Preparation, Characterization and Flame Retardancy of Expandable Graphite Modified by Ferric Hydroxide. Part I - Preparation and Characterization

A type of expendable graphite (EGFe) modified by ferric hydroxide was stepwise prepared through chemical oxidation and hydrolysis precipitation reaction. Its dilatability, crystal structure, main functional groups were all characterized. The synthesizing method of the EGFe with excellent flame retardancy for linear low density polyethylene (LLDPE) was optimized through L9(34) orthogonal experiment. Especially, the mass ratio of FeCl3 to normal expandable graphite (EG) prepared in advance with chemical oxidation method was 0.1:1, dosage of NH3·H2O with a wt% of 25% was controlled as 0.4 mL, the reaction lasted 2.5 h at room temperature, and the final drying temperature was 100°C. Characterizing results testified the EGFe kept a layer structure just like natural graphite, and the hydrolysis product of FeCl3 was Fe(OH)3, and it mainly covered on the outside surface of the EG. EGFe possessed a better dilatability and flame retardancy for LLDPE than the EG.