含氯对位芳香族聚酰胺热分解过程中的TG-FTIR与Py-GC/MS分析

对于两种不同相对分子质量的含氯对位芳香族聚酰胺(Cl-PPTA)薄膜样品和聚对苯二甲酰对苯二胺(PPTA)粉末样品,采用热失重-傅里叶变换红外光谱(TG-FTIR)和裂解色谱-质谱(Py-GC/MS)分析其热分解过程.由TG分析得到了样品在空气和氮气气氛下的特征性温度,表明在有氧情况下Cl-PPTA的热稳定性比PPTA好,而且在氮气气氛下高温残留率比PPTA高.在空气气氛下,ClPPTA热分解的主要产物为HCN、CO、CO2、NO2和H2O,且CO2吸收峰最强;将Cl-PPTA薄膜在氮气气氛下进行高温处理,对得到的产物进行IR分析,显示羰基吸收峰逐渐减弱且出现新末端基团或官能团;而高温下Py-GC/MS的结果表明CO2和苯环是Cl-PPTA主要的裂解产物;随着裂解温度的改变,Cl-PPTA气相色谱和质谱发生很大变化,这些裂解产物可以帮助分析Cl-PPTA薄膜的裂解机理.     

Mechanical Property and Crystal Structure of Poly (p-phenylene terephthalamide) (PPTA) Fibers during Heat Treatment under Tension

The relationship between property and structure of poly( p-phenylene terephthalamide)( PPTA) was investigated for the purpose of obtaining products with better performance. PPTA fiber subjected to heat treatment under different conditions was intensively studied. Simultaneous wide-angle X-ray diffraction( WAXD) technique was introduced to study the changes of crystal structure. It was found that the tensile modulus was strongly sensitive to the levels of temperature and tension. The structure parameters including crystal size and crystal orientation after heat treatment evolve similarly to the tensile modulus,indicating a direct structure-property relationship. The lattic c-dimension increases after heat treatment and is greatly affected by the tension. An optimal temperature can be found around 400 ℃,where big change can happen in the crystal structure due to α-relaxation in the crystal region as supported in dynamic mechanical analysis( DMA).