Graphene doped Sn flame retardant prepared by ball milling and synergistic with hexaphenoxy cyclotriphosphazene for epoxy resin

Sn-doped graphene nanoplatelets (GnPSn) was successfully synthesized by wet ball milling method from expandable graphite and Sn powder. The surface morphology, thickness, crystal structure and chemical structure were comprehensive characterized. Epoxy resin (EP) composites (EP/GnPSn or EP/HPCTP/GnPSn) were prepared by adding GnPSn alone or GnPSn and hexaphenoxy cyclotriphosphazene (HPCTP) together to EP to improve the fire resistance and smoke suppression. EP/6.3wt%HPCTP/2.7wt%GnPSn composite had the best flame retardancy with LOI value of 33.6%, UL-94 of V 0 grade, peak heat release rate and total heat release reduced by 44.80% and 23.93%, respectively. The results of thermogravimetry analysis, Raman spectroscopy and Fourier transform infrared spectroscopy showed that HPCTP and GnPSn can react to form Sn–O–P bonds to promote the compactness of the residual char in condensed phase, thereby preventing the combustion of EP matrix.