Comparative study of gamma-irradiated PP and PE polyolefins part 2: Properties of PP/PE blends obtained by reactive processing with radicals obtained by high shear or gamma-irradiation

Compared with neat polypropylene (PP), the addition of low contents (typically <20wt %) of polyethylene (PE) can improve the impact strength of PP based blends. In order to improve tensile properties as well, reactive extrusion has been carried out with radicals obtained by high shear or gamma-irradiation. The addition of a gamma-irradiation step in the processing sequence, between extrusion and injection, can be considered as an efficient way for improving the properties of our PP/PE blends. The improvement of mechanical properties has been discussed in terms of creation of secondary interactions or covalent bonds at the interface of the gamma-irradiated polymers, gamma-PP and gamma-PE. On one hand, the rheological measurements have highlighted an increase of the complex viscosity of the gamma-irradiated blends at low frequencies. On the other hand, the EPR spectrum simulation shows that the radicals are not the same in the blend and in the genuine gamma-PP and gamma-PE. Besides, the increase of temperature in the sample affects the shape of the EPR spectra, revealing that some macroradicals react one to another, which creates new macroradical structures of rather alkoxyl type. (C) 2015 Elsevier Ltd. All rights reserved.