washed and freeze-dried to prepare silica sol modified wood template. S2, polyethylene glycol phase change material, methyl methacrylate, 2,2-azobisisobutyronitrile and acetone solvent are mixed to form a mixed solution. The silica sol modified wood template obtained in step S1 is impregnated with the solution, then taken out and placed in an oven for a period of time, and then compressed by a hot press to obtain a phase change transparent wood-based composite material. S3, a polydimethylsiloxane solution containing cesium tungsten bronze alcohol solution and strontium aluminate alcohol solution is coated onto the phase change transparent wood matrix composite material obtained in step S2. After drying at low temperature for a period of time, a layer of PDMS is coated on the surface of the phase change transparent wood matrix composite material. After continuing to dry at low temperature under the same conditions, a multifunctional phase change transparent wood matrix composite material is obtained.

2. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The wood used in step S1 is balsa wood, and the sodium chlorite aqueous solution has a mass fraction of 2%.

3. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The silica sol aqueous solution in step S1 has a mass fraction of 0-15%.

4. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The polyethylene glycol phase change material in the mixed solution of step S2 is: methyl methacrylate: 2,2-azobisisobutyronitrile: acetone = (30-80): (20-70): (0.05-0.25):

100.

5. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The oven heating temperature in step S2 is 70℃, and the heating time is 5-8 hours.

6. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The compression method in step S2 is either compression of a single-layer impregnated wood template or compression of two impregnated wood pieces stacked alternately.

7. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The hot pressing pressure in step S2 is 10 MPa, and the compression time is 10 min.

8. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: In step S3, the concentration of the cesium tungsten bronze alcohol solution is 0.04-0.06 g / mL, and the concentration of the strontium aluminate alcohol solution is 2-4 g / mL; the mass ratio of PDMS, cesium tungsten bronze and strontium aluminate in the PDMS solution containing the cesium tungsten bronze alcohol solution and the strontium aluminate alcohol solution is 100:(0.8-1.2):(60-120).

9. The method for preparing a multifunctional phase change transparent wood-based composite material according to claim 1, characterized in that: The low-temperature drying temperature in step S3 is 30-40℃, and the drying time is 20-30h.

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