Thermal degradation kinetics of poly ( p-phenylene terephthalamide) fiber measured by thermogravimetry

摘要

Thermogravimetry analysis (TG) technique has been performed for evaluating the thermal degradation and the kinetics parameters of Poly (p-phenylene terephthalamide) (PPTA) fiber from 25 to 900 °C under nitrogen and air atmosphere. The decomposition rate and the characteristic temperatures are achieved from both the TG and DTG curves. The thermal degradation of Kevlar fiber follows more than one mechanism. The different methods have been introduced to describe the degradation kinetics of PPTA fiber. The respective activation energy, reaction order and the preexponential factor of the degradation of PPTA are achieved. The results show that the activation energy and reaction order of PPTA are higher in nitrogen than in air, which means that the thermostability of the fiber depends not only on its native character, but also on the testing atmosphere. The thermostable properties of these fibers in nitrogen can be used to reflect their natural character without the concurrent thermooxidative effect. The kinetic parameters based on different analytical approach taken in the analyses are summarized for comparative purposes. The correlation coefficient, larger than 0.996, was obtained through the Coats-Redfern method. The TG curves of PPTA fiber appear to be the best fit for the Coats-Redfern equation. Obviously, combining different mathematical methods conduced to solve the complex thermal degradation of PPTA fiber.