Researchers at the National University of Singapore's(NUS) Faculty of Engineering are working on a project that recycles waste paper into a cellulose aerogel with the potential to be used as an insulation material, or even for cleaning up oil spills.
According to the university the process is a world first, and successfully converts paper waste into green, non-toxic, ultralight, flexible, extremely strong and water repellent cellulose aerogels. In addition to cleaning up oil spills these materials are said to be well suited to heat insulation and packaging applications, and potentially for use as coating materials for drug delivery and as smart materials for various biomedical applications.
"Aerogels, which are among the lightest solid materials known to man, are one of the finest insulation materials available,” explained Department of Mechanical Engineering, Duong Hai Minh , the assistant professor who led the research.
“Traditional aerogels are mainly made of silica, which is not environmentally-friendly. In contrast, cellulose is low cost and makes up 75% to 85% of recycled paper,” added Minh.
“Our team developed a simple, cost-effective and fast method of converting paper waste into aerogels,” continued thee assistant professor. “In addition to low thermal conductivity, these novel aerogels have several unique features, one of which is super high oil absorption capacity - it is up to four times higher than commercial sorbents available in the market. We are very excited about the potential applications of this new material.”
The NUS team also claimed to have developed a more eco-friendly process to convert paper waste into aerogels.
"Our fabrication process uses 70% less energy, produces fewer polluting emissions into the air and water, as well as uses less dioxins in the chlorine bleaching process. It is also faster -- the entire process only takes three days," asserted Minh.
According to the researchers the cellulose aerogels developed at the university boast super high oil absorption capacity.
Coated with Trimethoxy-methylsilane (MTMS), the aerogels are said to be water repellent and are capable of absorbing oil (excluding water) up to 90 times their dry weight, making them up to four times more effective than commercial oil sorbents.
Furthermore, they can be squeezed to recover over 99% of the crude oil absorbed.
"Oil spills are serious disasters that threaten marine ecosystems,” elaborated Minh. “Sorption has been considered one of the most effective ways to clean oil spills. Polypropylene (PP)-based absorbents are widely used for oil absorption but they are non-biodegradable, and their absorption capabilities are both low and slow."
Another important application of the cellulose aerogels was said to be as insulation materials for buildings.
The researchers noted that in Singapore, air-conditioning of buildings take up about two-thirds of the energy consumption in buildings. About 25% to 50% heat losses are from windows, doors, basement and roof of the buildings.
This is said to have resulted in a high market demand for eco-friendly sorbents which have greater absorbency and water repellent properties, as well as effective heat insulation materials that are less costly to install.
"As a heat insulation material, our novel cellulose aerogels offer a few added advantages,” said Minh. “Their water repellent property allows them to be adaptable to both dry and rainy weather and their structure remains stable for about six months in tropical climate.”
“Being extremely strong, they increase building strength,” In addition, these aerogels are lightweight and slim, resulting in slimmer walls, thus increasing building space," he continued.
Packaging & Other Applications
According to the cellulose aerogels could also signal a change in the packing industry. Plastic-based packing materials such as the bubble wrap could be replaced with biodegradable aerogel-based foam or advanced cellulose aerogel nanosheets, which are environmentally-friendly, they said.
With high surface area and high porosity, the biodegradable aerogels could also potentially be used as coating materials in drug delivery or as smart materials.
The NUS team also claimed to have discovered a way of expanding the weight capacity of the cellulose aerogels.
This is said to be achieved by infusing the fibres of the cellulose aerogels with a solution of metallic nanoparticles. The cellulose aerogels are then hammered flat to remove most of the air, resulting in a magnetic thin film that has a weight capacity of over 28 tonnes per square centimetre.
MTMS-uncoated cellulose aerogels are hydrophilic, thus they can also absorb and retain huge volumes of polar fluids such as water and alcohol. Therefore, the researchers said they can be used in products such as baby diapers and sanitary napkins.
In addition, compressed cellulose aerogels can be used to plug life-threatening wounds such as a gunshot or stabbing lesion by injecting them into the wound cavity. The sponges expand inside the cavity, creating pressure that can block bleeding and life-threatening haemorrhage in 20 seconds or less. This incredible speed is a remarkable boon, which could greatly enhance survival rates.
The team has filed a patent for their invention in USA, China, India and Southeast Asia.
The technology has been licensed by the NUS Industry Liaison Office, which is part of NUS Enterprise, to Bronxculture Pte Ltd in November 2015 for commercialisation.
Bronxculture intends to manufacture the cellulose aerogels and further expand its applications in three areas, namely, insulating materials for packaging boxes, insulating layer for winter garment and oil absorption materials.
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