Brittle fracture of polymer transient networks

TL;DR

This study investigates the fracture behavior of reversible polymer networks, revealing how fracture regimes depend on stretching rate, network connectivity, and viscoelastic properties, with implications for understanding material failure.

Contribution

It provides a detailed state diagram and quantitative analysis of fracture mechanisms in reversible double transient networks, highlighting the role of network connectivity and viscoelasticity.

Findings

Filaments fracture when stretched faster than the inverse of the slowest relaxation time.

Dissipation processes are negligible under experimental conditions.

Deviations from parabolic crack profiles correlate with non-linear viscoelasticity.

Abstract

We study the fracture of reversible double transient networks, constituted of water suspensions of entangled surfactant wormlike micelles reversibly linked by various amounts of telechelic polymers. We provide a state diagram that delineates the regime of fracture without necking of the filament from the regime where no fracture or break-up has been observed. We show that filaments fracture when stretched at a rate larger than the inverse of the slowest relaxation time of the networks. We quantitatively demonstrate that dissipation processes are not relevant in our experimental conditions and that, depending on the density of nodes in the networks, fracture occurs in the linear viscoelastic regime or in a non-linear regime. In addition, analysis of the crack opening profiles indicates deviations from a parabolic shape close to the crack tip for weakly connected networks. We demonstrate a direct correlation between the amplitude of the deviation from the parabolic shape and the amount of non linear viscoelasticity.