Bonding Failures – Chapter 3: Primer for Adhesive Tapes
In the past few weeks, we’ve learned how to identify substrates and clean them. In many cases, this is enough to ensure effective bonding—just think of metals or high surface energy materials (see the table in Chapter 1 of “Bonding Failures”).
However, when dealing with a medium or low energy substrate, we need to go one step further: applying a primer for adhesive tapes.
What is a primer for adhesive tapes?
A primer, or adhesion promoter, is a liquid, transparent, volatile substance… with a very distinctive smell. It serves to chemically modify the surface of the substrate, making it compatible with the adhesive tape.
There are many different types. For this reason, you should never improvise: using the wrong primer can compromise bonding—or even damage the part.
What does a primer contain?
Generally, it consists of:
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Solvents (Isopropanol, Toluene, Cyclohexane…),
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Resins or cellulose in varying percentages.
The higher the solvent content, the more fluid and volatile the primer will be, working similarly to a cleaner.
In contrast, the more resin it contains, the more viscous and glue-like it becomes.
The most common mistakes when using primer
1. “This stuff stinks!”
Comments like “it smells like paint/gasoline/nail polish!” indicate inexperience.
Since primer is toxic and potentially carcinogenic, it must be used:
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In well-ventilated environments,
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With appropriate gloves and masks,
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Preferably under fume hoods, in industrial settings.
2. “It dried out—you sold me an expired one!”
Primer dries if not sealed properly.
Once opened, it should be used up. That’s why there are:
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Industrial formats (cans),
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Small formats (bottles with just a few ml),
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Single-use (wipes or impregnated swabs).
3. “I used a lot and it won’t stick!”
This is a classic mistake: too much primer creates a film that peels off.
Therefore, it must be applied in minimal, even amounts.
4. “I don’t remember if I used the primer”
Some primers include UV tracers. However, not all of them do! If yours doesn’t, a UV lamp won’t help.
5. “I used primer and it didn’t work”
When exactly?
“Six months ago.”
Primer is temporary. Its effect fades over time, especially on difficult surfaces. Applying it too early can make it useless.
6. “The primer damaged the part!”
Using the wrong primer on certain materials can cause damage. For example:
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Glass → needs silane-based primers.
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Transparent plastics → require gentle primers.
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Polyolefins → need aggressive primers.
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Concrete → dedicated primers only.
To avoid issues, always consult your technician.
7. “No need to clean—I’ll just use primer”
This is a serious mistake.
Primer does not replace cleaning. In fact, combining it with residual contaminants can trigger unpredictable reactions.
When the surface can’t be primed
Some substrates do not accept primer, such as:
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Fabrics, foams or absorbent surfaces,
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Materials treated with release agents,
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Surfaces where primer use is restricted for environmental or health reasons.
It’s important to remember that primer has several downsides:
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Toxic and carcinogenic,
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Strong smell,
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Requires protective equipment,
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Difficult to dispose of,
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Flammable.
Alternatives to primer: primerless adhesive tapes
In recent years, so-called “primerless adhesive tapes” have emerged—tapes designed to stick to challenging surfaces without any primer.
To reduce (or eliminate) the need for primer, large-scale manufacturers are investing in:
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Flame, plasma or corona treatments,
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High-performance adhesives.
Can we always do without primer?
Not yet, unfortunately.
Although primerless tapes are evolving, not all of them are compatible with all tricky substrates.
Nevertheless, the future is heading in that direction.
Until then, remember:
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Clean first,
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Use the right primer,
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Apply it properly,
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And avoid DIY approaches.
In the next chapter: Learn how to apply adhesive tape correctly to avoid new… bonding failures!
If you don’t know which primer to choose go to our website.
BMP staff