What we think of as polyester fabric is most often actually a blend of polyester and cotton, which has proven very difficult to recycle. A new solvent, however, breaks the blend down into its two components, leaving both almost completely reusable.
Made up of menthol and benzoic acid, the solution was developed by PhD student Nika Depope, Dr. Andreas Bartl and colleagues at the Vienna University of Technology.
Although both substances are solid at room temperature, they take on a "deep eutectic solvent" form when heated to a temperature of 216 ºC (421 ºF). When polycotton (polyester/cotton blend) textiles are immersed in that liquid, it causes the polyester to dissolve and separate from the cotton fibers within just five minutes.
The cotton isn't harmed by the process, and can subsequently be washed, dried and reused. The polyester precipitates from the solvent upon cooling, and can likewise be reused. In tests conducted so far, it has been possible to recover up to 100% of the cotton and 97% of the polyester.
"The truly remarkable thing about this new process is that neither the cotton nor the polyester is damaged or chemically altered," says Bartl. "Our analyses show that the cotton fibers remain stable and retain their typical properties – they can even be spun into new yarns again. And the polyester also remains unchanged: its structure and melting temperature are the same as before."
The scientists are now working on making the process more energy-efficient, by reducing the required heating temperature.
A paper on the research was recently published in the journal Waste Management.
Source: Vienna University of Technology
