摘要
使用质谱、热分析手段研究了PMMA热解反应 .结果表明 ,在氮气中 ,PMMA -CH =CH2 有两个失重阶段 ,分别对应于主链末端双键引发的断链和主链无规则断链反应 ,转折点的失重率约为 2 6 % .其中 ,第一阶段的失重速率受扩散过程控制 ,平均表观活化能E为 15 8.5kJ/mol,lnA为 2 7.6 9;第二失重阶段为 1.5级化学反应 ,平均表观活化能E为 2 14 .79kJ/mol,lnA为 4 0 .4 6 .在空气中 ,PMMA也有两个失重阶段 ,反应机理为 1级化学反应 ,转折点处的失重率约为 70 % .其中在第一失重阶段平均表观活化能E为 130 .32kJ/mol,lnA为 2 4 .81,在此阶段中 ,过氧化基团的分解反应对PMMA的失重速率有重要影响 ;在空气中第二失重阶段平均表观活化能E为 78.2 5kJ/mol,lnA为 13.97.
Effect of oxygen on the thermal degradation of PMMA was studied by mass spectrometry and thermal analysis with TG and DTA. For radical polymeric PMMA, there were two main degradation models in N-2: the end-chain scission model and the random chain-breaking model. The conversion rate at turning point was about 26%. Kinetic analysis results indicated the end-chain scission was controlled by diffusion process and the average activation energy E was 158.5 kJ/mol and InA was 27.69. The random chain-breaking reaction was 1.5 order chemical reaction. The average activation energy E and InA was 214.79 kJ/mol and 40.46, respectively. In air, there were also two stages of mass loss and the turning point conversion rate was about 70%. In the first stage, the decomposition of peroxy radicals has a notable effect on the overall degradation rate. The associated kinetic mechanism was first order chemical reaction and the average activation energy E was 130.32 kJ/mol and InA was 24.81. In the second stage of mass loss, PMMA had already burnt and the reaction was also first order chemical reaction. The average activation energy and InA were 78.25 kJ/mol and 13.97, respectively.
基金
香港理工大学策略性学术发展领域高密度都市先进建筑科技基金 (1-A0 38)资助
