The new waterproofing technology allows fabric to repel a variety of liquids, including coffee and soy sauce, without inhibiting the material's breathability. Photo by Varanasi and Gleason research groups/MIT
June 29 (UPI) -- Traditional waterproofing compounds, long-chain polymers, accumulate and persist in the environment and the human body, posing health concerns. Environmental regulators are expected to soon ban the use of the polymers.
As a result, material scientists are looking for a safer way to waterproof materials.
Researchers at MIT have developed a new type of coating. Not only is the new coating safer, it also works better, its inventors claim.
"Most fabrics that say 'water-repellent' are actually water-resistant. If you're standing out in the rain, eventually water will get through," MIT professor Kripa Varanasi said in a news release. "The goal is to be repellent -- to have the drops just bounce back."
All sorts of products rely on waterproofing, but traditional hydrophobic technologies suffer several problems. Most waterproofing coatings are liquid-based. Fabrics must be entirely submerged and then dried. The technique limits breathability.
To reopen sealed-over pores in the fabric, air is blown through the material, an additional manufacturing step. The additional step increases production costs and undermines the waterproofing effect.
The solution developed by Karanasi and his colleagues combines short-chain polymers, which don't accumulate as easily or persist in the environment, with a coating process called initiated chemical vapor deposition, or iCVD.
Researchers described the technology this week in the journal Advanced Functional Materials.
The technique doesn't involve liquids. Instead, the application process allows the polymer to form to the contours of the fabric's fibers without clogging pores. An added sand-blasting step can enhance the coating hydrophobic effect, but is not necessary.
"The biggest challenge was finding the sweet spot where performance, durability, and iCVD compatibility could work together and deliver the best performance," said former MIT postdoc Dan Soto.
Lab tests proved the coating technology works to waterproof a variety of fabrics and materials against a variety of liquids, including coffee, soy sauce, ketchup and sodium hydroxide. The coatings integrity also survived repeated washing and abrasion tests.
"Many fabrics can benefit from this technology," Varanasi said. "There's a lot of potential here."