AsianScientist (May. 6, 2020) – Having discovered a way to turn waste rubber into aerogels, researchers at the National University of Singapore have found a potential solution to the issue of scrap tires, one billion of which are generated every year. Their findings have been published in Colloids and Surfaces A: Physicochemical and Engineering Aspects.
Highly durable and non-biodegradable by design, spent rubber tires make for challenging waste disposal. Only 40 percent are recycled into low-value-added products, while 49 percent are incinerated to generate energy and the rest end up in landfills. Burning rubber produces toxic substances, which can also leak out of tires buried in landfills.
“The rate of tire recycling worldwide remains low because processing used rubber is costly and energy-intensive, coupled with a lack of monetary incentive. By converting waste rubber tires into high-value aerogels, we could enhance the monetary incentive for recycling rubber and in turn, cut down rubber waste,” explained study corresponding author Associate Professor Duong Hai-Minh.
To create the rubber aerogels, recycled car tire fibers are first blended into finer fibers. These fine rubber fibers are then soaked in water and very small amount of chemical cross-linkers. Next, the mixture of rubber fibers and eco-friendly solvents is dispersed uniformly using a stirrer for 20 minutes. The uniform suspension gel is then freeze-dried at minus 50 degrees Celsius for up to 12 hours to produce rubber aerogels.
“The fabrication process is simple, cost-effective and eco-friendly. The entire production process takes between 12 to 13 hours to complete and it only cost less than S$10 (US$7) to produce a sheet of rubber aerogel that is 1 sqm in size and 1cm thick,” Duong said. “The process can also be easily scaled up for mass production. This makes rubber aerogels a commercially attractive product.”
In addition to reducing rubber waste, the resulting aerogels can be put to use for environmental purposes. Since they are twice as absorbent as conventional absorbents such as polypropylene mat, they could be used to absorb oil spills. Unlike most other aerogels which tend to be fragile and brittle, the rubber aerogels can spring back to their original shape after being compressed, making them useful as insulators in industry and domestic settings.
“The potential markets of aerogels are huge. For example, vehicle noise and thermal comfort are vital in vehicle designs—the global automotive heat and sound insulation solution markets are expected to reach US$3.2 billion by 2022. In addition, the global oil spill management market is expected to reach US$182.7 billion by 2025,” added Professor Nhan Phan-Thien, who is a senior member in the research team.
The team, which received a donation of S$155,000 (~US$100,000) from Mapletree Investments to boost their research efforts, plan to commercialize and scale up their technology, conducting further studies to enhance the performance of the rubber aerogels and explore new applications.
The article can be found at: Thai et al. (2019) Advanced Fabrication and Multi-properties of Rubber Aerogels From Car Tire Waste.
Source: National University of Singapore; Photo: Unsplash.
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