Artificial weathering and recycling effect on intumescent polypropylene-based blends

The first part of this work deals with the effect of ageing (artificial weathering) on an intumescent flame-retarded ammonium polyphosphate (APP)/polyamide-6 (PA-6)/polypropylene (PP) blend. The study of the fire properties using the cone calorimeter shows a decrease in the performance caused by the artificial weathering. The chemical modifications of the blends after ageing are investigated by solid state P-31 NMR and SEM. It is shown that APP is degraded into ortho-, pyrophosphate and short chain polyphosphates. These modifications lead to the loss of the ammonium contents which could explain the decrease of fire performance. Moreover, some morphological changes appear which may lead to the change of fire and mechanical properties. A classical solution for re-using the material is the recycling. In the second part of this study, we examine the effect of recycling simulated by a multi-extrusion process. This treatment induces modifications which are different from those resulting from the effect of ageing. So, morphological and chemical changes induced by recycling are compared to the effects of ageing. It is shown that after recycling APP is also degraded in the same way as after ageing. In addition to the degradation of APP, a decrease in phosphorous concentration is observed which is attributed to the migration of phosphate species.