26 August 2024

Adhesion problems? Get the right pre-treatment!

“Why isn’t my adhesive sticking? Why doesn’t it stick anymore? I swear I haven’t changed anything!” Customers often find themselves in these types of nagging predicaments when manufacturing rubber adhesive compounds.

At Nordmann, and through our new partnership with H.B. Fuller, we’re able to support customers by drawing on years of experience in processing rubber compounds. We’ve found that around 90% of the adhesion problems that customers experience come down to inadequate pre-treatment, which is why we’d like to highlight seven important steps that you can take to make sure you get it right every time:

1. Prepare the adhesive

Stir the adhesive until you have a homogeneous liquid. Keep foam levels down (stir under a mirror).
Adjust the adhesive as appropriate for the desired application method.
Inspect the adhesive for quality (e.g. by measuring flow time).

2. Prepare the substrate

Use a suitable detergent to clean the substrate until it is free of oil, grease and/or dust.
Pre-treat the surface to increase its surface/contact area for the adhesive, e.g. by blasting/grinding.
Thoroughly clean the substrate again using an appropriate cleansing agent and ensure the surface is free of sanding/blasting dust.
Quality-check the substrate, e.g. through visual inspection and measuring its roughness

3. Apply the adhesive

Check application equipment and surroundings for possible contamination.
Apply a test layer of the adhesive and measure the its dry film thickness. Make any necessary adjustments.
Measure air temperature and humidity.
When using a water-based adhesive, ensure substrates are heated to 50-60 °C in order to achieve optimum film formation.

4. Dry as recommended by the technical data sheet

Dry the adhesive.
Allow for additional drying when applying primer and cover.

5. Store parts coated with adhesives properly

Protect parts coated with adhesive from contamination, e.g. dust, oil and mechanical stress.
Store parts coated with adhesive at room temperature and the appropriate level of humidity.
Be aware of the adhesive’s specific open time.

6. Vulcanize rubber components

Proceed according to the compound manufacturer’s recommendations.
Allow for an aging time of at least 48 hours before testing.

7. Cleanliness

Areas in which adhesives and substrates are prepared, applied and dried must be treated as cleanrooms in order to avoid soiling/contamination by dust, oil, etc.