What is Surface Tension, and How Does It Affect Folding Carton Converting?

In technical terms, surface tension is measured in units of dynes/centimeter or millinewtons per meter. In practical terms, dyne or surface tension measures how slick a surface is.

Lower surface tension means the surface is more slick, and adhesives cannot “wet out” as well, and it bead up on the substrate, which can lead to poor adhesive performance. Higher surface tension means an adhesive, or ink, can wet out properly, which is needed to form a strong bond.

A dyne of 38 is considered a minimum for substrates to be glueable with a water based adhesive, but 42+ is recommended.

For more on the specific challenges of bonding slick substrates like coated paperboard, see Avoiding the Insanity of Gluing Poly-Coated Substrates.

How Is Surface Tension Measured?

Dyne pens/solutions are an easy way to quickly check surface energy without expensive laboratory equipment.

Goniometers (also called an optical tensiometer) measure surface tension by analyzing the physical geometry or contact angle of a liquid droplet. Unlike the manual pass/fail method of a dyne pen, a goniometer provides precise, quantitative data through automated image analysis.

Conclusion

Understanding surface tension is crucial when converting a variety of materials. If you have issues bonding a substrate, make sure to check the dyne levels to ensure they can be bonded with a water based adhesive.

Capital Adhesives manufactures industry leading folding carton adhesives designed to run cleanly at high speeds, bond nearly any substrate, and minimize downtime. If you have a challenging substrate that your current adhesive cannot bond to, you can send it to our laboratory to test the dyne levels and provide a recommended adhesive that won’t fail.

Understanding Surface Tension

In the folding carton industry, the substrates are constantly changing. Paperboards, sizes, films, and coatings can vary significantly from job to job. Sometimes, a new job comes along that the glue struggles to bond. Often, this comes down to surface tension.