Preparation of expandable graphite via H2O2-hydrothermal process and its effect on properties of high-density polyethylene composites

This study presented a new way to prepare expandable graphite (EG), which is one kind of halogen-free flame retardant using the H2O2-hydrothermal process. Natural graphite was immersed in H2O2 and then put in autoclave to proceed the hydrothermal process. The EG was called as H2O2-HEG from the H2O2-hydrothermal process. The results showed that the expanded volume of EG using the H2O2-hydrothermal process was higher than that compared with convectional liquid phase synthesis, ultrasound irradiation, and hydrothermal method. Fourier transform infrared spectroscopy, X-ray diffraction patterns, scanning electron microscope, and X-ray photoelectron spectroscopy were used to analyze the structure and confirm that the EG had been prepared. Thermogravimetric analysis presents that H2O2-HEG can improve the thermal stability of composites. The cone calorimeter show that the peak heat release rate (HRR) values of composites decrease dramatically. Limiting oxygen index (LOI) value of H2O2-HEG composites is higher than that of high-density polyethylene (HDPE)/natural flake graphite. HDPE composites are capable of passing the V-0 classification and have antidripping behavior. LOI, UL-94, and the cone calorimeter results show that the HDPE/H2O2-HEG composite possess excellent flame retardant property. POLYM. COMPOS., 2012. (C) 2012 Society of Plastics Engineers