Chemical route a game-changer for mixed textiles

A new chemical recycling technology breaks down polyester and spandex into useful monomers while preserving cotton and nylon. It is thought the solution could be used to recycle up to 88% of textiles.

An estimated 100 billion items of clothing are sold annually, contributing to 92 million tonnes of textile waste each year, largely due to fast fashion. Less than 1% of this waste is currently recycled, with most ending up in landfills or incinerated.

Separating different fabrics requires significant labour and logistics, for relatively low gain, observes researcher Erha Andini from the US University of Delaware.

Microwaving mixed textiles

Andini led an R&D team to develop a simple, fast chemical recycling method for mixed textiles. The technique uses microwave-assisted glycolysis with a zinc oxide catalyst to separate polyester, cotton, nylon and spandex.

First, the team applied the catalytic conditions to pure polyester and cotton. Polyester degraded into monomers, with 90% yielding bis-2-hydroxyethyl terephthalate (BHET), a valuable component for yarns and resins. Cotton retained its integrity, experiencing only an 8% mass loss.

Testing on 50:50 polyester-cotton T-shirts showed that higher temperatures accelerated polyester breakdown, achieving complete depolymerisation at 210°C in less than 15 minutes.

Real-world application

The team then tested the process on textiles with various dyes and finishes. These additives reduced BHET yield, indicating that impurities can hinder the catalyst’s activity.

For blends of 90% nylon and 10% spandex, the nylon remained intact while the spandex broke down into useful monomers like 4,4′-methylenedianiline used in polyurethane foam and fibre glass plastics.

In mixtures containing polyester, cotton, spandex, and nylon, the method successfully depolymerised polyester and spandex while keeping cotton and nylon intact.

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