Reclaimed lignosulfonate-modified bamboo fibers prepared via layer-by-layer self-assembly to reinforce poly(3-hydroxybutyrate) biocomposite

Fiber-reinforced poly(3-hydroxybutyrate) (PHB) biocomposites have been increasingly applied in various fields, such as building structures, interior decorations, and product packaging, due to their high strength to weight ratios, low thermal conductivities, low carbon footprints, and biodegradabilities. However, poor compatibility between the hydrophilic natural fibers and the thermoplastic biocomposites limits their mechanical strengths. This work proposes a method based on layer-by-layer self-assembly (LbL) to improve the interfacial compatibility between the PHB and bamboo fibers (BFs). Sodium lignosulfonate (SL) derived from pulp and paper industry waste was used as the raw material. Then, long carbon chains were introduced into the SL via the Mannich reaction. A hydrophobic self-assembled multilayer structure (SMS) was constructed on the surfaces of the BFs. The preparation process was environmentally friendly, controllable and simple. The mechanical properties were improved by the modifications, including the tensile strength (44%), flexural strength (13%), and impact strength (41%). The thermal properties of the fiber-reinforced biocomposites were also enhanced. This study presents a novel strategy for high-value utilization of industrial byproducts and the enhancement of biocomposite interfacial compatibility.