From raincoats to military tents to rain boots, water-repellent clothing is crucial in our day to day life. The available water repellent coatings though are said to having the tendency to accumulate in our bodies and therefore isn’t a safer option. Researchers for a long time have wanted to develop better water-repellent clothing substitutes which are safer than their existing counterparts. A new team at MIT has done just that. The team proposes a new coating that makes natural fabrics such as cotton and silk water repellent and is also quite safer. The study was published recently in the journal Advanced Functional Materials and was written by Kripa Varanasi and Karen Gleason, both professors at MIT, Dan Soto former MIT postdoctoral student, and two others.
According to Varanasi, the alternative developed by the research team is much more superior than the conventional materials. “Most fabrics that say ‘water-repellent’ are actually water-resistant,” explains Varanasi. “If you’re standing out in the rain, eventually water will get through. Ultimately, “the goal is to be repellent — to have the drops just bounce back.” The new coating brings the team very close to achieving that goal. The coatings that are already available in the market are made up of long polymers with perfluorinated side-chains. They [coatings] are usually liquid-based and therefore the fabric should be first submerged in water and then dried off. The team at MIT developed a short-chain polymer and enhanced its hydrophobic tendencies. The process that they used, called initiated chemical vapor deposition (iCVD), helps develop a very fine thin coating and is not liquid based.
The process is versatile and proves useful on many fabrics like cotton, nylon, linen etc. but what’s surprising that it also works on materials which are not typically considered fabric, for example, paper. The process was tested on a variety of fabrics and also on different weave patterns of the same fabrics. The coated fabrics also underwent a lot of quality testing in MIT’s labs like a standard rain test. The coating repelled materials such as coffee, ketchup, sodium hydroxide and even acids and bases. When washed repeatedly to check if it would lead to the degradation of the coatings, the coating came out a super hero with no effect on its quality. It even stood strong in the face of serious abrasion tests. Even after 10,000 repetitions, the coating showed no wear and tear. But the researchers want us know that if the abrasion is too severe, “the fiber will be damaged, but the coating won’t”.