ADHESIVES, GLUES AND SEALANTS
What is surface preparation?
We define the surface preparation as the set of previous operations that are performed on the substrates, in order to improve wetting and adhesion properties of adhesive materials on substrates to be bonded.
The preparation of surfaces or surface preparation is one of the most important steps or processes when performing an adhesive bonding. It will not help the efforts invested during the design, selection and validation of the adhesive, if we do not make a good surface preparation on the surface that we will put the adhesive.
There are different methods, processes or techniques on surface preparation, the choice of either technique depends on:
The type of material of the substrate (metal, ceramic, glass or plastic)
The type of adhesive used to bond the substrates.
The surface conditions of the substrates (surfaces with oils, rusted surfaces, surfaces with dust ...)
The surface preparation process is divided into 3 distinct successive stages together:
Surface Post -treatment
The surface cleaning is used to eliminate all types of contaminants found on the surface of the substrates.
The contaminants are foreign agents that are weakly bonded to the substrate, the presence of these contaminants adversely affects the adhesion and wetting of the adhesive, if the adhesion occurs the connection system fails, due to the weak adhesion and cohesion of the contaminant to the substrate.
For surface cleaning we can use organic solvents or aqueous cleaners, the choice will depend on the type of material to be cleaned and the conditions in which the surface is clean.
Pre-treatment of surfaces is designed to remove the layer that is firmly attached to the material base, and activate the surface to improve the wetting and adhesion of the adhesive.
Depending on the type of material, we used one kind or another surface pretreatment technique, for example for metal is common to use blasting techniques, this technique is not suitable for pretreatment of plastics.
The post-treatment of surfaces is set of chemicals materials (activators and primers) used in conjunction with the adhesive during the application phase and are intended to:
Create active surface on the substrate.
Generate compatible surfaces with the adhesive resin
Reduce surface roughness
Each of the points mentioned above increases the wetting properties and adhesion between the substrate and the adhesive.
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