Fully Biobased Lignin-Bonded Bamboo Composites with Mold Resistance Based on Lignin Recycle Strategy

Bamboo has emerged as a promising biomass resource for sustainable development; however, its susceptibility to molds impedes further adoption. This study presents the synergistic preparation of lignin-bonded bamboo composites (LBCs) exhibiting superior mold resistance through alkali treatment and lignin compositing. According to the lignin recycling strategy, recycled lignin (RL) is extracted from the alkali waste liquid after the alkali treatment of bamboo bundles. Alkali treatment efficiently eliminates nutrients from bamboo bundles and establishes an alkaline environment that inhibits mold proliferation. Subsequently, RL is integrated into the alkali-treated bamboo bundles as an adhesive and mold inhibitor. Hot-pressing induces physical (phase change) and chemical (self-cross-linking reaction between applied lignin and residual lignin) cross-linking, endowing the bamboo composites with superior mechanical qualities. LBC demonstrated an almost complete absence of molds in the 28-day mold inhibition test, achieving 96% efficacy in mold inhibition. The flexural strength and flexural modulus are measured at 168.0 MPa and 14.7 GPa, respectively, while the flexural specific strength attains 128.74 MPa/(g/cm3). The superior mechanical qualities and mold resistance of LBC are anticipated to enhance its utilization in outdoor flooring, interior decoration, and other domains. The lignin recycle strategy reported in this study prepares bamboo composites with superior mold resistance by reintroducing lignin, highlighting its potential in mold resistance and adhesive applications and thereby facilitating sustainable utilization of bamboo materials.