Development of high-performance biocomposites through lignin modification and fiber reinforcement

This study aimed to develop and characterize novel biocomposites incorporating tall oil fatty acid (TOFA)-modified lignin (TeL), citric acid-esterified polyvinyl alcohol (CeP), and unbleached fibers (UNB) to enhance thermal and mechanical properties while utilizing renewable resources. The research addressed the growing demand for sustainable high-performance materials in various industrial applications. Kraft lignin was modified through esterification with TOFA, while polyvinyl alcohol (PVA) was crosslinked using citric acid. These modified components were combined with UNB to create biocomposites with varying compositions. The materials were characterized using Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile strength testing. FTIR analysis confirmed successful esterification of lignin and PVA, evidenced by a strong ester carbonyl peak at 1730 cm⁻¹. DMA results revealed significant improvements in viscoelastic properties, with the highest glass transition temperature (T_g) of 179.47 °C observed in the sample containing maximum TeL and CeP content. TGA demonstrated enhanced thermal stability, with samples containing higher TeL and CeP content exhibiting increased char formation and residual masses up to 47% at 500 °C. Mechanical testing showed a strong correlation between composition and performance, with the optimal formulation (TeL12-CeP4-UNB4) achieving a tensile strength of 8.7 MPa and a tensile modulus of 59.3 MPa. Potential applications of these high-performance biocomposites include sustainable alternatives for packaging, automotive components, building materials or insulation, electronic devices and other industries where enhanced thermal and mechanical properties are required. These materials present a viable option for replacing conventional petroleum-based polymers, contributing to the advancement of eco-friendly industrial solutions.