Preparation And Characterization Of Paraffin Microcapsules And Micro/nanocapsules With Polymethyl Methacrylate Shell

The phase change materials(PCMs)could absorb or release a lot of energy during the phase change processes with the surrounding temperature change,which are excellent energy storage materials.However,the leakage of PCMs during the phase transition processes limits the further applications.Microencapsulation technology is aimed to encapsulate PCMs into microcapsules to solve the inconvenience of paraffin in solid-liquid phase transition.Microcapsules with 50~#paraffin wax(T_m=50~52°C),58~#paraffin wax(T_m=58~60°C)and 26~#paraffin(T_m=26~28°C)as core materials and micro/nanocapsules with 58~#paraffin wax as core were prepared by suspension-like polymerization using polymethyl methacrylate(PMMA)as shell material,respectively.In order to prepare 50~#paraffin wax microcapsules with good performance,pentaerythritol tetraacrylate(PETRA)was chosen as the crosslinking agent and the optimum mass ratio of monomer/crosslinker was determined.The obtained microcapsules had good spherical shape and high core content calculated as 73.2 wt%.Furthermore,microcapsules-hydroxyl terminated polybutadiene(HTPB)polyurethane elastomers composites were synthesized by adding the microcapsules in the preparation of polyurethane elastomer.For the preparation of 58~#microcapsules,the microencapsulated paraffin could be up to 89.5 wt%.For 26~#paraffin microcapsules,the highest content of core material was 54.9 wt%.58~#paraffin micro/nanocapsules were prepared by suspension polymerization.Moreover,the effects of type and content of dispersant,and mass ratio of core/shell to the encapsulation tightness of shell material were investigated.The prepared micro/nanocapsules were regularly spherical in shape within micro and nano dimension,and the phenomenon that nanocapsules filled into the interior of microcapsules was observed.The micro/nanocapsules had better thermal stability than that of microcapsules.The shell PMMA could encapsulate paraffin compactly with little decreasement in melting enthalpy after washed with petroleum ether.The particle size of micro/nanocapsules decreased with the increase of PVP content from 5%to 9%.The paraffin content of prepared micro/nanocapsule could reach to 80.2 wt%.Using SMA as emulsifier,the synthesized microcapsules were smooth and free of debris in surface,with particle sizes about 1~5?m.Furthermore,the phase transition enthalpy of microcapsules was pretty high and the core content was 61.5 wt%,which indicated SMA a suitable emulsifier for preparing paraffin wax microcapsules.The micro/nanocapsules-polyurethane elastomer composites were synthesized sucessfully with good properties by adding micro/nanocapsules into preparation system of polyurethane.