Synthesis of a novel compound based on chitosan and ammonium polyphosphate for flame retardancy applications

In this investigation, a novel compound (NCSAPP) based on chitosan (CS) and ammonium polyphosphate (APP) was synthesized by employing solutions of chitosan and ammonium polyphosphate. The synthesized compound was characterized using FTIR, PXRD, XPS, FESEM, EDX, TGA and a Micro Calorimeter. Finally, NCSAPP was inserted into vinyl ester resin and study the thermal and flammable properties. The FTIR spectrum of NCSAPP suggested the reaction between chitosan and APP and that formation of –NH³⁺–O⁻P– bonds with the –NH₃ ⁺ peak at 1533 cm⁻¹. The XPS spectrum showed a characteristic peak at 401.36 eV corresponding to the N_1s of –NH³⁺. PXRD suggested the amorphous nature of NCSAPP. FESEM coupled with EDX depicted a rough morphological pattern for NCSAPP with C, N, O and P. The thermal decomposition of NCSAPP was observed to be active at lower temperatures. However, at elevated temperatures (> 315 °C), a slow degradation rate with significantly higher thermal stability than that of CS was observed. The peak release rate (16.9 w/g) and total heat release (0.9 kJ/g) were significantly lower than those of CS. Besides, vinyl ester composite of NCSAPP obtained superior fire-retardant properties than vinyl ester composites of CS and APP. The obtained results indicate that NCSAPP can be applied in thermal applications operating at high temperatures.