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 surface were obtained at 190-degrees-C with a parallel plate instrument. The dynamic mechanical behavior of these composites was significantly influenced by the surface character of the silicon 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. Treatment of the silicon dioxide with either gamma-aminopropyltriethoxysilane (gamma-APS) or gamma-methacryloxypropyl-trimethoxysilane (gamma-MPS) increased the dynamic shear modulus 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 gamma-APS and gamma-MPS before incorporation into multicomponent composites. The surface character of the filler influenced the properties of the composites. There is evidence for a reaction between gamma-APS and EPDM-MA during processing on the roll mill.