Effect of molecular weight on brittle‐to‐ductile transition temperature of polyetherimide

The fracture and yield strength of polyetherimide was evaluated over a temperature range of 23 to 140°C for materials with number‐average ( M n ) and weight‐average molecular weight ( M w ) ranging from 15.6 to 22.8 and 36.6 to 52.3 kg/mol, respectively. The brittle‐to‐ductile transition temperature, where an equal probability exists that an impact will result in a brittle or ductile failure, was determined by evaluating the temperature at which fracture and yield strength are equal. The transition temperature decreased from 155 to 60°C with increasing molecular weight and provided a measure of relative ductility between material samples. As a case study, the practical impact strength of an injection‐molded food service tray was determined at 20°C and correlated with fracture strength as a function of molecular weight. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1666–1671, 2004