Researchers at the University of Toronto have developed a way to help reduce one of the biggest sources of the plastic pollution choking our oceans: not single-use straws or bags, but tiny fibres shed from synthetic fabrics like polyester and nylon.
When clothing made from these fabrics is washed, the friction causes tiny tears that release fibres less than 500 micrometres long, which end up in local waterways and eventually the ocean. The plastic threatens marine life, and can even make its way through the food chain into humans. Filters on washing machines can help, but a better solution is to prevent the production of the microfibres in the first place.
Kevin Golovin, a mechanical engineer at the University of Toronto, and his team were originally working on replacements for “forever chemicals” such as PFOAs used for waterproofing clothes. They noticed that some of the substances they were studying had a very low coefficient of friction, so Golovin wondered if they might help with reducing microfibres.
The most promising were polydimethylsiloxane (PDMS) brushes – tiny, single polymer chains that stand up from a surface like bristles on a brush. This environmentally friendly organic silicon compound is used as a food additive to keep oils from foaming, and in shampoo to make hair shiny and slippery. If applied to a fabric, the slippery layer could prevent the fibres from abrading as they rub against each other in the wash.
The problem was that the PDMS brushes would not stay on the fabric, it came off in the wash. So Golovin’s colleague Sudip Kumar Lahiri developed a primer based on fabric dyes that could bind them to the cloth. They tested the combination on woven nylon fabrics like those used in waterproof jackets, and found it did a good job of cutting the production of microplastic fibres.
“When both layers are applied to fabric there is a 93% reduction in microfibres, even after multiple washes,” says Golovin.
Anil Kumar, who spent 12 years in the textile industry before studying microfibre pollution at the University of Alberta, says the coating could be a useful way of reducing microfibre shedding, if it can be commercialized. But there are hurdles to overcome before that will be feasible, he says.
First, the tests were done only on nylon fabrics, which are a small part of the problem when it comes to microfibres. Nylon accounts for just 10 per cent of synthetic fabric production, compared with 50-60 per cent for polyester, and it produces fewer microfibres. “Nylon’s contribution to the problem is much less than polyester,” says Kumar.
Second, the process of applying the coating, which involves plasma treatment for the primer, and vapour deposition of the PDMS brushes, is probably too complicated and expensive for most manufacturers. “When making a fabric, adding so many steps and specialised machines adds to the cost,” he says. “And cost is a very big factor in the industry.”
Heather Elliot, product integrity manager for the textile company Smartwool, says the coating looks promising, but points out it was only tested on hydrophobic nylon fabrics. She would want to see how it works on sweat-wicking hydrophilic polyesters, such as those used in workout clothing. “People wash their workout tops more than their jackets,” she says.
Golovin acknowledges these shortcomings, but expects his team will be able to overcome them soon. They are already working on new primers with different chemical compositions that can bind to polyester fabrics, and even blends of two different fabrics. “It’s not overly complicated, people have been making new things for fabrics for years,” he says. “It’s a fun engineering challenge.”
They are also working on developing a new application process that is more user-friendly for textile mills, and hope to have pilot trials underway later this year. “Then there will be very little stopping it from being scalable and commercially available,” he says.