Irradiation of isotactic polypropylene and polypropylene/ethylene-propylene (diene-monomer) blends

The influence of electron beam irradiation on rheological properties and morphology of polypropylene and polypropylene/ethylene-propylene rubber blends was studied. Electron beam irradiation of isotactic PP causes pronounced chain scission (degradation) at dosis = 100 kGy. Melt viscosity can be controlled easily up to this dose for pure PP. For the blend, however, an anomalous rheological behaviour is observed. Attempts have been made to induce a special morphology and to retain this morphology during subsequent shaping processes via fixation by radiation induced crosslinks. Radiation crosslinking of the dispersed EPDM phase and a simultaneous grafting of PP onto EPDM is proposed to be the explanation for both the anomalous rheological and an enhanced morphology fixation. This idea is supported by gelfraction measurements