Dynamic Viscoelasticity of Poly(butylene terephthalate) during Isothermal Crystallization

Abstract

The dynamic viscoelastic behavior during isothermal crystallization of poly(butylene terephthalate) (PBT) has been investigated as a function of crystallization temperature (T_c). The enthalpy of crystal formation during the isothermal crystallization is also examined by differential scanning calorimetry (DSC). The equilibrium degree of crystallization in the long time limit is about 30%, almost independently of T_c. Correspondingly, the viscoelastic parameters at the equilibrium of crystallization are also independent of T_c. The crystallization rate decreases with increasing T_c, and the T_c dependence is well approximated by the Arrhenius type equation. The effect of crystallization on the viscoelasticity is considerably small in the initial stage of crystallization whereas it becomes pronounced in the later stage.