Mechanisms of antioxidant action: Nitrosamines as heat and light stabilisers for polypropylene

N-Nitrosamines are shown to be very effective melt stabilisers for polypropylene and one of these, derived from the hindered amine light stabiliser, Tinuvin 770, is almost twice as effective as the latter. The mechanism is believed to involve the formation of two kinds of nitroxyl radical, the first derived from the amine and the second formed by the reaction of nitric oxide with alkyl, and possibly alkoxyl, radicals. Nitrosamines which do not dissociate to NO are neither melt stabilisers nor uv stabilisers.