Molecular Orientation and Degree of Crystallinity of Piezoelectric Poly(Vinylidene Fluoride) Films Exclusively in the β Phase

Abstract

Oriented β -phase films were obtained by drawing exclusively β -phase films obtained from dimethylformamide solution crystallization at 60 °C with subsequent pressing. Wide angle X-ray diffraction and pole figure plots showed that drawing at 90°C and with R = 4 of originally β -phase films results in exclusively β -phase films with crystallinity degree of 49% and orientation factor of 0.885. For comparison, with the conventional drawing technique from α-phase material, films oriented at a ratio (R) of 5 still contain about 20% of phase α, a crystallinity degree of 40% and β -phase crystallographic c-axis orientation factor of 0.655.

Keywords:

• Poly(vinylidene fluoride)
• molecular orientation
• crystallinity
• crystalline phase
• pole figure

Acknowledgments

The authors thank the CNPq, FAPESP, the program Alfa-Plastinet and the Portuguese Foundation for Science and Technology – FCT (Grant POCI/CTM/59425/2004) for financial support. M. C. Branciforti wishes to thank FAPESP for the research funding and Dr. R. Machado for the Polo2003 software elaboration. V. Sencadas thanks to FCT for the PhD Grant (SFRH/BD/16543/2004).

Notes

*: porous sample; B: sample without porosity.