Evidence of surface accumulation of fillers during the photo-oxidation of flame retardant ATH filled EVA used for cable applications

This paper is devoted to the photo-oxidation of a fire retardant polymer used for cable jacketing and an emphasis was put on understanding how highly filled composites (Ethylene-Vinyl Acetate filled with Aluminium Tri-Hydroxide) behave under UV irradiation. Samples have been irradiated during several thousand hours and the degradation has been studied at the surface but also within the polymer bulk. The degradation of the polymer part, because of a massive chain scissions process, leads to a progressive enrichment of the inorganic part at the surface which then acts as a screen for the bulk. Thus, the degradation is very heterogeneous along the polymer thickness and the degradation profiles well correlate with the evolutions of the mechanical properties (i.e. mechanical properties are not influenced if the degradation profile remains small compared with the total sample thickness).