Plastic fantastic: UV recycling

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  • Published: Dec 1, 2014
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
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Naturally degradable

Researchers at North Dakota State University, Fargo, have developed a process using biomass to create plastic which can be broken down by exposing it to ultraviolet light at 350 nanometers for three hours. L-R Angel Ugrinov, staff scientist in the Department of Chemistry and Biochemistry at NDSU, graduate student Ramya Raghunathan, and Retheesh Krishnan, postdoctoral fellow.

A new type of degradable polymer made from a fructose-derived monomer can be broken down when exposed to ultraviolet light and release material that can be recycled into new polymer, according to US researchers.

We live in the plastic age and don't we know it, with a plastic bag in almost every tree, landfills stuffed to the brim and our oceans and beaches awash with the polymeric flotsam and jetsam. Polymers, are of course, also an essential part of our daily lives from hygienic food and pharmaceutical packaging to medical devices, the components of the device on which you are reading this article to the padding in your office chair and myriad other applications.

There are laws in place to help us to recycle plastics and there are biodegradable forms that have none of the thousand-year longevity of most polymers. However, there is a pressing need for a way to combine the concept of degradability with a simpler and more straightforward way to recycle. Now, researchers at North Dakota State University, in Fargo, USA, believe their approach holds the key to avoiding waste and opening up plastics recycling.

FDCA to PET

Writing in the journal Angewandte Chemie, the team offers a proof of principle experiment developed at NDSU's Center for Sustainable Materials Science. The Center brings together chemists Mukund Sibi, Jayaraman Sivaguru, Saravana Rajendran, Ramya Raghunathan, Retheesh Krishnan, Angel Ugrinov, Dean Webster and Ivan Hevus. The researchers' broad focus is on biomass research, using oilseed from agricultural crops, cellulose, lignin and fructose to generate the building blocks of molecules that can then be polymerised. Biomass, of course, offers the modern panacea of a renewable, and so sustainable chemistry and a release from the grip of petrochemicals as industrial feedstock and fuel. "Real sustainability involves breaking it back into the building blocks," explains Sibi. "We have shown that we can break it down into the building blocks and re-make the polymer."

In the demonstration, the team converts the fruit sugar fructose, which can be obtained from biomass and other plant sources, into 2,5-furandicarboxylic acid (FDCA), which can then be polymerised. FDCA is listed among the top fourteen bio-based chemicals by the US Department of Energy, the team reports. It is possible that FDCA might be used as a replacement for the conventional monomer starting material terephthalic acid used to make in polyethylene terephthalate (PET), a widely used polyester. Indeed, the FDCA-glycol polymer has properties not dissimilar to PET. Importantly, however, when the fructose-derived polymer is exposed to 350 nanometre ultraviolet light for three hours it breaks down into the soluble building blocks from whence it came; these can then be processed further.

Rocking the cradle

"This cradle-to-cradle approach to create a plastic which can be degraded easily offers scientific potential for eventual products that could lessen dependence on fossil fuels and decrease the amount of raw materials needed," explains Webster. "Our strategy has the potential to build novel materials from biomass that are degradable with light after usage, mitigating the stress of unwanted chemicals in our environment. Studies to address these aspects are currently underway in our laboratories," adds Sivaguru. Before such materials might be commercialised there is plenty of evaluation still needed to test the durability and strength of potential bio-plastics. As such, the team will spend the next two years examining different starting materials, their conversion into monomers and the polymers they can generate with a specific focus on the plastics used in cars, electronics and other items.

Related Links

Angew Chem Int Edn, 2014, online: "Programmed Photodegradation of Polymeric/Oligomeric Materials Derived from Renewable Bioresources"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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