Preparation of high performance copolymer microcapsule encapsulated heat storage material without supercooling

ABSTRACT

The methyl methacrylate (MMA)-based copolymer microcapsules encapsulating Rubitherm®27 (RT27) used as a phase change material were successfully prepared by microsuspension polymerization. The influence of three types of crosslinked comonomers such as ethylene glycol dimethacrylate), trimethylolpropane trimethacrylate, and divinylbenzene (DVB) on the microcapsule formation was studied at various ratios of MMA:crosslinked comonomer. It was found that using MMA:DVB at 70:30 wt% was the optimum ratio. The obtained microcapsules were nonspherical in shape with a dent and high shell strength. In addition, the latent heats of melting and crystallization of the encapsulated RT27 were about 140 J/g-RT27 which were close to those of the original RT27. However, the crystallization temperatures (T_c) of the encapsulated RT27 (14°C) were lower than that of the original RT27 (25°C) which was called supercooling. To prevent supercooling, the effect of nucleating agents (emulgen 150, 1-octadecanol, and RT58) on decreasing supercooling of the encapsulated RT27 was investigated. The results clearly presented that the addition of at least 5 wt% of RT58 significantly increased T_c (25°C) of the encapsulated RT27, whereas the observed latent heats were pretty close to original RT27.