Stress-induced crystallization and melting of natural and synthetic cis-isoprene are compared by simultaneous Wide Angles X-ray Scattering (WAXS) and mechanical measurements.

Natural (NR) and synthetic polyisoprene (SR) rubbers have the same composition and sulfur crosslink density. At fixed elongation and during cyclic deformation, the properties X of the semi crystalline phase are determined as function of draw ratio λ; X being crystallites dimensions and orientation, half-time of crystallization, melting temperature, crystallinity and crystalline zone dimensions around a crack tip. It is shown that all the curves X(λ) of both types of rubber at room temperature can be superposed by a simple translation δλ along the draw ratio axis. This translation factor of the order of 0.5 to 1 does not depend on the property X. These effects are explained by the decrease of the melting and crystallization temperatures due to the presence of chain defects in synthetic rubber.

This content is only available as a PDF.
You do not currently have access to this content.