Comparative study on the degradation effects initiated by gamma ray and electron beam irradiation in polypropylene

Abstract

The aim of this paper is to investigate the potential effects of gamma ray and electron beam irradiation, ranging between 25 and 200 kGy on unstabilised Polypropylene (PP). The PP samples were subjected to a range of characterisation techniques in order to identify any modifications to the material properties. Melt flow index (MFI) revealed that the melting strength and molecular weight of PP was significantly reduced with irradiation where the gamma irradiated samples were proven to be more affected. Fourier transform infrared spectroscopy (FTIR) demonstrated that gamma irradiation initiated more structural changes to occur in PP in contrast to electron beam irradiation. In addition, the gamma irradiated samples had extra oxidation groups present. Rheological studies evidently showed that the predominant phenomenon was chain scission in PP after electron beam and gamma irradiation. Although, the gamma ray process generated additional degradation effects in the material. Discolouration was quantified by utilising a colorimeter which determined that the gamma ray process produced more yellowing to transpire in the PP material at low irradiation doses (25 kGy). Finally, scanning electron microscope (SEM) identified that the surface morphology of the samples was much smoother subsequent to electron beam irradiation.