Home / Knowledge / News / Textiles / MIT's coating for water-repellency in natural fabrics
MIT's coating for water-repellency in natural fabrics
03
Jul '18
Courtesy: Massachusetts Institute of Technology
Courtesy: Massachusetts Institute of Technology
A team at MIT scientists has developed a coating that not only adds water-repellency to natural fabrics such as cotton and silk, but is also more effective than the existing coatings. The coated fabrics have been bombarded not only with water but with other liquids such as coffee, ketchup, sodium hydroxide, and various acids and bases, and have repelled all.

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

“The challenge has been driven by the environmental regulators” because of the phaseout of the existing waterproofing chemicals, Varanasi explains. But it turns out his team’s alternative actually outperforms the conventional materials.

“Most fabrics that say ‘water-repellent’ are actually water-resistant,” says Varanasi, who is an associate professor of mechanical engineering. “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 comes closer to that goal, he says.

Because of the way they accumulate in the environment and in body tissue, the EPA is in the process of revising regulations on the long-chain polymers that have been the industry standard for decades. “They’re everywhere, and they don’t degrade easily,” Varanasi says.

The coatings currently used to make fabrics water repellent generally consist of long polymers with perfluorinated side-chains. The trouble is, shorter-chain polymers that have been studied do not have as much of a water-repelling (or hydrophobic) effect as the longer-chain versions. Another problem with existing coatings is that they are liquid-based, so the fabric has to be immersed in the liquid and then dried out. This tends to clog all the pores in the fabric, Varanasi says, so the fabrics no longer can breathe as they otherwise would. That requires a second manufacturing step in which air is blown through the fabric to reopen those pores, adding to the manufacturing cost and undoing some of the water protection.

Research has shown that polymers with fewer than eight perfluorinated carbon groups do not persist and bioaccumulate nearly as much as those with eight or more — the ones most in use. What this MIT team did, Varanasi explains, is to combine two things: a shorter-chain polymer that, by itself, confers some hydrophobic properties and has been enhanced with some extra chemical processing; and a different coating process, called initiated chemical vapour deposition (iCVD), which was developed in recent years by co-author Karen Gleason and her co-workers. Gleason is the Alexander and I Michael Kasser Professor of Chemical Engineering and associate provost at MIT. Credit for coming up with the best short-chain polymer and making it possible to deposit the polymer with iCVD, Varanasi says, goes primarily to Soto, who is the paper’s lead author.

Using the iCVD coating process, which does not involve any liquids and can be done at low temperature, produces a very thin, uniform coating that follows the contours of the fibres and does not lead to any clogging of the pores, thus eliminating the need for the second processing stage to reopen the pores. Then, an additional step, a kind of sandblasting of the surface, can be added as an optional process to increase the water repellency even more. “The biggest challenge was finding the sweet spot where performance, durability, and iCVD compatibility could work together and deliver the best performance,” says Soto.

Testing of the coated surfaces shows that it gets a perfect score on a standard rain-repellancy test. The coatings are suited for substrates as diverse as fabrics, paper, and nanotextured silicon.

The process works on many different kinds of fabrics, Varanasi says, including cotton, nylon, and linen, and even on nonfabric materials such as paper, opening up a variety of potential applications. The system has been tested on different types of fabric, as well as on different weave patterns of those fabrics. “Many fabrics can benefit from this technology,” he says. “There’s a lot of potential here.”

The coated fabrics have been subjected to a barrage of tests in the lab, including a standard rain test used by industry. The materials have been bombarded not only with water but with various other liquids including coffee, ketchup, sodium hydroxide, and various acids and bases — and have repelled all of them well.

The coated materials have been subjected to repeated washings with no degradation of the coatings, and also have passed severe abrasion tests, with no damage to the coatings after 10,000 repetitions. Eventually, under severe abrasion, “the fibre will be damaged, but the coating won’t,” he says. (SV)

Fibre2Fashion News Desk – India


Must ReadView All

Pic: Shutterstock

Apparel/Garments | On 25th Nov 2020

Bangladesh reduces REX fee for RMG export to EU

Bangladesh's Export Promotion Bureau recently reduced the service...

Pic: Shutterstock

Textiles | On 25th Nov 2020

EACHAM-LOBA MoU to improve logistics between Cambodia, PRC

Cambodia's Logistics Business Association (LOBA) and the European...

Pic: Shutterstock

Apparel/Garments | On 25th Nov 2020

JETRO, Bangladesh's CCCI sign MoU to foster trade ties

The Japan External Trade Organisation (JETRO) and Chittagong Chamber...

Interviews View All

Top executives, Textile industry, India

Top executives
Textile industry, India

Such fairs are a must for industry to showcase new innovations

Textile Industry, Head honchos

Textile Industry
Head honchos

Farmers who produce seeds earn 50 per cent more

Ghanshyam Ghoghari, Kimora Fashion

Ghanshyam Ghoghari
Kimora Fashion

Bridalwear is not about reds and whites anymore

Erik Sy,

Erik Sy

Manila-based CustomThread is a start-up offering premium custom apparel...

Boban Charly,

Boban Charly

Bierrebi designs and manufactures automatic machines that cut fabric into...

Awanda Booth,

Awanda Booth

Held every year in New York City, Surtex is a global business-to-business...

Ian Russell, Pireta

Ian Russell
Pireta

UK-based Pireta has developed a unique free-form process to add durable,...

Sanjay Raut, Garware Technical Fibres Ltd

Sanjay Raut
Garware Technical Fibres Ltd

Garware Technical Fibres Ltd (formerly Garware-Wall Ropes Ltd) is a...

Wolfgang Plasser, Lenzing AG

Wolfgang Plasser
Lenzing AG

The Lenzing Group is an international company headquartered in Austria...

Tony Ward, Tony Ward

Tony Ward
Tony Ward

"You have to truly understand what your client wants, know her needs, what ...

Sanjukta Dutta, Sanjukta's Studio

Sanjukta Dutta
Sanjukta's Studio

<b>Sanjukta Dutta</b> creates unique garments by clubbing prints of...

Varsha Wadhwa, VW

Varsha Wadhwa
VW

Coming from a family that ran a business of jute and linen mills since...

Press Release

Press Release

Letter to Editor

Letter to Editor

RSS Feed

RSS Feed

Submit your press release on


editorial@fibre2fashion.com

Letter To Editor






(Max. 8000 char.)

Search Companies





SEARCH

Leave your Comments


November 2020

Subscribe today and get the latest update on Textiles, Fashion, Apparel and so on.


Advanced Search