We just got a secret weapon that makes cotton the best for reusable face masks

While some are still struggling to wear masks for a year in an epidemic, scientists are ready to work out which strategy is best – and the cotton face mask has got another tick of approval.

Various studies have recommended combinations of different materials and cloth masks for the general public based on their findings by health officials such as the World Health Organization and the CDC. But some of these studies have overlooked one real-world factor – the cloth covering this face gets wet with our breath.

Now, a team of researchers has tested the mask material in high humidity conditions that mimics the air that comes out of our mouths.

U.S. “This new study shows that cotton fabrics actually perform better in masks than we thought,” said Christopher Zhangmister, a material scientist at the National Institute of Standards and Technology (GNIST).

Zangmister and colleagues have tested nine different types of cotton and six types of synthetic fibers, including polyester and rayon, with 99 percent moisture (how moist our breath is) and 55 percent moisture.

This resulted in a significant difference in the performance of cotton.

While synthetic fabrics, which also performed poorly compared to dry cotton, did not change performance under damp conditions, cotton fabrics Increased Their ability to capture particles by 33%.

The researchers used particles of different sizes of salt as a test alternative to virus-transporting dots and aerosol particles, and these water appeared to absorb some of the moisture trapped by the attracted cotton fibers. The particles swell in volume, making it difficult for them to pass through the blocked fabric.

Synthetic fibers, however, bring back water, thus not creating a humid environment inside the mask for this barrier to occur. The medical mask has not been modified either – but it is designed to work at a higher level in all situations (the equivalent of cotton).

According to the results, the best performing type of cotton was flannel.

Microscopic images of the material show quite a difference in structure – an orderly weave pattern in synthetic polyester compared to a chaotic network of crisscrossing fibers that make the flannel feel soft-touch.

NIST researchers believe that this disintegration of the fibers is such that the aerated particles passing through the mask will collide and stick to the fabric.

Cotton flannel (right), polyester (left).  (NIST)Cotton flannel (left), polyester (right). (EP Vicenzi / Smithsonian Museum / NIST)
However, this does not mean that wet masks are better: if your mask gets wet, it should be replaced. In this humid condition the amount of liquid in the mask is only a few drops, which does not change the breathing of the material – the team found that the air pressure on both sides of the fabric was relatively equal.

This is also great news from an environmental point of view. With the increase in waste from microplastics flowing disposable surgical masks, there is comfort in knowing that there is a safe, reusable option.

Research suggests that having a set of reusable masks that can be machine washed together is the most environmentally friendly option to keep you and your loved ones safe.

While the team says more research is needed to fully appreciate the interaction between masks, moisture and aerosol particle transmission, their study contributed to the first international standards for fabric masks, slowing the spread of COVID-19, recently released by the standards. Is for. -Developed organization ASTM International.

“In order to understand how these materials work in the real world, we need to study them in real-world situations,” he said.

This research was published ACS Applicable Nano Materials.