Surface energy and labels | Everything you need to know about adhering labels on the surfaces

Manufacturers provide various types of labeling solutions to their customers based on their applications and requirements. As you have read before, choosing an adhesive is yet important consideration for your labeling project, and surface energy is one of the most critical factors. 

Discover everything you need to know about surface energy and labels in this article.

The higher the surface energy, the easier it is for the label to adhere, and vice versa.

Surface energy is a key factor determining label adhesion. Manufacturers choose labels based on their ability to stick to the required surface.

Surface energy for the labeling industry defines the degree to which the label adhesive sticks or repels from the bond surface. 

When a material has high surface energy, the molecules on the surface are more attracted to each other, leading to better wetting and adhesion. In contrast, low surface energy indicates weaker intermolecular forces at the surface, making it more challenging for adhesives to spread and adhere effectively.

In short:

• High surface energy: More attractive forces at the surface, better wetting, and potentially better adhesion.
• Low surface energy: Weaker attractive forces at the surface, less wetting, and potentially more challenging adhesion.

Let’s take an example to understand this phenomenon, using the water drop test.

Place a water droplet on the surface. Observe the droplet behavior. If it spreads out and is quickly absorbed then the material has high surface energy. The surface energy is low if the droplet forms a tight bead and resists flowing outward.

How do you choose a label based on the surface energy?

High surface energy applications typically require only general-purpose adhesives. For low surface energy applications, a specialized acrylic or rubber-based adhesive may be required.

In the case of the above test, a general-purpose adhesive is suitable for the surface where water droplets spread. For the surfaces where the water droplet beads up, a specialized label adhesive is required.

When labeling metal, glass, or high-density plastics, manufacturers lean towards labels with general-purpose acrylic adhesives. For low surface-energy plastics, manufacturers choose labels with specialized adhesives engineered for challenging bond surfaces.

Alternate method for choosing labels

Another method for testing surface energy is the Dyne Test. Let’s see how manufacturers perform the test:

• Use a dyne pen with a known surface tension value (expressed in dynes).
• Apply the dyne solution on the material’s surface using the pen.
• Observe if the liquid wets the surface uniformly. If it does, the material’s surface energy is likely close to or greater than the dyne pen’s value.

Now, the labeling solution is made based on the test results:

• Choose labels with adhesives designed for surfaces with a similar or slightly lower surface energy than the determined dyne value.
• Adhesives with formulations matching the surface energy ensure optimal adhesion.

For example, if the dyne test indicates a surface energy of 38 dynes, manufacturers choose labels with adhesives designed for surfaces with a similar or slightly lower dyne value.

It’s all about project and manufacturing experience.

Experience with diverse, custom-solution manufacturing projects offers a valuable foundation for informed decision-making when choosing labels based on surface energy. It involves practical knowledge, past project experience, and leveraging subject matter experts to ensure a reliable result.