Isothermal and nonisothermal crystallization of poly(aryl ether ketone ketone) with all-para phenylene linkage

Isothermal and nonisothermal crystallization behavior for PEKK(T) was studi ed using differential scanning calorimetry (DSC), transmission electron mic roscopy (TEM), and electron diffraction (ED). In the isothermal crystalliza tion process, the Avrami parameters obtained were n = 2.33-2.69, which show s crystal growth of two-dimensional extensions consistent with our observat ions by TEM. The lamellar thickness increases with the crystallization temp erature of PEKK(T) crystallized isothermally from the melt. However, for th e nonisothermal crystallization of PEKK(T), the results from the modified A vrami analysis show two different crystallization processes. Avrami exponen ts n(1) = 3.61-5.30, obtained from the primary crystallization process, are much bigger than are the secondary n(2) = 2.26-3.04 and confirmed by the o bservation of the spherulite morphology. PEKK(T) crystallized isothermally from the melt possesses the same crystal structure (Form I) as that from no nisothermal melt crystallization. The results from TEM observation show tha t the spherulite radius decreases with an increasing cooling rate. (C) 2001 John Wiley & Sons, Inc.