Study On Preparation And Performance Of Gypsum-based Composite Phase Change Materials

In recent years,with the rapid development of our country’s economy,the contradiction between energy supply and demand has sharply increased,at the same time,the accompanying environmental pollution and other problems have become more and more serious.How to improve the utilization rate of energy and improve the quality of living environment has become a hot research topic today.This article is based on the combination of phase change materials and building materials to prepare building composite phase change materials.The storage and release of thermal energy of phase change materials are used to automatically adjust the energy of the building space environment,thereby improving work and life comfort.In this paper,liquid paraffin and 48 # solid paraffin were used as phase change raw materials.Eutectic mixture was prepared by melt blending.The step-cooling curve method was used to determine the crystallization temperatures of different solid-liquid mass ratios.The results showed that the eutectic mixture with a solid-liquid paraffin mass ratio of 5: 5 slowed down the temperature trend at 43.2 ° C and the phase transition lasted the longest;Differential scanning calorimetry(DSC)test results showed that the phase transition temperature was 24.52 ℃,and the latent heat of phase transition was 88.11 J / g;Fourier transform infrared spectroscopy(FT-IR)results showed the molecular structure of the eutectic mixture was no change,the process was only physical recombination;the freeze-thaw cycle test results showed that the eutectic mixture had little change in crystallization temperature and good thermal stability.The ceramic and paraffin composite phase change materials(CE/PA-PCMs)and expanded perlite and paraffin composite phase change materials(EP/PA-PCMs)were prepared by vacuum adsorption with ceramsite(CE)and expanded perlite(EP)porous materials as matrix materials and low eutectic mixture as matrix materials.DSC test results showed that the phase change latent heat of CE/PA-PCMs and EP/PA-PCMs were in positive phase with the content of low eutectic mixture.The results of FT-IR showed that there was no chemical change in the adsorption process.The results of TG and SEM showed that the composite phase change material had good stability.The results of leakage test showed that the best vacuum time of CE/PA-PCMs was 4h,and the adsorption rate was 108.9%.The best vacuum adsorption time of EP/PA-PCMs was 1h,and the adsorption rate was 498.3%.The compressive strength and flexural strength of the samples with CE/PA-PCMs and EP/PA-PCMs mixed with building gypsum increased from 0 to 30% were tested.The results showed that the flexural strength of the samples with CE/PA-PCMs decreased from 1.53 MPa to 0.94 MPa,the compressive strength decreased from 3.3 MPa to 2.5 MPa,the flexural strength of the samples with EP /PA-PCMs decreased from 1.53 MPa to 0.74 MPa,and the compressive strength decreased from 3.3 MPa MPa to 1.5 MPa.The test results of mechanical properties after 100 freeze-thaw cycles showed that with the increase of CE/PA-PCMs content,the flexural strength of the specimens decreases from 1.5 MPa to 0.8 MPa,and the compressive strength decreases from 3.2 MPa to 2.4 MPa.while with the increase of EP/PA-PCMs content,the flexural strength of the specimens decreases from 1.5 MPa to 0.7 MPa,and the compressive strength decreases from 3.2 MPa to 1.4 MPa.After 100 cycles of freeze-thaw,the maximum mass loss rate of two kinds of gypsum energy storage blocks was 0.17% and 1.4%,respectively.Compared with the blank gypsum board,the temperature of phase change model room was reduced by 2.49℃ and 2.4℃ respectively.The temperature control effect was good,so the phase-change energy storage gypsum board was used well as the building envelope,and on the premise of satisfying the mechanical properties,the phase-change energy storage gypsum board as the building envelope,the effect was better when the content of more was selected.The composite phase change materials prepared in this experiment has suitable phase transition temperature and phase change latent heat.The porous material has good thermal stability after adsorption,and is closely combined with building gypsum.Application prospects.