Preparation And Properties Of Medium-Low Temperature Phase Change Polyurethane Rigid Foam Composites

Promoting green building is one of the important ways to achieve the goal of "double carbon".The application of phase change materials to buildings to improve the thermal comfort of lightweight structures has become a hot spot for research on green building materials.In this paper,we develop polyurethane rigid foam composite insulation materials with medium and low temperature phase change function for the application of building energy-saving thermal storage materials.In the experiment,octadecane/expanded graphite spherical phase change material and 70# paraffin wax/expanded graphite spherical phase change material were prepared by vacuum adsorption method and compounded to obtain double-order phase change material with temperature regulation and temperature control function in the middle and low temperature region,which was compounded and filled with modified polyurethane rigid foam(RPUF)to prepare a polyurethane rigid foam composite material with temperature regulation and temperature control and functionalization,and the main experimental results are as follows.The octadecane/expanded graphite shaped phase change material was prepared by vacuum adsorption method,and the effects of octadecane content on microstructure and enthalpy of phase change were investigated.The results showed that no leakage occurred at 90% wt of octadecane,the structure stability was high,the melting temperature and solidification temperature were 27.15? and 26.38?,the enthalpy of melting and solidification were 188J/g and 186.9J/g,and the crystallinity was as high as 85.5%.The 70# paraffin wax//expanded graphite sizing phase change material was prepared by vacuum adsorption method,and the effects of 70# paraffin wax content on the microstructure and phase change enthalpy were investigated.The results showed that no leakage occurred in the prepared sizing phase change material with the content of 70#paraffin wax at 92%wt.The melting and solidification temperatures were 70.2°C and67.93°C,respectively,and the enthalpies of melting and solidification were 190.8J/g and185.9J/g,respectively,with 80% crystallinity.The double-order composite phase change materials were prepared by compounding octadecane/expanded graphite spherical phase change material and 70# paraffin wax//expanded graphite spherical phase change material,and the effects of different compounding ratios on the phase change enthalpy and temperature regulation performance of the composites were investigated.When the compounding ratio is 1:1,the prepared double-order phase change materials can effectively slow down the heating rate to achieve the temperature regulation effect,and meet the requirements of-30?-70? use temperature of energy-saving building materials.The results showed that the heat absorption/exhaustion peaks appeared near 27? and 60?,and the enthalpy of melting and solidification were 213.4J/g and 205.4J/g,respectively,and the starting thermal weight loss temperature of the double-order phase change material was increased and had good thermal stability.The double-order phase change composites were blended with polyurethane to prepare rigid polyurethane phase change materials,and medium and low temperature phase change polyurethane rigid foam was prepared.The effects of the content of the double-order phase change material on the bubble structure,apparent density,mechanical properties,enthalpy of phase change and thermal conductivity were investigated.The results showed that the apparent density increased by 1.43 times with increasing addition amount and the compression strength decreased significantly.The medium and low temperature phase change polyurethane rigid foam prepared at 95 %wt of addition can effectively reduce the heat loss caused by heat transfer,and has excellent temperature regulation and control ability to achieve the purpose of energy saving and consumption reduction.Compared with the results of the same type of study,the prepared medium and low temperature polyurethane rigid foam has a higher enthalpy value.The test results show that the temperature difference between the medium and low temperature phase change polyurethane rigid foam and the pure RPUF is about 6.1? at the maximum during the simulated environment temperature rise/fall,and the temperature of the two only reaches the same after 8460 s.As the double-order phase change materials exerted phase change,a plateau period with significantly lower temperature than pure RPUF occurred around 26°C and 60°C,holding 570 s and 285 s,respectively.