The Loop-Opening Model for the Intrinsic Fracture Energy of Elastomers

The intrinsic fracture energy of elastomers is a key factor in determining the mechanical durability of products such as rubber and tires. Historically, the intrinsic fracture energy has been described by the Lake–Thomas model, despite its known limitations. A loop-opening model has been proposed to describe the intrinsic fracture energy of gels prepared at semidilute conditions. In this work, we performed fatigue experiments on highly elastic end-linked polydimethylsiloxane (PDMS) elastomers and further combined these results with existing data from various elastomers to validate the applicability of the loop-opening model to elastomers. Our findings show that the intrinsic fracture energy per chain scales with the product of the fracture force and the contour length of the bridging chains between constraints, suggesting that unentangled and slightly entangled elastomers also follow the loop-opening model. However, in elastomers, overlapping chains constrain the opened loops and prevent them from fully extending. This result is supported by both experimental data and molecular dynamics simulations. This study extends the applicability of the loop-opening framework from gels to elastomers, providing a more quantitative and predictive description of intrinsic fracture energy across diverse polymer networks.