Isotactic Poly(propylene)/Wood Sawdust Composite: Effects of Natural Weathering,Water Immersion,and Gamma-Ray Irradiation on Mechanical Properties

Isotactic poly(propylene) (iPP)/wood sawdust composite containing 30 wt.% of the natural fibers was first prepared by melt-mixing in a twin screw extruder and later molded into various shaped specimens by injection molding machine. The effect of natural weathering, water immersion, and gamma-ray irradiation on mechanical properties of the specimens were studied. All of the tensile properties were improved with initial increase in the exposure time of natural weathering of up to 30 days and decreased afterwards. Similarly, the tensile strength and the Young's modulus of the composite increased with initial increase in the radiation dosage and decreased afterwards. On the contrary, the tensile strength and the elongation at break of the composite were unchanged after having been immersed in water for the first 15 days, but increased slightly afterwards. The alteration in these properties were postulated to be a result of the interplay between the cross-linking and the chain scission reactions that occurred during natural weathering and gamma-ray irradiation and the plasticizing effect of the absorbed water molecules during water immersion.