Investigation of hindered phenol antioxidant effects on the aging performance of cross-linked LDPE in the presence of copper

In this study, LDPE materials with different kinds of antioxidants were prepared by melt-blending method. To reveal the aging mechanism and the anti-oxidation efficiency of LDPE in the presence of copper, series of characterizations including tensile testing, Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC), scanning electronic microscopy (SEM) and computation simulation were performed. The experimental results indicated that the aging process significantly decreased the tensile strength and elongation of those aged samples except 1024, which retarded the aging degradation of LDPE at the same condition. These results were further confirmed by the FTIR analysis with the carbonyl index values. Additionally, the melting peaks of DSC plots became broader and shifted to the lower temperatures during the aging process for S-0, S-3114 and S-1010, whereas no obvious changes were observed for S-1024. Importantly, according to the results obtained from computation simulation, a strong metal-ligand interaction between hydrazide group and copper ions was formed to prevent the further oxidation, which accounted for the excellent anti-oxidation behavior of 1024 for LDPE in the presence of copper.