Mechanical degradation:
Polymer such as poly-styrene dissolved in a solvent, when subjected to vigorous stirring or beating, under-goes considerable molecular degradation or fragmentation.
In fact in the rubber industry, the rubber is masticated by passing it through two rotating rollers to reduce its molecular weight & make it more processable. This mastication converts hard & tough rubber into soft, supple & even semisolid mass.
Due to mechanical force, mechanical degradation is occured. Milling, grinding, extrusion, mastication, agitation, are other well known methods of mechanical degradation for polymer. The bigger molecules are found to be affected much more than the smaller ones during mechanical degradation. This means the larger the initial molecular weight, the greater the molecular weight drop due to mechanical degradation. So, generally molecular weight decreases by mechanical degradation.
