二元低共熔脂肪酸相变微胶囊的设计与工艺优化

Design and process optimization of binary low eutectic fatty acid phase change microcapsules

单一脂肪酸的相变温度普遍较高且易泄漏,不能满足其作为相变材料对夏季建筑空调能耗调节的需求。本工作基于真实溶剂类导体屏蔽模型(conductor-like screening model for real solvents,COSMO-RS),采用COSMOthermX软件对7种中链脂肪酸和10种长链脂肪酸两两组合的136种二元低共熔脂肪酸进行设计计算,筛选预测其共熔温度与摩尔比。进而将最优组合作为芯材,三聚氰胺-尿素-甲醛树脂(MUF)为壁材,通过原位聚合法制备相变微胶囊,系统地探讨不同工艺条件(芯壁比、反应温度、反应时间和反应转速等)对该微胶囊热物理性能的影响。结果表明:COSMO-RS模型可以直观地判断材料氢键供体(hydrogen bond donor,HBD)与受体(hydrogen bond acceptor,HBA)之间的关系,最优组合月桂酸(lauric acid,LA)与肉豆蔻酸(myristic acid,MA)摩尔比为0.66∶0.34的LA-MA(LM)理论共熔温度(33.25℃)与实验结果(33.1℃)相似度达98.08%;在芯壁比2∶1、反应时间3 h、反应温度80℃、搅拌转速200 r/min的条件下,MUF对芯材LM的包覆效率为61.37%,较好地解决了泄漏问题,对降低建筑空调制冷能耗具有潜在的应用价值。

The phase transition temperature of single fatty acids is generally high and prone to leakage,which cannot meet the demand for using them as phase change materials for regulating the energy consumption of building air conditioning in summer.Based on conductor-like screening model for real solvents(COSMO-RS),136 binary low eutectic fatty acids of 7 medium chain fatty acids and 10 long chain fatty acids were designed and calculated by using COSMOthermX software,and the eutectic temperature and molar ratio of binary low eutectic fatty acids were predicted.Furthermore,the optimal combination was used as the core material,and melamine-urea-formaldehyde(MUF)resin was used as the wall material to prepare phase change microcapsules through in-situ polymerization.The effects of different process conditions(core-to-wall ratio,reaction temperature,reaction time,reaction speed,etc.)on the thermal and physical properties of the microcapsules were systematically discussed.The results show that the COSMO-RS model can judge the relationship between hydrogen bond donor(HBD)and hydrogen bond acceptor(HBA)more intuitively.The eutectic temperature(33.25℃)in theory is 98.08%similar to the experimental temperature(33.1℃)of lauric acid(LA)-myristic acid(MA)(LM)with the optimal combination of LA and MA with a molar ratio of 0.66 to 0.34.Under the conditions of a core-to-wall ratio of 2∶1,reaction time of 3 h,reaction temperature of 80℃,and stirring speed of 200 r/min,the encapsulation efficiency of MUF on the core material LM is 61.37%,which effectively solves the leakage problem and has potential application value in reducing the energy consumption of building air conditioning refrigeration.