Preparation Of Towel Gourd-based Phase Change Composite Material And Its Application In Textile Thermal Protection

In recent years,the problems of energy shortage and greenhouse gas emission have received global attention,and the contradiction with economic development also needs to be solved urgently.Thus,renewable and sustainable energies can be utilized to decrease fossil fuel consumption and relieve environmental pollution.Solid-liquid phase change energy storage technology is to store and release heat energy through the phase change of substance,and to convert and store unnecessary or redundant energy for reuse.However,the problems of leakage and poor thermal conductivity of solid-liquid phase variable material(PCM)have been greatly limited in practical application.In this paper,the phase change composites with stable physical and chemical properties,latent heat storage,temperature regulation,heat management,heat insulation protection or electro-thermal conversion were prepared by using fresh towel gourd(FT)and loofah sponge(LS)as raw materials,polyethylene glycol(PEG)as phase change material for energy storage,combined with the principles and technologies of freeze-drying,high temperature carbonization and physical adsorption.Firstly,biomass-based porous carbon(CT)was made from FT through freeze-drying followed by high temperature carbonization,and shape-stable phase change composite(PCC)was fabricated by incorporating PEG with CT via vacuum impregnation.The effects of different carbonization temperatures on the structure and properties of CT and PCC were discussed.The results showed that CT displayed a unique three-dimensional lamellar tissue structure and high specific surface area characteristics,which was caused by high temperature carbonization.The CT900,prepared by carbonization at 900 ~oC,had excellent structural characteristics,with a specific surface area of 409.95 m~2/g,high adsorption capacity(94.5wt%)and good adsorption stability for PEG.The corresponding PCC900 demonstrated high latent heat of 164.3 J/g for melting enthalpy and 144.1 J/g for crystallization enthalpy.After100 thermal cycles,the PCC900 can still maintain stable phase transition characteristics and had good thermal energy management ability.The thermal protection test showed that the bag fabric with PCC had a superior thermal insulation protection effect on human skin.Then,LS fiber was selected as the supporting material,and the phase change composites(PCLS)were prepared by physical adsorption with different PEG concentrations.When the PEG concentration was less than 0.24 g/m L,the adsorption capacity of LS fiber for PEG increased with the increase of PEG concentration,and the adsorption capacity for PEG gradually approached the maximum limit as the PEG concentration continued to increase.The bundle like structure of LS fiber can adsorb PEG stably,and the two had good chemical compatibility.The prepared PCLS had high melting/crystallization enthalpies,good thermal cycling stability and leak-proof properties.The phase transformation behaviors of PEG in PCLS were almost unaffected by LS structure and PEG adsorption capacity.The temperature regulation test and self-assembly temperature control test showed that PCLS had a certain heat insulation and temperature regulation effects,and when other conditions were the same,the bigger adsorption capacity of PEG can increase the holding time of PCLS.Finally,in order to optimize the structure and properties of LS fiber,carbonized loofah sponge(CL)was prepared by carbonization of LS fiber at different temperatures,and then phase change composite(PCCL)was prepared by physical adsorption of PEG.With the increase of carbonization temperature,the graphitization degree and specific surface area of CL increased,and the specific surface area(up to 668.75 m~2/g)and pore size distribution of CL900 were better.The carbonization retained the tube bundle structure of LS.The adsorption capacity of CL for PEG was up to 87.7 wt%,which was significantly higher than that of LS,and the melting/crystallization enthalpies of PCCL were 137.6 J/g and 132.2 J/g,respectively,which were higher than that of PCLS,and PCCL had excellent leak-prevention performance.Infrared thermal images showed that PCCL900 had the functions of latent heat energy storage and temperature regulation.The three-dimensional conductive network formed by CL900 can make PCCL900 form a loop under low potential,which combined the electro-thermal conversion with latent heat energy storage,and provided a boost for the development of electro-thermal insulation textiles with thermal protection effect.