Exploring lignin potential on polyurethane-silica hybrid coatings tribological, anticorrosive and bactericidal properties

This study investigates the potential of lignin as a sustainable alternative to petroleum-based polyols in the production of polyurethane-silica (PU-Si) coatings with improved tribological, anticorrosive and bactericidal properties. To achieve this goal, hybrid PU-Si coatings were developed and modified by incorporating varying amounts of lignin into the PU macromer chain, which were then applied to carbon steel substrates. Analysis through Fourier-transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (13C NMR) analyses confirmed complete integration of the lignin into the PU chains. Additionally, 29Si NMR revealed that lignin incorporation acted to increase the condensation degree of the silica. Lignin had a smoothing effect in the hybrid coatings, leading to reduced roughness. Mechanical tests showed that the presence of lignin decreased the friction coefficients of the coatings, while enhancing their wear resistance and critical delamination loads, compared to the coating without lignin. The best PU-Si-lignin coating presented outstanding anticorrosive performance, achieving low-frequency impedance values up to 100 GΩ cm2, without failure for over 100 days. Furthermore, the incorporation of lignin inhibited E. coli biofilm formation. These multifunctional properties suggest that these coatings have promising applications across various industries, from infrastructure to healthcare.