Thermal and Dynamic Mechanical Properties of Low Density Polyethylene-Silica Nanocomposites: Effect of Zinc-Ion Coating on Nanosilica

Low-density polyethylene (LDPE)/silica nanocomposites were developed by conventional melt blending in a sigma internal mixer. Two types of composite, each with 2.5 wt% filler, were produced. The first was obtained by melt blending nano-silica with LDPE in a co-rotating sigma internal mixer. The second was obtained by melt blending the same LDPE, with zinc-ion coated nano-silica. In the case of zinc-ion coated nano-silica- filled LDPE, wide-angle X-ray diffraction (WAXD) showed a decrease in the interplanar distance and an increase in lamellar crystal size when compared to nano-silica filled LDPE. DSC and TGA results showed the zinc-ion coated nano-silica filled LDPE has higher thermal stability, heat of fusion, melting temperature and crystallinity than LDPE filled with nano-silica. AFM surface topography images showed a uniform surface and lower roughness in the case of zinc-ion coated nano-silica filled LDPE than nano-silica filled LDPE. Furthermore, the zinc-ion coating over nano-silica showed improvements in storage modulus E’, static modulus and thermal properties - a 26% increase in static elastic modulus and a rise in degradation onset temperature from 337 °C to 355 °C, in comparison to the nano-silica.