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.