Abstract
AbstractThe heat capacity at constant pressure of liquid PEEK, poly(oxy‐1,4‐phenylene‐oxy‐1,4‐phenylene‐carbonyl‐1,4‐phenylene), has been measured by scanning calorimetry from 420 to 680 K, and that of PC, poly(4,4′‐isopropylidenediphenylene carbonate), from 325 to 610 K. These new data were combined with data‐bank data for PC and PET, poly(ethylene terephthalate), over wide temperature ranges. An addition scheme for liquid heat capacities of similar macromolecules has been obtained. In addition, values of absolute entropy, residual entropy for the glassy state, enthalpy, and Gibbs function are estimated for these three polymers. Both melting and glass transition temperatures have been confirmed. The heat capacity increases at the glass transition temperature have been determined by making use of previously calculated solid‐state heat capacities.
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