Starting with sugars, researchers have made sustainable plastics that perform as well, or even better, than commonly available plastics, and also degradable and easy to recycle. Plus, unlike other recyclable plastics, their mechanical properties don’t worsen after being reprocessed.
The researchers made two types of materials: one that is stretchy like rubber, and another that is tough but pliable like many plastics used in everyday life. Their work appears in the Journal of the American Chemical Society.
As the problem of plastic pollution worsens, researchers are doubling down on efforts to make sustainable plastics from non-petroleum sources. Biodegradable plastics made from renewable plant sources like corn or sugarcane starch are already on the market and becoming a popular alternative to petroleum plastics. But their biodegradability can be questionable—they typically biodegrade only in industrial compost facilities—and they need to be recycled separately from other plastics.
The mechanical properties of known sustainable plastics also don’t match those of commercially available plastics, says Matthew Becker, a chemistry professor at Duke University, who led the new work with University of Birmingham, UK chemistry professor Andrew Dove. “Many others have used sugar and sustainably sourced feedstocks to synthesize materials,” he says. “However, the properties are often poor and therefore not useful in commercial application.”
Becker, Dove, and their colleagues made two different organic compounds from sugar alcohols, and used them as the building blocks for their plastics. The two compounds contain ring-like structures made of the same atoms, but their properties differ based on how the atoms are arranged relative to each other in three-dimensional space.
Plastic made from one of the compounds is as stiff yet malleable as common plastics, and about as strong as high-tech plastics such as Nylon-6. The other compound gives plastics that are just as strong but also has elastic properties that are better than known rubbers.
Both materials maintained these properties after they were heated and reformed using the typical commercial recycling process for plastics. Preliminary tests in the lab also showed that the new plastics should be able to degrade, albeit slowly, if they were released into the environment.
“The mechanical and degradation properties exhibited by the materials are tunable, which will be important to many of the applications we are targeting,” Becker says. “These materials could be applied to a number of replacement applications including food packaging.”
Source: Connor J. Stubbs et al. Sugar-Based Polymers with Stereochemistry-Dependent Degradability and Mechanical Properties. Journal of the American Chemical Society, 2022.
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