What is surface energy?| Solids and Liquids

Surface energy is a way to measure the energy that is present at the surface of a solid. People typically use this term for solids, and use “surface tension” when talking about liquids. The atoms inside the solid are stable and have a balanced set of bonds. However, the atoms on the surface are not completely bonded and have some unused bonding energy.

This ‘free’ energy on a solid’s surface plays a big role in how it reacts with its surroundings. Take Teflon, for example—it has a low surface energy, which makes it an excellent choice for frying pans since it barely interacts with food. On the other hand, wood has a much higher surface energy, making it easy to paint and coat.

In industries, we often work with popular plastics like Polypropylene (PP), Polyethylene (PE), Nylon (PAx), and Polycarbonate (PC). These materials typically have a medium surface energy, ranging from 30mN/m to 40mN/m. Materials with low surface energy, usually considered to be less than 40mN/m, interact less and less with their surroundings as their surface energy decreases.

Daily Life Examples

1. Water Beads on Car: Water forms droplets on a car due to its low surface energy.
2. Sticky Notes: The adhesive is designed to stick well but also remove easily.
3. Surfboard Wax: Wax increases surface energy for better grip.
4. Ink on Paper: Ink spreads on paper because of its high surface energy.
5. Dishwashing: Soap reduces water’s surface energy to better clean grease from dishes.
6. Painting: Cleaning and sanding walls increase surface energy for better paint adherence.
7. Window Cleaning: Cleaning glass restores its high surface energy for more effective washing.
8. Stickers: The adhesive needs the right surface energy to stick and be removable.
9. Non-stick Pans: Teflon’s low surface energy makes it non-stick.
10. Fabric Wetting: Cotton absorbs water due to high surface energy, while polyester repels it.

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