Melt State Dynamic Mechanical Properties of Polyethylene/EPDM/Silicon Dioxide Composites

Dynamic mechanical spectra of composites of high density polyethylene (PE), ethylene propylene diene rubber (EPDM), and silicon powder with an oxidized sur face were obtained at 190°C with a parallel plate instrument. The dynamic mechanical be havior of these composites was significantly influenced by the surface character of the sili con dioxide powder. Composites of silicon dioxide in PE displayed higher reinforcing effects than expected based on the properties of the constituent materials assuming spherical particles. Treat ment of the silicon dioxide with either gamma-aminopropyltriethoxysilane (γ-APS) or gamma-methacryloxypropyl-trimethoxysilane (γ-MPS) increased the dynamic shear mod ulus of these composites. Composites were also made with EPDM and EPDM grafted with maleic anhydride (EPDM-MA) and silicon dioxide in PE. The rubber addition had a significant effect on the properties of the resultant composites. The silicon dioxide was also treated with γ-APS and γ-MPS before incorporation into multicomponent compos ites. The surface character of the filler influenced the properties of the composites. There is evidence for a reaction between γ-APS and EPDM-MA during processing on the roll mill.