The combination of expandable graphite, organic montmorillonite, and magnesium hydrate as fire-retardant additives for ethylene-propylene-diene monomer/chloroprene rubber foams

The fire retardancy and flame-retardant mechanism of expandable graphite (EG), organic montmorillonite (OMMT), and magnesium hydrate (MH) in ethylene-propylene-diene monomer/chloroprene rubber (EPDM/CR) foams were investigated. The results indicated that the combination of EG and OMMT remarkably improved the fire-retardant property compared to the control samples, and better fireproof performance was achieved when MH was used as the third coretardant unit. The structure of the obtained EPDM/CR/OMMT composites was characterized by X-ray diffraction, and the results showed that the composites had an intercalated nanostructure. The limiting oxygen index, vertical burning test, and cone calorimeter test results showed that the LOI values and UL-94 rating increased while the second peak of the heat release rates (HRR) decreased within the EG/OMMT system. In particular, the second pHRR disappeared when the EG/OMMT/MH system was used as a flame retardant. Moreover, the results of thermogravimetric analysis showed that the combination of EG and OMMT reduced the thermal-degradation rates and mass-loss percentages. Furthermore, observation by scanning electron microscopy revealed that EG and OMMT left over after combustion formed a complete, compact, and rigid charred layer with a mosaic structure of expanded graphite embedded in cortical-honeycomb layers of OMMT. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44929.