Surface modification of cellulose nanocrystal and its applications in flame retardant epoxy resin

In this work, surface modification of cellulose nanocrystal (CNC) with diphenyl phosphate and Zn(OAc) 2 ·2H 2 O was prepared by a green method to obtain CNC-based flame retardant CNC@DPP@Zn and then added into epoxy resins (EP). The structure, morphology, and thermal stability of CNC@DPP@Zn were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TG). Flame retardancy and combustion behavior of EP/CNC@DPP@Zn composites were characterized by TG, limiting oxygen index (LOI) test, vertical burning (UL-94) test and cone calorimeter tests (CCT). The results of CCT demonstrated that the peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) of EP/8CNC@DPP@Zn composites reduced by 38.3%, 15.5%, and 36.0%, respectively, compared with pure EP. The char residues after CCT were characterized by laser Raman spectroscopy (LRS) and scanning electron microscope (SEM). Finally, the flame retardancy mechanism of CNC@DPP@Zn was proposed.