Application Of Paraffin Based PCM In Low-infrared-radiation Coatings

In this paper, the preparation and characteristics of composite paraffin were discussed. The phasechange coating was prepared and preliminary study on its temperature control performance wascarried out. Two projects was designed for the preparation of the composite low-radiation coating, inaddition, the effects of the Al powder and PCM on radiation of the coating were investigated.SiO2aerogel was mixed with melting paraffin, and the form-stable paraffin was formed throughphysical absorption. The structure and thermal property were characterized by SEM、IR、DSC andheat leakage test. The results showed that the form-stable paraffin has better stability in heat, greaterenergy storage density. Two kinds of paraffin with different melting point could composite a new kindof paraffin. The melting point of the new paraffin changed with the change of two components’ massratio. The results of DSC indicate that the melting point and latent of new paraffin were between thoseof two components. Paraffin and octadecanoic acid/cetylic acid mixed and formed the PCM with newphase change temperature and latent. The content of octadecanoic acid/cetylic acid was higher, thephase change temperature and latent of the new PCM was higher.The form-stable paraffin was grinded and through mesh screening (100mesh). Then the phasechange coating was prepared using these small grains of paraffin, and the temperature controlperformance of the coating was characterized. The content of PCM was higher, the time oftemperature control was longer, so the control effect was better. The thickness and area of the coatingwere bigger, the temperature control effect was better. The heat conductivity of the coating wassmaller, the falling of temperature was higher and the time of temperature control was longer. Whenthe ambient temperature was slightly higher than the phase change temperature of PCM, the PCM hasthe best control effect.Double-layer low-radiation coating was designed by the composition of low-emissivity coatingand phase change coating. The low-emissivity coating contained40%Al powder, and the phasechange coating contained30%form-stable paraffin. The radiating capacity of the double-layer coatingwas estimated by emissivity and temperature testing. The emissivity was between0.1and0.2, and thetemperature was reduced about5℃.The single-layer low-radiation coating was prepared on the basis of the idea of double-layercoating. Al powder and PCM were mixed to coating material. The emissivity and temperature weretested with changing the content of Al and PCM. The content of Al was higher, the emissivity was lower and the reducing of temperature was smaller. However, the content of PCM was higher, theemissivity was higher and the reducing of temperature was bigger. As the controlling of temperaturewas within7℃, emissivity was the main factor affecting the level of radiation.