plastic bottle waste

Plastic bottle waste converted into useful aerogels with new process

Image credit: DT

A new process has been developed which converts plastic bottle waste into aerogels, a valuable material used to insulate buildings, clean up oil spills and absorb carbon dioxide.

Plastic bottles are commonly made from polyethylene terephthalate (PET), which is the most recycled plastic in the world.

The PET aerogels developed by a team at the National University of Singapore (NUS) are derived from plastic bottle waste and are soft, flexible, durable, extremely light and easy to handle.

They also demonstrate superior thermal insulation and strong absorption capacity. These properties make them attractive for a wide range of applications such as heat and sound insulation in buildings, oil-spill cleaning and a lightweight lining for firefighter coats and carbon dioxide absorption masks that could be used during fire rescue operations and fire escape.

Globally, the annual consumption of plastic bottles has been rising steadily and is expected to exceed half a trillion tonnes per year by 2021.

“Plastic bottle waste is one of the most common types of plastic waste and has detrimental effects on the environment,” said associate professor Hai Minh Duong, who led the team.

“Our team has developed a simple, cost-effective and green method to convert plastic bottle waste into PET aerogels for many exciting uses.

“One plastic bottle can be recycled to produce an A4-sized PET aerogel sheet. The fabrication technology is also easily scalable for mass production. In this way, we can help cut down the harmful environmental damage caused by plastic waste.”

The research team took two years to develop the technology to fabricate PET aerogels.

Professor Nhan Phan-Thien, who also worked on the project, said: “Our PET aerogels are very versatile. We can give them different surface treatments to customise them for different applications.

“For instance, when incorporated with various methyl groups, the PET aerogels can absorb large amounts of oil very quickly. Based on our experiments, they perform up to seven times better than existing commercial sorbents, and are highly suitable for oil-spill cleaning.”

Another novel application for the material is to harness its heat insulation properties for fire safety applications.

Existing firefighter coats are bulky and are often used with other breathing and safety equipment. This could take a toll on firefighters, especially during extended operations.

When coated with fire-retardant chemicals, the novel lightweight PET aerogel demonstrates superior thermal resistance and stability.

It can withstand temperatures of up to 620°C – this is seven times higher than the thermal lining used in conventional firefighter coats, but it is only 10 per cent of the weight of conventional thermal lining. The soft and flexible nature of the PET aerogel also provides greater comfort.

Nhan explained: “By adopting PET aerogels that are coated with fire retardants as a lining material, firefighter coats can be made much lighter, safer and cheaper. It is also possible to produce low-cost heat-resistant jackets for personal use.”

When coated with an amine group, the PET aerogel can also quickly absorb carbon dioxide from the environment. Its absorption capacity is comparable to materials used in gas masks, which are costly and bulky.

To illustrate this application, the team embedded a thin layer of PET aerogel into a commercial fine-particle mask to create a prototype that can absorb both dust particles and carbon dioxide effectively.

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