Radiation effects on polyethylene and polypropylene by electrons and protons

Abstract

The irradiation of low-density polyethylene and polypropylene films has been carried out by using 20-keV proton and 8-MeV electron beams. Measurement of mechanical properties and X-ray diffraction have shown that the tensile strength and elongation of electron-irradiated polyethylene have improved as a function of electron dose, suggesting the occurrence of cross-linking with proper irradiation dosage. On the contrary, rapid degradation of electron-irradiated polypropylene has been noticed. Protons have quite different effects on these two polymers: they caused a small decrease in the mechanical properties of polyethylene on the one hand, and on the other the mechanical properties of polypropylene were greatly improved (increase in its tensile strength σ ( kg cm 2 ) by 51% and that of its elongation ϵ t by 36%. This effect may be attributed to the collision of the incident proton beam with protons in the polypropylene chains, forming cross-links between macromolecules of propylene. This is probably the first time that the cross-linking of polypropylene by proton bombardment has ever been observed.