The mechanical and physical properties of polyurethane composites based on rice husk and polyethylene glycol

In this study, polyurethane composites have been produced with rice husk (RH) and polyethylene glycol, molecular weight (M-w) of 200 (PEG200), used as a polyol. The effect of % of RH (by weight), % of RH hydroxyl (OH) groups and RH size on the flexural, tensile and impact properties were investigated. For most tests, the properties increased as the % of RH or % of RH OH groups was increased. However, after exceeding a threshold value, the properties started to decrease. This phenomenon was attributed to two factors (i) % of RH (by weight) or % of RH OH groups (ii) amount of homogeneous PU matrix. The size of RH also played a significant role in the properties, where smaller size RH produced composites with higher strength. This is due to the greater surface area for interaction between OH groups from RH and isocyanate (NCO) groups from MDI, which could be detected by scanning electron microscope (SEM) analysis. Dimethylformamide (DMF) immersion tests showed that absorption and swelling decreased as the % of RH was increased. The increase in water absorption and thickness swelling as the % of RH was increased was attributed to the ability of RH OH groups to absorb water causing the cell wall to swell. (C) 2003 Elsevier Science Ltd. All rights reserved.