Thermal Decomposition Kinetics of Polyimide Polymer for Non-isothermal Conditions

• Main Authors: Guo-Ting Liao, 廖國廷
• Other Authors: Rong-Chi Wang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/vx389n

碩士 === 大同大學 === 化學工程學系(所) === 95 === Studies of non-isothermal decomposition of a new diamine monomer led to a series of novel polyimide polymer (a)-(f) when reacted with six dianhydrides were measured by thermogravimetric analysis (TGA) at a heating rate of 20℃/min in nitrogen and air atmospheres. Three single heating-rate integral methods by Coats-Redfern, Horowitz-Metzger and Van Krevelen that were analysed using the non-isothermal data with different expressions of solid state reactions, i.e., g(a) would be used to estimate the activation energy (E), pre-exponential factor (A), and order of reaction (n). The F1 and R2 models were selected as the best mechanisms for solid-state reactions to fit experimental TG curves in nitrogen and air atmospheres, individually. Mathematical verification of using different integral methods shows that the Coats-Redfern method is more precise than the Horowitz-Metzger and Van Krevelen methods since the other two methods are dependent on the arbitrary selection of the reference temperatures. From the molecular structure point of view, the order of the activation energy of polyimide under nitrogen is PI-e(DSDA) =PI-f(6FDA) >PI-a(PMDA) >PI-d(ODPA) =PI-b(BPDA) >PI-c(BTDA); however, under air it is PI-f(6FDA) >PI-a(PMDA) >PI-d(ODPA) =PI-c(BTDA) >PI-b (BPDA) =PI-e(DSDA). In this study, it is found that the activation energy and pre-exponential factor show the same trend, i.e., both values increase with increasing the order of reaction for each sample, i.e., polyimide (a)-(f). On the other hand, the parameter values in air are lower than those in N2. It can be attributed to that not only the molecular structure but also combustion of oxygen would affect the value of activation energy.