聚氨酯相变微胶囊的储能和热分解性能

Energy storage and thermal decomposition performance of polyurethane microcapsules

以聚氨酯为囊壁,二十烷为囊芯通过界面聚合法制备微胶囊,采用光学显微镜(OM)、扫描电子显微镜(SEM)对该微胶囊材料进行表征,采用示差扫描量热仪测量分析微胶囊的热性能和储能性能及其相变机理,采用Kissinger法和Ozawa法研究该微胶囊材料的热分解动力学。结果表明,制得的微胶囊呈规则球形,表面形貌光滑致密,粘连少,平均粒径18μm,囊壁厚度为1.80μm,产率为91.00%,囊芯质量分数为58.46%。经过多次热循环得到微胶囊的DSC曲线,均表现为单一熔融峰和双重结晶峰,其相变过程中同时发生固-固和固-液相变,相变机理属于随机成核和随后生长,相变机理函数为G(a)=-ln(1-a),相变过程表现为一级反应。相变储能材料存在三个热失重阶段,聚氨酯囊壁的保护作用使得相变储能材料的起始分解温度提高23℃,储热能力较好。根据Kissinger和Ozawa方程计算该微胶囊的活化能分别为311.27 kJ/mol、293.16 kJ/mol,热分解过程为一级反应。

The microcapsules were prepared by interface polymerization with polyurethane as the capsule and wall and eicosane as the capsule core.The microcapsules were characterized by optical microscope(OM)and standard electronic modules(SEM).The energy storage performance and thermal performance and its phase change mechanism were measured and analyzed by differential scanning calorimeter.The Kissinger and Ozawa methods were used to study the thermal decomposition kinetics.The results showed thatthe microcapsules were regularly spherical in shape with a dense and smooth surface morphology and little adhesion.The average particle size was 18.18μm and the capsule wall thickness was 1.80μm.The productivity was approximately 91.00%and the capsule core content was 58.46%.The DSC curves obtained from multiple thermal cycles all exhibited single melting peak and double crystallization peak.The simultaneous solid-solid and solid-liquid phase transitions occurred during the heating process and the phase transition process belonged to random nucleation and subsequent growth.The integral equation of the phase transition mechanism function was G(a)=-ln(1-a),and the phase change reaction was the first order reaction.There were three stages of thermal weight loss.The protective effect of polyurethane capsule wall increased the initial decomposition temperature of phase change energy storage materials by 23 C,and the heat storage capacity was good.According to the Kissinger equation and Ozawa equation,the activation energies of microcapsules were calculated to be 311.27 kJ/mol and 293.16 kJ/mol,respectively and the thermal decomposition process was a first order reaction..