Friction-induced electroactive β polymorph of poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) has been widely used in electric devices due to electroactive β polymorph. In this article, we probe the formation of β phase under friction by spectroscopy and thermal analysis. During continuous friction, entire sliding of PVDF is identified with two regimes, i.e., running-in and steady-state. At initial running-in period, friction surfaces are dominated by plastic strain, which leads to striking formation of β phase from α polymorph (α→β). Subsequently, melting-flow domains almost cover friction surfaces at steady-state. Thus, formation of β crystal is correspondingly induced by shear crystallization. Nevertheless, β-crystal content at steady-state is lower than that at running-in. With sliding proceeding, moreover, β-crystal content exhibits a gradually decreasing tendency, attributed to rising surface temperature. Besides, the friction-induced β phase is further confirmed by evaluation of wear debris. Overall, friction plays a crucial role as to the formation of β phase. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46395.