Effect of Silica Containing Immobilized Nanosilver on the Structure and Selected Properties of Wood-Filled High-Density Polyethylene Composites

The influence of silica containing immobilized nanosilver (SGS-Ag) on the structure, thermal, mechanical and bactericidal properties of wood-filled high-density polyethylene composites was investigated. All materials were compounded in a co-rotating twin-screw extruder and then injection molded. The composites were characterized with scanning electron microscope (SEM) and differential scanning calorimeter (DSC) methods. The thermal decomposition was studied by thermogravimetric analysis (TGA). The mechanical properties and heat distortion temperature were also determined. The addition of silica in the presence of maleated high-density polyethylene (MHDPE) improves adhesion between the HDPE and wood fiber. Storage modulus values of prepared composites containing nanosilica measured by dynamic thermomechanical analysis (DMTA) were sensitive to the microstructure of the nanocomposites. Higher silica contents resulted in higher storage modulus, proving that the material became stiffer. Crystallization rates and crystallinity were found to increase by adding MHDPE as well as nanosilica. The thermal stability of the wood-filled HDPE composites containing SGS-Ag was better compared to either wood-filled HDPE or neat HDPE. The gradual enhancement in tensile and flexural strengths of the wood-filled HDPE composites containing MHDPE was observed. The addition of silica nanoparticles to the wood-filled HDPE composites increased tensile and flexural modulus, pointing to a synergistic effect arising from the presence of the reinforced HDPE phase, containing high amounts of the finely dispersed wood fiber. Moreover, improved resistance to microorganisms (Escherichia coli, Staphylococcus aureus and Salmonella typhimurium) of the composites modified by silica containing immobilized nanosilver was observed.