The mechanochemical reactions of polyvinyl chloride (PVC) were investigated at room temperature by using a self-made high pressure apparatus capable of simultaneous shear deformation. Static pressures applied were 5, 10, 15kbar for hard PVC resin and less than 5kbar for soft PVC resin. The shearing curves for hard PVC resin showed the decrease of shearing stress at the initial stage of shearing because of the occurrence of the major mechanochemical reaction at this stage. The mechanochemical reaction rate and the limiting molecular weight were evaluated by fitting the rate equation to the experimental data on molecular weight of hard PVC resin. All shearing curves for soft PVC resin did not show any definite yield point. Although the addition of plasticizer affected the shearing behavior, the shear-strength under pressure was not appreciably affected by adding over 50wt-% to pure PVC. No general conclusion about the effect of plasticizer content on the molecular weight was obtained.
