Solvent-free coatings based on bio-sourced benzoxazines resins with healing, repair, and recycling capabilities.

Conventional benzoxazine resins, in spite of their excellent thermo-mechanical properties and good solvent resistance, suffer from high curing temperatures and limited self-healing/ reprocessability. In this frame, bio-sourced phenol (Phloretic acid), various diols (Dodecandiol/PEG200/Ethylene glycol), and amine (monoethanolamine) have been used in appropriate proportions to synthesize innovative benzoxazine precursors bearing exchangeable ester functions following a solventless method. They can be directly handled and used for coating applications without using any solvent. The overall synthesis was followed by Nuclear Magnetic Resonance and Fourier transform infrared spectroscopy (FT-IR). The reduced curing temperature, thermal stability, good thermo-mechanical performance, and ester bond exchange-ability system were demonstrated by Differential Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), and Dynamic mechanical analysis (DMA - stress relaxation testing), respectively. The elaborated resins were applied on etched aluminum 1050 without solvent and the corrosion resistance of the coatings was investigated by electrochemical impedance spectroscopy (EIS). The electrochemical results showed proper corrosion protection on aluminum substrates. The best result was obtained with Dodecandiol-based benzoxazine coating due to its longer aliphatic chain and hydrophobic property. Comparing this coating with an epoxy-based benchmark showed enhanced corrosion resistance for the benzoxazine after 50 days of immersion, making it an interesting candidate for future industrial use. • Bio-sourced benzoxazines resins were synthesized. • The crosslinked polymers have healing, repair, and recycling properties. • Solvent-free coatings were applied. • Coatings show good anticorrosion behavior on AA1050 aluminum alloy. [ABSTRACT FROM AUTHOR]