Influences of water absorption on the properties of foamed poly(vinyl chloride)/rice hull composites

The current study investigates the influences of water absorption on the physical and mechanical properties of foamed poly(vinyl chloride) (PVC) and rice hull composites for building material application. Zinc oxide-modified azodicarbonamide was used as a blowing agent; its contents were varied from 0.5 to 2.0 wt%. Physical and mechanical properties of the unfoamed and foamed PVC/rice hull composites were determined after they had been immersed in water for a maximum duration of 90 days. Experimental results indicated that the water absorption mechanism of foamed PVC/rice hull composites followed the kinetics of Fickian diffusion theory. Slight increases in both the flexural modulus and the flexural strength were observed in all compositions due to the leaching of some PVC additives. Microscopic observation on the surfaces of the foamed PVC/rice hull composites revealed abundant surface openings depicting the passages of water diffused into the PVC/rice hull foamed composites.