Spain/USA: Chemical Recycling Researchers Develop Fully Recyclable Class of Plastics

Researchers at the UPV/EHU-University of the Basque Country and Colorado State University (USA) have developed a new class of biorenewable, biodegradable plastics. The scientists claim that their plastics are an improvement on existing ones and would promote the circular economy.

Bilbao/Spain; Fort Collins/USA — Plastics have become indispensable items in our everyday lives. But their growing production and use are threatening to pollute the entire planet, in particular the oceans, the final destination for tonnes and tonnes of plastic, a material that may take centuries to disappear. The researchers Haritz Sardón, Ainara Sangroniz and Agustin Etxeberria at the UPV/EHU’s Faculty of Chemistry, together with the researchers Eugene Y.-X. Chen, Jian-Bo Zhu and Xiaoyan Tang at Colorado State University (USA), have designed fully recyclable packaging materials that, according to the scientists, promote the circular economy for plastic packaging materials where design and production fully comply with requirements pertaining to reuse, repair and recycling. Their study has been published recently in Nature Communications and constitutes a step forward in solving the problem of plastic.

The lack of suitable recycling systems plus their non-degradable nature have led to the build-up of plastic in the environment. In the quest to solve this problem, biodegradable materials have aroused great interest. In the right conditions these polymers degrade to form carbon dioxide, water, biomass, etc. According to researcher Haritz Sardón, Poly(lactic acid) is among the most promising biodegradable polymers. Yet its high rigidity plus its low barrier character would mean that this material is inadequate for replacing commercial materials, he explained.

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That accounted for the recent growth in the importance of chemical recycling. Once materials of this type reached the end of their useful service life, the UPV/EHU researcher went on, they could be recycled chemically and the original monomer or new monomers could be obtained. The monomer can be re-used to synthesise the material again.

This work explores two chemically recyclable homopolymers: poly(gamma-butyrolactone), which displays suitable mechanical properties, but high permeability to various gases and vapours. By contrast, poly(trans-hexahydrophthalide) displays the opposite properties: it is very rigid and has low permeability. So the researchers opted to develop copolymers by combining both compounds/monomers. By varying their composition it was possible to synthesise materials with suitable mechanical and barrier properties that are better than biodegradable polymers and similar to commercial materials currently used in packaging.

Reference: A. Sangroniz, J.-B. Zhu, X. Tang, A. Etxeberria, E.Y.-X. Chen, H. Sardon: Packaging materials with desired mechanical and barrier properties and full chemical recyclability; Nature Communications, 2019, 10, 3559; DOI: 10.1038/s41467-019-11525-x

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