Effect of high pressure on mechanical degradation of isotactic polypropylene under plastic flow

Molecular mass distribution of isotactic polypropylene was studied under sh ear deformation on Bridgman anvils at pressures of 2 and 5 GPa. It was esta blished that the values of M-W and M-n averaged over the entire sample decr ease as the shear angle increases. The M-n value drops to higher extent wit h pressure compared to the value of M-W. At 2 and 5 GPa, the M, values decr ease in a similar manner. At 1 GPa, the M-W/M-n ratio is virtually independ ent of the shear angle, whereas at pressures of 2 and 5 GPa, molecular mass distribution becomes wider and, eventually, takes a bimodal character. A t wo-stage process of mechanical degradation of PP was observed under the stu died conditions, and the kinetics of each stage call be described by a firs t-order equation.