热处理对PMMA@PCM纳米胶囊相变特性的影响及机理

The Effect of Heat Treatment on the Phase Transition Characteristics of PMMA@PCM Nano-capsules and the Mechanism

采用界面聚合法制备了以石蜡为芯材、聚甲基丙烯酸甲酯为壳层的纳米胶囊相变材料。胶囊的直径为100-400nm，相变焓可达29J／g，封装比率约为35％。采用差示热扫描量热仪（DSC）对PMMA@PCM经40℃、60℃及100℃热处理后相变特性的变化进行了探讨。结果显示，随着热处理时间的延长，相变温度均有所升高。凝固温度的升高是由于胶囊表面形成了一定量的相变晶种，而熔化温度的升高则是由于纳米胶囊体积的增加而引起的热传导率降低。这一研究结果将有助于分析纳米胶囊相变过程的微结构变化理论。

The interracial polymerization method was used to prepare nano-capsules with paraffin as the core and PMMA as the shell. The particle size of capsules was 100-400nm with the latent heat of -29J/g and the encapsulation ratio of -35%. Differential scanning calorimeter（DSC） was used to study the effect of heat treatment situation, such as at 40℃, 60℃ and 100℃, on the phase transition characteristics of PMMA@PCM. The analysis shows that with the heat treating time increasing, the phase change temperatures all increase. The increase of freezing temperature should be the aggregation of crystal seed in the surface of the capsules. The improving of melting temperature should be the increasing of capsule volume, which will decrease the pyroconductivity of capsules. These analysis results are helpful for the study of micro-structure change of capsules during phase change process.