MODULATED TEMPERATURE DSC MEASUREMENTS RELATING TO THE COLD CRYSTALLIZATION PROCESS OF POLY(ETHYLENE-TEREPHTHALATE)

The modulated temperature differential scanning calorimetric method (M T-DSC) yields three temperature dependent signals, an underlying heat capacity curve from the underlying heat flow rate (corresponding to th e conventional DSC signal), and a complex heat capacity curve with a r eal part (storage heat capacity) and an imaginary part (loss heat capa city). These curves have been measured in the cold crystallization reg ion for poly(ethylene terephtalate) with a modified Perkin-Elmer DSC-7 . The underlying curve shows the well known large exothermic crystalli zation peak. The storage heat capacity shows a step change which repro duces the change in heat capacity during crystallization. This curve m ay be used as baseline, to separate the crystallization heat flow rate from the underlying heat flow rate curve. The loss heat capacity curv e exhibits a small exothermic peak at the temperature of the step chan ge of the storage curve. It could be caused by changes of the molecula r mobility during crystallization.