3D printing of Mucuna pruriens pod- derived lignin- reinforced PLA biocomposites for sustainable biomedical and tissue engineering applications

The results demonstrate that silane-treated lignin composites exhibit significantly improved performance compared to untreated counterparts. Among all formulations, PTL1 (5 vol.% silane-treated lignin) showed superior fatigue resistance, withstanding 24,657, 21,694 and 18,694 cycles at 25%, 50% and 75% of ultimate tensile strength, respectively, representing substantial improvements over neat PLA due to enhanced interfacial bonding and efficient stress transfer. PTL2 (10 vol.% silane-treated lignin) exhibited the best creep resistance, showing the lowest creep strains at 5,000, 10,000 and 15,000 s. PTL2 also recorded the highest swelling (19.61%) and degradation rate (10.26% mass loss after 4 weeks), indicating increased water diffusion and controlled degradation. Thermogravimetric analysis confirmed enhanced thermal stability, with PTL2 showing the highest onset and maximum degradation temperatures (335°C and 386°C). SEM observations corroborated uniform lignin dispersion and strong interfacial adhesion in treated composites, while untreated samples displayed agglomeration and interfacial defects. Overall, the developed silane-treated lignin/PLA composites are promising candidates for lightweight additively manufactured components subjected to cyclic and sustained loading, including automotive interior parts, consumer products, packaging, biodegradable fixtures and low-load structural components where improved fatigue resistance, dimensional stability, thermal durability and controlled biodegradability are desirable.