Study of the crystallization and melting region of PET and PEN and their blends by TMDSC

The cold crystallization and melting of poly( ethylene therephthalate) ( PET), poly( ethylene 2,6-naphthalene dicarboxylate) ( PEN) and their blends were studied using temperature modulated differential scanning calorimetry (TMDSC) at underlying heating rates of between 1 and 3 K min(-1) and periods ranging from 30 to 90 s. The amplitude of modulation was selected in order to give an instantaneous heating rate betagreater than or equal to0. Heat flow is analyzed by the total heat flow signal phi, which is equivalent to the conventional DSC signal, and the reversing heat flow phi(REV), which only detects the glass transition and the melting processes. The dependence of the melting region in the reversing heat flow on the frequency of modulation is analyzed. The use of the so-called non-reversing heat flow phi(NREV) (=phi-phi(REV))) and the effect of frequency and amplitude on the complex heat capacity are also studied. The results show the complexity of these magnitudes.