Waterproof coatings do make products such as outerwear much more useful, but they also drive up the price. A new coating, though, is claimed to be 90 percent cheaper to produce, while still being highly effective and more eco-friendly.
The solution is currently being developed at Vancouver's Simon Fraser University, by a team led by Prof. Hogan Yu. Unlike many conventional waterproof coatings, it doesn't contain any fluorinated compounds, which are highly toxic.
Instead, it consists of a mixture of water, a relatively safe industrial solvent such as hexane, and a chemical known as octadecyltrichlorosilane (OTS). When materials like wood, metal, glass or fabric are sprayed with the coating – or dipped into it – the liquid forms into a flexible waterproof film on their surface.
It should be noted that in its regular state, OTS is very flammable. Yu tells us that after it reacts with the water, however, it changes into a non-flammable silicate-like material.
In lab tests, the coating's hydrophobic (water-repelling) characteristics were compared to those of commercially available waterproofing solutions such as Scotchgard. It was found that when a water droplet was deposited onto the film, that droplet had a higher contact angle than with any of the other products – the greater the contact angle, the more likely a droplet is to simply roll off of a material instead of soaking in.
Subsequent experiments showed that the coated items remained waterproof for at least 18 months, although tests are being conducted to see how much longer the effect lasts. The scientists are also investigating how the coating stands up to harsh physical conditions.
It is hoped that once developed further, the technology could find use in applications such as anti-biofouling coatings for ship hulls, ice-resistant paint for buildings, filtration membranes that separate oil from water, plus of course coats and jackets.
"We believe this product could help improve people's lives in a number of ways, such as keeping us dry and comfortable on rainy days, which are common on the West Coast where we love to live," says Yu.
The research is described in a paper that was recently published in the journal Nature Communications.
Source: Simon Fraser University