Preparation and properties of bio-based intumescent flame retardant containing chitosan functionalized ammonium polyphosphate for polyurethane

In this study, chitosan (CS) from fish waste was used to prepare bio-based environmentally friendly flame retardants. After the hydroxyl group (−OH) of CS and the ammonium group (NH4+) of ammonium polyphosphate (APP) underwent reactions, they were filtered and dried to obtain CS-APP. The amino group of CS-APP then reacted with the epoxy group of 4,4′-methylenebis(N,N-diglycidylaniline) (NDY) to form CS-APP-NDY. Isophorone diisocyanate, polyol, and 3-aminopropyltriethoxysilane reacted to form silicon polyurethane. CS-APP-NDY was then mixed with Si-PU to prepare polymer composites. To determine the structure, thermal properties, flame retardancy, and mechanical properties of the composites, Fourier-transform infrared spectroscopy, thermogravimetric analysis, limiting oxygen index (LOI), cone calorimetry, UL-94, thermal analysis-FTIR (TA-FTIR) spectroscopy, universal machine testing, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were performed. The TGA results revealed that, after the addition of CS-APP-NDY, char yield increased from 0.5 wt% to 25.8 wt%, and the thermal stability of pristine PU also improved. In addition, the LOI and UL-94 results indicated that, after the addition of CS-APP-NDY, the LOI increased from 18.2% to 26.3%, and the UL-94 level improved from “Fail” to V-1. Overall, these results indicated that the addition of CS-APP-NDY to pristine PU increased its flame-retarding performance.