Abstract
In the crystallization of a commercially available 6 ㎛ thin PVDF film from the melt under an electric field, the effect of the field upon the overall crystallization rate, the nucleation rate of each crystal phase, the radial growth rate of each spherulite, the rate of transition from α-phase to γ-phase, and crystalline morphology were investigated using polarizing microscopy, infrared spectroscopy, and differential scanning calorimetry. When PVDF was crystallized at crystallization temperatures below 159℃ where only α-crystals of lamella splay type spherulites are formed, an electric field increased the rate of α-nucleation slightly, but reduced the radial growth rate somewhat. When crystallized in the temperature range of 162∼166℃, α-crystal forms dominantly along with γ-crystal in the early stage of crystallization. Both nucleation rate and radial growth rate of α-crystals decreased with increasing electric field strength, but the content of γ-crystals formed initially increased with increasing electric field. After the early stage of crystallization, a considerable amount of the α-crystals is transformed to another crystal, which is called γ'-crystal. The electric field reduced the α→γtransition rate. Even though there was little change in birefringence of spherulite after the α→γtransition, γ'-crystal appeared to be more birefringent than the γ-crystal formed initially.
