Isothermal crystallization of poly(ether ether ketone) with different molecular weights over a wide temperature range

A systematic investigation to determine the importance of molecular weight on the isothermal crystallization kinetics of PEEK across a broad temperature range is presented for three commercial PEEKs (Victrex 150G, 450G, and 650G). The Avrami crystallization model is fit to the isothermal crystallization kinetics of PEEK as a function of crystallization time. To describe the secondary crystallization kinetics, a modified Avrami model is suggested by introducing a second Avrami exponent. The primary and secondary Avrami exponents of PEEK are 3.3 ± 0.4 and 2.3 ± 0.3. Using both standard differential scanning calorimetry (DSC) and fast scanning chip calorimetry (FSC), isothermal PEEK crystallization kinetics are investigated in a wide range of crystallization temperatures (158°C < T_c < 336°C). As the molecular weight is increased, the crystallization kinetics decrease. The crystallization half-times from DSC and FSC are well described by the Hoffman-Lauritzen model over the entire range of possible crystallization temperatures.