Durable PVC less likely to shed microplastics

PVC (polyvinyl chloride) plastics currently rank third among the most used plastics worldwide. Despite its widespread use, pure PVC is brittle and sensitive to heat, and manufacturers can only utilise it after stabilising its properties with other chemicals. 

However, these plasticisers are only a short-term fix for stabilising PVC. Over time, plasticisers leach from the plastics, which allows the material to deteriorate into potentially hazardous organics and microplastics.

Now, a team led by Christo Sevov, the principal investigator of the study and an associate professor in chemistry and biochemistry at The Ohio State University, found that using electricity to permanently attach those chemical additives can prevent such unwanted reactions. 

“Instead of mixing in those chemicals, our method involves chemically bonding the plasticiser compound directly to PVC by grafting them onto the backbone of the polymer,” Sevov said in a statement.

According to the University, altering PVC molecules in this way allows for them to become more durable and resistant to chemical changes, eventually leading to materials with more robust properties. 

“This is really one of the few examples that we have where there’s this much control over changing the properties of PVC,” said Sevov. “So this is the first step in controllably modifying PVC to give it properties you’re interested in, whether it’s hard, stretchy or soft.”

The team faced challenges during their work; synthetic polymer modifications often fail because the reactions were originally developed for small-molecule analogues, not big-molecule analogues such as pure PVC. To solve this, researchers optimised the catalyst they used in their process, and through trial and error, were able to overcome the issues that arise when editing big molecules. 

The study was recently published in the journal Chem. 

The team’s work has implications for the environment in that putting a cap on how quickly plastics degrade can help curb the release of microplastics.

Today, scientists know that these particles, which have been found to pollute the air, water and our food supply, are harmful to humans and wildlife. The average person likely ingests between 78,000 and 211,000 of these particles annually. 

As experts are beginning to understand the long-term impact microplastics, organic chemists are racing to find ways to phase them out of everyday life, said Sevov. 

“Many chemists are shifting their efforts to studying big molecules and developing new chemistries for upcycling, recycling and modifying well-known polymers,” he said. Trying to recycle PVC products can cause further degradation to the material due to the high temperatures it takes to convert plastic into something else, so the process is not very efficient. 

Sevov said that by using his method, there is potential to reuse the material many more times before it really begins to fall apart, improving its lifetime and reusability.