Abstract: As a novel type of low-temperature phase change materials, the microcapsules with the core of liquid paraffin and shell of melamine-formaldehyde resin (MF resin) were synthesized by using in-situ polymerization process. The effects of emulsion formulations, pre-polymerization conditions, shell material content and reaction time were investigated to obtain the optimized microcapsules. The as-prepared products under the optimal conditions showed high quality, their surface was smooth and dense, and free of any adhesion. The experimental characterization showed that in the microcapsules over 75%(ω) paraffin liquid was well encapsulated by MF resin, of which the thickness was in the range of no less than 50~100 nm. The microcapsule size was within the range of 1~5 μm and most intense distribution at 3.32 μm. DSC measurements gave two endothermic peaks with the initial phase change temperatures of 4.4 and 28.6℃ respectively, and the total enthalpy was 14.9 J/g which is comparable to the latent heat of commercial liquid paraffin. The microcapsules keep stable up to a high temperature 215℃ or a pressure of 1.0 MPa, as well as excellent thermal resistance against long-term thermal aging and thermal cycle near 300 times.

Key words: phase change material, microcapsule, liquid paraffin, melamine-formaldehyde resin, in situ polymerization

摘要： 采用原位聚合法制备以液体石蜡为囊芯、密胺树脂为囊壁的相变微胶囊，考察了乳化工艺、预聚时间、囊壁含量和聚合反应时间对微胶囊质量的影响，优化了制备工艺. 利用电子天平、扫描电镜、激光粒度仪、傅里叶红外光谱仪(FT-IR)、热分析仪(DSC和TG/DTA)分别研究了优化工艺下微胶囊的囊芯含量、形貌特征、粒径分布、结构和热性能，并考察了其循环稳定性、抗压性能、抗渗透性. 结果表明，微胶囊包覆完整无粘连，表面光洁致密，囊芯含量76%(w)，囊壁厚度至少可达50~100 nm，粒径分布集中在1~5 mm，平均为3.32 mm. DSC显示有2个吸热峰，起始相变温度分别为4.4和28.6℃，总相变潜热14.9 J/g. 胶囊耐热温度可达215℃，能承受1.0 MPa外压，经300次冷/热循环仍保持良好稳定性，且有很高的抗渗透性.

关键词: 相变材料, 微胶囊, 液体石蜡, 密胺树脂, 原位聚合