Molecular fracture in polystyrene

Molecular fracture in atactic polystyrene was studied by observing the effect of slicing by microtoming on the viscosity average molecular weight Mv. It was found that when PS rods were sliced a significant reduction in molecular weight occurred due to primary bond rupture. The magnitude of the reduction in molecular weight depended strongly on the initial molecular weight and increased with Mv. This effect was adequately described by a theoretical model which counted the number of random walk interpenetrated chain sphere envelopes intersecting the fracture plane. The reduction in Mv was shown to depend on the square root of the initial Mv. The dependence of the molecular weight reduction on the initial Mv and fracture surface area was obtained and accu rately described the experimental data. The critical entanglement molecular weight Mne = 30,000 for PS was obtained from the experiment.