Phase change energy storage transparent wood composite material and preparation method and application thereof

Abstract

The invention belongs to the technical field of phase change materials, and particularly relates to a phase change energy storage transparent wood composite material and a preparation method and application thereof. According to the invention, TPU is introduced as a packaging substrate of PEG. TPU has excellent mechanical properties, and the overall mechanical strength and environmental tolerance of the composite material can be remarkably improved. Meanwhile, the PEG and the TPU show good compatibility, the fluidity at high temperature is reduced after compounding, the formability is remarkably improved, and a stable solid structure and mechanical properties can be maintained. In addition, the TPU and the cellulose base material framework with similar refractive properties are adopted, so that the high light transmission characteristic of the transparent wood can be realized. On the basis, by constructing a PEG-TPU blending system, the comprehensive performance of the phase-change energy-storage transparent wood is optimized, so that the transparent wood has the high phase-change latent heat and temperature adjustability of PEG and the mechanical strength, high light transmittance and sustainability of transparent wood, and a feasible solution is provided for practical application of the transparent wood in the fields of intelligent windows and the like.

Description

Technical Field

[0001] This invention belongs to the field of phase change materials technology, specifically relating to a phase change energy storage transparent wood composite material, its preparation method, and its application. Background Technology

[0002] Phase change materials (PCMs) have significant application value in the field of phase change energy storage. Phase change energy storage technology is based on the property of materials to absorb or release heat during phase change, enabling energy storage and release. Organic PCMs can absorb a large amount of latent heat within a narrow temperature range, thus achieving efficient energy storage. These materials typically possess characteristics such as high phase change enthalpy, good chemical stability, and a suitable phase change temperature range.

[0003] PEG, as an organic phase change material, is widely used in energy storage due to its excellent phase change characteristics and biocompatibility. During phase change, PEG can absorb or release a large amount of latent heat, resulting in high energy storage density. Simultaneously, PEG is non-toxic, chemically stable, and not easily degraded, making it suitable for long-term use, especially in building energy conservation and thermal management. However, PEG has certain limitations as a phase change material: First, its high-temperature stability is poor, and it is prone to leakage at high temperatures, leading to degradation of its physical properties, thus making it difficult to use as an independent structural material; second, PEG has weak mechanical properties, with poor strength, toughness, and impact resistance, failing to meet the mechanical performance requirements of functional materials. Summary of the Invention

[0004] The purpose of this invention is to provide a phase change energy storage transparent wood composite material, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a transparent wood composite material for phase change energy storage, comprising the following steps: The wood is bleached to obtain pretreated wood; The pretreated wood is vacuum impregnated in a polymer solution and then cured to obtain the phase change energy storage transparent wood composite material. The polymer solution comprises polyethylene glycol and thermoplastic polyurethane.

[0006] Preferably, the bleaching solution used in the bleaching pretreatment includes sodium chlorite solution or sodium hypochlorite solution; The bleaching solution has a mass concentration of 2-3%; The pH value of the bleaching solution is 4.6~5.5.

[0007] Preferably, the bleaching pretreatment is performed at a temperature of 75-85°C for 5-7 hours. The bleaching pretreatment is carried out under stirring conditions.

[0008] Preferably, the mass ratio of polyethylene glycol to thermoplastic polyurethane is 4~7:3~6.

[0009] Preferably, the solvent in the polymer solution includes at least one of chloroform, dimethylformamide, tetrahydrofuran, and acetone; The mass concentration of thermoplastic polyurethane in the polymer solution is 7-10%.

[0010] Preferably, the vacuum impregnation is repeated 3 times, and the total vacuum impregnation time does not exceed 5 minutes.

[0011] Preferably, the curing temperature is 24~30℃ and the humidity is 60~75%.

[0012] Preferably, the dimensions of the wood are 30*30*1mm; The bleaching pretreatment also includes drying the wood.

[0013] The present invention also provides a phase change energy storage transparent wood composite material prepared by the preparation method described above, comprising wood and a transparent film wrapped around the surface of the wood; the material of the transparent film includes polyethylene glycol and thermoplastic polyurethane.

[0014] The present invention also provides the application of the phase change energy storage transparent wood composite material described in the above technical solution in intelligent windows for building thermal management.

[0015] This invention provides a method for preparing a phase change energy storage transparent wood composite material, comprising the following steps: bleaching and pretreating wood to obtain pretreated wood; vacuum impregnating the pretreated wood in a polymer solution and then curing it to obtain the phase change energy storage transparent wood composite material; wherein the polymer solution comprises polyethylene glycol and thermoplastic polyurethane.

[0016] This invention introduces thermoplastic polyurethane (TPU) as the encapsulation matrix for PEG. TPU possesses excellent mechanical properties, significantly improving the overall mechanical strength and environmental resistance of the composite material. Simultaneously, PEG and TPU exhibit good compatibility; after composite formation, fluidity decreases at high temperatures, moldability is significantly improved, and a stable solid structure and mechanical properties are maintained. Furthermore, using TPU with similar refractive properties and a cellulose matrix skeleton achieves the high light transmittance of transparent wood. Based on this, this invention optimizes the comprehensive performance of phase change energy storage transparent wood by constructing a PEG-TPU blend system, combining the high latent heat of phase change and temperature adjustability of PEG with the mechanical strength, high light transmittance, and sustainability of transparent wood, providing a feasible solution for its practical application in fields such as smart windows. This invention successfully prepares a PEG phase change energy storage transparent wood material with temperature-responsive characteristics by compositing PEG / TPU materials with a transparent wood matrix. This composite material exhibits transparency at high temperatures, achieving not only efficient utilization of biomass resources but also meeting the dual requirements of thermal management and high optical transmittance. Attached Figure Description

[0017] Figure 1 A schematic diagram of the phase change process of the transparent wood composite material for phase change energy storage provided by the present invention; Figure 2 Transmittance diagrams of the phase change energy storage transparent wood composite material provided by the present invention before and after phase change; Figure 3 The DSC curve of the transparent wood composite material for phase change energy storage provided by the present invention. Detailed Implementation

[0018] This invention provides a method for preparing a transparent wood composite material for phase change energy storage, comprising the following steps: The wood is bleached to obtain pretreated wood; The pretreated wood is vacuum impregnated in a polymer solution and then cured to obtain the phase change energy storage transparent wood composite material. The polymer solution comprises polyethylene glycol and thermoplastic polyurethane.

[0019] This invention involves bleaching wood to obtain pretreated wood.

[0020] This invention does not specifically limit the type of wood used; any wood well-known to those skilled in the art can be used. In a specific embodiment of this invention, the wood is preferably balsa wood. In this invention, the dimensions of the wood are preferably 30*30*1mm; before the bleaching pretreatment, the wood is preferably dried; the drying temperature is preferably 95~105℃, and the drying time is preferably 2 hours.

[0021] In this invention, the bleaching solution used in the bleaching pretreatment preferably includes sodium chlorite solution or sodium hypochlorite solution; the mass concentration of the bleaching solution is preferably 2-3%; the pH value of the bleaching solution is preferably 4.6-5.5; and the solvent for adjusting the pH value of the bleaching solution is preferably glacial acetic acid solution. This invention does not have specific limitations on the concentration and amount of the glacial acetic acid solution added, as long as the desired pH value is achieved.

[0022] In this invention, the bleaching pretreatment temperature is preferably 75-85℃, specifically 75℃, 80℃, or 85℃, and the time is preferably 5-7 hours, specifically 5 hours, 6 hours, or 7 hours. The bleaching pretreatment is preferably carried out under stirring conditions; the stirring speed is preferably 100-200 rpm. After the bleaching pretreatment, this invention further preferably includes rinsing the obtained wood with an ethanol-water solution. In this invention, the pretreated wood preferably has a graded porous skeleton structure.

[0023] In this invention, bleaching the wood removes lignin and hemicellulose, resulting in a wood substrate with a hierarchical porous framework structure composed of cellulose. Rinsing with an ethanol solution removes residual chemical solutions from the wood surface, ensuring the bleached wood retains its original shape after dehydration and drying, preventing pore shrinkage and enhancing permeability, thus improving the impregnation effect of the pretreated wood. Bleaching pretreatment under these conditions effectively removes lignin and hemicellulose, achieving a better bleaching effect, higher whiteness, less fiber loss, and a moderate bleaching rate.

[0024] After obtaining the pretreated wood, the present invention vacuum impregnates the pretreated wood in a polymer solution and then performs a curing treatment to obtain the phase change energy storage transparent wood composite material.

[0025] In this invention, the polymer solution comprises polyethylene glycol (PEG) and thermoplastic polyurethane (TPU). The preferred mass ratio of PEG to TPU is 4-7:3-6, specifically 7:3, 6:4, 5:5, or 4:6. The solvent in the polymer solution preferably includes at least one of chloroform, dimethylformamide, tetrahydrofuran, and acetone; the preferred mass concentration of TPU in the polymer solution is 7-10%, more preferably 8%. The preferred method for preparing the polymer solution includes: dehydrating PEG and TPU separately, and then dissolving them in a solvent; the dissolution is preferably carried out in a white, sealable polypropylene bottle; the dissolution is preferably carried out under stirring conditions, and the stirring time is preferably 3 hours.

[0026] In this invention, the vacuum impregnation is preferably repeated 3 times, and the total vacuum impregnation time is preferably no more than 5 minutes.

[0027] In this invention, the curing temperature is preferably 24~30℃, specifically 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃; the humidity is preferably 60~75%, specifically 60%, 65%, or 70%. Curing under the above conditions results in a high yield rate.

[0028] In this invention, pretreated wood is impregnated in a polymer solution, and polyethylene glycol is loaded onto the pretreated wood using thermoplastic polyurethane to achieve phase change energy storage functionality in the wood-based composite material. Polyethylene glycol and thermoplastic polyurethane exhibit good compatibility with the cellulose microfibers in wood, enhancing not only the mechanical strength of the wood but also improving the practicality of transparent wood materials. Furthermore, this material is low-cost, simple to prepare, and easy to install, possessing good economic efficiency and feasibility. Pure PEG is easily crystallized, has a large latent heat of phase change, and a simple structure. Its phase change temperature can be adjusted by molecular weight; for example, the phase change temperature of PEG with a specific molecular weight is approximately 30.29℃, which falls within the comfortable temperature range for human activities. It also possesses a high phase change enthalpy (≥140 J / g), all of which give it high application potential in the field of building energy storage materials.

[0029] The present invention also provides a phase change energy storage transparent wood composite material prepared by the preparation method described above, comprising wood and a transparent film wrapped around the surface of the wood; the material of the transparent film includes polyethylene glycol and thermoplastic polyurethane.

[0030] In this invention, the phase change energy storage transparent wood composite material has a room temperature transmittance of 46.06~58.47% and a high temperature transmittance of 63.09~75.91%; a phase change temperature of 34.69~39.44℃ and a phase change enthalpy of 68.15~93.91J / g; and a thermal conductivity of 0.17~0.22 W / (m·K).

[0031] Figure 1 This is a schematic diagram of the phase change process of the transparent wood composite material for phase change energy storage provided by the present invention.

[0032] The present invention also provides the application of the phase change energy storage transparent wood composite material described in the above technical solution in intelligent windows for building thermal management.

[0033] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0034] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Example 1 The dried balsa wood (30mm×30mm×1mm in size) was placed in a sodium chlorite solution with a concentration of 2wt% and a pH of 4.6 (the pH was adjusted using glacial acetic acid solution) for bleaching pretreatment. The bleaching temperature was 75℃, the bleaching time was 5h, and the stirring speed was 100rpm. Then it was rinsed with an ethanol aqueous solution to obtain the pretreated wood. Using chloroform as a solvent, dehydrated PEG and TPU were mixed in a white sealable polypropylene bottle at a mass ratio of 7:3, with the mass ratio of TPU maintained at 8wt%. The mixture was stirred with a magnetic stirrer for 3 hours to fully dissolve the TPU and obtain a polymer solution. The pretreated wood was placed in a polymer solution and vacuum impregnated three times, with a total time not exceeding 5 minutes. The impregnated wood was placed in a constant temperature and humidity chamber and cured at 24°C and 60% humidity. After curing, a phase change energy storage transparent wood composite material (denoted as PSTW1) was obtained.

[0036] Example 2 The dried balsa wood (30mm×30mm×1mm in size) was placed in a sodium chlorite solution with a concentration of 2wt% and a pH of 4.6 (the pH was adjusted using glacial acetic acid solution) for bleaching pretreatment. The bleaching temperature was 75℃, the bleaching time was 5h, and the stirring speed was 100rpm. Then it was rinsed with an ethanol aqueous solution to obtain the pretreated wood. Using chloroform as a solvent, the dehydrated PEG and TPU were mixed in a white sealable polypropylene bottle at a mass ratio of 6:4, with the mass ratio of TPU maintained at 8wt%. The mixture was stirred with a magnetic stirrer for 3 hours to fully dissolve the TPU and obtain a polymer solution. The pretreated wood was placed in a polymer solution and vacuum impregnated three times, with a total time not exceeding 5 minutes. The impregnated wood was placed in a constant temperature and humidity chamber and cured at 24°C and 60% humidity. After curing, a phase change energy storage transparent wood composite material (denoted as PSTW2) was obtained.

[0037] Example 3 The dried balsa wood (30mm×30mm×1mm in size) was placed in a sodium chlorite solution with a concentration of 2 wt% and a pH of 4.6 (the pH was adjusted using glacial acetic acid solution) for bleaching pretreatment. The bleaching temperature was 75℃, the bleaching time was 5h, and the stirring speed was 100rpm. Then it was rinsed with an ethanol aqueous solution to obtain the pretreated wood. Using chloroform as a solvent, the dehydrated PEG and TPU were mixed in a white sealable polypropylene bottle at a mass ratio of 5:5, with the mass ratio of TPU maintained at 8wt%. The mixture was stirred with a magnetic stirrer for 3 hours to fully dissolve the TPU and obtain a polymer solution. The pretreated wood was placed in a polymer solution and vacuum impregnated three times, with a total time not exceeding 5 minutes. The impregnated wood was placed in a constant temperature and humidity chamber and cured at 24°C and 60% humidity. After curing, a phase change energy storage transparent wood composite material (denoted as PSTW3) was obtained.

[0038] Example 4 The dried balsa wood (30mm×30mm×1mm in size) was placed in a sodium chlorite solution with a concentration of 2wt% and a pH of 4.6 (the pH was adjusted using glacial acetic acid solution) for bleaching pretreatment. The bleaching temperature was 75℃, the bleaching time was 5h, and the stirring speed was 100rpm. Then it was rinsed with an ethanol aqueous solution to obtain the pretreated wood. Using chloroform as a solvent, dehydrated PEG and TPU were mixed in a white sealable polypropylene bottle at a mass ratio of 4:6, with the mass ratio of TPU maintained at 8wt%. The mixture was stirred with a magnetic stirrer for 3 hours to fully dissolve the TPU and obtain a polymer solution. The pretreated wood was placed in a polymer solution and vacuum impregnated three times, with a total time not exceeding 5 minutes. The impregnated wood was placed in a constant temperature and humidity chamber and cured at 24°C and 60% humidity. After curing, a phase change energy storage transparent wood composite material (denoted as PSTW4) was obtained.

[0039] Performance testing Figure 2 The transmittance diagrams of the phase change energy storage transparent wood composite materials provided in Examples 1-4 before and after the phase change are shown in Table 1. Table 1. Light transmittance of the transparent wood composite materials obtained in the examples

[0040] Figure 3The DSC curves of the phase change energy storage transparent wood composite materials provided in Examples 1-4 are shown in Table 2, with PEG as a control. Table 2. Phase transformation parameters of the transparent wood composite materials obtained in the examples.

[0041] Comparative Example 1 The composite material was prepared according to Example 1, wherein the mass ratio of PEG to TPU was adjusted to 8:2; however, the composite material prepared in this comparative example could not maintain a stable physical structure and exhibited severe leakage.

[0042] Comparative Example 2 The composite material was prepared according to Example 1, wherein the mass ratio of PEG to TPU was adjusted to 3:7; after testing, the phase change energy storage transparent wood composite material prepared in this comparative example did not show obvious phase change function.

[0043] Test results show that the composite material exhibits excellent thermal insulation properties, with a low thermal conductivity (Table 3), which is significantly superior to traditional glass materials. Its low thermal conductivity endows the material with excellent thermal insulation performance, effectively blocking indoor and outdoor heat exchange and significantly reducing energy consumption for building temperature regulation. Secondly, the moderate thermal conductivity regulates the phase change kinetics, ensuring both the necessary thermal response speed and extending the duration of thermal regulation by delaying the phase change process. The composite material successfully integrates the thermal insulation properties of transparent wood matrix and the thermal storage function of PEG phase change material, achieving an integrated "thermal insulation-energy storage" thermal management mechanism through their synergistic effect. This design not only significantly improves the material's thermal performance but also effectively maintains indoor temperature stability, providing a novel intelligent material solution with practical application value for the field of building energy conservation.

[0044] Table 3 shows the properties of the transparent wood composite materials obtained in the examples.

[0045] Because the refractive index of TPU (1.51) is closer to that of cellulose (1.53), the main component of wood, the addition of TPU significantly improves light transmission efficiency, resulting in higher light transmittance. In other words, the introduction of PEG / TPU endows the material with phase change energy storage capabilities while maintaining the excellent optical properties of a transparent wood matrix. This combination of temperature response, high light transmittance, and phase change energy storage makes the composite material demonstrate significant application value in the field of intelligent energy-saving buildings, providing innovative ideas for the development of new green building materials.

[0046] Due to the good compatibility of TPU and PEG with cellulose and the synergistic effect of capillary forces, the composite material exhibits excellent stability at a long-term high temperature of 60℃. It not only maintains the complete physical structure and has no PEG leakage, but also can still achieve intelligent conversion of optical state, and has high reliability under the actual application temperature conditions.

[0047] In summary, the phase change energy storage transparent wood composite material provided by this invention can undergo a phase change at high temperatures. During the phase change process, it can absorb or release latent heat, exhibiting high energy storage density and excellent thermal management capabilities. By compositing PEG / TPU material with a transparent wood matrix, a PEG phase change energy storage transparent wood material with temperature-responsive characteristics was successfully prepared. This composite material exhibits transparency at high temperatures, achieving not only efficient utilization of biomass resources but also meeting the dual requirements of thermal management and high optical transmittance.

[0048] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a transparent wood composite material for phase change energy storage, characterized in that, Includes the following steps: The wood is bleached to obtain pretreated wood; The pretreated wood is vacuum impregnated in a polymer solution and then cured to obtain the phase change energy storage transparent wood composite material. The polymer solution comprises polyethylene glycol and thermoplastic polyurethane.

2. The preparation method according to claim 1, characterized in that, The bleaching pretreatment uses a bleaching solution including sodium chlorite solution or sodium hypochlorite solution; The bleaching solution has a mass concentration of 2-3%; The pH value of the bleaching solution is 4.6~5.

5.

3. The preparation method according to claim 1, characterized in that, The bleaching pretreatment is performed at a temperature of 75-85℃ for 5-7 hours. The bleaching pretreatment is carried out under stirring conditions.

4. The preparation method according to claim 1, characterized in that, The mass ratio of polyethylene glycol to thermoplastic polyurethane is 4~7:3~6.

5. The preparation method according to claim 1 or 4, characterized in that, The solvent in the polymer solution includes at least one of chloroform, dimethylformamide, tetrahydrofuran, and acetone; The mass concentration of thermoplastic polyurethane in the polymer solution is 7-10%.

6. The preparation method according to claim 1, characterized in that, The vacuum impregnation is repeated 3 times, and the total vacuum impregnation time does not exceed 5 minutes.

7. The preparation method according to claim 1, characterized in that, The curing process is carried out at a temperature of 24-30°C and a humidity of 60-75%.

8. The preparation method according to claim 1, characterized in that, The dimensions of the wood are 30*30*1mm; The bleaching pretreatment also includes drying the wood.

9. The phase change energy storage transparent wood composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It includes wood and a transparent film wrapped around the surface of the wood; the transparent film is made of materials including polyethylene glycol and thermoplastic polyurethane.

10. The application of the phase change energy storage transparent wood composite material as described in claim 9 in intelligent windows for building thermal management.

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