Researchers from the University of Birmingham, U.K., and Duke University, U.S., have developed recyclable plastics based on sugars. Thus created a new family of polymers from sustainable sources that retain all of the same qualities as common plastics. But are also degradable and mechanically recyclable.
The scientists used sugar-based starting materials rather than petrochemical derivatives to make two new polymers. One which is stretchable like rubber and another which is tough but ductile, like most commercial plastics.
The researchers made the new polymers using isoidide and isomannide as building blocks. Both these compounds have made from sugar alcohols and feature a rigid ring of atoms. The researchers found that the isoidide-based polymer, showed a stiffness and malleability similar to common plastics. And a strength that is similar to high grade engineering plastics such as Nylon-6. Despite isoidide and isomannide only differing by the 3D spatial orientation of two bonds, known as stereochemistry. The isomannide-based material had similar strength and toughness but also showed high elasticity, recovering its shape after deformation. Notably, the materials retained their excellent mechanical properties following pulverisation and thermal processing, which is the usual method for mechanically recycling plastics.
What are sugar alcohols?
Contrary to their name, they do not belong to either sugar in the traditional nor or alcohol. Sugar alcohols are polyhydric alcohols formed from the reduction of carbohydrates, – the process which oxygen is removed from a compound. They are also found in nature, but can also be produced artificially.
Cutting edge computational modelling simulated how the polymer chains pack and interact to produce such different polymer properties. The unique 3D shapes of the sugar derivatives facilitate different movements and interaction of the long chains. Causing the huge difference in physical properties that has observed.
By creating copolymers that contain both isoidide and isomannide units, the researchers found that they could control the mechanical properties and degradation rates independently of one another. Hence, this system opens the door to using the unique shapes of sugars to independently tune the degradability for a specific use. Without significantly altering the properties of the material.
The chemical similarity of the polymers of recyclable plastics based on sugars means that, unlike a lot of current commodity plastics, they can blended together to yield materials with comparable or improved properties.
Professor Andrew Dove, who led the research team from Birmingham, noted. “This study really shows what is possible with sustainable plastics. While we need to do more work to reduce costs and study the potential environmental impact of these materials. In the long term it is possible that these sorts of materials could replace petrochemically-sourced plastics. That don’t readily degrade in the environment”.
A joint patent application has been filed by University of Birmingham Enterprise and Duke University. The researchers are now looking for industrial partners who have interested in licensing the technology.
(source: University of Birmingham)
