Engineers at the Massachusetts Institute of Technology (M.I.T.) may have solved a key issue discouraging apparel makers from working with polyethylene (PE), the material commonly used in plastic wrap and grocery bags.
Though thin, lightweight and cooler than most other materials, PE’s anti-wicking properties lock in water and sweat, effectively shutting the door on any hope of using the material as a wearable textile. A team at M.I.T., however, has developed a material that channels the cooling benefits of PE while also wicking away moisture faster than cotton, nylon and polyester.
The researchers published their findings Monday in the academic journal “Nature Sustainability” and are currently collaborating with companies like nearby New Balance to get the technology adopted on a large scale.
Despite the apparel industry’s sustainability-motivated move away from plastics, the research presents the new material as an environmentally friendly solution. According to Svetlana Boriskina, a research scientist in M.I.T.’s Department of Mechanical Engineering and an author on the study, the team tested the material using the Higg Index. The results, she said, show it created a “significantly lower” environmental footprint during the production phase when compared with other natural and synthetic materials.
Once produced, the material’s stain resistance and fast-drying functionality should contribute to a lower footprint during the use phase, Boriskina added. Furthermore, the fabric itself is designed to be fully recyclable at the end of its lifecycle.
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Though the researchers used virgin plastic for their research, the material could be made from recycled plastic bags and other PE products. This potential, Boriskina suggested, could incentivize recycling.
“PE is very low cost, which is the reason it is one of the most-produced plastics in the world, and the reason why it is not recycled on a large scale unfortunately,” Boriskina told Sourcing Journal. “Added-value products such as textiles and garments may help to address this challenge by making PE recycling economically viable.”
The manufacturing process opens up several other opportunities for environmental savings. The PE fabric relies on a dry-coloring process, “resulting in dramatic water savings.” PE has a lower melting temperature than other synthetic polymer materials, so less energy is required to heat it up. Synthesis of raw PE releases less greenhouse gas and waste heat than polyester or nylon.
The study also touts the PE material’s ultra-light weight, low material costs and high-performance properties. Unlike previously explored nanoporous PE materials, it noted, those created by the M.I.T. team were made from fibers melt, spun and woven on standard equipment used by the textile industry worldwide and do not require any chemical coatings.
Boriskina described the textile as having “a soft and silky handle.” Though a higher-strength material like high-density polyethylene would take away some softness, fiber texturing during fabrication can be used to modify this, she added. The fabric can be washed and dried—just not on the hot cycle—but owing to its stain resistance and fast-drying functionality, these cycles can be shortened for energy savings.
Shirley Meng, a materials scientist at the University of California at San Diego who was not involved in the research, said she found the design of experiments and the data to be “quite convincing.”
“Based on the data presented in the paper, the particular PE fabric reported here depicts superior properties than those of cotton,” Meng said. “The main point is that recycled PE can be used to make textile, a product with significant value. This is the missing piece of PE recycling and [the] circular economy.”
The M.I.T. team is currently looking into ways to incorporate PE fabrics into lightweight, passively cooling athletic apparel, military attire and next-generation spacesuits.
Boriskina said there are no obvious obstacles to a fast rollout of the material. While a student team at MIT is working to spin off a new startup to commercialize the technology later this year, she said the researchers are also collaborating with companies like Dow, New Balance and Braskem in an effort to get it adopted on a large scale.
Creating the fabric
The engineers began with PE in its raw powder form. Depending on the type of PE used, Boriskina noted, differences in tensile strength could be observed. For the purpose of their research, the researchers worked with one of the weakest forms of PE, linear low-density polyethylene. High-performance materials for specialized applications might require using specific types of virgin PE stock, either by itself or in blends, Boriskina said.
To manufacture their fabric, the engineers melted and extruded the PE powder into thin fibers. This process slightly oxidized the material, making it weakly hydrophilic. They then bunched multiple fibers together to make a weavable yarn that proved to possess wicking properties. After optimizing fiber arrangements and dimensions to accentuate these capabilities, the team tested the material against common textiles. Every time, it evaporated water faster.
The M.I.T. researchers noted that the PE material did lose some of its water-attracting ability with repeated wetting. But, by adding friction—rubbing it against itself, for example—or exposing it to ultraviolet light, they found they could induce it to become hydrophilic again.