Optimising wheat straw alkali-organosolv pre-treatment to enhance hemicellulose modification and compatibility with reinforcing fillers

Hemicellulose acetylation, filler compatibility and film hydrophobicity were enhanced by optimising alkali-catalysed organosolv treatment conditions for wheat straw before hemicellulose extraction. Two optimum (OPT) conditions were established by varying organosolv components’ concentrations [ethanol (EC) (50–80%) and NaOH (1–13%)], and time (2–6 h), in a Box-Behnken experimental design. The OPT1 (1% NaOH/50% EC/6h) that enhanced acetylation and filler compatibility, and OPT2 (13% NaOH/80% EC/5h) that enhanced hydrophobicity by minimising degree of acetylation (DS), uronic acid content and arabinose/xylose ratio. The films made from OPT2 hemicellulose had higher water contact angle (68.1°) than OPT1 hemicellulose (39.90°). However, OPT1 hemicellulose had a higher DS (1.7 vs 0.4), and their acetylated nanocellulose reinforced films had higher tensile strength (10.59 vs 4.87 MPa) and Young modulus (590.15 vs 323.64 MPa) than OPT2 hemicellulose. Therefore, hemicellulose acetylation, hydrophobicity and filler interaction can be engineered by manipulating the organosolv treatment conditions.