When considering the material that may become the fabric of the future, scientists have largely abandoned a widely used option: polyethylene.

The material for plastic packaging and food bags, polyethylene is thin and light, which can keep you cooler than most textiles because it allows heat to pass through instead of trapping heat inside. But polyethylene also locks in water and sweat, because it cannot pump away and evaporate water. This anti-wicking property has been a major factor hindering the use of polyethylene as a wearable textile.

Now, engineers at the Massachusetts Institute of Technology spin polyethylene into fibers and yarns to absorb moisture. They woven the yarn into a silky, lightweight fabric that absorbs and evaporates water faster than ordinary textiles such as cotton, nylon, and polyester.

They also calculated the ecological footprint of polyethylene in the production and use of textiles. Contrary to most assumptions, they estimate that polyethylene fabrics may have less impact on the environment during their life cycle than cotton and nylon textiles.

Researchers hope that fabrics made of polyethylene can encourage the recycling of plastic bags and other polyethylene products into wearable textiles, thereby increasing the sustainability of the material.

“Once someone throws plastic bags into the sea, that’s a problem. But these bags are easy to recycle. If you can make polyethylene into sneakers or hoodies, it makes economic sense to pick up these bags and recycle them. ," said Svetlana Boriskina, a research scientist in the Department of Mechanical Engineering at MIT.

Boriskina and her colleagues published their findings in Nature Sustainability today.

Polyethylene molecules have a skeleton of carbon atoms, and each carbon atom is connected to a hydrogen atom. This simple structure, repeated many times, forms a structure similar to Teflon, which can resist the adhesion of water and other molecules.

"Everyone we interviewed said that polyethylene can keep you cool, but it does not absorb water and sweat, because it does not absorb water, therefore, it cannot be used as a textile," said Boryskinner.

Despite this, she and her colleagues tried to use polyethylene to make woven fibers. They start with polyethylene in raw powder form and use standard textile manufacturing equipment to melt and extrude the polyethylene into fine fibers, similar to making spaghetti. Surprisingly, they found that this extrusion process slightly oxidizes the material, changes the surface energy of the fiber, makes the polyethylene weakly hydrophilic, and can attract water molecules to its surface.

The team used a second standard extruder to gather multiple polyethylene fibers together to make a braidable yarn. They found that in a strand of yarn, the spaces between the fibers form capillaries. Once attracted to the fiber surface, water molecules can be passively absorbed through the capillaries.

In order to optimize this new wicking ability, the researchers modeled the characteristics of the fiber and found that fibers of a specific diameter are arranged in a specific direction throughout the yarn, which improves the wicking ability of the fiber.

Based on their model, the researchers made polyethylene yarn with more optimized fiber arrangement and size, and then used industrial looms to weave the yarn into a fabric. Then they tested the wicking ability of polyethylene fabrics on cotton, nylon and polyester by immersing the fabric strips in water and measuring the time required for liquid to wick or climb up each strip. They also placed each fabric on a scale on a drop of water and measured its weight over time as the water was absorbed by the fabric and evaporated.

In each test, polyethylene fabric absorbs and evaporates moisture faster than other ordinary textiles. The researchers did observe that polyethylene loses some water absorption capacity when it is repeatedly wetted, but by simply applying some friction or exposing it to ultraviolet light, they can induce the material to become hydrophilic again.

"You can renew the material by rubbing against itself so that it can maintain its wicking ability," Boriskina said. "It can continuously and passively pump away water."

The team also found a way to incorporate colors into polyethylene fabrics, which has been a challenge, again due to the material's resistance to binding with other molecules, including traditional inks and dyes. The researchers added colored particles to powdered polyethylene before extruding the material into fiber form. In this way, the particles are wrapped in the fibers, successfully imparting color to them.

"We don't need to immerse textiles in harsh chemical solutions to complete the traditional dyeing textile process," Boriskina said. "We can color the polyethylene fiber in a completely dry manner, and at the end of its life cycle, we can melt, centrifuge and recycle the pellets for reuse."

The researchers say that the team's dry coloring process helps polyethylene have a relatively small ecological footprint when used to make textiles. The team calculated this footprint using life cycle assessment tools commonly used in the textile industry. Taking into account the physical properties of polyethylene and the processes required to manufacture and dye fabrics, the researchers found that compared with polyester and cotton, the production of polyethylene textiles requires less energy.

"For example, polyethylene has a low melting temperature, so you don't have to heat it to make yarn like other synthetic polymer materials," Boriskina explains. "Compared with synthetic more traditional textile materials (such as polyester or nylon), the synthesis of virgin polyethylene also releases less greenhouse gases and waste heat. Cotton cultivation also requires a lot of land, fertilizer and water, and the use of harsh chemicals For processing, all of this comes with a huge ecological footprint."

She said that during the use phase, polyethylene fabric has a smaller impact on the environment because it requires less energy to clean and dry the material than cotton and other textiles.

"It won't get dirty because nothing sticks to it," Boriskina said. "You can wash polyethylene for 10 minutes in a cold cycle, and cotton for an hour in a hot cycle."

The team is exploring ways to incorporate polyethylene fabric into lightweight, passively cooled sportswear, military uniforms, and even next-generation spacesuits, because polyethylene can withstand harmful X-ray radiation in space.

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