Alt-text: Water droplets on a surface illustrating surface energy and wetting behavior
Surface energy plays a critical role in manufacturing processes that involve bonding, coating, printing, or sealing. It affects how well adhesives, inks, paints, or coatings stick to a material. Low surface energy makes it harder for coatings, adhesives, or inks to stick properly, leading to weak bonds and poor product quality.
In industries like electronics, automotive, packaging, and medical devices, managing surface energy is essential for product performance and process efficiency.
This article explains what surface energy is, why high surface energy matters, how it’s measured, and how plasma surface treatment can improve it in industrial applications.
What Is Surface Energy?
Surface energy refers to the force at the surface of a material that affects how well other materials stick to it. It’s the reason why some surfaces bond easily, while others resist adhesives, inks, or coatings.
Materials with high surface energy, such as metals or glass, let liquids spread out smoothly across the surface. Low surface energy materials, like plastics (PP, PE, PTFE), repel liquids, making bonding difficult.
Why High Surface Energy Matters
In manufacturing, high surface energy means better bonding, stronger adhesion, and fewer product failures.
When a surface has high energy:
- Adhesives stick better
- Coatings spread evenly
- Printing quality improves
- Bonded parts last longer
Industries that depend on high surface energy include:
- Automotive (interior and exterior bonding)
- Electronics (wire bonding, PCB coating)
- Medical devices (sterile packaging sealing)
- Packaging (label adhesion, print quality)
Surface energy is the work needed to create a new surface. The basic formula is:
Surface Energy (γ) = Energy ÷ Surface Area
Units of measurement are usually:
- mN/m (millinewtons per meter)
- dynes/cm (older unit, same value as mN/m)
Most manufacturers don’t calculate surface energy — they measure it using practical tools.
Surface Energy Measurement in Manufacturing
In manufacturing, testing surface energy is a routine step before bonding, coating, or printing. It’s a quick way to confirm whether a surface is ready to form a strong bond — especially when working with materials like plastics that naturally resist adhesion.
There are two common methods manufacturers use to measure surface energy:
Contact Angle Measurement
This method uses a small drop of liquid placed on the material’s surface. The shape of the droplet indicates how well the surface can be bonded.
- A smaller contact angle means the liquid spreads out easily — a sign of high surface energy and good wettability.
- A large contact angle means poor wetting and low surface energy, which could lead to bonding issues.
Dyne Pen Testing
Dyne pens contain liquids with a specific surface tension measured in mN/m. The liquid is applied to the surface in a line or stroke.
- If the liquid stays spread out, the surface has at least that level of energy.
- If the liquid beads up or breaks apart, the surface energy is lower than that dyne level.
In most industrial applications, a surface energy reading of at least 38 mN/m is the minimum target for reliable adhesion. Higher readings are even better for critical bonding or coating processes.
How Plasma Surface Treatment Increases Surface Energy
Plasma surface treatment is a clean and efficient method manufacturers use to increase the surface energy of materials, especially those that are difficult to bond like plastics or composites.
The process works by exposing the surface to ionized gas (plasma), which cleans and modifies the material at a microscopic level.
Here’s what happens during plasma treatment:
- It removes microscopic contaminants such as dust, oils, and organic residues that interfere with bonding.
- It alters the surface chemistry, making it more reactive and improving its ability to bond with adhesives, coatings, or inks.
- It increases surface energy without leaving any chemical residues behind.
Because of these benefits, plasma treatment is widely used in manufacturing right before processes like:
- Bonding
- Coating
- Printing
- Sealing
Another advantage of plasma surface treatment is that it’s environmentally friendly. Unlike traditional chemical primers or wet cleaning methods, plasma uses no solvents, produces no hazardous waste, and integrates easily with automated production lines — making it a practical solution for high-volume, modern manufacturing.
Surface Energy Units Explained
In manufacturing, surface energy is always measured using standard units that help evaluate how well a material will bond with adhesives, coatings, or inks.
The most common unit you’ll see is mN/m (millinewtons per meter), which is the industry standard today. This measures the force per unit length needed to create new surface area — in other words, it tells you how “bondable” a surface is.
Another unit still used in some industries is dynes/cm (dynes per centimeter). It’s an older measurement, but it means the same thing. In fact, the conversion is simple:
- 1 mN/m = 1 dyn/cm
Most manufacturers use these values during surface energy measurement to determine if a material is ready for bonding or coating. The higher the number, the better the surface will hold adhesives, paints, or labels.
For reference, many production environments aim for surface energy levels above 38 mN/m to ensure good adhesion.
Surface Energy: Final Thoughts
Surface energy is a key factor in manufacturing processes that involve bonding, coating, printing, or sealing. A high surface energy surface leads to better adhesion, fewer defects, and higher product reliability.
Plasma surface treatment is one of the most effective ways to increase surface energy safely and cleanly — without chemicals or solvents.
Looking to improve bonding or coating results? Talk to our team or explore our plasma surface treatment solutions catalog for equipment designed for manufacturing needs.
