Nonsteady fracture of transient networks: The case of vitrimer

Significance This paper explores the unusual fracture behavior of vitrimers, a transient polymer network whose rupture displays various regimes including flow, crack propagation and arrest, controlled by loading rates. The existence of these regimes was not previously reported in the literature and cannot be explained by current fracture theories. This study therefore extends the fracture criterion to a time-dependent version and relates crack velocity in a vitrimer to the force-dependent kinetics of the bond exchange reaction. This framework not only successfully describes experimental results over a large range of loading conditions but also pinpoints the distinct roles of network kinetics and external loading on the deformation history of a pre-existing defect.