STUDIES OF THE ENTHALPY RELAXATION AND THE MULTIPLE MELTING BEHAVIOR OF SEMICRYSTALLINE POLY(ARYLENE ETHER ETHER KETONE) (PEEK)

We report the results of an investigation by differential scanning cal orimetry (DSC) of two mobility controlled processes in the amorphous p hase of semicrystalline PEEK - enthalpy relaxation below the glass tra nsition (T-g) and secondary crystallization above T-g. Both result in the observation of an endothermic peak just above the annealing temper ature in the DSC scan of the polymer - the enthalpy recovery peak and the low temperature melting peak, respectively. There is a striking si milarity in the time and temperature dependence of the endothermic pea k for these two processes. These results are reminiscent of those obta ined from small strain creep studies of ''physical aging'' of semicrys talline PEEK below and above T-g.