Characterization of Rice Husks as Potential Reinforcement for Polymer Composites

Plastic consumption has continued to grow over the years. Meanwhile, conventional petroleum-based plastics are associated with challenges like environmental unsustainability. As a result, bio-based polymer composites have received much attention in past decades. Polymer matrices can not only be easily be reinforced with agricultural fibers to reduce price, but also improve mechanical and thermal properties. The aim of this study was to investigate the effect of magnesium hydroxide modification on properties of K85 and K98 rice husk varieties in Uganda for their use as reinforcement in polymer composites. Raw rice husks underwent pre-treatment in 4% Mg(OH)2 concentration for 1 h at room temperature. Water absorption, thermogravimetric analysis (TGA), energetic density (ED), and fuel value index (FVI) of rice husks were investigated. Raw husks exhibited higher water absorption capabilities (9.1–11.2%) than modified rice husks (5.6–5.89%). TGA confirmed that alkali modification of rice husks provides a higher resistance to thermal degradation than that of raw husks. Mean reactivity to char residues ratio reduced from 4.3 × 10−4 to 3 × 10−4 °C/min upon modification of K85 rice husks while modification of K98 rice husks led to increasing mean reactivity to char residues ratio by 11.4%. ED sharply reduced upon alkali modification of both K85 and K98 rice husks. FVI of rice husks greatly depended on the amount of ash in the rice husks. As such, K85 husks had higher FVI than K98 husks as the former had lower ash compositions (21.2%). The results suggest that alkali-modified rice husks can be successfully used as reinforcement in polymer composites.