Fracture behavior of PBT-ABS blends compatibilized by methyl methacrylate-glycidyl methacrylate-ethyl acrylate terpolymers

The fracture properties of blends of poly(butylene terephthalate), PET, with acrylonitrile-butadiene-styrene materials, ABS, compatibilized by a methyl methacrylate-glycidyl methacrylate-ethyl acrylate terpolymer, MGE, have been characterized by Izod impact and single-edge notch, three-point bend (SEN3PB) type tests. The impact properties have been shown to be very sensitive to specimen thickness and mildly sensitive to notch sharpness. Blends containing 30 wt% ABS and molded into 3.18 mm samples are super tough in the absence of a compatibilizer: however, 6.35 mm specimens require higher ABS contents and compatibilization to achieve significant toughness. Low quantities of MGE (1 wt%) are required to produce super tough blends of 6.35 mm thickness; whereas, higher quantities of MGE result in a decrease in the impact strength. A dual mode of deformation during Izod impact testing has been observed for uncompatibilized blends molded into 6.35 mm samples where brittle failure occurs in the region of fracture initiation and ductile failure occurs in the region of crack termination. Similarly, a more brittle mode of failure occurs for SEN3PB samples with long ligament lengths and ductile failure for samples with short ligament lengths. The distance a crack can propagate and the size of the stress whitened zone created during Izod impact testing have been shown to be related to the impact properties determined by Izod and SEN3PB tests. (C) 1999 Elsevier Science Ltd. All rights reserved.