Dielectric strength of γ-radiation cross-linked, high vinyl-content polyethylene

We explore γ-radiation cross-linking of high vinyl-content low-density polyethylene (LDPE) and its potential use as a high-voltage insulation material. Of the three investigated resins containing 1, 0.5 and 0.17 vinyl groups per 1000 carbons, respectively, only the highest vinyl-content material featured a sufficiently high gel content of more than 70% and hot-set elongation below 175%, when cross-linked with a γ-radiation dose of at least 68kGy. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) reveal that neither the crystallinity nor the lamellar thickness of the highest vinyl-content LDPE are negatively affected by γ-radiation cross-linking. As a result, we find that the dielectric strength, as characterized by electrical tree initiation experiments, can be maintained upon γ-radiation cross-linking.