UV stability of HMS-PP (high melt strength polypropylene) obtained by radiation process

HMS-PP in grains was synthesized by the gamma irradiation of PP under a crosslinking atmosphere of acetylene, followed by thermal treatment for radical recombination and thermal treatment for annihilation of the remaining radicals. The UV stability of the material was evaluated in pellet form. The accelerated weathering test of HMS-PP samples were performed under artificial ultra-violet light and in a condensation chamber Comexim (C-UV type) apparatus with UV exposure for 120 and 240 h. The results were compared to those from ageing caused by sunlight and dew under natural exposition. This work investigated changes in mechanical proprieties (elongation and rupture strength), Fourier transform infrared spectroscopy (FTIR), optical microscopy (MO), scanning electron microscopy (SEM) and rheological properties of HMS-PP after the UV ageing. We find that the HMS-PP has more degradation than regular PP and undergoes predominate chain scission in aggressive UV ageing conditions.