Preparation And Properties Of Porous Form Stable Phase Change Materials

Porous form stable phase change material is a new kind of intelligent double-functional material with stable shape memory and phase change energy storage.In this paper,the polyvinyl alcohol(PVA)solution was mixed with phase change microcapsule emulsion,and ?-cyclodextrin(?-CD)was selected to improve the bubble stability of the composite emulsion.The PVA-based porous form stable phase change material was prepared by physical foaming,cyclic freeze-thaw and freeze-drying methods.Firstly,experiments were designed and PVA porous shape memory materials were prepared.The pore structure,adsorption property,thermal stability,crystallization property,mechanical property and heat-induced shape memory property of the samples were compared under different stirring speeds and freeze-thaw cycles to explore the influence of stirring speeds and freeze-thaw cycles on the material properties.Secondly,Samples with different ?-CD and phase change microcapsule emulsion contents were prepared.The viscosity and starting stability of composite emulsions with different ?-CD content were characterized.The pore structure,adsorption performance,phase change energy storage performance,thermal stability,crystallization performance,mechanical properties,thermally induced shape memory performance of samples with different ?-CD and phase change microcapsule emulsion contents were tested.The influence of the content of ?-CD and phase change microcapsule emulsion on its properties was investigated.Finally,the room temperature phase change microcapsule emulsion was selected as raw material to prepare the room temperature porous form stable phase change materials,and its pore structure,adsorption performance,phase change energy storage performance,thermal stability,mechanical properties,and thermally induced shape memory performance were characterized.The self-recovering fabric was prepared by combining the porous form stable phase change material at room temperature with cotton fabric.The mechanical properties and the dual-response shape memory performance of moisture and heat of the self-recovering fabric were tested.The results show that the sample with a stirring speed of 1500 r/min has a uniform pore structure and good water absorption and water retention.Multiple freeze-thaw cycles can promote the entanglement of PVA molecular chains in the matrix and improve the mechanical properties of the material.After the sample was compressed and deformed,it can completely return to its original shape within 5 min at 80?,and the sample has good thermally induced shape memory performance.When the content of ?-CD is 3wt% of PVA,the viscosity of composite emulsion and bubble stability can be improved,and the sample has uniform pore structure.The crystallization of PVA in the matrix tends to be disordered with the addition of ?-CD,but the sample still has good mechanical properties and thermally induced shape memory properties.With the increase of phase-change microcapsule emulsion,the porosity of the sample becomes lower,the pore diameter becomes smaller,and the uniformity of the pore becomes worse.The phase change latent heat of the sample with phase change microcapsules accounting for 60wt% of PVA can reach 31.22 J/g,and the phase change latent heat does not significantly decrease after 50 phase change cycles.The color of the sample changes during the phase change process,and the visualization of phase transition is realized.The PVA-based porous form stable phase change material has good thermally induced shape memory performance,and the shape recovery rate can reach 100% within 5 min at 80?.The room temperature porous form stable phase change material has a uniform pore structure,high water absorption,high water retention,good thermal stability and good mechanical properties.The phase change latent heat of the sample can reach 34.69 J/g,and it still reaches 33.67 J/g after 50 phase change cycles.It has excellent and durable phase change energy storage performance and thermally induced shape memory performance.The self-recovering fabric prepared by compounding the room temperature porous form stable phase change material with cotton fabric has good mechanical properties.After the self-recovering fabric was bent and wrinkled at 90°,it can be completely recovered within 5 min at 80°C.Under the extreme deformation condition of 180° bending and wrinkling,the sample can reach 100% shape recovery rate after adsorption and saturation in water,and it has good shape memory performance with dual response of water and heat.The PVA-based porous form stable phase change material prepared in this study has a uniform pore structure,good mechanical properties,excellent phase change energy storage performance and shape memory performance.The composite of different phase change microcapsules and matrix proves the good compatibility between PVA substrate and other materials,which lays a foundation for the preparation of new multi-functional smart materials through material design in the future.The development of self-recovering fabrics has broadened the application range of porous form stable phase change materials,which meets people's demand for functional intelligent fabrics and has a wide application prospect.