Influences of particle sizes and contents of chemical blowing agents on foaming wood plastic composites prepared from poly(vinyl chloride) and rice hull

This research aims to investigate the effects of chemical blowing agent (CBA) contents and particle sizes on the properties of foamed poly(vinyl chloride) (PVC)/rice hull (RH) composites. Fine particles of azodicarbonamide (AC) at 5, 8, 11 and 22 μm were modified with 20% by weight of ZnO and used at 0–3.0% by weight. The average cell size and density of the PVC/RH foamed profiles were reduced as the content of modified azodicarbonamide (mAC) increased. Larger mAC particles lowered the density more effectively. Maximum reduction of density by 46% was achieved when mAC 22 μm was applied at 2.0% by weight. Larger blowing particles led to PVC/RH foam with greater flexural modulus and strength. Greater impact strength, observed when 5 μm mAC was applied, resulted from the rather thick cell wall created abundantly when fine mAC was applied.