Anaerobics are similar to epoxies in terms of being highly crosslinked systems, but are very different from a chemical point of view. They are single-component adhesives based on multifunctional methacrylate monomers, and cure is initiated by small amounts of catalysts, which interact with metal surfaces. Commonly used as threadlockers for fasteners, full cure typically takes 24 hours. They can be formulated to give varying final bond strengths and heat resistance up to about 250°C. Similar to epoxies, there is some evidence that incomplete curing takes place at ambient temperatures. Anaerobics are normally used on metals and will stress crack some thermoplastics. Both epoxies and anaerobics are characterized by forming somewhat brittle bonds with very high strength and excellent fluid and heat resistance.

Reactive acrylics are two-component adhesives originally formulated to address some of the weaknesses of epoxies. They cure very quickly, bond a wide range of substrates (including plastics) and are toughened with dissolved rubbers. However, particular monomers are chosen to give less crosslinking than in anaerobics, and this allows the formulation of tough, somewhat flexible adhesive bonds. There is, however, a trade-off in heat resistance, which is limited to around 120°C. Reactive acrylics are widely used for bonding unprepared metals, plastics and composites. ASI

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