UV-Curable Coatings Reinforced with Methacrylated Lignin and Esterified Cellulose Nanocrystals Derived from Oil Palm Waste

The valorization of lignocellulosic biomass into functional materials offers a sustainable pathway to reduce dependence on petroleum-derived polymers. Here, lignin and cellulose nanocrystals (CNCs) were extracted from oil palm empty fruit bunches (EFBs) via p-toluenesulfonic acid fractionation and microwave-assisted acid hydrolysis. Lignin was functionalized with methacrylate groups, while CNCs were esterified with a chain transfer agent and subsequently grafted onto methacrylated lignin through RAFT polymerization, yielding ML-g-CNC hybrid fillers. These bio-derived fillers were incorporated into UV-curable coatings (0–20 wt %), and their structural, thermal, and mechanical properties were evaluated. The optimal formulation containing 10 wt % ML-g-CNC achieved a pull-off strength of 2.17 MPa, a pencil hardness of 2H, and a contact angle of 85.5°, outperforming the neat coating. Thermal analysis further revealed enhanced stability with a maximum decomposition temperature of 416 °C and a glass transition temperature of 146.5 °C. This work demonstrates that EFB-derived ML-g-CNC provides a renewable and high-performance reinforcement for UV-curable coatings, highlighting its potential for scalable and sustainable surface engineering applications.