Mechanisms of antioxidant action: Stabilisation of nitrile rubber by interpenetrating networks based on thiol adducts

Nitrile rubbers containing three thiol antioxidants ((I) to (III)) in bound form have been evaluated as masterbatch concentrates by dilution in unstabilised nitrile rubber both at the latex stage and in the polymer melt. Both procedures give effective substantive systems in the case of the hindered phenol (I) and the aromatic thiol amide (II). Both show a high level of antioxidant retention under very severe technological conditions (oil/air oven cyclical test at 150°C). Antioxidant (III), which has only a minor structural difference from (II), is very much less effective as a substantive antioxidant.