When clothes made from synthetic fabrics, such as nylon, polyester, acrylic and rayon, are cleaned in washing machines, the friction caused by cleaning cycles produces tiny tears in the fabric. These tears cause microplastic fibres measuring less than 500 micrometres in length to break off and make their way to waterways.
Once microplastics end up in oceans and freshwater lakes and rivers, the particles are difficult to remove and will take decades or more to fully break down. The accumulation of this debris in bodies of water can threaten marine life and also become part of the human food chain through its presence in food and tap water.
Governments have been looking for ways to minimise the pollution that comes from washing synthetic fabrics and washing machine filters are emerging as a solution. In Ontario, a bill has been introduced a bill that would require filters in new washing machines in the province.
“And yet, when we look at what governments around the world are doing, there is no trend towards preventing the creation of microplastic fibres in the first place,” said research lead Professor Kevin Golovin.
Golovin and his team have created a two-layer coating made of polydimethylsiloxane (PDMS) brushes, which are linear, single polymer chains grown from a substrate to form a nanoscale surface layer.
Experiments showed that this coating can reduce microfibre shedding of nylon clothing after repeated laundering, and the team’s findings have been published in Nature Sustainability.
“My lab has been working with this coating on other surfaces, including glass and metals, for a few years now,” Golovin said in a statement. “One of the properties we have observed is that it is quite slippery, meaning it has very low friction.”
Textile engineer Dr Sudip Kumar Lahiri, a postdoctoral researcher in Golovin’s lab and lead author of the study, surmised that if they could reduce the friction that occurs during wash cycles with a PDMS-based fabric finish, then that could stop fibres from rubbing together and breaking off during laundering.
To make sure the PDMS brushes stayed on the fabric, Lahiri, developed a molecular primer based on his understanding of fabric dyes.
Lahiri rationalised that the type of bonding responsible for keeping dyed apparel colourful after repeated washes could work for the PDMS coating.
Neither the primer nor the PDMS brushes work separately to decrease the microplastic-fibre shedding, but together they created a finish that reduced the release of microfibres by over 90 per cent after nine washes.
Since PDMS is a hydrophobic material, the researchers are currently working on making the coating hydrophilic, so that coated fabrics will be better able to wick away sweat. The team has also expanded the research to look beyond nylon fabrics, including polyester and synthetic-fabric blends.
“Many textiles are made of multiple types of fibres,” said Golovin. “We are working to formulate the correct polymer architecture so that our coating can durably adhere to all of those fibres simultaneously.”
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