Adhesion Testing

Failing Paint
Adhesives must adhere to be effective, right?

But not all paints and glues and other adhesives stick to all substrates in the same way. Chemical interactions sometimes impair effective bonding between the two materials. Since there is no immediate visual cue when that happens, the bond’s adhesion must be tested to ensure that it performs to satisfactory standards when functioning live.

Adhesion, the measure of how well the fixative has bonded to its substrate, is calculated through adhesion testing. This information can be used to determine the failure point of the adhesive — the least amount of duress which will cause the product to fail — for quality control and safety purposes.

Test Methods Include:
  • Cross-Cut Test: accomplished by cutting into the adhesive (all the way down to the substrate) in one of two patterns with a utility knife, applying pressure-sensitive tape over the area, and quickly pulling it off
    • Quick
    • Qualitative
    • Results are either pass/fail or judged on a 0-5 scale
    • Can be performed with a knife instead of tape
    • Used specifically for paints and coatings
    • ASTM D3359 standard testing method (A2LA Accredited)
Methods (continued)
  • Scrape Test: accomplished by using balance-beam scrape-adhesion tester to scrape adhesive off the substrate by way of a rounded stylus applied with increasing amounts of pressure
    • Cannot be performed on-premises
      • Laboratory setting
    • Quantitative
    • Can only be performed on flat material
    • Used for paints, coatings, varnishes, and lacquers
    • ASTM D2197 standard testing method
  • Pull-Off Test: achieved by sticking a dolly to the test material and pulling it off with a machine
    • Measures the amount of pressure it took to remove the dolly (adhesive layers and all)
      • Can instead stop at a predetermined value
    • Applies tensile stress instead of shear stress
      • Meaning these results are a measure of a different value than the previous two tests
    • Could be performed on-site
    • Quantitative
    • More variables apply than with other tests
    • Used for any coating on a flat surface
    • ASTM D4541 and ISO 4624 standard testing methods

Each of these tests may be performed at multiple temperatures to account for the materials expanding or contracting due to heat. These factors can also play a role in the test materials’ adhesion to its substrate. Although other standards can be used to perform adhesion testing, the methods listed above are the most commonly used.

Applied Technical Services does all of this and more

For 50 years, we have been providing materials testing, equipment inspections, and structural analysis services to our satisfied clients. We at ATS have a collection of certifications and accreditations that qualify us to take care of a plethora of client needs, including any adhesion testing they may need performed.

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