Approximately one tonne of textile waste is generated every five minutes in Singapore. However, researchers from NUS Mechanical Engineering have found a way to turn people’s unwanted clothing into the world’s first ultralight cotton aerogel, which has wide-ranging applications including in haemorrhage control and heat insulation.
Aerogels are among the world’s lightest materials, are highly porous and have strong absorption capacity and low thermal conductivity. This makes them suitable for applications in areas such as oil-spill cleaning, personal care products such as diapers, as well as for heat and sound insulation. While aerogels were first created in 1932, industries have been slow to adopt its use due to high production costs.
In response to this, Associate Professor Hai Minh Duong and Professor Nhan Phan-Thien have developed a fast, cheap and green method of converting cotton-based fabric waste into aerogels. The eco-friendly material is highly compressible, thereby reducing storage and transportation costs, and can be fabricated within eight hours — nine times faster than the team’s earlier invention of paper-waste cellulose aerogels and 20 times faster than current commercial fabrication processes. A tonne of cotton fibre is able to produce up to 22,000 A4-sized pieces of aerogel.
An important use of the material could be in the form of aerogel pellets for haemorrhage control devices. This would entail filling a syringe with a mix of cotton and cellulose aerogels coated with chitosan — a natural agent derived from the shells of shrimp and other crustaceans that promotes blood clotting — and inserting the syringe into the wound, where the pellets expand and apply pressure to stop the blood flow.
“Each cotton aerogel pellet can expand to 16 times its size in 4.5 seconds — larger and more than three times faster than existing cellulose-based sponges — while retaining their structural integrity. The unique morphology of the cotton aerogels allows for a larger absorption capacity, while the compressible nature enables the material to expand faster to exert pressure on the wound,” explained Assoc Prof Duong.
The findings for this novel application were published in the scientific journal Colloids and Surfaces A in January.
The aerogels could also be used to keep military water bottles cold, lowering the risk of heat stroke and increasing productivity for soldiers. In a project done in collaboration with DSO National Laboratories, the researchers invented a lightweight thermal jacket for military canteens by embedding a cotton aerogel layer within commonly used fabrics. The thermal jacket can maintain the temperature of ice slurry — crushed ice and water — at below one degree Celsius for over four hours, compared to about 30 minutes without the sleeve.
“The heat insulation property of the novel cotton aerogels can be applied to various consumer products, such as cooler bags to keep food items fresh. We also foresee tremendous potential for other high value applications, such as pipeline insulation and transportation of liquefied natural gas which needs to be stored at a low temperature,” said Prof Nhan.
The team has filed a patent for the cotton aerogels and is exploring opportunities for commercialisation.