Melting of PEEK

The DSC curves at the bottom of Fig. 6.96 represent an analogous set of crystallization experiments, but grown from the melt. TTie melt-crystallized polymer shows higher perfection in both the annealing peak and the melting peak for the primary crystals. Ultimately, both peaks are expected to come together. 

primary crystallization of PEEK is analyzed in Fig. 6.98 using long-time, quasi-isothermal TMDSC at 606.5 K, and in Fig. 6.99, using TMDMA at 605 K. The analysis of the TMDSC data is further illustrated in Fig. 6.100 and reveals an increase in heat capacity with time and crystallinity, instead of the decrease expected from a lower heat capacity of a semicrystalline sample. The crystallinity is derived from the integral of the total heat-flow rate, with time in Fig. 6.98. From Fig. 6.99 it 

Merziyakov, and C. Schick, J. Thermal Anal. Calorlm., 60, 807 (2000). 

A considerable secondary crystallization, typical for PEEK, is seen in Fig. 6.99. Only about 50% of the total crystallinity can be assigned to primary crystallization. Secondary crystallization starts at about 28 h ( 10 s). At that time, the reversing amplitude of the storage modulus is almost constant. At later times, it decreases slowly, indicating very different processes for primary and secondary crystallization. 

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Cheng SZD, Cao M-Y, Wunderlich B (1986) Glass Transition and Melting of PEEK. Macromolecules 19 1868-1876. 

Dynamic study of microstmctures during crystallization and melting of PEEK/PEKK blend. Macromolecules, 30, 4544-4550. 

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