Description of the irreversible melting of polymers measured by temperature modulated calorimetry

The melting behaviour of polymers is investigated by temperature modulated differential scanning calorimetry (TMDSC). The measurements are performed i n both the quasi isothermal and the scanning mode. For the scanning mode me asurements the specific complex heat capacity (given by real c' and imagina ry part c ") was determined. The assumption that the crystals melt from the ir lateral surface only and that the melting rate is caused by superheating yields to a prediction of the frequency and underlying heating rate depend ence of c ". These results are verified experimentally. By adaptation of th is model a model function for description of \c\ (the modulus of the comple x specific heat capacity) in quasi isothermal experiments is obtained. The comparison of this function with experimental data from poly(ethylene terep hthalate) and syndiotactic polypropylene shows a good correspondence. (C) 1 999 Elsevier Science B.V. All rights reserved.