Synergistic effect of expanded graphite, diammonium phosphate and Cloisite 15A on flame retardant properties of EVA and EVA/wax phase-change blends

The influence of the introduction of expanded graphite (EG), as well as combinations of EG with Cloisite 15A clay and diammonium phosphate (DAP), into EVA and an EVA/wax blend on the thermal stability and flammability of the polymer and blend was investigated. In the presence of EG + Cloisite 15A, the material formed a dense and stable char layer (carbonized ceramic) which significantly improved the flame resistance of the materials, while the presence of EG and EG + DAP much less uniform char layers were formed and the improvement in flame resistance was not so significant. X-ray diffractometry investigations showed intercalation of EVA into the organoclay, which became more effective in the presence of wax. It was, however, found that there was little separation of the EG platelets, although the presence of wax caused a decrease in the sizes of the EG agglomerates. The thermal stability of EVA and the EVA/wax blend improved in the presence of EG and its combination with Cloisite 15A and DAP.