Preparation of Silane-Grafted and Moisture Crosslinked Low Density Polyethylene. Part II: Electrical,Thermal and Mechanical Properties

Among different polyethylene cross-linking methods, such as peroxide, irradiation, and silane cross-linking, silane-based methods are the most suitable methods for producing cable insulation and hot water pipe materials due to process simplicity and superior properties of its product. Some electrical, thermal and mechanical properties of silane-grafted water-cross-linked polyethylene were investigated. The effects of silane grafting and gel content on volume resistivity, tensile properties and melting behavior of low density polyethylene (LDPE) were studied. Results indicated that volume resistivity increased with increasing gel content. Stress at break increased with increasing grafting level and gel content. Elongation at break increased with grafting and decreased with gel content. High temperature tensile properties showed that cross-linked polyethylene (XLPE) is more stable than LDPE at high temperature. In differential scanning calorimetry (DSC) analysis a broad endothermic peak appeared for XLPE due to phase separation. Melting point and crystalline percentage decreased with increased grafting level and gel content. Incorporation of carbon black into XLPE reduced the volume resistivity and degree of crystallization.