The wearing and washing of textile/apparel products, made from synthetic fibers, are recognized as a major source for microplastic pollution in the environment. According to a report from the Changing Markets Foundation, synthetic fibers, such as polyester, nylon and acrylic - mainly used in fast fashion - account for about 69% of global textile production, and this is expected to increase to nearly 75% by 2030.  

General synthetic fabric usage, along with the friction/rubbing of fibers during laundering process, has been shown to shed microplastics. The resulting microplastics range from about 0.001 mm to 5 mm in size, as well as into smaller nanoplastics. This plastic waste pollutes the air, land, waterways worldwide. Professor Kevin Golovin and his team of researchers at the University of Toronto are developing a solution to reduce the shedding of microplastic fibers when textiles made of synthetic fibers are washed.

Golovin’s DREAM (Durable Repellent Engineered Advanced Materials) Lab has created a silicon-based coating that reduces friction in the laundering process and prevents the fibers from breaking off. “When we looked at what governments around the world were doing, it appeared there was no trend towards the prevention of microplastic fibers in the first place,” says Golovin. “Our research is pushing this in a different direction, where we actually solve the problem, rather than putting a ‘Band-Aid’ on the issue.”

The two-layer coating made of polydimethylsiloxane (PDMS) brushes, consists of a linear, single polymer chain grown from a substrate to form a nanoscale surface layer. This PDMS silicon-based material is known for its biocompatibility, and experiments conducted by the team have shown that its coating can significantly reduce microfiber shedding of nylon clothing after repeated laundering. The coating has been tested on both nylon and polyester fabrics. The results indicate that the shedding of the coated microplastic fabric was reduced up to as much as 96% compared to the uncoated fabric.

“The PDMS brushes are environmentally-friendly, because they are not derived from petroleum like many polymers used today,” notes Golovin. “With the addition of a primer, our coating is robust enough to remain on the garment and can continue to reduce microfiber shedding over time.”

Since PDMS is a naturally hydrophobic (water-repellent) material, the researchers are currently working on making the coating hydrophilic, so the coated fabrics will be better able to wick away sweat. The team has also expanded its research, looking beyond nylon fabrics, including polyester and synthetic-fabric blends.  “Many textiles are made from multiple fibers,” states Golovin. “We are currently working to formulate the correct polymer architecture, so that our coating can durably adhere to all of those fibers simultaneously.”

The silicon coating was only tested with machine washed fabrics, using tap water.  Subsequently, Amanuel Goliad, a leading researcher on the project wondered how the coating would work in hand-washing cycles.  Goliad whose family is from Ethiopia, knows handwashing is prevalent in much of the world, he noted, “Nearly two-thirds of the world does not have access to washing machines.”

To evaluate the effect of hand washing, a bamboo washboard-based method was used. To check any differences in the type of water used, both coated and uncoated polyester fabrics were handwashed in both deionized water and Lake Ontario water. After the fabric was washed, the wash-water with the microplastic fibers was analyzed. The deionized water that had almost all minerals and dissolved substances removed, showed no Total Dissolved Solids (TDS), while natural lake water had high TDS contents with minerals, tiny particles, and microscopic life mixed into it.  

These results indicated that the coated fabrics reduced shedding by 92% in the deionized water, but only by 37% in the Lake Ontario water. This illustrates how the coating’s efficacy declines, based on the type of wash- water used. Another surprising finding was that higher TDS levels result in shorter fiber lengths.

Goliad says, “That’s important because shorter fibers are harder to filter out in filtration systems. These fibers spread more quickly, and can be more easily ingested by aquatic life.”

Regarding the result of the supplemental research, Golovin states, “we now have a new hypothesis that dissolved minerals in hard water may break the fibers into smaller pieces.” Golovin indicates that his lab is researching a fabric coating that can better withstand being hand-washed in water with higher TDS. He adds, “I hope this work highlights the environmental impact of hand-washing and the need for more inclusive research.”