Effects of stretching on phase transformation of PVDF and its copolymers: A review

Abstract Poly(vinylidene fluoride) (PVDF) and its copolymers are promising candidates for energy-harvesting devices because of their flexibility, environmental friendliness, lightweight, high halogen acid resistance. However, the relatively low piezoelectricity limits applications. The PVDF highly depends on polar β-phase, while non-polar α-phase is most common one. As a result, β-phase formation α- to transformation have attracted much attention in recent years. Stretching widely used method induce improvement piezoelectricity. In this work, influences parameters during stretching phase evolution discussed summarized. Besides, nontraditional methods also introduced discussed. This work will provide important information preparing high-performance piezoelectric polymer films.