Lignin nanoparticle reinforced infusible thermoplastic composites with enhanced UV shielding

The growing demand for sustainable, high-performance materials has motivated the exploration of lignin as a functional additive in polymer composites. This work investigates the development of lignin nanoparticle (nL) reinforced Elium® nanocomposites aimed at improving ultraviolet (UV) resistance and thermomechanical performance. Spherical lignin nanoparticles were synthesised from sulphur-free biorefinery lignin using a solvent-shifting method and incorporated into the Elium® matrix via in-situ free radical polymerisation. Elium®, a recyclable, infusion-processable thermoplastic acrylic resin, offers a sustainable alternative to conventional thermosets while maintaining comparable mechanical performance. The effect of nL loading on UV shielding, mechanical, thermal, and rheological properties was systematically examined. Incorporation of lignin nanoparticles significantly enhanced UV absorption and thermal stability, with optimum performance achieved at 0.5 wt% loading. At this concentration, the composite exhibited a 54% improvement in UV shielding, along with ∼30% and 22% increases in tensile (∼30%) and flexural strengths (22%) without adversely affecting viscosity or cure behaviour. This study, the first to report lignin nanoparticle reinforcement in Elium® resin, demonstrates that lignin nanoparticles can impart multifunctionality to recyclable thermoplastic composites.