Morphology and properties of sol-gel prepared LDPE silica nanocomposites

Abstract

Blending of polymers is an effective way to manufacture materials with specific properties. Nanofillers play an important role to enhance the thermal and mechanical properties of the polymers. In our work, LDPE and LDPE-g-MA based nanocomposites were prepared using sol-gel derived nanosilica. LDPE was grafted with maleic anhydride to introduce functional groups that could interact with nanosilica. Oxidized paraffin wax was also introduced into the nano-composites as possible compatibilizer. The thermal, mechanical and thermomechanical properties of the nanocomposites were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing, and dynamic mechanical analysis (DMA). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscope (TEM) were employed to determine the morphologies of the composites. FTIR, TEM and SEM analyses of LDPE-g-MA/silica, LDPE-g-MA/wax and LDPE-g-MA/wax/silica samples showed that there was an interaction between the different components and a reduction in silica agglomeration compared to the LDPE-based samples. Generally, the total sample crystallinity increased with an increase in wax content, but the crystallinities of the composites depended on the interactions between the components and the resulting sample morphology. In the case of LDPE the presence of wax reduced the thermal stabilities of the samples, but the presence of silica had little influence. The pr sence of wax as well as silica had little influence on the thermal stability of LDPE-g-MA, but the LDPE-g-MA/wax/silica composites showed a reduction in thermal stability with increasing wax content. Changes in the tensile properties with addition of silica nano-particles, and with increasing wax content in the samples, reflected the interactions between the different components and the resulting sample morphologies. The DMA results of all the composites and blends show that the presence of silica nanoparticles and wax, as well as the interactions between the different components, had an observable influence on the sample morphology and mobility of the polymer chains.