Effects of nano-silica on the crystallization, structure, and mechanical properties of crosslinked ethylene-octene copolymer/nano-silica composites

Abstract

Nano-silica (SiO2) has been widely used to fill rubbers (crosslinked) and usual polyolefin elastomers (POEs). SiO2 filled POE with crystalline structure can also be crosslinked. Crystallization, structure, and mechanical properties of crosslinked POE/SiO2 composites can be affected by SiO2. In this paper, crosslinked POE/SiO2 composites were obtained through two different methods: dynamic crosslinking in molten state and static crosslinking. For the non-crosslinked and static crosslinked composites, SiO2 had a more significant effect on the nucleation in non-crosslinked POE than in static crosslinked POE. For the dynamic crosslinked composite, SiO2 and crosslinking points hindered the mobility of POE chains and suppressed the POE crystallization, resulting in smaller and fewer crystals. Dynamic mechanical analysis showed that the SiO2 and POE were compatible, as evidenced by the lower tan(δ) value in SiO2-filled samples. The latter was more consistent with the higher tensile strength and elongation at break for the non-crosslinked and static crosslinked composites than for the non-filled samples. However, the dynamic crosslinked composite exhibited the worst elongation at break, resulting from the lowest number of crystals and shortened molecular chains due to the shearing that occurred during crosslinking process. The SiO2 had no observable effect on the permanent deformation of samples.