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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 31P 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.

This work deals with the effect of recycling on halogen-free flame retarded polypropylene blends. The intumescent ammonium polyphosphate/polyamide-6/polypropylene blend is considered. The study of the fire properties using cone calorimeter shows a decrease in the fire performance. Recycling the blends induces chemical modifications of polymer and additives. The chemical modifications due to the recycling are investigated by solid state31P NMR. It is shown that APP is degraded. These modifications induce a loss of the ammonium contents, which could explain the decrease in the fire performance.

Multilayer systems consisting of flame retarded and reinforced layers of recycled polymer were formed. The structure and the thickness of the interfacial layer between the phases were analysed by Differential Scanning Calorimetry and Raman microscopy. The sequence order of the layers was varied for achieving improvement in both the flame retardancy and mechanical performance of recycled polymers and for obtaining upcycled product this way. Investigation of injection moulded and compression moulded products demonstrated the advantage of reinforced core and flame retarded shell over the opposite structure. The multilayered structure was found an economic way for producing recycled polymer materials of improved fire resistance, flexural strength and modulus.