Effect of monomer type on polydopamine modification of bamboo flour and the resulting interfacial properties of bamboo plastic composites

Abstract Bamboo flour (BF) was modified with mussel-inspired polydopamine to enhance compatibility with high-density polyethylene (HDPE) in BF/HDPE composites. Polydopamine was synthesized using dopamine, catechol, and dopa as monomers. The modified BF exhibited better physicochemical properties. Dopamine-modified BF surface showed the greatest elevation in free energy and roughness. The largest increase in wettability, specific surface area, and thermal degradation temperature was displayed by dopa-modified BF. The improved processability of modified BF boosted interaction between BF and HDPE, thus physicomechanical performance of compression-molded composites was promoted. Composites with dopamine-modified BF won the strongest interfaical bonding, the lowest water sorption, the best mechanical performance, and the highest heat distortion temperature. The highest glass transition temperature and melting temperature were found in composites with catechol-modified BF. Composites with dopa-modified BF triggered the biggest thermal degradation activation energy. Overall, dopamine modification gave composites more merits, but catechol and dopa were useful when tailoring some thermal properties.