Study on the mechanical properties and flame retardancy of tannic acid-based non-isocyanate rigid polyurethane foam according to the content of crosslinking agents

Abstract Study on non-isocyanate polyurethane (NIPU) has been gaining attention as an environmentally friendly alternative to conventional polyurethane. However, current non-isocyanate polyurethane foams (NIPUFs) face limitations in practical applications due to its low mechanical strength and limited flame retardancy. In this study, tannic acid-based non-isocyanate polyurethane resins were synthesized using tannic acid with good chemical reactivity and flame retardancy as precursors. Tannic acid-based non-isocyanate rigid polyurethane foam (T-NIPUF) was then prepared using hexamethylenetetramine, citric acid, and glutaraldehyde as crosslinking agents. The structure of the synthesized T-NIPUF was analyzed using FT-IR and 1 H NMR, and the mechanical properties and flame retardancy according to the various crosslinking agent contents were evaluated by UTM, SEM, TGA, LOI, and ignition tests.