Jean-Luc Gardette, Clermont-Auvergne University, France, discussed the challenges of ensuring that weathering, and in particular ultraviolet radiation (UV), does not deteriorate the properties of flame-retarded polymers. Deterioration is generally related to the polymer itself rather than to additives. Interactions with UV absorbers, anti-oxidants and catalyst-deactivation also need to be verified. PIN effervescent FRs have been shown not to deteriorate polypropylene (PP), nor to interfere with HALS (UV stabilisers). On the other hand, certain nanoclays showed to accelerate PP deterioration, probably because of metal impurities present in the grades tested.
Rémy Mangin, Lorraine University, France, demonstrated the difficulties of developing reliable formulations with PLA (poly lactic acid). Testing included combinations with PMMA polymer (poly methyl methylacrylate = Plexiglass) and PIN FRs (ammonium polyphosphate and sepiolite nanoclays). Flame-retarded PLA shows deteriorated physical and fire properties after a few weeks of humidity ageing. This is significantly mitigated in a 50%/50% PLA/PMMA blend, showing a positive effect of incorporation of PMMA in PLA.