Thermal cracking characteristics of PEEK under different environments by the TG/FTIR technique

The thermogravity/Fourier transform infrared (TG/FTIR) system was used to a nalyze the mechanism and kinetics of the thermal cracking of poly(ether eth er ketone) (PEEK) under different environments. The thermal cracking of PEE K in a helium atmosphere showed that there were two stable cracking reactio n regions. In the first-stage reaction, the thermal stability of the ketone group in PEEK was thermally more stable than the ether group. The cracking of the fluorenone structure in the carbonization showed it dominated the c racking scheme in the second-stage reaction. The thermal cracking of PEEK i n air was governed by a random main-chain-scission and carbonization mechan ism that increased with the cracking temperature under the influence of an increased thermal-oxidation mechanism. This mechanism predominated the PEEK solid reaction system until the compound completely was combusted. In air, the solid reaction rate of PEEK that produced a stable fluorenone structur e was faster than that in helium and imparted a higher retarding effect on cracking in the initial lower temperature region. By means of the stable av erage activation energy for the kinetic parameter calculation for the order of reaction and pre-exponential factor, the theoretical TG curve was calcu lated and found to be identical to the observed TG curve. The kinetic model for thermal cracking of PEEK in air also is discussed. (C) 1999 John Wiley & Sons, Inc.