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
amaximum 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.