Proton (3 MeV) and copper (120 MeV) ion irradiation effects in low-density polyethylene (LDPE)

Low-density polyethylene (LDPE) was irradiated with proton (3 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical and structural properties. In the present investigation, the fluence for proton irradiation was varied up to 2×10¹⁵ protons cm^?2, while that for copper beam was kept in the range of 1×10¹ to 1×10¹³ ions cm^?2 to study the swift heavy ion-induced modifications in LDPE. Ultraviolet–visible (UV–vis), FTIR and X-ray diffraction (XRD) techniques were utilized to study the induced changes. The analysis of UV–vis absorption studies reveals that there is decrease of optical energy gap up to 43% on proton irradiation (at 2×10¹⁵ ions cm^?2), whereas the copper beam (at 1×10¹³ ions cm^?2) leads to a decrease of 51%. FTIR analysis indicated the presence of unsaturations due to vinyl end groups in the irradiated sample. The formation of OH and CO groups has also been observed. XRD analysis revealed that the semi-crystalline LDPE losses its crystallinity on swift ion irradiation. It was found that the proton beam (2×10¹⁵ ions cm^?2) decreased the crystallite size by 23% whereas this decrease is of 31% in case of the copper ion-irradiated LDPE at 1×10¹³ ions cm^?2.