Poly(ether ketone ketone) (PEKK) is a relatively new engineering plastic with high temperature stability and excellent chemical and solvent resistance. The ratio of terephthaloyl (T) and isophthaloyl (I) moieties, see scheme 1, can be varied to control the crystallization rate and crystallinity of PEKK without substantially changing the end-use temperature [1,2]. Sauer et al. [3,4] reported that PEKK and a thermoplastic polyimide (PI) synthesized from 4,4'-bis(3-aminophenoxy)-biphenyl and pyromellitic dianhydride were miscible in the amorphous phase. Both homopolymers are semi-crystalline, so the phase behavior of PEKK/PI blends can be complex. Crystallization of either or both components in the blends depends on the miscibility of the two polymers in the melt, the temperature history during cooling from the melt and the kinetics of crystallization of the two polymers. In this study, we investigated the effect of crystallization in PEKK/PI blends on the thermal transitions and crystalline structure using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and wide-angle X-ray diffraction (WAXD).
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