Could upcycled aerogel solve a burning issue?

Scientists at NUS have developed the world’s first aerogel made from recycled plastics. Constructed from old soft-drink bottles, the aerogel could find useful applications in everything from sound proofing to oil spills, and could also be a novel way to combat the global plastic waste epidemic. 

Developed by a team from NUS Engineering led by Assoc Prof Hai Minh Duong and Prof Nhan Phan-Thien, the aerogel is made from the most recycled plastic in the world — polyethylene terephthalate (PET). Like all aerogels, it is an ultralight and porous solid, but being made from plastic also gives it the advantage of being soft, flexible and very durable.

With the annual consumption of plastic bottles set to be more than half a trillion by 2021, the aerogel could be a useful way to reduce the environmental impact of these disposables. “Plastic bottles are one of the most common types of plastic waste, and have many detrimental effects on the environment,” explained Assoc Prof Duong. “To combat this, our team has developed a simple, cost-effective, and green method to convert plastic bottle waste into PET aerogels for many exciting uses.”

Assoc Prof Duong added, “With our new method, one plastic bottle can be recycled to produce an A4-sized PET aerogel sheet. The technology is also easily scalable for mass production. In this way, we can help cut down the environmental damage caused by plastic waste.” 

From left: Research Engineer Mr Duyen Khac Le; Final year NUS Mechanical Engineering student Ryan Leung; Prof Nhan; Assoc Prof Duong; and Singapore Institute of Manufacturing Technology collaborator Dr Wendy Zhang took two years to develop the heat-resistant recycled aerogel

Another advantage of this new material is its versatility. The team discovered that different surface treatments meant that the aerogel could be used for many diverse applications. For example, if the PET aerogel incorporates a variety of methyl groups on its surface, it has the ability to absorb large amounts of oil up to seven times more effectively than other commercially available products.

But perhaps the most exciting application of the aerogel could be its use in fire safety equipment. When coated with fire retardant chemicals, the aerogel was shown to withstand temperatures up to 620°C. Amazingly, this temperature resistance is seven times higher than conventional firefighter coats would allow, yet it could result in coats that are 11 times lighter.

“By adopting our PET aerogels that are coated with fire retardants as a lining material, firefighter coats can be made much lighter, safer, and cheaper. It would even be possible to produce low-cost heat-resistant jackets for personal use with this technology,” said Prof Nhan.

The fire safety applications don’t stop at heat-resistant coats. The team discovered that when the aerogel is coated with an amine group, its carbon dioxide absorbing abilities are comparable to the materials used in gas masks.

Therefore, a plastic bottle could be recovered, recycled into PET aerogel sheets, and embedded as a thin layer in a commercial dust particle mask. A PET aerogel mask fabricated in this way could capture dust particles at the same time as carbon dioxide, something no masks currently available can do.

The researchers envision that these masks could be used to help people safely escape from building fires. “In places like Singapore with many high-rise buildings, both the carbon dioxide absorption masks and heat-resistant jackets could be placed alongside fire extinguishers to provide added protection to civilians when they escape from a fire,” Prof Nhan explained. “The masks could even be used daily to avoid air pollution, seasonal allergies, and health hazards.”

Fitting these aerogel sheets into a mask makes them suitable as fire safety equipment

The research was published in the scientific journal Colloids and Surfaces A in August, and expands upon the team’s earlier discoveries of aerogels made from recycled paper and cotton. The team has filed a patent for its novel PET aerogel technology, and will continue to enhance the aerogel’s performance and explore new applications of the material. The NUS researchers are also keen to work with companies to bring the exciting technology to market.

See press release.