Rupture of Viscoelastic Elastomers: Rate and Temperature Effects

Rupture of covalently cross-linked elastomers can be sensitive to both stretch rate and temperature. At temperatures far above glass transition temperature, stretching is only elastic, and rupture usually occurs at higher tensile strength (σb) and rupture strain (λb) when stretched faster or at lower temperatures. In this study, we examine the rupture behavior of viscoelastic elastomers whose stress responses are both rate and temperature dependent. Using in situ birefringence measurements, we show that the viscoelasticity primarily arises from embedded entanglement plausibly due to chain uncrossability whose contributions increase with the applied stretch rate and are stronger at lower temperatures. This transient crosslink-like effect promotes non-Gaussian stretching, boosting intrachain stress levels in the form of pronounced strain hardening and causing rupture to occur on shorter time scales and lower strains at lower temperatures. At temperatures sufficiently close to the glass transition temperature Tg, interchain interactions make a notable contribution to stress while inducing greater participation of entanglement. We conclude that rupture characteristics such as σb and λb depend on how viscoelasticity in the form of transient entanglement affects chain tension buildup in network strands with little viscous energy dissipation.