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

Abstract

Abstraet-The polymerization of anaerobic adhesives is a complex reaction which is influenced by many parameters such as the atmosphere, the temperature, and the nature of the substrates to be bonded. The aim of this work was to explore a simple and reliable analytical method using differential scanning calorimetry (DSC) to investigate the parameters which affect the polymerization of three commercial adhesive products. The kinetics of the reaction is deduced from values of the activation energies E_a, and the influence of the polymerization conditions on the autoacceleration of the systems is shown, i.e. the time at which an increase of reaction speed occurs. The reactivity of the anaerobic adhesives is largely favoured by the use of copper metal rather than iron or aluminium as previously assumed and by the absence of oxygen in the ambient. However, in this last case surprisingly the autoacceleration proceeded more slowly than for experiments conducted in the presence of air. This trend was observed irrespective of the substrate under investigation.

Keywords:

• Anaerobic adhesives
• differential scanning calorimetry
• autoacceleration
• gel effect
• activation energies