What is ePTFE? Why is it used in Airllo's masks?

Airllo’s proprietary technology, Spyderweb, is a Teflon®-based ePTFE (polytetrafluoroethylene) membrane that can capture particles up to 0.075 microns. The use of this membrane in Airllo masks takes mask-wearing to a new level; providing comfort, breathability, and protection, all in one. Airllo makes no compromises when it comes to the air we breathe. We created a mask that filters out 95% of bacteria and viruses. With Airllo, you can have peace in mind that you are well-protected with the world’s most breathable mask.

Meltblown masks and its short life

During the COVID-19 pandemic, N95s and surgical masks are a hot commodity. It is effective in filtering out respiratory droplets that contain viral particles. The effective filtration relies on the thin filter that is sandwiched between two outer layers of fabric. The medical-grade material effectively filters out 95% of microbes while allowing ample air to pass through.

The process to make the filter, the melt blown material, is called melt blown extrusion. The material is made of thousands of non-woven fibers, where each fiber is thinner than a strand of hair. In order to make this material, fine white plastic fibers made of a polypropylene polymer are fed through thousands of tiny precision-formed holes. Hot air is blown at the fibers so that they fuse and form a material so tightly packed that only air can pass between the fibers and 95% of microbes can’t get through.

Additionally, melt blown fabrics are electrostatically charged, which enhances filtration efficiency without increasing air flow resistance. The electrostatic force traps airborne particles by relying on the charges of the particle and mask fibers. The electrostatic charges will attract and bind particles to the fibers. 

Since meltblown masks rely on the charges for effective filtration, the charge must be maintained. However, electrostatic charges deteriorate once it comes in contact with humidity and moisture. When you talk into your mask, the filtration of your mask is steadily declining and needs to be replaced with a new one. The loss in filtration efficiency is a problem, thus new materials, such as PTFE, are being used as a material for masks.

What is PTFE, aka Teflon®?

Polytetrafluoroethylene or PTFE is a synthetic fluoropolymer, and is known for its trademark name Teflon®. It is a polymer, a material that is made of many repeating subunits to form a large molecule. Specifically, PTFE is made up of carbon and fluorine atoms, where the fluorine atoms fully surround the carbon atoms. This characteristic makes PTFE very stable. Thus, giving it extraordinary resistance to many different conditions including, but not limited to temperature, chemicals, and UV radiation.

PTFE was accidentally discovered by Dr. Roy Plunkett, a chemist working at Dupont. Originally, he was attempting to make a refrigerant from tetrafluoroethylene. He left the batch of tetrafluoroethylene overnight, and the next morning he found that a white solid had formed. 

Dr. Plunkett, being a curious scientist, tested the material and found that this white solid was impenetrable to corrosive acids and impervious to extremely high or low temperatures. These durable characteristics make it an extremely sturdy material. It could endure temperatures ranging from -260 to 260°C. PTFE is also resistant to disinfectants such as 70% ethanol. Thus, PTFE can be disinfected by 70% ethanol while sustaining its durability.

Another unique property is the low friction coefficient. A material with a low friction coefficient will be more slippery than a material with a high friction coefficient. An object on a smooth surface (lower friction coefficient) will be more slippery than an object on rough surfaces (higher friction coefficient). This makes PTFE resistant to binding with other objects since they merely “slip off.”

PTFE’s inactivity and inertness make it a great coating for non-stick pans. Not only was it extensively used in cookware, but PTFE is also found in many different applications in different industries such as medical, aerospace, communications, electronics, industrial processes, etc.

What is the difference between PTFE and expanded PTFE?

Bill Gore experimented with PTFE to see if there were more applications for it. Through experimentation, he stretched and expanded a PTFE rod to incorporate air. One of his final experiments created a sheet of expanded PTFE that consists of 70% air. The resulting material was light weight, strong, cheap and highly porous. 

Expanded PTFE (ePTFE) is a porous membrane that is stretched into a thin sheet. It shares many of the same properties as PTFE. An advantage that ePTFE has over PTFE is its ability to maintain strength even under pressure, having a high strength-to-weight ratio. Airllo has demonstrated this characteristic with its own proprietary ePTFE film. When the film is placed over a coffee cup and water is poured onto it, it can withstand the weight of water without breaking. Additionally, the material is hydrophobic, so the material itself is naturally water repellent.

Smoke cannot pass through an ePTFE membrane

Another valuable characteristic of ePTFE’s is its tiny pores allow gases (including oxygen and carbon dioxide) and water vapor to pass through. However, it does not permit liquids, such as sneeze droplets, to pass through. The tiny pores enhance breathability, yet it is extremely effective in capturing the tiniest particles. When vapor is blown into a cone sealed with Airllo’s ePTFE membrane, the vapor does not escape the membrane, as seen in the above GIF. In the same way, Airllo’s mask will stop droplets from passing through the mask which prevents it from coming into contact with the user.

Why is it used in Airllo’s masks?

The unique characteristics of ePTFE makes it an extremely suitable material to be used in masks. The stability and inertness of ePTFE means that physical forces (extreme temperatures)and chemical forces (70% ethanol) cannot affect it. The low friction coefficient prevents other objects from attaching or penetrating the material, as objects just “slip off”. Additionally, ePTFE has a high strength-to-weight ratio but has enough pores throughout the membrane, resulting in a sturdy yet breathable membrane suitable for use in masks. 

Airllo’s proprietary technology can create tinier pores than the industry standard, enhancing the breathability yet maintaining its air filtration efficiency. Airllo’s proprietary technology can make ePTFE as thin as 0.0003mm. This creates billions of tiny pores to physically block out harmful particles without the extra stuffiness of wearing an extremely protective mask.

At the end of the day, Airllo can be disinfected or washed, a unique characteristic of ePTFE that other mask materials do not have. Once clean, it could be reused for up to 100 hours with the same efficiency of capturing tiny particles in the air. This drastically reduces the waste entering the environment. Environmental stewardship doesn’t mean compromise to your comfort and safety!