MASTER CURVE APPROACH TO POLYMER CRYSTALLIZATION KINETICS

Nonisothermal crystallization kinetic data obtained from differential scanning calorimetry (DSC) for a poly(ethylene terephthalate) are corr ected for the effects of temperature lag between the DSC sample and fu rnace using the method of Eder and Janeschitz-Kriegl which is based on experimental data alone without resort to any kinetic model. A method is presented for shifting the corrected nonisothermal crystallization kinetic data with respect to an arbitrarily chosen reference temperat ure to obtain a master curve. The method is based on experimental data alone without reference to any specific form of kinetic model. When t he isothermal crystallization kinetic data for the same material are s hifted with respect to the same reference temperature, a master curve is also obtained which overlaps to a large extent the corresponding ma ster curve from nonisothermal data. It follows that nonisothermal DSC measurements provide the same crystallization kinetic information as i sothermal DSC measurements, only over a wider range of temperatures. T he shift factors obtained from experimental data alone are compared in turn with the corresponding values calculated from the Avrami equatio n, the Hoffman-Lauritzen expression, and the Nakamura equation as a me ans of evaluating these models individually. It is concluded that the Avrami equation is very good at describing isothermal crystallization kinetics, the Hoffman-Lauritzen extrapolation of the limited isotherma l data to a wide range of temperatures is quite good, and the Nakamura equation yields reliable crystallization kinetic information over a n arrower range of temperatures than nonisothermal data alone without us ing any specific model.