Isothermal Melt Crystallization Kinetic Behavior of Poly (vinylidene fluoride)

Isothermal melt crystallization kinetics of PVDF was investigated by differential scanning calorimetry. Thin PVDF film has been fabricated by the solvent casting technique using dimethylformamide (DMF). Then, the samples were melted and subsequently crystallized in the range of the crystallization temperature (Tc) between 138 and 145 °C. The crystallization kinetics was derived from Avrami equation. Avrami parameter (n) was found in a range from 1.5 to 2.4 and the values of the crystallization rate parameters (k) increased with decreasing Tc. So the crystallization rate parameters suggested that PVDF crystallize slower with increasing of Tc. The Hoffman–Weeks equation has used to approximate the equilibrium melting point of PVDF which was concluded to be 182 °C. Likewise, the activation energy was estimated to be 103.2 kJ/mol for isothermal crystallization. In this research, Lauritzen- Hoffmann theory was employed to analyze crystallization kinetics. Accordingly, regime "I" found appropriate to describe the present case of PVDF crystallization.