The thermal and mechanical properties of semi-crystalline polymers are heavily influenced by their crystallinity. The importance of a controlled thermal history- heating, cooling, and isothermal holds- directly affects the crystallinity and morphology. With the development of fast scanning calorimeters (FSCs) with scan rates up to 1M K/s, the scan rate limitations of standard differential scanning calorimetry (scan rates centered around 10<sup>o</sup>C/min) are eliminated. The faster, controlled heating and cooling rates of FSC allow for the ability to characterize fast crystallizing materials more precisely. One such material is poly(ether ketone ketone) (PEKK), a semi-crystalline, high-performance thermoplastic with tunable crystallization kinetics. A grade of PEKK with a terephthaloyl/isophthaloyl (T/I) ratio of 80/20 is of particular interest as it undergoes fast crystallization that requires FSC to properly analyze. When analyzing the crystallinity of a PEKK 80/20 sample after a specific thermal treatment, a melting peak above the reported equilibrium melting temperature of PEKK 80/20 was observed. Upon further investigation into PEKK crystallization literature, it was discovered that the method used to determine the equilibrium melting temperature reported in the 90’s and commonly cited for PEKK had deficiencies in its methodology mostly due to the limitations of the heating and cooling rates of the instrumentation available at the time. Utilizing the Mettler Toledo Flash DSC 1, the equilibrium melting temperature for the commercially available Kepstan PEKK 8001 has been determined by two methods- with and without the assumption of a melt-recrystallization-remelt upon heating.

Effect of low isophthaloyl content on the crystallization kinetics of poly(ether ketone ketone) utilizing fast scanning calorimetry

ACS Spring 2022

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