PE/CaO薄膜的光热降解行为

Thermal and photo-degradability of PE/CaO films

采用热重法(TG)和人工加速老化法分别模拟聚乙烯/氧化钙(PE/CaO)薄膜的焚烧和光照过程,研究了PE/CaO薄膜的光热降解行为.研究结果表明,采用Kissinger和Ozawa法对添加不同含量CaO的PE薄膜的热降解过程进行计算,得到PE/CaO薄膜的动力学参数,2种方法求出的表观活化能基本吻合.采用Crane方程计算出PE和PE/CaO薄膜热降解的反应级数,结果显示均为一级反应.对添加10%、20%、25%CaO的PE薄膜的热降解过程采用Kissinger法计算,其表观活化能分别为220.4、197.6、217.8kJ·mol-1,均比纯PE薄膜的表观活化能224.0kJ·mol-1低,其热降解性能更好.添加CaO的PE薄膜在光照下,产生氢过氧化物和自由基,主要发生NorrishⅡ型断裂反应,增加了自由基的生成,加快了降解速度.

The thermal and photo-degradability of PE/CaO films were investigated by thermogravimetric analysis （TG） and artificial accelerated aging tests to simulate incineration and solar irradiation, respectively. The kinetic parameters of PE films with various CaO contents were calculated both by the Kissinger and the Ozawa methods. The results show that the apparent activation energies calculated from the two methods are comparable. According to the Crane equation, the thermal-degradation of PE or PE/CaO film has been found to follow first-order reaction kinetics. The apparent activation energies （by Kissinger equation） of PE/CaO films with CaO contents of 10% , 20% and 25% are 220.4, 197.6 and 217.8 kJ·mol^-1 ,respectively. The values are lower than that of PE film （224.0 kJ·mol^-1） , suggesting that the thermal-degradability of PE/CaO film is better than that of pure PE film. It is clear that hydroperoxides and free radicals are formed when PE/CaO film is exposed to UV radiation. The free radicals lead to Norrish type Ⅱ chain-breaking reactions, primarily. The chain scission process produces more free radicals, which result in acceleration of the degradation.