Strain induced nanocavitation and crystallization in natural rubber probed by real time small and wide angle X‐ray scattering

Abstract

ABSTRACT The concomitant appearance of crystallites and nanocavities under uniaxial strain is investigated by X‐ray scattering in a model natural rubber system. The nanocavities appear after crystallization and only when the true stress is above a critical cavitation stress σ Cav . The presence of crystallites alone does not influence the calculation of the void volume fraction ϕ void . The nanocavities formed are 20–50 nm in size with a constant aspect ratio. The presence of filler shifts the critical crystallization extension ratio λ Cry , λ Cav , and σ Cav to lower values. The clear correlation between σ Cav and the crystallinity at the onset of cavitation χ C ( λ Cav ) implies that the crystallites take most of the mechanical loading thus delaying the cavitation in the amorphous phase. Under cyclic loading, nanocavitation is significant only in the first loading and in the successive loadings if the extension ratio is above its maximum historical value. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1125–1138