Changes in the physical and chemical properties of PVDF irradiated by 4 MeV protons

Abstract

The behavior of poly-vinylidene fluoride (PVDF) under bombardment of different kinds of radiation is of interest due to the polymer's unique piezo-electric properties and various crystalline forms. In this work, PVDF film samples of 0.3 mm thickness and density 1.76 g/cm$^3$ were irradiated with 4 MeV protons from the Instituto de Física 9SDH-2 Pelletron Accelerator. Changes in the physical and chemical properties were investigated using Fourier Transform Infrared Spectroscopy (FTIR) with ATR, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and gel fraction measurements. The gel percent increases with fluence to almost 60% for a fluence of 10$^{13}$ cm$^{-2}$, and then more slowly up to 100% for a fluence of 3 $\times$ 10$^{14}$ cm$^{-2}$. The DSC curve of the control sample shows a sharp band at 176 $^\circ$C with a shoulder on the low temperature side. A well defined lower temperature peak, related to the relaxation of inter-crystalline regions appears at a fluence of 10$^{13}$ cm$^{-2}$. At 3 $\times$ 10$^{14}$ cm$^{-2}$ there are no melting peaks, due to complete destruction of the crystalline structure. This was confirmed at this high fluence by the FTIR spectra, and by x-ray diffraction, where an amorphous structure was observed.