Characterisation and density functional theory study of epoxy–microcrystalline cellulose primer coating

This work aimed to assess the capability of a newly synthesised primer coating for sustainable metal protection. Green wood pulp cellulose, namely microcrystalline cellulose (MCC) was incorporated into epoxy resin to produce a novel primer coating. Different MCC loadings (0–9 wt%) were investigated to identify the optimal formulation for achieving the best barrier performance. The interaction between MCC and epoxy was analysed using density functional theory (DFT) and compared with the experimental results obtained from Fourier transform infrared (FTIR) spectroscopy. According to DFT analysis, the geometrically optimised structure of epoxy–MCC exhibited distortion, promoting increased interaction between the epoxy matrix and MCC through hydrogen bonding. This finding was consistent with the FTIR analysis. Scanning electron microscopy (SEM) analysis of the composition containing 5 wt% MCC revealed a homogeneous and minimally aggregated structure, with MCC fully integrated into the pores of the epoxy matrix. Epoxy with 5 wt% MCC significantly enhanced the mechanical properties of the primer coating, achieving an optimal pencil hardness of 6H. Furthermore, contact angle measurements at 5 wt% MCC obtained the highest values, with an advancing angle of 114.02° and a receding angle of 69.03°. These results were supported by corrosion tests, which revealed that 5 wt% MCC resulted in the lowest coating failure, with minimal pore formation, fewer cracks, and minor detachments. Overall, this work demonstrated the successful utilisation of MCC as a novel reinforcement filler in epoxy primer coating systems, enhancing strategies for maintaining the integrity of the metal.