Figure 7 illustrates the influences of the water uptake on the notched Izod impact strength of the foamed composites over the immersion times of 0 to 90 days. Overall, the impact strength decreased slightly as the immersion time increased.
At 90 days of soaking, maximum decrement in the impact value by 8.0 % was found when 2.0 wt% mAC was applied.
This was believed to be the consequence of the leaching of PVC additive from the PVC, especially the water-soluble DOP plasticizer, out of the PVC structure, making the soaked PVC stiffer.
Numerous reports indicated that the DOP could easily leach out of the PVC under the presence of moisture [18, 19]. Being hydrophilic, the rice hull particles might have also absorbed water, expanded, and become another possible factor inducing the loss of adhesion between the rice hull filler and the PVC matrix [20–23].