Isothermal and Nonisothermal Crystallization of Poly(aryl ether ketone ketone) with All-para Phenylene Linkage

摘要

Isothermal and nonisothermal crystallization behavior for PEKK(T) was studied using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and electron diffraction (ED). In the isothermal crystalliztion process, the Avrami parameters obtained were n=2.33-2.69, which shows crystal growth of two-dimensional extensions consistent with our observations by TEM. The lamellar thickness increases with the crystallization temperature of PEKK(T) crystallized isothermally from the melt. However, for the nonisothermal crystallization of PEKK(T), the results from the modified Avrami analysis show two different crystallization processes. Avrai exponents n_1=3.61-5.30, obtained from the primary crystallization process, are much bigger than are the secondary n_2=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 observation of the spherulite morphology. PEKK(T) crystallized isothermally from the melt possesses the same crystal structure (Form I) as that from nonisothermal melt crystallization. The results from TEM observation show that the spherulite radius decreases with an increasing cooling rate.