Model for the fracture energy of glassy polymer–polymer interfaces

The increase in the interfacial fracture energy ( G c ) with increasing interfacial width ( a i ) goes through a transition at a critical value of a i that is unique to each polymer–polymer system. This transition point does not scale with the bulk entanglement spacing ( d t ) for different systems, implying that the role of chain friction in reinforcing these interfaces is more important than previously thought. A theoretical model has been developed to calculate G c as a function of the interfacial stress transfer due to individual polymer chains. When including the effects of chain friction only, the model reproduces the nonuniversal behavior of G c with respect to a i / d t but yields poor fits for a i / d t > 1. The effects of entanglements are then added by calculating the fraction of entangled chains as a function of a i / d t . This contribution, although not material specific, matches the qualitative behavior of G c for large values of a i / d t . When both contributions are included in the model, excellent fits are obtained for all data sets.