Surface energy comes from the attraction between molecules at the surface of a material. These attractions arise from the distribution and movement of electrons within those molecules, and they can be grouped into two categories: dispersive and polar forces.
Together, these two components determine a surface’s ability to interact with liquids, adhesives, coatings, and contaminants.
Dispersive forces are created by temporary fluctuations in electron clouds around molecules, producing short-lived positive and negative areas that attract other molecules. These interactions exist in all materials and are relatively weak.
Dispersive forces differ from material to material, but they are not meaningfully adjustable through manufacturing processes. Polystyrene, PVC, and other polymers with aromatic rings or larger electron systems tend to have higher dispersive components, but these values remain essentially fixed.
In short: dispersive forces are real and measurable, but they are not something manufacturers can control.
Tip from a Surface Scientist:
If a force cannot be influenced by cleaning or treatment, it doesn’t belong in your process-control strategy. Dispersive forces fall into that category.
Polar forces arise from permanent dipoles, which are regions of a molecule that always have slightly positive or slightly negative charge. These interactions are significantly stronger than dispersive forces and are directly responsible for the ability of adhesives, coatings, and inks to form strong bonds with a surface.
Unlike dispersive forces, the polar component of surface energy can be engineered. Processes such as plasma treatment, corona treatment, flame treatment, solvent cleaning, aqueous cleaning, or light abrasion alter how electrons are distributed on a surface, raising or lowering the polar component.
Because polar forces respond to surface conditioning, they are the part of surface energy that manufacturers intentionally control.
Tip from a Surface Scientist:
If you’re adjusting a process to “improve adhesion,” what you’re really doing is modifying the polar component of the surface energy, even if you’re not calling it that.
Polar interactions determine whether a surface will wet properly, hold onto an adhesive, or resist contamination during storage. They also degrade fastest when surfaces are not controlled or when cleaned parts sit before use.
Even environmental exposure, such as packaging materials or airborne contaminants, can lower the polar component over time.
This makes ongoing measurement essential for maintaining consistent adhesion and coating outcomes. The most practical way to track these molecular changes is through water contact angle.
While this formula is conceptually useful, calculating total surface energy directly is complex and susceptible to error. Manufacturers typically avoid full calculations and instead measure the polar component through WCA, which is more stable, sensitive, and proven to correlate with adhesion performance.
In real-world manufacturing, there is no functional difference between the two terms. Both refer to the energetic condition of a surface relevant to bonding, printing, coating, and cleaning.
What matters is understanding which part of that energy your process can control, and that is the polar component.
Surface energy is therefore a practical engineering parameter, not just a theoretical concept. It represents the molecular readiness of a surface to participate in adhesion-driving interactions.
This relationship makes WCA the most practical method for monitoring surface readiness throughout production. It’s why tools such as the Surface Analyst and the BConnect platform are built around capturing, tracking, and analyzing contact angle data.
Tip from a Surface Scientist:
If you catch a shift in contact angle early, you prevent downstream defects. If you wait until the bond fails, the surface has been wrong for hours, or days.
Surface energy, whether you call it surface energy or surface free energy, is a critical manufacturing property that determines how well surfaces interact with the materials applied to them. Although both dispersive and polar forces contribute to total surface energy, only the polar component responds to cleaning and treatment. This makes it the primary focus for process development, quality control, and supplier verification.
By incorporating contact angle measurement at key Critical Control Points and integrating that data into BConnect, manufacturers gain real-time visibility into surface quality and the molecular conditions that drive adhesion reliability.
To deepen your understanding of contact angle and its role in manufacturing and supply chain quality, explore the eBook “What Is Contact Angle? Bridging the Gap: How Contact Angle Insights Drive Manufacturing & Supply Chain Innovations.”