热降解动力学方法研究ABS的降解机理

在空气气氛下，采用热重分析(TGA)研究了不同升温速率下丙烯腈-丁二烯-苯乙烯共聚物（ABS）的热降解过程，分别使用Flynn-Wall-Ozawa法和Kissinger法对降解过程进行动力学分析。结果表明，ABS降解包含2个阶段，350~450 ℃之间发生降解反应，同时伴有交联反应，降解活化能（Ea）在200 kJ/mol左右，转化率在80 %~90 %时发生炭化反应，Ea提高到262.81 kJ/mol；500~600 ℃之间是残炭的氧化，Ea降低到130 kJ/mol左右，炭层稳定性较差。ABS的降解过程反应级数为0.946，降解受到随机成核与生长机理控制，降解在ABS基体内进行，而不是表面，所以降解气体燃烧不完全，易产生黑烟和熔融滴落。

Degradation Mechanism of ABS by Thermal Degradation Kinetics

In air atmosphere, the mass loss of ABS resin at four different heating rates was investigated using TGA. The kinetics of thermal degradation was described using Flynn-Wall-Ozawa and Kissinger methods. It showed that there were two degradation stages; the first stage between 350 and 450 ℃ was the rapid degradation with activation energy (Ea) about 200 kJ/mol; the cross-linking reaction coupled with the degradation. When the mass loss in the range of 80 %~90 %, char formation was observed with Ea increasing to 262.81 kJ/mol. The second stage was the oxidation of carbon with Ea decreasing to 130 kJ/mol, so the carbon had a poor thermal stability. The reaction order of ABS thermal degradation was found to be 0.946, so the mechanism of ABS thermal degradation was controlled by the processes of random nuclear formation and growth. The thermal degradation occurred in the bulk rather than surface of ABS, so the gas of thermal degradation could not be burnt completely and lead to black smoke and dripping.