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Surface preparation for adhesive bonding

Dr. Dmitri Kopeliovich

Preparation of the substrate surfaces prior to adhesive bonding is mandatory stage of the bonding process.

The stages of surface preparation performed prior to adhesive bonding:

Degrease

Proper degrease provides good wetting of the substrate with the adhesive material. Clean substrate surfaces enhance formation of intermolecular and chemical bonding between the substrate and adhesive molecules.

At this stage the following contaminants are removed from the substrate surface: mineral oils (Rust protection oils, Cutting fluids (coolants), greases, etc.), miscellaneous organic soils (paints, animal lubricants and vegetable lubricants, fingerprints).

The most popular degrease technologies are:

  • Solvent cleaning - removal of organic soils (mineral oils, fingerprints etc.) by dissolving them in a solvent.
  • Alkaline cleaning – removal of organic soils (mineral oils,fingerprints, wax etc.) and some solid particles by hot alkaline solutions.
  • Spray cleaning – cleaning by aqueous solutions (alkaline or mild acids) delivered to the part surface through spray nozzles at high pressure.

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Abrading

Roughened (abraded) substrate surfaces provide better bonding strength due to interlocking the adhesive material in the surface micro-voids.
Abrading also removes oxides, scale, smut, rust, paints and other solid contaminants from the surface.
Abrading techniques:

  • Wire brushing;
  • Sanding by glass paper (80-150 grade for steels, 300-600 grade for non-ferrous alloys).

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Chemical pretreatment

Etching by acids (acid activation) and priming are used for additional cleaning, activation and chemical modification of substrate surfaces.

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Physical pretreatment

The substrate surface may be modified and activated by physical methods:

  • Plasma treatment;
  • Corona discharge;
  • Flame treatment.

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surface_preparation_for_adhesive_bonding.txt · Last modified: 2023/12/13 by dmitri_kopeliovich
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