Thermal-stability and Crystallization of Poly(aryl Ether Ether Ketone)

Jonas, Alain M. [UCL] Legras, Roger [UCL]

The molecular weight distribution of poly(aryl ether ether ketone) (PEEK) has been measured as a function of the melt holding temperature and time in air and in an inert environment. A branching mechanism was observed to occur in the usual melt processing conditions, which was much stronger in air than in vacuum or nitrogen. This degradation mechanism is correlated to a volatile emission observed with thermogravimetric analysis. The influence of the degradation on the PEEK crystallization is discussed. A considerable decrease in crystallization rate is observed associated with the decreased molecular mobility due to the molecular weight increase. and a crystallinity decrease associated with the structural defects introduced along the chains by the branching process. The self-nucleation in PEEK has also been examined through optical microscopy. It was concluded that to get rid of the self-nucleation phenomenon, it is necessary to bring the polymer to temperatures where degradation is already present.