Effect of chain structure on ductile–brittle transition in some polyestercarbonates

The relation between chain structure and ductile–brittle transition (DBT) in polyestercarbonates (PEC) was investigated by measuring the fracture energy and observing the fracture surfaces of a homologous series of PEC containing phthalate units. DBTs were determined in terms of various test conditions including specimen thickness, test speed, and notch-tip radius. With an increase in the phthalate content, transition was found to shift to a thinner specimen, a lower test speed, and a higher notch-tip radius. It was concluded that the DBT is directly affected by the extent of entanglement in these copolymers.