The promising impacts of electron beam radiation on the melt strength and cell behavior of heterophasic ethylene-propylene copolymer (HEPC)

Electron beam irradiation is a high-tech process widely used to enhance the melt strength of polypropylene (PP). In this research, heterophasic ethylene-propylene copolymer (HEPC) as a grade of PP with high-impact strength was irradiated by exposing granules to several doses (25-125 kGy), under nitrogen gas atmosphere. The changes in the structure and properties were assessed by different methods including infrared spectroscopy, thermal/thermomechanical analysis and extensional rheology. As the radiation dose increased, strain hardening behavior was observed which indicates chain branching and improved melt strength. Tensile strength was decreased from 30.7 ± 1.0 to 21.9 ± 0.2 MPa, impact strength decreased from 48 kJ/m 2 to 10 kJ/m 2 at the highest dose of radiation. Irradiation effects on the L929 fibroblast cell behavior were also studied and compared to a commercially branched PP grade (PF-814). By quantifying the number of the cells on the surface, it was shown that radiation of PP at doses higher than 50 kGy (75,100,125 kGy), can result in a significantly higher number of cells on the surface of the films. This finding was attributed to the higher chain mobility after irradiation. Results of this research shed light on the favorable changes in the cell behavior induced by electron beam irradiation, paving the path for future development of PP-based biomaterials. • Irradiation by electron beam improved melt strength of PP. • Electron beam irradiated PP showed strain hardening behavior. • Irradiation slightly affected the melting point and crystallinity. • Morphology of fibroblast cells on the films was improved after electron beam irradiation.