Analysis Method

Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline α-phase. It has found various applications during the last decades and the most important applications lies in its pyro- and piezoelectric properties. The β-phase content is of prime importance in these applications so that increasing β-phase content of the polymer has always been of great concern in this field. Calorimetric studies and FTIR spectra show the appearance of β-phase in compression molded films of two different grades of PVDF resin. β-phase formation is more evident in stretched films by a transformation mechanism of α to β-phase via the formation of a necking region during stretching. By using FTIR techniques, a maximum content of 74% for β-phase was calculated. This was achieved during stretching at 90 °C and for a stretch ratio between 4.5 and 5. FTIR spectra offer a precise method for detecting the variations of β-phase in polymer films.