Silane Grafting and Crosslinking of Metallocene-catalysed LLDPE and LDPE

Two grades of metallocene-catalysed LLDPE and one grade of low-density polyethylene (LDPE) have been silane grafted and crosslinked by contact with water and their performance has been compared and evaluated. The effects of vinytrimethoxysilane (VTMOS) levels on the degree of crosslinking for each grade were also studied. It was found that increasing level of silane increases the degree of crosslinking. However, no significant increase of the gel content was observed beyond 1.5 phr of silane concentration. All grades studied are shown to crosslink adequately, albeit with differing sensitivities to the level of silane, curing time and temperature. However, metallocene-catalysed LLDPE grades performed better in terms of crosslinking than LDPE, and among the metallocene-catalysed grades; EG 8150 has achieved a higher degree of crosslinking under the same level of silane concentration, and same processing conditions. The influences of curing time and temperature on the degree and rate of crosslinking were investigated, and it was observed that increasing curing time and temperature had a significant effect of increasing both the degree and the rate of crosslinking for all grades. The mechanical properties of all crosslinked samples are reported and correlated with their silane content results, which shows the increase of tensile strength and decrease of elongation at break.