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Self-cleaning technology
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The invention of self-cleaning glass was a real breakthrough in the glass sector. This product uses a special coating, which is applied to the surface during the manufacturing process. All major glass manufacturers have their own self-cleaning products. Let's take a closer look:
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 Several approaches have been made in recent years to fight dirt build-up on roofs, facades and windows. Self-cleaning coatings are improving constantly. Window manufacturers can be very demanding when it comes to the quality of the coatings. Not only maintenance of the facades must be minimized by the self-cleaning function, but durability for the lifetime of the facade, optical quality and scratch resistance are equally important. Currently, there exist two main categories of self-clean coatings: hydrophobic and hydrophilic.
Hydrophobic
Hydrophobic coatings repel water and dirt and prevent water drops from drying on the glass pane and leaving ugly stains. The biggest problem of this type of coating is that most hydrophobic coatings do not exhibit enough hydrophobicity (contact angle with water > 1500) for the self-cleaning effect to work. These coatings are often termed easy-clean.
Hydrophilic
It literally means 'attracting water', and is the opposite of 'hydrophobic' (water-repellent). That makes water droplets spread out, across the surface of the glass. Basically, it means water spreads evenly over the surface of the glass to form a thin film that washes away and dries off quickly without leaving unsightly 'drying spots'. Hydrophilic - water attracting - coatings can be photocatalytically active and break-up organic dirt, which can be washed away by the water-sheeting effect on hydrophilic surfaces. Hydrophilic coatings are mechanically much more stable. They face challenges by metal ions from rainwater poisoning their photocatalytic activity over time and some also exhibit a certain color tint.
Both approaches are promising, but there is still room for improvement. Read more on the selected links.
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Photos: Optics
Last review: August, 2006 |
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| Other Net Sources |
No Dirty Looks
Publication by Dr. Rolf Claessen about self-cleaning coating technology.
UniSci
Tracking water's hydrophilic-hydrophobic behavior
SGG Bioclean™
Bioclean interactive presentation.
Pilkington
Official website of the self-cleaning glass Pilkington Activ.
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