Characterization of organosilicon films synthesized by N2-PACVD. Application to fire retardant properties of coated polymers

Organosilicon thin films, obtained from the polymerization of 1,1,3,3-tetramethyldisiloxane monomer pre-mixed with oxygen using a cold remote nitrogen plasma process, are used to improve flame retardant properties of polyamide-6 (PA-6) and polyamide-6 clay nanocomposite (PA-6 nano) substrates. A comparison between virgin PA-6 and coated PA-6 nano shows that the clay addition combined with the coating leads to an efficient fire retardant effect. The limiting oxygen index increases by 130% while, at the same time, the rate of heat release and the total heat evolved decrease by 41% and 33%, respectively. The nanocomposite structure leads to the formation of a silicon and carbonaceous protective layer during the combustion. This layer acts as a barrier limiting heat and mass transfers between the polymer and the flame, and this effect is reinforced by the coating.