Calorimetric investigation of autoacceleration in the metal-catalysed cureof anaerobic adhesives

The polymerization of anaerobic adhesives is a complex reaction which is in fluenced by many parameters such as the atmosphere, the temperature, and th e nature of the substrates to be bonded. The aim of this work was to explor e a simple and reliable analytical method using differential scanning calor imetry (DSC) to investigate the parameters which affect the polymerization of three commercial adhesive products. The kinetics of the reaction is dedu ced from values of the activation energies E-a, and the influence of the po lymerization conditions on the autoacceleration of the systems is shown, i. e. the time at which an increase of reaction speed occurs. The reactivity o f the anaerobic adhesives is largely favoured by the use of copper metal ra ther than iron or aluminium as previously assumed and by the absence of oxy gen in the ambient. However, in this last case surprisingly the autoacceler ation proceeded more slowly than for experiments conducted in the presence of air. This trend was observed irrespective of the substrate under investi gation.