原位聚合法制备相变材料微胶囊及其致密性

采用原位聚合法以三聚氰胺-尿素-甲醛预聚物为壁材, 包覆一种相变点为24 ℃、相变焓为225. 5 J / g 的有机相变材料, 制备一种具有调温储热功能的复合材料。通过改变三聚氰胺和尿素摩尔比对微胶囊壁材渗透性和强度进行研究。相变材料受热时会在微胶囊内部产生较大的蒸汽压使微胶囊壁破裂渗出芯材, 采用TGA 测定微胶囊热失重温度得到胶囊壁破裂时的温度。采用压力法观察微胶囊受力后的形貌, 对其强度进行评价。采用752型紫外分光光度仪对微胶囊壁渗透性进行表征。实验结果表明: 微胶囊呈球形, 平均粒径小于5μm , 固化剂滴加速度为0. 8 mL/ min 时微胶囊形貌最好。当尿素质量为反应总单体质量的20 %时, 与不加尿素相比, 微胶囊热失重温度大约提高30 ℃, 可以承受6. 0 MPa 压力而不破损, 并且渗透性并不增加。 

Preparation and penetrability of microencapsulated phase change materials

Through the in-si t u polymerization method , a kind of phase change materials microcapsule was preparedby using melamine-urea-formaldehyde resin as the shell material and a phase change material as the core , of whichthe melt point and phase change enthalpy are 24 ℃and 225. 5 J / grespectively. The penet rability and st rength of microcapsule were investigated by altering the mole ratio of urea to melamine. The thermal damage mechanism is thatthe phase change materials leak out f rom the microcapsule when they are heated , and the breakage of the shell wasdue to the thermal expansion of the core and shell materials at high temperature. The damage temperature of the microcapsule shell can be obtained by TGA. The st rength of the shell was evaluated through observing the surfacechange under pressure by mean of scanning elect ron microscopy. The penet rability of the microcapsule was characterized in ethyl alcohol by mean of 752 spect rophotometer. As a result , the average diameter of the microcapsule issmaller than 5μm , and the particle size is cent ralized when the dropping rate of the solidifying solvent is less than018 mL/ min. The mass loss temperature of the microcap sule can be further enhanced up to 30 ℃while the reactionsystem contains 20 % (mass f raction) urea. The microcapsules do not rupture under a pressure of 6. 0 MPa , and thecore material leaks out very slowly from the microcapsule in ethyl alcohol.