Preparation And Characterization Of Particle Size Controllable Microcapsules/Nanocapseies Phase Change Materials

Nanoncapsulated PMMA/HD phase change materials (microPCMs) were prepared by emulsion polymerization, with hexadecane (Hexadecane) as core material, polymethyl methacrylate (PMMA) as wall material. The influence on nanocapsules properties of key factors (emulsify way, HLB value, emulsifier content, HD:MMA ratios, type and content of initiator, cross-linking agent content) were systematically evaluated. The morphology, chemical structure, phase transition temperature and enthalpy, thermal properties of the nanocapsules were investigated by FT-IR, SEM, DSC and TGA. The results show that the optimum conditions for the preparation of nanocapsules were:Span-80/Tween-80 as emulsifiers, HLB value of 10, emulsification time for 1h, emulsifier content is 5%,4% AIBN as the initiator, the core/shell ratio is 2:1,25% PETRA as crosslinker, the system concentration less than 12.5%. The nanocapsules are spherical, compact surface and the average diameters were 300 nm indicated by SEM, The HD content reaches 64% by DSC, the latent heat and phase translation temperature of nanocapsules are 150.1 J·g-1,17.61℃ indicated by DSC. TGA analysis indicated that crosslinker can raise the heat resistant temperature of nanocapsules, with a heat resistant temperature of 170℃.Microencapsulated PMMA/HD phase change materials are prepared by suspension polymerization using styrene-maleic anhydride(SMA) as dispersant, the effect on microcapsules properties of key factors (dispersant content, methyl cellulose (MC)/SMA as dispersant, stirring speed and SiO2 content) were systematically evaluated. Results show that the optimum conditions for the preparation of microcapsules were:SMA:MC= 2:1, the stirring speed of 500-2000rpm, mass ratio of SiO2/microcapsules is 0.1:1. The prepared microcapsules are spherical and the particle size is 10～200μm, HD content reaches 65%, the ratio of oil/water is 0.6:1, with a heat resistant temperature of 180℃. This paper realized the diameter controllable of microapsules/nanocapsules through the selection of polymerization method and the other factors in preparation process. Thus developed the application fields of phase change materials.