Morphological study of polystyrene crazes using small-angle x-ray scattering

An extensive study of the crazing phenomenon in polystyrene with respect to molecular weight parameters and stress history has been performed. Experiments employed the small angle x-ray scattering camera in the National Center for Small Angle Scattering Research (NCSASR) at the Oak Ridge National Laboratory. Analysis was performed using reflection theory for the tensile axis scattering, and diffraction theory for the nontensile axis scattering from bulk crazed specimens. Results show that craze morphology is sensitive to structural characteristics of the polymeric glass, as defined by molecular weight parameters. Also, a fracture mechanism is developed from stress analysis based on void fraction and craze density measurements. Finally, the open-celled foam model of craze morphology is supported from diffraction patterns of crazes where reflection is not observed.