Anaerobic and Acrylic Adhesives

Acrylics, unsaturated polyesters and other monomer-based adhesives containing ethy-lenic unsaturation, cure by formation of free peroxide radicals formed with transition metal ion donators such as cobalt, iron, copper and nickel. In engineering applications the presence of transition metals on surfaces sees them act as initiators by forming the free peroxide radicals from the added peroxide compound(s). The base monomers usually contain inhibitors such as phenols or other materials classed as peroxide stabilisers to 

Anaerobic adhesives contain reactive monomer(s), accelerators, stabilisers or inhibitors, fillers, colorants, modifiers, tougheners (rubbers, butadiene graft, etc.). The chemistry of anaerobic adhesive is complex but the schematic brief of the reaction may be shown as follows  

Anaerobic adhesives require confinement on an active metal surface. Substrates such as plastic, cadmium and zinc are slow but can be improved with the use of accelerators or primers. 

Acrylic adhesives (or structural adhesives) are essentially a two-part product radical polymerisation is initiated by use of a second component which is supplied as a primer. The curative of these products is divided between the two parts with one half containing 

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