Engineers: When to Specify Non-Stick, Hydrophobic, High-Slip and/or High-Release Properties Related to Surface Energy
In the industry of advanced coatings and engineered surfaces, terms such as non-stick, hydrophobic, high-slip, and high-release are often used interchangeably. Although these properties can be related and can be formulated to be achieved in the same coating system, they describe different aspects of surface performance.
The common thread connecting these properties is surface energy, a fundamental material characteristic that governs how a surface interacts with liquids, solids, contaminants, adhesives, and even ice. Understanding these distinctions is critical when selecting a coating for a specific application.
What Is Surface Energy?
Surface energy can be thought of as a measure of a surface’s tendency to attract or repel other materials.
- High surface energy surfaces attract liquids and promote wetting, spreading, and adhesion.
- Low surface energy surfaces resist wetting and reduce adhesion, making them useful for release, repellency, and non-stick applications.
Clean glass and metals typically exhibit relatively high surface energy, while fluoropolymers such as PTFE and many silicone-based coatings exhibit very low surface energy.
As surface energy decreases, surfaces generally become more resistant to sticking, wetting, and contamination. However, different performance characteristics emerge depending on how the surface interacts with specific materials and conditions.
Categories of Surface Energy Performance
Surface properties generally fall into four broad categories:
1. Wetting Behavior
These properties describe how liquids interact with a surface/substrate material.
Hydrophobic
Hydrophobic surfaces repel water, causing droplets to bead rather than spread. Hydrophobicity is typically characterized by a water contact angle greater than 90 degrees.
Examples include:
- Waxed surfaces
- Polyethylene and polypropylene
- Fluoropolymer coatings
Superhydrophobic
Superhydrophobic surfaces take water repellency to the extreme, exhibiting contact angles greater than 150 degrees and very low roll-off angles.
Examples include:
- Lotus leaf-inspired coatings
- Self-cleaning architectural surfaces
- Advanced anti-fouling coatings
Hydrophilic
Hydrophilic surfaces attract water and promote spreading. These surfaces exhibit high surface energy properties that become desirable as it can improve coating adhesion or liquid coverage.
Examples include:
- Clean glass
- Metal oxides
- Plasma-treated polymers
Oleophobic
Oleophobic surfaces repel oils and other low-surface-tension liquids. Because oils wet surfaces more readily than water, oleophobicity requires even lower surface energy than hydrophobicity.
Examples include:
- Fingerprint-resistant smartphone screens
- Anti-smudge coatings
- Fluorinated surface treatments
Omniphobic
Omniphobic surfaces repel both water and oils, combining hydrophobic and oleophobic performance.
Examples include:
- Advanced self-cleaning surfaces
- Chemical-resistant protective coatings
2. Each of these can Impact Adhesion and Release Behavior
These properties describe how strongly materials bond to a surface and how easily they separate.
High-Release
High-release surfaces minimize adhesion and allow materials to separate easily after contact.
Examples include:
- Mold-release coatings
- Composite tooling surfaces
- Release liners for pressure-sensitive adhesives
Non-Stick
Non-stick is a broader term describing resistance to material buildup or adhesion. While often associated with low surface energy, it does not specify the exact mechanism responsible for the behavior.
Examples include:
- Cookware coatings
- Food processing equipment
- Anti-build-up industrial coatings
Iceophobic
Iceophobic surfaces reduce ice formation and/or the ability of the ice to adhere.
Unlike simple hydrophobicity, iceophobic performance often depends on a complementary combination of surface energy, elasticity, texture, and thermal behavior.
Examples include:
- Aircraft surfaces
- Wind turbine blades
- Utility infrastructure
Adhesion-Promoting Surfaces
At the opposite end of the spectrum are surfaces engineered to maximize bonding by increasing surface energy.
Examples include:
- Corona-treated films
- Plasma-treated plastics
- Primers and adhesion promoters
3. Friction and Slip Performance
These properties describe how easily materials move across a surface.
High-Slip
High-slip surfaces exhibit low friction, allowing materials to slide easily.
While high-slip coatings are often low in surface energy, friction and adhesion are not identical properties.
Examples include:
- Conveyor surfaces
- Low-friction liners
- Lubricious industrial coatings
4. Surface Protection and Fouling Resistance
These properties focus on preventing contamination, staining, or material accumulation.
Anti-Fouling
Designed to resist contamination, biological growth, or deposit formation.
Examples include:
- Marine coatings
- Medical device coatings
- Water treatment systems
Easy-Clean
Facilitates the removal of contaminants with minimal effort.
Examples include:
- Architectural glass
- Food processing equipment
- Consumer products
Anti-Graffiti
Prevents paints, inks, and markers from strongly adhering.
Examples include:
- Transportation infrastructure
- Building facades
- Public facilities
Anti-Fingerprint
Reduces the adhesion and visibility of skin oils.
Examples include:
- Consumer electronics
- Stainless steel appliances
- Display screens
The Most Common Source of Confusion
Among engineers and manufacturers, perhaps the most common misunderstanding involves the terms high-slip, high-release, and non-stick.
Because many low-surface-energy coatings exhibit all three characteristics, the terms are often treated as synonyms. In practice, they frequently overlap—but they are not technically equivalent.
High-Slip: How Easily Does It Slide?
High-slip refers to friction. A high-slip surface has a low coefficient of friction, allowing materials to move across the surface with minimal resistance.
The key question is: “How easily does it slide?”
High-Release: How Easily Does It Let Go?
High-release refers to adhesion. A high-release surface minimizes bonding between two materials, allowing clean separation after contact.
The key question is: “How easily does it let go?”
Non-Stick: The General Outcome
Non-stick is a broader performance description.
A surface may be called non-stick because materials do not accumulate, adhere, or remain attached—but the underlying reason may involve release properties, friction reduction, liquid repellency, or a combination of factors.
Why Molding Engineers Often Use the Terms Interchangeably
In molding and tooling applications, high-slip and high-release often produce the same practical result: parts release from the mold more easily.
For example, PTFE-coated tooling surfaces exhibit both low friction and low adhesion.
As a result, molders commonly use terms such as:
- High-slip
- High-release
- Non-stick
to describe essentially the same outcome.
However, the underlying mechanisms remain different.
A coating can be:
- High-slip but not particularly high-release
- High-release but not exceptionally low-friction
- Hydrophobic without being an effective mold-release surface
- Non-stick for certain materials while still allowing others to adhere
This distinction becomes increasingly important when selecting coatings for demanding manufacturing environments.
Surface Energy Is the Foundation—Not the Whole Story
Surface energy strongly influences wetting, adhesion, release, and contamination resistance. However, it is not the sole determinant of performance.
Properties such as:
- Surface roughness
- Elastic modulus
- Surface texture
- Coating chemistry
- Environmental conditions
- Temperature
can significantly affect how a surface behaves in real-world applications.
As a result, two coatings with similar surface energy values may perform very differently depending on the application.
Final Thoughts
Surface energy provides the foundation for understanding how engineered surfaces interact with their environment. However, terms such as hydrophobic, non-stick, high-slip, and high-release describe different performance outcomes rather than identical properties.
A simple way to remember the distinction is:
- Hydrophobic: How does it interact with water?
- High-Slip: How easily does it slide?
- High-Release: How easily does it let go?
- Non-Stick: Does material resist remaining attached?
While these properties often overlap, especially in low-surface-energy coating systems, understanding their differences enables more effective specification, testing, and selection of surface technologies for demanding industrial application.
If you would like assistance on choosing your coatings, please email us at info@ecs-ww.com or call us at 816.381.9900.
