Effect of colloidal silica nanoparticles extracted from agricultural waste on physical, mechanical and antifungal properties of wood polymer composite

Physical, mechanical and biological properties of wood polymer nanocomposite made of poplar wood were investigated in current research. Colloidal silica nanoparticles were produced from agricultural waste (rice husk ash) under alkaline digestion. Specimens were divided into five groups; control, impregnated with nano silica (NS), nano composite (NC) (monomer included nano), nano silica- styrene (NSt) (nano and monomer, respectively), and styrene (St) specimens. Impregnation was conducted using vacuum/pressure method with nano silica suspension and styrene monomer, respectively. Styrene polymerized in situ wood porous structure from styrene monomer through thermal-catalyst treatment. Nano silica retention was 2.8%. The results of weight percent gain (WPG) for styrene monomer, NSt and NC were 95.9, 106.7 and 114.8%, respectively. Samples treated with nano silica and styrene composite indicated higher density and mechanical properties, but lower water absorption and dimensional changes. Individual treatments of nano and monomer illustrated an increasing effect on the fungal resistance. Significant difference was found between the individual and combined treatments. In all properties, nanocomposite treatment by creating a smooth surface without cracks and reinforcing role of nano particles in polymer had more intensifying effect than nano silica-styrene treatment. Nano composites samples showed the lowest volumetric swelling due to decrease of water uptake capacity. Furthermore, modulus of elasticity, modulus of rupture, hardness and compression strength of nano composite compared to control samples increased 33.3, 13.1, 53.5 and 44.7%, respectively. Nanocomposite with uniform distribution and colloidal silica nanoparticles reinforcement in polymer structure increased interaction of silica nanoparticles with styrene and wood, and presented the best enhancement in all properties.