Failure of a Polystyrene-Polyisoprene-Polystyrene Gel in Mineral Oil

Fracture of gels subjected to load during their applications is an unwanted phenomenon. Here, we present the fracture behavior of a gel consisting of polystyrene-polyisoprene-polystyrene in mineral oil, a midblock selective solvent. The collapsed polystyrene blocks form aggregates acting as the crosslinking points, whereas, the solvated polyisoprene blocks bridge those aggregates. Fracture in these gels mostly occurs by the endblock pullout from the aggregates. Fracture energy for these gels depends on the chain pullout energy and on the viscous dissipation process. Tensile test results capture an increase in fracture stress and strain with the increasing strain rates. Quasistatic fracture tests capture the crack-tip velocity dependence of fracture energy for these gels. The creep tests performed over a range of applied stress values indicate a decrease in failure time with the increase in applied stress.