Synthesis of itaconic acid-based non-isocyanate polyurethane coating with excellent heat insulation and corrosion resistance

Abstract

The objective of this study is to explore an environmentally friendly route for synthesizing non-isocyanate polyurethane (NIPU) coatings from renewable resources. A carbamate diol (CD10), featuring hydroxyl groups at both ends of the molecular chain, was synthesized by a melt ring-opening reaction using propylene carbonate (PC) and decanediamine (DDA). Due to the inherent rigidity and brittleness of CD10, it cannot form a high-performance coating independently. To address this limitation, biobased NIPUs were synthesized by incorporating itaconic acid (IA), a biobased material, as a soft chain segment into the CD10 structure. By varying the number of soft chain segments, it is possible to produce NIPUs coatings with tunable properties that cure naturally at room temperature without the need for curing equipment. The structure and physical properties of the NIPUs were characterized using Fourier transform-infrared (FT-IR), 1 H nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), thermal conductivity testing, water contact angle measurement, and pencil hardness testing. Additionally, their environmental stability was assessed by measuring water absorption in deionized water, acidic and alkaline solutions, and organic solvents. Additionally, their corrosion resistance in saltwater was evaluated. The results indicate that the coatings demonstrate significant performance due to the abundance of ester and urethane groups within the macromolecular chains of the NIPUs, leading to the formation of numerous intramolecular and intermolecular hydrogen bonds and an increase in cross-linking density. The potential application of these materials as film-forming agents for coatings, including heat-insulating and anticorrosive coatings, is promising. This study follows the concept of sustainable green development.