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)center dot 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.