Dual-function epoxy nanocomposite coatings with GNP and polysulphide for mechanical protection and rain erosion resistance

This study presents a novel epoxy-based nanocomposite coating incorporating graphene nanoplatelets (GNP) and epoxy-terminated polysulphide (EPS35) to enhance mechanical durability and rain erosion resistance. A range of formulations with varying GNP loadings (0–0.1 wt%) and EPS35 contents (0–20 wt%) were developed, and selected compositions were assessed for mechanical performance, viscoelastic behaviour and erosion resistance under high-speed water impact. EPS35 improved flexibility and impact resistance, with optimal performance at 15 wt% due to controlled phase separation. GNP addition showed a concentration-dependent effect: while agglomeration in neat epoxy reduced toughness, its dispersion within the EPS35-modified matrix significantly enhanced performance at low concentrations. The optimised formulation, P-28 (5 % EPS35, 0.025 % GNP), exhibited no cracking under mandrel bending or impact testing and showed a 223.6 % increase in crosslink density, confirming improved matrix reinforcement. Under simulated rain erosion at 100 and 150 bar, P-28 significantly outperformed a commercial polyurethane-based coating (CP), with a 38.9 % reduction in material loss and up to 95.9 % improvement in crack resistance. These improvements are attributed to the synergistic roles of EPS35 and GNP: EPS35 enhanced deformation capacity and crack resistance, while GNP improved structural integrity by impeding crack propagation, deflecting crack paths, and attenuating stress waves. The resulting biphasic morphology offered an optimal balance of stiffness and toughness. Unlike CP, which contains environmentally hazardous isocyanates, the developed system provides a safer, more sustainable alternative. These findings highlight the potential of EPS35/GNP-modified epoxy coatings for wind turbine blade protection and other applications requiring enhanced erosion resistance and long-term mechanical reliability. • EPS35 at 15 % optimises flexibility and eliminates cracks under bending stress. • GNP at 0.025 % reinforces crosslink density and improves impact performance. • P-28 (0.025 % GNP, 5 % EPS35) improves crack-induced erosion resistance by 95.9 %. • GNP and EPS35 synergistically deflect cracks and dissipate stress waves. • Excess GNP (≥0.05 %) causes agglomeration, reducing erosion and crack resistance.