Standardization of PCM characterization via DSC.

This work investigates the influence of particle size on crystallization behaviour of microencapsulated and emulsified n-octadecane using differential scanning calorimetry (DSC) and laser diffraction. Analyses of microcapsules show a stepwise decrease of nucleation temperature (from 26 °C to 14 °C) with decreasing particle size (from 300 μm to 3 μm). Further reduction of particle size in emulsions (< 0.2 μm) results in a slight decrease of nucleation temperature (<2 °K). Analyses of cooling thermograms of emulsions show two peaks, a minor peak around 8-9 °C and a major peak, which onset nucleation temperature Tc is influenced substantially by the lipophilic character of the surfactants (Tc varies between 13 °C and 22 °C).
The minor peak is attributed to the transition from rotator to stable crystal phase and its signal increases with decreasing particle size.

本研究采用差示扫描量热法（differential scanning calorimetry, DSC）与激光衍射法，探究了粒径对微胶囊化及乳化正十八烷结晶行为的影响。对微胶囊样品的分析结果表明，随着粒径从300 μm降至3 μm，其成核温度呈逐步下降趋势（从26 ℃降至14 ℃）。当乳液体系中粒径进一步降低至0.2 μm以下时，成核温度仅出现小幅下降（降幅小于2 °K）。对乳液冷却热谱图的分析显示存在两处特征峰：一处为8~9 ℃附近的次要峰，另一处为主峰；主峰的起始成核温度Tc受表面活性剂的亲脂性显著影响，其波动范围为13 ℃至22 ℃。该次要峰归因于从旋转相到稳定晶相的相变，且其信号强度随粒径的减小而增强。