New coating makes fabrics water repellent

MIT researchers have developed a water repellent coating for natural fabrics that is more effective – and less harmful - than existing coatings.

The new solution is said to eliminate the need for a second processing stage commonly used to produce water repellent fabrics, and has proven its durability in tests.

The new findings are described in Advanced Functional Materials, in a paper by MIT professors Kripa Varanasi and Karen Gleason, former MIT postdoc Dan Soto, and two others.

Because of the way they accumulate in the environment and in human body tissue, the US Environmental Protection Agency (EPA) is in the process of revising regulations on the long-chain polymers that have been the industry standard for water resistant materials.

The coatings currently used to make fabrics water repellent generally consist of long polymers with perfluorinated side-chains. Shorter-chain polymers are less hydrophobic than longer-chain versions. Existing coatings are also liquid-based, so the fabric has to be immersed in the liquid and then dried out, which can clog all the pores in the fabric and make them less breathable.