Characterization of β-PVDF Films Prepared at Different Conditions

Poly(vinylidene fluoride) films, in the ferroelectric P phase, were prepared with different techniques: crystallization by solution, mechanical stretching and electrospinning. Using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), we observed that films obtained from crystallization in dimethylformamide (DMF) solution at 60 degrees C contain only non-oriented beta phase. Films obtained by uniaxial stretching at 80 degrees C and draw ratio 4, of samples originally in the (x phase, result predominantly in the oriented P phase, though with still a small amount of the (x phase. Membranes prepared by electrospinning method are constituted by nanofibers exclusively in the beta phase and with the chain axis preferably aligned along the fibers, parallel to the membrane surface. The crystallinity percentage and the melting temperature, both inferred from calorimetric measurements (DSC), were little influenced by the techniques employed.