挤塑聚苯乙烯泡沫热解特性和动力学研究

Study on Decomposition Characteristics and Kinetics of Extruded Polystyrene Foam

基于热重红外分析仪对挤塑聚苯乙烯泡沫(XPS)的热解特性和动力学机理进行研究。在空气和氮气气氛下选取10、20、40、50℃/mim四种升温速率。改进的Vyazovkin方法用于计算XPS热解的活化能,多元非线性回归方法用于确定动力学模型和相应的动力学参数。结果表明,随着转化率的增加,XPS在空气中分解的活化能由128.3 k J/mol增加到159.2 k J/mol;而在氮气中XPS分解的活化能维持在171.1 k J/mol左右。XPS在空气中热解为连续的两步反应,可分别由二级反应模型(F2)和简单的Prout-Tompkins方程(B1)描述。在氮气中分解为单步反应,可由三维相界反应模型(R3)描述。通过对比非等温和等温条件下实验和计算得到的热重曲线,对反应动力学模型进行了验证。

The decomposition characteristics and kinetic mechanism of extruded polystyrene foam( XPS) were studied by thermogravimetric infrared spectroscopy( TG-FTIR). Thermogravimetric analyses were performed under air and nitrogen atmosphere at heating rates of 10,20,40,50 ℃/min. The modified Vyazovkin method was used for evaluating the dependence of the activation energy on conversion degree. The multivariate non-linear regression method was further applied for investigation the reaction model and the corresponding kinetic parameters. Activation energies found for decomposition in air atmosphere ranges from 128. 3 to 159. 2 k J/mol and for decomposition in nitrogen atmosphere remains nearly constant at about 171. 1 k J/mol. The thermal decomposition of XPS in air indicates a two step process and follow second-order reaction model →simple Prout-Tompkins equation model( F2→B1),while decomposition in nitrogen appears to be a single step process follows three-dimensional phase boundary reaction model( R3). The accuracy of the reaction models were further verified by checking the agreement between experimental and calculated thermogravimetric curves in non-isothermal and isothermal conditions.