Molecular orientation and degree of crystallinity of piezoelectric poly(vinylidene fluoride) films exclusively in the β phase
Oriented -phase films were obtained by drawing exclusively -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 90C and with R = 4 of originally -phase films results in exclusively -phase films with crystallinity degree of 49% and orientation factor of 0.885. For comparison, with the conventional drawing technique from -phase material, films oriented at a ratio (R) of 5 still contain about 20% of phase , a crystallinity degree of 40% and -phase crystallographic c-axis orientation factor of 0.655.
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