Characteristic analysis of biaxially stretched PVDF thin films

By use of biaxial stretching process of poly(vinylidene fluoride) fabrication to gain high piezoelectricity is the focus in this article. The influence of different stretch ratio and temperature are investigated and compared to uniaxial stretching process. The Fourier transform infrared spectroscopy and X‐ray diffraction are used to observe the β‐phase fraction and the degree of crystallinity. The piezoelectric coefficients (d₃₃, d₃₁) and the sensitivity are also measured. All the above characteristic examinations show the same consequences that equi‐biaxial stretching process employed with same stretch ratio in both axial directions of poly(vinylidene fluoride) fabrication is the focus in this article. And heating temperature would have adequate piezoelectricity approximate to uniaxial stretching. In observation of surface morphology by using scanning electron microscopy, uniformity in biaxial direction is gained. However, biaxial stretching with higher stretch ratio of R = 4 × 4 would produce porosity and crack. Via atomic force microscopy, biaxial stretching with higher stretch ratio attains better surface chain orientation and smoothness. To sum up, the biaxial stretching approach has the advantage of low stretch ratio requirement to preserve good fabrication quality. Set up with stretch ratio in‐between R = 3 × 3 and R = 4 × 4 at 80 °C is suggested to use in biaxial stretching. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46677.