CRYSTALLIZATION KINETICS OF POLY(ARYL ETHER ETHER KETONE) - TIME-TEMPERATURE-TRANSFORMATION AND CONTINUOUS-COOLING-TRANSFORMATION DIAGRAMS

The isothermal and nonisothermal crystallization of poly(aryl ether ether ketone) (PEEK) films have been investigated using differential scanning calorimetry, density and wide-angle X-ray scattering. An original method to determine the crystallization domains taking into account the crystallized fraction is proposed. Based on metallurgy concepts, Time-Temperature-Transformation (TTT) and Continuous-Cooling-Transformation (CCT) diagrams for isothermal and nonisothermal conditions, respectively, are established for PEEK. The ''C'' shape of the TTT diagram gives evidence for the competition between nucleation and growth phenomena. At high temperature, crystallite growth predominates while at low temperature, nucleation phenomenon prevails. Changes in lamellae thicknesses, according to the crystallization temperature, have been related to the predominance of nucleation or growth phenomenon. The CCT diagrams show a similar shape and give evidence for a decrease in crystallization ability of PEEK with increasing the cooling rate. Isothermal and nonisothermal crystallizations are discussed through the Avrami analysis.