Preparation And Properties Of Clay-Based Form-Stable Phase Change Thermal Storage Wood Plastic Composites

Wood-plastic composites(WPC)is green ecological materials,which are widely used in the field of household products and building materials.However,the function of WPC is relatively single.Phase change materials(PCM)can improve energy efficiency through phase transformation and achieve the purpose of energy conservation and emission reduction.Therefore,the research on phase change thermal storage wood-plastic composites(TS-WPC)is of great significance for the development of new bio based green energy-saving materials.In this paper,form-stable phase change materials(FS-PCM)were fabricated by incorporating PCM into inorganic clay,and the prepared clay-based FS-PCMs were introduced to WPC to obtain the TS-WPC with latent heat storage function.The interface compatibility and the leakage of the PCM in FS-PCM were solved and the thermal storage and release mechanism of TS-WPC were also explored.The main conclusions were summarized as follows:(1)Diatomite(Dt),montmorillonite(Mt)and expanded perlite(EP)were modified by octadecyl trimethyl ammonium chloride(OTAC)andγ-Aminopropyl triethoxysilane(KH550)to regulate the pore structure of clay.The results showed that the modification treatment does not change the crystal and chemical structure of clay.OTAC formed a protective film on the surface of clay by replacing the inorganic cations with organic cations through ion exchange,which increased the distance between clay particles and prevented agglomeration.The layer space of Mt-O increased by 35.6%,and the specific surface area increased by 27.5%.(2)Clay-based FS-PCM were prepared by one-step and two-step methods,which was based on the organic and inorganic clay as the packaging materials and polyethylene glycol 800(PEG 800)as the phase change material.The clay-based FS-PCM prepared by two-step method had better loss resistance,thermal storage capacity and thermal stability than FS-PCM prepared by one-step method.The enthalpy value reaches more than 94%of the theoretical enthalpy value,and the leakage rate is less than 5%.The optimum loading of Dt,Mt and EP on phase change materials are 60wt%,70wt%and 80wt%,respectively,which is 10wt%,25wt%and 15wt%higher than that of unmodified clay.The melting enthalpy of Diatomite,Montmorillonite and expanded perlite-based FS-PCMs are 105.35J/g,124.11J/g and 141.35J/g,respectively,and the crystallization enthalpy is 101.33J/g,121.12J/g and 136.08J/g,respectively.(3)Clay-based TS-WPC were fabricated using the clay-based FS-PCM prepared by two-step method as thermal storage component.When the addition of FS-PCM is 30%,the phase transition temperature range of TS-WPC is 10-30℃;the melting enthalpy is 60.42 J/g,68.69 J/g and 76.06 J/g,respectively;the thermal conductivity is 27.1%,9.2%and 13.3%higher than that of wood plastic composites;the thickness expansion of water absorption is 0.63%,0.56%and 0.59%,respectively;the bending strength is 13.9 MPa,10.5 MPa and 10.7MPa,respectively;the tensile strength is 19.3 MPa,17.5MPa and 17.4MPa,respectively;the impact strength is 9.5 KJ/m~2,10.8 KJ/m~2 and KJ/m~2,respectively;the tensile and impact properties of clay-based TS-WPC have reached the highest value of current research.(4)The packaging ability of clay to PEG is improved through the van der Waals force and hydrogen bond between OTAC and KH550 with PEG.The interface compatibility of ternary composite system(clay-based FS-PCM,wood fiber and HDPE)is increased through the bridging effect of coupling agent.The internal heat conduction of clay-based TS-WPC mainly depends on the vibration of polymer matrix molecular chain and filler lattice,which is realized by phonon diffusion.Clay materials provide a certain amount of orderly and connected heat conduction path for phonon transmission,which improves the thermal conductivity of clay-based TS-WPC.