Decomposition of peroxides by transition metal ions in anaerobic adhesive cure chemistry

Abstract

Anaerobic adhesives are single component acrylic adhesives which remain stable for long periods of time but polymerize rapidly when confined between two closely fitting metallic surfaces. Transition metal ions on the substrate surface play a key role in catalysing the decomposition of cure initiators to generate free radicals. Readily reducible organic peroxides, e.g. hydroperoxides and perbenzoates, are the most commonly applied initiators which are used in combination with an organic acid and a tertiary amine as accelerators. Anaerobic adhesives are sensitive to the nature of the substrate, for example they cure rapidly on iron and copper rich surfaces but slowly or not at all on cobalt or zinc plated metals. This study investigates the ability of transition metal ions to decompose t-butyl perbenzoate, t-butyl hydroperoxide and benzoyl peroxide and also investigates the influence of saccharin, maleic acid and adhesive accelerators on this process.