Polyvinyl chloride (PVC) is one of the most produced plastics in the US and the third highest by volume in the world. However, producers and scientists have been struggling to recycle the material for decades. A new R&D project at University of Michigan brings hope.
PVC is pretty much all around us: in window frames, flooring, pipes and hospital equipment such as tubing and blood bags. And yet, in the US the material has a zero recycling rate. Now researchers Danielle Fagnani and Anne McNeil say they’ve found a way to chemically treat PVC despite its tricky plasticisers.
Their work at the University of Michigan aims to break down as many polymers as possible into their constituent parts to produce non-degraded materials that industry can incorporate back into production. Plastic is typically recycled by melting it down and reforming it. However, when heat is applied to PVC, toxic plasticisers leach out of the material very easily. ‘This contaminates everything in the recycling stream,’ the researchers say.
Another problem is that the hydrochloric acid contained in PVC can corrode recycling equipment and burn skin and eyes. On top of this, the phthalates are highly toxic endocrine disruptors that could interfere with thyroid and growth hormones and those involved with reproduction.
‘So we have to find a way to recycle PVC that does not require heat,’ Fagnani argues. Her team turned to electrochemistry, which introduces an electron into the system causing a negative charge. This breaks the carbon-chloride bond and yields a negatively charged chloride ion.
‘What we found is that this approach still releases hydrochloric acid but at a much slower, more controlled rate,’ she explains. The acid can later be used by industries as a reagent for other chemical reactions. Chloride ions can also be used to chlorinate arenes, small molecules which are frequently used in pharmaceutical and agricultural components.