How cool would it be to transform plastic bag waste into clothing, tackling two unsustainability issues in one? Until now, it wasn’t thought possible – largely because the plastic from which bags are made doesn’t absorb moisture and would trap in sweat.
But scientists, reporting in the journal Nature Sustainability, say they’ve worked out how to spin polyethylene (PE) – the most common form of plastic and easily recycled – into silky, light fabric that can absorb water and dry off more efficiently than existing textiles.
Not only could this help clean up the Earth’s plastic pollution, the researchers calculated that the plastic-derived fabric’s production and use is relatively gentle on the planet – another sorely needed innovation, given fashion uses around 62 million tonnes of fabric every year and is one of the top polluting industries.
“We engineered PE fibres, yarns and fabrics to achieve efficient water wicking and fast-drying performance,” write Matteo Alberghini from MIT, US, and colleagues, “which, combined with their excellent stain resistance, offer promise in reducing energy and water consumption as well as the environmental footprint of PE textiles in their use phase.”
Unwoven recycled plastic is currently used in shoes, lab outfits and protective clothing, among other things. Polyethylene terephthalate (PET), a harder plastic which is used in bottles, has been recycled into fleece for years, but researchers had yet to find a similar application for plain polyethylene. Exploring its potential, the team had previously showed that polyethylene’s infrared transparency lets body heat flow out, creating a cooling effect.
In the current study, the researchers melted down powdered polyethylene and squeezed it into thin fibres. Fortuitously, they found this process creates slight oxidation, causing the plastic to attract water molecules. Using the fibres to create yarn, they discovered the spaces between them formed ducts that then allowed the water molecules to be absorbed.
They then wove the yarn into fabric on regular equipment used globally by the textile industry, without the need for any chemical coating.
To finetune the process, they modelled the fibre’s properties and found that creating a certain diameter and weaving it in particular directions improved its water absorption properties.
Then, the team compared the plastic fabric with cotton, nylon and polyester by dipping each one in water, showing that it absorbed and evaporated the moisture faster than the others. The plastic did lose its water absorption capacity with repeated dips, but regained it with friction or ultraviolet light.
“You can refresh the material by rubbing it against itself, and that way it maintains its wicking ability,” says senior author Svetlana Boriskina. “It can continuously and passively pump away moisture.”
The researchers also worked out how to colour the fabric by adding dye while the plastic was in powder form – avoiding the current fashion industry need to soak it in chemical solutions that release vast amounts of toxic wastewater.
“We can colour polyethylene fibres in a completely dry fashion,” says Boriskina, “and at the end of their lifecycle, we could melt down, centrifuge and recover the particles to use again.”
Calculations based on sustainability indices such as the Higgs Index showed the fabric requires less energy to produce than polyester and cotton. This is because it has a lower melting temperature and releases less greenhouse gases and waste heat, and it doesn’t need the land, fertiliser and water used to grow cotton.
Confirming its stain resistance, the researchers showed it would also use less water to wash. “It doesn’t get dirty because nothing sticks to it,” explains Boriskina. “You could wash polyethylene on the cold cycle for 10 minutes, versus washing cotton on the hot cycle for an hour.”
The plastic – which doesn’t need to be combined with other textiles – could be used to make clothing accessories including buttons, hooks, zippers and labels, “enabling a single-material platform ideal for efficient automated recycling”.
The researchers now have their sights on creating high performance applications of the passively cooling fabric for athletes, farmers, military personnel and even astronauts to help shield space explorers against harmful radiations.