The authors describe a synthesis method for a series of pulverized expandable graphite (pEG)/melamine-formaldehyde (MF) resin core-shell structure particles. The particles are also added into rigid polyurethane foams (RPUF) to characterize the flame-retardant, mechanical, and thermal insulation properties of the RPUF/pEG-MF composites. It was found that the pEG/MF particles showed good flame-retardant performance in the composites by providing a physical barrier effect....