Thermal Mechanical analysis (TMA) has been used to study the crystallization
behavior of poly (ether ether ketone) (PEEK) and its blends with poly (ether
imide) (PEI). The two crystallization stages of PEEK are clearly
distinguished by measuring the variation of film thickness with time during
isothermal crystallization. Upon blending with PEI, the distinction of the
two PEEK crystallization stages becomes obscure. This is attributed to the
depressions in both nucleation density and spherulite growth rate upon
blending with PEI.
An Avrami analysis, Modified by considering both primary and secondary
crystallization, is used to extract the respective kinetic behavior of these
two crystallization stages. The results indicate that the secondary
crystallization proceeded slower than the primary crystallization in the
diffusion-controlled crystallization region. On the other hand, these two
crystallization stages proceeded at comparable rate in the
thermodynamically-controlled crystallization region. It is also found in the
diffusion-controlled crystallization that blending with PEI induced a larger
depression in the secondary crystallization rate than in the primary
crystallization rate. Explanations for these observations are proposed and
discussed.