World’s First Ultralight Aerogels from Plastic Waste Suitable for Wide-Ranging Applications

A noteworthy contribution towards resolving the global problem of plastic waste has been made by scientists from the National University of Singapore (NUS), who have created a way to transform plastic bottle waste into aerogels for many beneficial applications.

A team led by researchers from the National University of Singapore has found a way to turn plastic bottle waste into ultralight polyethylene terephthalate (PET) aerogels that are suitable for various applications, including heat insulation and carbon dioxide absorption. (Credit: NUS)

Plastic bottles are usually made from polyethylene terephthalate (PET), which is the world’s most recycled plastic. The PET aerogels produced by the NUS-led research team using plastic bottle waste—a world’s first—are extremely light, soft, flexible, durable, and easy to handle. They also exhibit greater thermal insulation and robust absorption capacity. These properties render them desirable for a wide variety of applications, such as for oil spill cleaning, heat and sound insulation in buildings, and also as a lightweight lining for firefighter coats and carbon dioxide absorption masks that could be worn during fire rescue operations and fire escape.

This pioneering work was accomplished by a study team led by Associate Professor Hai Minh Duong and Professor Nhan Phan-Thien from the Department of Mechanical Engineering at NUS Faculty of Engineering. The technology to create PET aerogels was established in partnership with Dr Xiwen Zhang from the Singapore Institute of Manufacturing Technology (SIMTech) under the Agency for Science, Technology and Research (A*STAR).

Recycling plastic bottle waste

Plastic waste is non-biodegradable and toxic. Such waste commonly ends up in landfills and oceans, impacting marine life and causing issues such as land scarcity and groundwater contamination. Internationally, the annual consumption of plastic bottles has been rising progressively, and it is projected to surpass half a trillion tons per year by 2021.

Plastic bottle waste is one of the most common type 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.

Hai Minh Duong, Associate Professor, Department of Mechanical Engineering, NUS Faculty of Engineering.

Versatile PET aerogels

The researchers took two years (from August 2016 to August 2018) to create the technology to fabricate PET aerogels. Their efforts have been reported in the August 2018 issue of the scientific journal Colloids and Surfaces A.

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.

Nhan Phan-Thien, Professor, Department of Mechanical Engineering, NUS Faculty of Engineering.

Lighter and safer firefighter coats

Another innovative application is to exploit the heat insulation property of the PET aerogels for fire safety applications.

Current firefighter coats are bulky and they are frequently used along with other breathing and safety equipment. This could be hard on firefighters, particularly during prolonged operations.

When coated with fire retardant chemicals, the unique lightweight PET aerogel exhibits greater thermal resistance and stability. It can endure temperatures of up to 620 °C—this is seven times more than the thermal lining used in conventional firefighter coats, but weighs just about 10% of the weight of conventional thermal lining. The flexible and soft nature of the PET aerogel also offers much comfort.

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.”

2-in-1 mask that absorbs harmful carbon dioxide and dust particles

When the PET aerogel is coated with an amine group, it can rapidly absorb carbon dioxide from the environment. Its absorption capacity is comparable to materials used in gas masks, which are expensive and bulky. To demonstrate this application, the team embedded a thin layer of PET aerogel into a commercial fine particle mask to produce a prototype mask that can absorb both carbon dioxide and dust particles effectively.

Prof Nhan said, “In highly urbanised 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.”

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.

Hai Minh Duong, Associate Professor, Department of Mechanical Engineering, NUS Faculty of Engineering.

NUS scientists are also aiming to make simple surface alteration to the PET aerogels for absorption of poisonous gases such as carbon monoxide, which is the most lethal component of smoke.

In their previous work, the study team had effectively converted paper and fashion waste into cellulose and cotton aerogels, respectively. Along with this latest innovation involving the recycling of plastic bottle waste into aerogels, the NUS team was recently bestowed the first place in the Sustainable Technologies category of the 2018 Create the Future Design Contest by Tech Briefs.

Next steps

The researchers have filed a patent for its novel PET aerogel technology, and will continue to improve the performance of the PET aerogels and search for new applications. The NUS team also aims to work with companies to commercialize the technology.

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