National University of Singapore

NUS researchers convert plastic bottle waste into ultralight ‘supermaterial’

The scientists at the National University of Singapore (NUS) have developed an ultralight polyethylene terephthalate (PET) aerogels from plastic bottle waste that can be used in various applications, in response to the global issue of plastic waste.

The aerogels are ideal for applications such as carbon dioxide absorption and heat insulation. The new method is the first in the world to make aerogel from recycled plastics.

Finding a solution for Global Plastic Issue

Plastic waste is toxic and does not biodegrade. It generally ends up in oceans and landfill sites, contaminating groundwater and affecting marine life. The annual consumption of plastic bottles is anticipated to surpass half a trillion tons in a year by 2021.

Plastic bottles are generally made from PET, which is the most recycled plastic in the world. The NUS-led research team turned plastic bottle waste into PET aerogels, which are durable, soft, extremely light, flexible and easy to handle. This aerogels also feature strong absorption capacity and superior thermal insulation. It is suitable for a broad range of applications like oil spill cleaning, heat and sound insulation in buildings, as well as a lightweight lining for firefighter coats and carbon dioxide absorption masks that could be used during fire escape and fire rescue operations.

Associate Professor Hai Minh Duong and Professor Nhan Phan-Thien from the Department of Mechanical Engineering at NUS Faculty of Engineering led the development team.

In partnership with Dr Xiwen Zhang from the Singapore Institute of Manufacturing Technology (SIMTech) under the Agency for Science, Technology and Research (A*STAR), the technology to make PET aerogels was developed.

Assoc Prof Duong said:
“Plastic bottle waste is one of the most common types of plastic waste and has detrimental effects on the environment. 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.”

PET Aerogels

After the two years of research and development, the team developed the technology to fabricate PET aerogels. The scientific journal Colloids and Surfaces A published this work in August 2018.

Professor Nhan Phan-Thien added:
“Our PET aerogels are very versatile. We can give them different surface treatments to customize 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 current commercial sorbents, and are highly suitable for oil spill cleaning.”

2-in-1 Mask With Harmful Carbon Dioxide & Dust Particles filters

The PET aerogels can absorb carbon dioxide from the surrounding air, when coated with an amine group. Its absorption capacity is proportional to materials used in gas masks that are bulky and costly. To demonstrate this application, the team implanted a thin layer of PET aerogel into a commercial fine particle mask to make a prototype mask that is capable of absorbing both carbon dioxide and dust particles effectively.

Prof Nhan said:
“In highly urbanized countries like Singapore, the carbon dioxide absorption masks and heat-resistant jackets made using PET aerogels can be placed alongside fire extinguishers in high-rise buildings to provide added protection to civilians when they escape from a fire.”

Assoc Prof Duong added:
“Masks lined with amine-reinforced PET aerogels can also benefit people living in countries such as China, where air pollution and carbon emission are major concerns. Such masks can be easily produced, and can also potentially be made reusable.”

Lighter and Safer Firefighter Coats

The lightweight PET aerogels coated with fire retardant chemicals can illustrate superior thermal resistance and stability. This coating made it withstand temperatures as high as degree Celsius, which is seven times higher than the thermal lining utilized in standard firefighter coats. It weighs only 10% of the weight of the traditional thermal lining.

Prof 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.”

Furthermore, scientists are looking to make a simple surface modification to the PET aerogels for absorbing toxic gases like carbon monoxide, which is the fatal component of smoke.

They have also filed a patent for its novel PET aerogel technology, and will continue to enhance the performance of the PET aerogels and explore new applications. The NUS researchers are also interested in collaborating with companies to launch the technology in the market.

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