Contents

Surface free energy (SFE) / surface energy

Pronunciation: /ˈsɜːrfɪs friː ˈɛnərdʒi/

Surface free energy is the excess energy of the molecules at the surface of a solid compared with those in the bulk, expressed per unit area in mJ/m². It decides whether liquids, inks, coatings and adhesives wet and bond to that surface.

Also called

Surface energy SFE Solid surface tension

Related terms

Critical surface tension (Zisman) OWRK method Surface energy components

Topics

Surface energy Wetting Adhesion
Book a 15 minute demo Read the surface energy measurement guide

At a glance

Definition, typical values and how it is found.

What it is

Surface molecules have fewer neighbours than bulk ones, so they carry extra energy. For liquids the same quantity is called surface tension, as our article on surface tension vs surface energy explains.

Related terms

Terms that build on surface free energy.

Related terms

  • Surface energy components
  • OWRK method
  • Critical surface tension (Zisman)
  • Surface tension

FAQ

Short answers to common questions about surface free energy.

Why does surface energy matter for printing and bonding?

An ink or adhesive wets well only when the surface energy is high enough. Film converters raise it with corona treatment and check it with dyne tests under ASTM D2578, as in corona treatment monitoring for print quality.

Can you measure surface energy directly?

Not for solids. You measure contact angles of liquids with known surface tension and calculate it with a model. Students practise this in experiment 6 on multiple liquids, and a fused silica case study shows it on glass.

References

Primary sources and further reading.

1. Owens, D. K., and Wendt, R. C. (1969). Estimation of the surface free energy of polymers. Journal of Applied Polymer Science, 13(8), 1741 to 1747. https://doi.org/10.1002/app.1969.070130815
2. Kwok, D. Y., and Neumann, A. W. (1999). Contact angle measurement and contact angle interpretation. Advances in Colloid and Interface Science, 81(3), 167 to 249. https://doi.org/10.1016/S0001-8686(98)00087-6
3. Surface energy measurement guide
4. OWRK method
5. Surface energy components