Preparation And Properties Characterization Of Polyurethane Microencapsulated Phase Change Materials

The increasing seriousness environmental problems caused by the development of society and the consumption of traditional petrochemical energy makes researchers devote themselves to the development and utilization of new energy.Phase change materials are not only a new type of materials which can store and release energy,but also environmentally friendly and harmless,more and more attention have been paid to it.However,the direct use of pure phase change materials are limited due to the change of phase state and low thermal conductivity.In order to solve this problem,the technology of microencapsulated phase change materials?MEPCMs?have been developed by researches.At present,the most studied are MEPCMs with polymer as shell materials and organic phase change material as core material.But the poor compactness and supercooling of MEPCMs with polymer shell materials limit its application.This paper mainly focuses on the problems such as poor compactness and supercooling of traditional MEPCMs with polymer shell materials.?1?The larger the size of MEPCMs,the better the compactness.Therefore,a large size MEPCMs with polyurethane?PU?as shell material was synthesized by interfacial polymerization between polyurethane prepolymer and polyol in oil-in-water emulsions.The results showed that the employment of the synthesized PU prepolymer was beneficial to synthesize the MEPCMs with more than 100?m average particle size,when the agitation speed increased from 200 rpm to 500 rpm,the diameter of MEPCMs decreased from 433?m to 63.3?m,but the weight loss of MEPCMs increased from 10.47 wt%to 43.49 wt%at high temperature,the compactness became worse.The MEPCMs with better mechanical properties can be obtained with PEG content of 20 wt%-30wt%in the prepolymer,and when the core/shell mass ratio was 3:1,the core material content of MEPCMs was as high as 75.18%,and showed good thermal stability and storage stability.?2?PU MEPCMs were prepared by Pickering emulsion polymerization.The results showed that average particle size of MEPCMs prepared by Pickering emulsion polymerization was also more than 100?m.The MEPCMs prepared at a certain nano-Ti O₂concentration had good compactness,mechanical properties and thermal stability and possessed promising thermal cycling stability,chemical stability and storage stability.The DSC results showed that the change of nano-Ti O₂concentration would affect the phase change behaviors of MEPCMs,the temperature of heterogeneous nucleation of phase change materials increased from-20.96?to-18.35?with the nano-Ti O₂concentration increased from 0.03%to 0.24%.?3?PU MEPCMs containing mixed core materials were prepared through interfacial polymerization by adding solid paraffin replacing part methyl laurate,and the related properties of MEPCMs were studied.The results showed that the chemical structure,the mechanical properties,compactness,particle size distribution and thermal stability of MEPCMs were not influenced by the addition of solid paraffin,but the phase change behavior of MEPCMs was affected.When the solid paraffin content increased 0 to 4%,the freezing point of methyl laurate in MEPCMs increased from-19.83?to-10.12?,but the thermal storage capacity reduced by 21.4%relatively.