超支化聚硅氧烷的紫外光固化行为及固化动力学研究

采用等温差示光量热技术(DPC)研究了超支化聚硅氧烷的紫外光固化行为及固化动力学. 探索了引发剂浓度、 光强度、 聚合温度和环境气氛对固化行为的影响规律. 研究结果表明, 增加光引发剂浓度和光强度及提高环境温度均可提高其固化速率和双键最终转化率. 在空气中固化时存在氧阻聚现象, 增大光强度可以显著缩短诱导期. 运用带扩散因子的自催化固化动力学模型研究了其光固化动力学, 计算出特定条件下的光固化动力学参数, 反应总级数约为6—7, 表观活化能为9.95 kJ/mol. 通过超支化聚合物与两种结构类似的低官能度单体光固化行为的对比, 研究了超支化聚合物固化行为与其分子结构的关系, 发现由于超支化大分子的独特结构, 在固化初始阶段便产生凝胶, 因此双键的最终转化率偏低.

UV Curing Behavior and Kinetics of Hyperbranched Polysiloxane

Ultraviolet(UV) curing behavior and kinetics of hyperbranched polysiloxane(HBP) were studied via isothermal Differential Photo Calorimeter(DPC) technology. Firstly, the influences of the factors such as photoinitiator's concentration, light intensity, temperature and atmosphere, on UV curing behavior were investigated in detail. It is found that both curing rate(R) and ultimate vinyl conversion(C) could be raised by the increase of photoinitiator's concentration and UV light intensity as well as elevating temperature. Oxygen possessed an inhibition effect on the curing, however, it could be reduced by enhancing UV light intensity. The results could be confirmed by that induction period can be reduced by higher UV light intensity. Secondly, curing kinetics were also studied by using an autocatalytic model with a diffusion term attached. The kine-tic parameters were calculated from that model, and correspondingly, the total apparent reaction exponent and apparent activation energy were obtained within the range of 6—7 and 9.95 kJ/mol, respectively. Comparative results between kinetic calculations and experimental measurements show that the autocatalytic model used was suitable to simulate the autocatalysis phenomena at the initial stage and the termination process could be controlled by diffusion. Finally, comparison of curing behavior between the HBP and two low-functionality monomers indicates that the unique hyperbranched structure and the corresponding high multifunctionality led to the gelation at the very initial stage of curing, as a result, relatively low ultimate vinyl conversion was observed.