ADHESIVES, GLUES AND SEALANTS
What is the ageing of adhesives?
The ageing of an adhesive or an adhesive bonding is defined as the change in the quality of adhesive bonding as a function of time and external effects that provoke the change.
There are 3 groups of external factors that cause ageing phenomenon both within the adhesive itself (cohesion) and the junction of the adhesive and the substrate (adhesion).
Effect of humidity and water condensation
Effect of atmospheric oxygen
Concentrations of gases, solvents, salts .... in the environment.
Each of these effects directly affect to the adhesive joint, both in the adhesion and cohesion area, the result of the action of these factors on the adhesive joint depends on the type of substrate used and on the adhesive system (surface preparation of the substrate, activator, primer, adhesive ...)
For example, the presence of water on an adhesive joint can affect irreversible when using cyanoacrylate adhesives, this is produced because there is a hydrolytic cleavage of covalent bonds (hydrolysis) due to water penetration through the phenomenon of diffusion, reducing the mechanical properties of the adhesive. However this effect does not occur in adhesive joints using silicone adhesive or epoxy adhesives.
In order to prevent these effects, it is necessary to perform a series of accelerated ageing tests taking into account all factors that can act on the joint for life, in order to predict the behavior of the adhesive joint and select the appropriate adhesive system.
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