Fracture toughness and solvent crack for simultaneously polymerized polymethacrylate/polyurethane

Abstract

Solvent cracking occurs when polymer materials are exposed to solvents under stress much lower than their strength. Previously, we reported on methacrylate/urethane polymer blends that underwent simultaneous polymerization. This paper investigates the effect of the degree of cross-linking on the fracture toughness and solvent cracking of these polymer blends. The HEMA-copolymerized methacrylate chains were partially cross-linked with the urethane chains through a reaction between the hydroxy and isocyanate groups. Regardless of the cross-link density, the fracture toughness of the polymer blends was improved by the formation of multiple crazes occurring in the polymer blends. Meanwhile, poly(methyl methacrylate) (PMMA) and the PMMA/polyurethane blend without the cross-linking showed remarkable solvent cracking. The HEMA 5.42 mol% copolymer blend was less susceptible to solvent cracking because cross-linking restricted the mobility of the molecular chains in the methacrylic matrix phase.