On the measurement of the fracture resistance of polyacrylamide hydrogels by wire cutting tests

The applicability of wire cutting in determining the fracture resistance, G_c, of polyacrylamide (PAAm) hydrogels, with different polymer contents and mechanical stiffness, was investigated. The various gels were synthesized both in the form of cylindrical and bar-shaped samples. Following the experimental scheme proposed in literature for wire cutting, each hydrogel, in the form of cylindrical specimen, was subjected to wire cutting with wires of different diameters. For each hydrogel, G_c was also separately measured by more conventional fracture tests on notched specimens prepared from the bar-shaped samples.The results demonstrated that, although G_c of the PAAm hydrogels here examined could not be evaluated by the direct application of the simple scheme proposed in literature, wire cutting is a promising approach for the measurement of the fracture resistance of chemical gels with relatively high stiffness, also in consideration of its proven experimental simplicity.