Temperature-modulated fast scanning calorimetry of isothermal crystallization of Poly(butylene terephthalate)

Crystallization kinetics of poly(butylene terephthalate) under high supercooling was examined by TemperatureModulated Fast Scanning Calorimetry (TM-FSC). By using temperature modulation for isothermal crystallization, we can determine the temperature dependence of crystal growth rate. The positive/negative dependence brings the negative/positive sign of the phase angle of dynamic heat capacity, respectively. The obtained dependence was compared with that of peak time of heat flow on isothermal crystallization. The isothermal peak time is inversely proportional to the crystallization rate and showed a double peak, corresponding to the crystal-growthand nucleation-dominant temperature ranges. The result of TM-FSC over the entire temperature range including the nucleation-dominant lower temperature range was in agreement with the temperature derivative of the fitting curve of the crystal-growth-dominant higher-temperature peak. Hence, the present analysis confirmed that TM-FSC detected the change in crystal growth rate but not in nucleation rate. The crystal growth rate was practically determined by a mobility factor near the glass transition.