In this study, the effect of processing cycles and two pollutants (engine oil (HM) and ethylene glycol (EG)) on the thermal and rheological properties of polypropylene-based materials (108MF97 and 7510) has been studied. It was investigated if polymers coming from bumper face bar could keep their properties and can be reused after recycling. The different results demonstrate that the two polymers that were polluted and recycled do not show any decrease of their intrinsic properties. Moreover, for one of the two polymers (108MF97), the presence of engine oil enables to increase the thermal stability and reaction to fire. Finally, it appears that the reuse of such polymers is possible.

The fire‐retardant properties of a recycled poly(propylene)‐based material were investigated and compared to the non‐recycled formulation. An intrinsic intumescent system and zinc borate were used to flame‐retard these polymers. By mass loss calorimetry, the best results were obtained with 20 wt.‐% of additives. Synergisms between AP765 and ZB were observed in the non‐recycled blends but not in the recycled ones. Solid‐state NMR showed that chemical reactions during the decomposition process were leading to the formation of borophosphates, reinforcing the efficiency of the intumescent char. From a ‘physical’ point of view, it was shown that the fire retardant properties of the materials are related to the formation speed of the intumescent structure and not on the char thickness. magnified image

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.