the relationship between the percentage of water absorption and the soaking time of the unfoamed and foamed PVC/rice hull composites was illustrated in Fig. 1. The water absorption of all the PVC/rice hull composites studied increased with immersion time, reaching a constant value at the saturation
point where no more water was absorbed and the composite's water content remained constant.
This absorption behavior can be separated as two steps of diffusion; the first one occurred over a rapid diffusion rate while the second step was found at a slower absorption rate close to zero.