Effects of gamma irradiation on the properties of wood composite from polypropylene

Abstract

Polypropylene wood composites as wood-substituted materials have received increasing attention due to their easy processability low cost as well as reasonable mechanical characteristics. However, the main problems encountered in PP/wood composites are poor creep resistant and low compatibility between woodflour and the PP matrix. In this work, gamma radiation was used to improve creep performance of the PP wood composites. Effects of gamma irradiation on properties of PP/wood composites with and without the presence of PP-g-MA compatibilizer are studied. The specimens are irradiated with gamma radiation at various doses of 5, 10, 20 and 30 kGy in both air and nitrogen atmospheres. The results demonstrated that it was possible to use low radiation doses 10 kGy to safely modify PP and its wood composites. The wood composite specimens radiated with 10 kGy provided about of less than 23% increase in flexural modulus compared with the unirradiated samples. The strength of the irradiated PP was 18.8% greater than that of the unirradiated PP. Creep strain of the irradiated composite has maximum decrease in the value due to the possible formation of crosslinking as confirmed by solvent extraction experiment. In addition, the combined effect of the use of gamma radiation and PP-g-MA rendered PP wood composite with maximum creep resistance. Furthermore, irradiation was found to show marginal effects on thermal properties of the PP and the PP/wood composites. Finally with increasing radiation dose, the interfacial adhesion between the woodflour and the polypropylene was enhanced as evidenced by SEM micrographs.