Invisible but functional - anti-fog coatings

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Invisible but FunctionalAnti-fog coatingsSmart Coating Application Lab30.09.161 sirris | www.sirris.be | [email protected] |

Fogging/condensation30.09.162Clear/transparent substrateGlass/plastics

Relative humidityDelta T

Water condensates to form dropletsObscured vision resulting in safety issues

sirris | www.sirris.be | [email protected] |

Anti-fogging solution30.09.163 sirris | www.sirris.be | [email protected] |Treatment to prevent water condensation (small droplets on surface)

Originally developed by NASAPrevent fogging of interior helm visor during space walks

3

Anti fog mechanism30.09.164Preventing condensation by increase wetting ability of the substrateMake the substrate water-lovingIncrease surface energy

SuperhydrophillicityNo water droplets formationWCA < 5http://www.weetect.com/anti-fog-solution-guide/http://www.ceyecare.net/Content/eyeglasses/lenses/essilor/optifog/default.aspx

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.4

30.09.165 sirris | www.sirris.be | [email protected] |

How?30.09.166You need a coating with water loving ingredientsPresence of polar groups (-OH, -COOH, -NH3, PO) increases attraction towards water


Example: Sugar30.09.167Very soluble in water because of OH functional polar groups


Anti-fog products30.09.168 sirris | www.sirris.be | [email protected] |

Easy to apply (spraying) No curing needed Cheap

Not permanentNo chemical bonding with substrateSaturation of coating with water

Permanent high-end anti-fog coating30.09.169Require advanced technologyDipcoatingFlowcoating

Curing at higher temperatures needed (120C-130C)Temperature resistance substrate!Hardness and durability of the coating sirris | www.sirris.be | [email protected] |

Source: Universit Laval Press ReleasePolyvinyl alcohol4 successive layersChemical bonding

Demo30.09.1610 sirris | www.sirris.be | [email protected] |

Conclusions Anti-Fog30.09.1611Transparency is keySuperhydrophillic surfaceAttract water to form a thin layer of waterLots of products (choice)High-end or low-end use sirris | www.sirris.be | [email protected] |

30.09.16 sirris | www.sirris.be | [email protected] |http://www.sirris.be#sirrishttp://www.linkedin.com/company/sirrishttp://techniline.sirris.be

Testing performance anti-fog coatings30.09.1613Breathing testHeat and humidity cycleHeat and cold cycle sirris | www.sirris.be | [email protected] |

Invisible but functional - anti-fog coatings

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