Abstract:

The phase change of microcapsules was prepared by in-situ polymerization using 32℃ phase change wax as the core material and melamine-formaldehyde resin as the wall material. The modified nano-SiO₂ was used to form a hybrid layer on the surface of paraffin emulsion to improve the performance of microcapsules. The organic modification effect of KH-570 on nano-SiO₂ was investigated by contact Angle tester. Scanning electron microscope(SEM) and X-ray energy spectrometer(EDS) were used to analyze the surface morphology of microcapsules and the chemical elements on the surface of shells. The thermal properties of phase change of microcapsules were measured by DSC. The results showed that KH-570 had a significant effect on the organic modification of nano-SiO₂ particles. When the addition amounts of modified SiO₂ reached 3%, the microcapsule surface was smooth and spherical, and the modified SiO₂ particles were dispersed evenly on the capsule surface. The formation of SiO₂ hybrid layer can effectively improve the thermal stability of microcapsules. The phase transition enthalpy of microcapsules was 135.1J/g, the phase transition process lagged behind, and the permeability of microcapsule core materials in organic solvents decreased from 66.1% to 45.8%. After 1000 thermal cycles, the mass and phase transition enthalpy loss rates were only 7% and 24.4%, respectively.

Key words: nano-SiO₂, microcapsules, phase change material, melamine-formaldehyde resin, hybrid layer, permeability

摘要：

以相变温度为32℃的石蜡为芯材，三聚氰胺-甲醛树脂/改性SiO₂杂化层为壁材，采用原位聚合法制备相变微胶囊。使用接触角测定仪考察了KH-570对纳米SiO₂的有机改性效果；运用扫描电子显微镜（SEM）和X射线能谱仪（EDS）分析了微胶囊表面形貌及壳层表面的元素分布；采用差示扫描量热仪（DSC）测定了相变微胶囊的热性能参数。结果表明：使用KH-570有机改性的纳米SiO₂颗粒制备杂化层能显著提升微胶囊的热稳定性与使用耐久性。当改性SiO₂质量分数为3%时，制得的微胶囊呈光滑球形，SiO₂颗粒在胶囊壳层表面分散均匀，其相变焓为135.1J/g，相变过程滞后，并且微胶囊芯材在有机溶剂中的渗透率由66.1%降至45.8%，经历1000次热循环后的质量与相变焓损失率仅为7%与24.4%。

关键词: 纳米SiO₂, 微胶囊, 相变材料, 三聚氰胺-甲醛树脂, 杂化层, 渗透率