Reprocessed High Impact Polypropylene Containing Oil Pollutant Exhibiting Flame Retardant Properties

Summary:In this work, the reaction to fire of reprocessed polypropylene (PP)/Ethylene Propylene Rubber (EPR) materials containing engine oil as pollutant was investigated by mass loss calorimetry. It was compared to the behaviour of the corresponding original high impact PP material. In order to flame retard the polymers, an intumescent system was studied in combination with zinc borate (ZB) as potential synergistic agent. It is shown that 20% of additives are necessary to obtain good FR properties. The use of ZB greatly improves the reaction to fire of original PP/EPR materials due to the formation of borophosphates during the degradation process that permit to reinforce the char structure. In the case of the polluted and reprocessed formulations, ZB has no influence on the fire performance because the minerals included in the engine oil act also as a flame retardant. For the two types of materials, it is demonstrated that the expansion rate at the beginning of the intumescent process plays a crucial role in the formation of an efficient insulating layer at the surface of the substrate. On the contrary, the fire performance is not related to the thickness of the carbonaceous shield.