Highly filled adhesives feature good dispensing properties

Fillers in adhesives, potting compounds and encapsulants can lead to mechanical abrasion in dispensing systems. Notwithstanding such potentially abrasive behaviour, the adhesives can be dispensed assuredly and precisely over the long term. This is the outcome of experimental tests conducted by ViscoTec and DELO Industrial Adhesives, covering more than six million dispensing cycles.

The eco-PEN and RD dispensing units from ViscoTec with two elastomer stators each were examined in this test series. Six epoxy resins from DELO with different fillers were used. The filler content in all cases was between 25% and 50%, typical for adhesives.

Firstly, the stators were placed in adhesive for 168 hours to examine their general chemical suitability for long-term contact. After, the change in mass, the dimensional accuracy as well as the hardness and elasticity of the elastomers were examined. This exhibited no abnormalities or deviations from the tight production tolerances. Chemical interactions between the two components, which would influence subsequent results, could thus be excluded.

“The tests show that even hard fillers in combination with high filler contents do not impede permanently reliable and reproducible dispensing of our high-performance adhesives”, says Karl Bitzer, head of product management at DELO.

“Permanently reproducible and accurate dispensing was possible for all dispensers and stators. This is made clear by the fact that, despite the abrasive test media and the large number of dispensing cycles, our dispensing units did not reach the end of their lifetimes within the test period”, added Manuel Paintmayer, relationship management material manufacturing at ViscoTec. “That is a really great result.”