用自由体积理论研究玻璃态PS的焓松弛

Enthalpy relaxation of polystyrene reinvestigated based on free volume theory

以玻璃化转变的自由体积理论为基础对聚苯乙烯(PS)焓松弛动力学进行了考察,低温下平衡态的热力学性质用两种模型描述,一是假设自由体积为0(模型M1),二是假设自由体积在TgF以下冻结(模型M2),松弛时间采用Vogel方程计算.结果表明,采用模型M2计算所得归一化比热pN与样品实测结果方差小于模型M1,极限假想温度f、吸热峰值温度max也更接近实验结果,Vogel模型参数的热历史依赖性有明显降低.采用模型M2计算所得Kohlrausch指数随热处理条件变化呈现比模型M1更加合理的变化规律.这说明假设聚合物在g以下平衡态的自由体积冻结于大于0的数值能更合理地解释聚合物的焓松弛数据,也与Flory的自由体积理论相一致.

The enthalpy relaxation of PS was restudied based on the free volume theory of glass transition. Two models for describing the thermodynamic properties of the equilibrium state of polymer at low temperature were proposed. The flee volume was assumed to be zero and to be froze at the values of the equilibrium state of the polymer at temperature TgF in modelsMlandM2, respectively. The relaxation time was calculated by using Vogel model. It was found that the fitting results of CNp using model M2 are better than those of using M1. Meanwhile, the obtained T＇f and Tmax values are more close to the experimental data. The thermal history dependence of the Vogel model parameters decreases greatly and a more reasonable thermal history dependence of Kohlrausch stretch exponent fl is obtained when M 1 is instead by M2.