Polymer discovery brings new hope for plastics recycling

United States – Although only 2% of the world’€™s 78 million tonnes of manufactured plastics are recycled into a similar product, a new polymer created by US researchers could reshuffle the cards for plastics recycling. Their breakthrough is a ‘multiblock polymer’ that, when added in small measure to a mix of two otherwise incompatible materials such as polyethylene (PE) and polypropylene (PP), creates ‘a new and mechanically-tough polymer’.

A long-standing problem for plastics recyclers is that PE and PP, which make up two-thirds of the world’s plastics, have different chemical structures and thus cannot be repurposed together, notes Tisch University’s Professor of Chemistry and Chemical Biology, Geoffrey Coates.

He addressed the issue jointly with the University of Minnesota. The researchers added a miniscule amount of their tetrablock (four-block) polymer – with alternating PE and PP segments – to yield a material with a strength superior to the diblock (two-block) polymers previously tested. Two strips of plastic film were welded together using different multi-block polymers as adhesives, and then mechanically pulled apart.

‘While the welds made with diblock polymers failed relatively quickly, the weld made of the new tetrablock additive held so well that the plastic strips broke instead,’ the researchers report.

‘What’s exciting about this is we can go to as low as 1% of our additive, and you get a plastic alloy that really has super-great properties,’ Coates comments.

This polymer discovery ‘shows promise for improving recycling’ and could create a whole new class of ‘mechanically tough’ polymer blends, he adds.