Water absorption test
The water absorption test was conducted in accordance with ASTM D 570 which indicates the estimation of the water absorption rate of polymers when they are soaked. The test was applied to observe the absorption of water by the foamed PVC/rice hull composites with various mAC contents. Each of the water absorption values was averaged from three replicated samples. The water absorption behavior during immersion can be determined by using
Eq. (1) [3, 11]:
where ΔMt is the water uptake (in percent) and m0 and mt are the masses of the specimen before and during immersion in the water (in gram), respectively.