Preparation And Performance Research Of Polypyrrole-Modified Yeast Phase-Change Microcapsules And Phase-Change Gypsum Board For Electromagnetic Protection

Energy is an important material basis for promoting the progress of human civilization and social development.It is related to the security,stability,prosperity and development of a country.The world is undergoing profound changes in a century now.In addition,the sudden outbreak of COVID-19 has brought far-reaching impacts to countries.A new round of technological revolution and industrial transformation has developed in depth.People’s lifestyle are shifting to low-carbon production at an accelerating pace.Saving and developing energy is essential to ensure national energy security and achieve carbon peak and carbom neutrality.It is also an important support for promoting economic development and environmental protection.The development of phase change energy storage technology promotes the utilization and continuous optimization of renewable energy.The latent heat of phase change can be used to store a large amount of thermal energy and reduce energy consumption,which is conducive to solving the opportunities and challenges faced by the modern energy system.In this paper,yeast wrapping phase change material microcapsules(YPs)were prepared by using yeast cell wall(YCW)to wrap binary eutectic fatty acids(CA/LA)prepared with a certain ratio of capric acid and lauric acid.The surface of the microcapsules was modified with polypyrrole to obtain polypyrrole-modified yeast wrapping phase change microcapsules(PYPs).Then the PYPs were incorporated into the gypsum board to prepare the electromagnetic protection phase change gypsum board(EP/PYPs-GB).The microstructure and thermal properties of YPs and PYPs were characterized by SEM,DSC and FI-IR.The influence of PYPs on the properties of gypsum board was also analyzed.The main contents are as follows:Firstly,CA/LA was prepared with the mass fraction ratio of capric acid and lauric acid at 6:4to satisfiy the comfortable temperature range of human body(18～28°C).The cell wall extracted from yeast was used to wrap CA/LA to prepare YPs.The effects of embedding temperature,embedding time,core-to-wall ratio and ethanol content on the encapsulation rate of YPs were investigated by single factor experiments,and the optimal conditions for preparing YPs were obtained by combining with orthogonal experiments.The optimal reaction conditions were as follows: the embedding temperature was 55℃,the embedding time was 6h,the core-wall ratio was 2:1 and the ethanol content was 0ml,and.Under the optimal conditions,the maximum encapsulating efficiency of YPs4 was 48.3% and the mass loss rate was 0.98%.The characterization results showed that YPs4 was ellipsoid with a particle size of 2～5μm,and the phase transition temperature and latent heat of phase transition during melting were 20.7°C and75.7J/g,respectively.Secondly,the surface of YPs was modified by polypyrrole with good electrical conductivity through chemical oxidative polymerization.It was found that when sodium dodecyl sulfonate(SDS)with large hydrophilic equilibrium value(HLB)was used as the surfactant,the conductivity of PYPs(SDS)was the best,and the resistivity was 1.343Ω·cm.The particle size of PYPs particles was larger than that of YPs under scanning electron microscope.The particle size of polypyrrole particles on PYPs surface was in the range of 50～200nm.The photothermal conversion efficiency of PYPs(SDS)was 53.3%.The phase transition temperature was close to that of YPs,and the latent heat value of phase transition was 54.9 J/g.The binding mode between polypyrrole and YPs was physical binding.Finally,EP/PYPs-GB was prepared with gypsum powder as the main raw material and PYPs(SDS)as the absorbing material.The performance test results of EP/ PYPs-GB showed that the maximum reflectivity of EP/ PYPs-GB prepared with different dosage of PYPs(SDS)can reach8.6d B in the frequency range of 2～18GHz.PYPs(SDS)formed a conductive network in the gypsum board and effectively attenuated electromagnetic radiation.Compared with the gypsum board without PYPs(SDS),the seven-day flexural strength and compressive strength of EP/PYPsGB decreased with the increase of the content of PYPs(SDS),and the thermal conductivity increased with the increase of the content of PYPs(SDS).In addition,the temperature control effect of EP/PYPs-GB was also tested.The results showed that the heating and cooling rate and peak temperature of EP/PYPs-GB20 were lower than those of EP/PYPs-GB0,which indicated that PYPs(SDS)had a certain temperature control capability.When the content of PYPs(SDS)is 20%,the gypsum board has the best absorbing performance and can meet other usage standards.