Amorphization kinetics of poly(vinylidene fluoride) on high-energy ion irradiation

The crystalline fraction of irradiated semi-crystalline polyvinylidene form II (PVDF alpha) is measured as a function of dose (or fluence) and energy loss (dE/dx) using high energy particle beams at room temperature. The dependence of the rate of crystallinity loss on the fluence is different between low dE/dx particle- and high dE/dx ion-irradiations. In particular, the amorphization is retarded at low dose for electron, O or Ne irradiation, whereas the amorphization is direct with heavier projectiles. The relation between the absorbed dose and the crystalline fraction is investigated. We analyze the effects which can affect the crystallinity in the 1-10 MGy dose range: 1) the collapse of a crystalline region induced by several overlapping damaged tracks; 2) the propagation of disorder from the amorphous interface into the crystallite.