Crystal structure and thermal properties of poly(vinylidene fluoridehexafluoropropylene) films prepared by various processing conditions

Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) films were prepared using either a melt pressing or solution casting methods. The resulting PVDF-HFP films were drawn uniaxially at various drawing temperatures and speeds. The mp-PVDF-HFP films were more transparent and had more drawability than the sc-PVDF-HFP films. The crystal form of the initial films was the alpha-phase (non polarity) of PVDF. The maximum draw ratio was 7.6. The mp-PVDF-HFP films were prepared at a drawing speed of 2500 %/min at 100 °C. With increasing drawing speed, the beta-phase (polarity) became the dominant phase of PVDF in mp-PVDF-HFP films. The thermal properties of the resulting PVDF-HFP films improved with increasing drawing temperature.