Researchers in Singapore have come up with a quick, low-cost and green method to convert cotton-based textiles into light, spongy aerogels. The research, published in the journal Colloids and Surfaces A, shows a path to making a valuable product from waste fabrics and old clothes.
The cotton aerogel could be used as an absorptive material to control bleeding, sop up oil spills, and in diapers. It could also find use in insulation. “We foresee tremendous potential for high value applications, such as pipeline insulation and transportation of liquefied natural gas which needs to be stored at a low temperature,” said Nhan Phan-Thien, a professor of mechanical engineering at the National University of Singapore.
Today’s fast-changing fashion carries an enormous environmental burden. Growing cotton takes a lot of energy and water. Synthetic fabrics are a leading cause of microplastic pollution, much of it swirling in oceans. One garbage truck full of textiles is landfilled or incinerated every second, according to the Ellen MacArthur Foundation. And there is no effective recycling technology for cotton or fiber blends.
Aerogels are porous, ultralight, materials that can be made from a variety of chemical compounds, such as silica, carbon, and alumina. But they are generally expensive to make.
The team of mechanical engineers had previously found a way to make aerogels from paper waste. But the new cotton aerogel is stronger and more eco-friendly. It can also be made much faster: 20 times faster than it takes to make conventional aerogels. The aerogels can be easily compressed, and quickly recover up to 97 percent of their original size when soaked.
To demonstrate practical use, the researchers made absorptive pellets from the aerogel that could be used to stop hemorrhaging. Today, medical responders insert such pellets, made of cellulose-based sponge, into deep gunshot wounds and battlefield injuries, where they exert pressure to stop blood flow.
The researchers extracted cotton fibers from fabric waste, and mixed it with cellulose in a 2:1 ratio to make aerogels. They coated the aerogels with chitosan and then compressed them to make the absorptive pellets. The pellets performed better than commercial ones, expanding more and faster, and exerting more pressure.
They also made an insulation sleeve for water bottles. The sleeve kept icy water at a around freezing temperature for over four hours, comparable to commercial insulated water bottles, which are much heavier and more expensive.
Source: Hai M. Duong et al. Compressed hybrid cotton aerogels for stopping liquid leakage. Colloids and Surfaces A: Physiochemical and Engineering Aspects. 2018.