Invisible but functional - anti-fog coatings
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Smart coating roadshow - 30 September 2016 Invisible but functional - anti-fog coatings
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Invisible but functional - anti-fog coatings
- 1. Invisible but Functional Anti-fog coatings Smart Coating Application Lab 27/10/2016 1© sirris | www.sirris.be | info@sirris.be |
- 2. Fogging/condensation 27/10/2016 2 Clear/transparent substrate Glass/plastics Relative humidity Delta T Water condensates to form droplets Obscured vision resulting in safety issues © sirris | www.sirris.be | info@sirris.be |
- 3. Anti-fogging solution 27/10/2016 3© sirris | www.sirris.be | info@sirris.be | Treatment to prevent water condensation (small droplets on surface) Originally developed by NASA Prevent fogging of interior helm visor during space walks
- 4. Anti fog mechanism 27/10/2016 4 Preventing condensation by increase wetting ability of the substrate Make the substrate “water-loving” Increase surface energy Superhydrophillicity No water droplets formation WCA < 5° http://www.weetect.com/anti-fog-solution-guide/ http://www.ceyecare.net/Content/eyeglasses/lenses/essilor/optifog/default.aspx
- 5. 27/10/2016 5© sirris | www.sirris.be | info@sirris.be |
- 6. How? 27/10/2016 6 You need a coating with water loving “ingredients” Presence of polar groups (-OH, -COOH, -NH3, PO) increases attraction towards water © sirris | www.sirris.be | info@sirris.be |
- 7. Example: Sugar 27/10/2016 7 Very soluble in water because of –OH functional polar groups © sirris | www.sirris.be | info@sirris.be |
- 8. Anti-fog products 27/10/2016 8© sirris | www.sirris.be | info@sirris.be | Easy to apply (spraying) No curing needed Cheap Not permanent No chemical bonding with substrate Saturation of coating with water
- 9. Permanent high-end anti-fog coating 27/10/2016 9 Require advanced technology Dipcoating Flowcoating Curing at higher temperatures needed (120°C-130°C) Temperature resistance substrate! Hardness and durability of the coating © sirris | www.sirris.be | info@sirris.be | Source: Université Laval Press Release Polyvinyl alcohol 4 successive layers Chemical bonding
- 10. Demo 27/10/2016 10© sirris | www.sirris.be | info@sirris.be |
- 11. Conclusions Anti-Fog 27/10/2016 11 Transparency is key Superhydrophillic surface Attract water to form a thin layer of water Lots of products (choice) High-end or low-end use © sirris | www.sirris.be | info@sirris.be |
- 12. 27/10/2016© sirris | www.sirris.be | info@sirris.be | http://www.sirris.be #sirris http://www.linkedin.com/company/sirris http://techniline.sirris.be
Editor's Notes
- What causes the "fogging" effect? Both atmospheric fog and "window" fog are made of tiny droplets of water, but they are not the same thing. In both cases, the tiny droplets scatter light in all directions rather than allowing light to pass straight through. Condensation forms because of a temperature difference between a surface and air. The fog on the inside of a window is a comparatively small amount of water. An anti-fog coating causes the water to form a layer of water rather than droplets, resulting in a very thin layer of water that is easy to see through A hydrophobic, or "water hating" surface, causes water to form droplets on the surface and easily leave the surface. A hydrophilic, or "water loving" surface, causes water to spread out and cover a surface rather than bead, These types of surfaces are especially useful to avoid loss of visibility due to condensation. As we just discussed, water condensates on glass and causes it to become "foggy" because the tiny water droplets formed on the surface scatter light. When a hydrophilic anti-fog coating is applied to the glass, however, the condensation forms a thin, even layer of water instead of the droplets and the glass remains transparent.