Breathability is back
A new fabric, AirCore, represents a step forward in breathable weather protection, Polartec says.
Fabric developer Polartec has launched a new, air-permeable, three-layer laminate fabric, calling the product AirCore. It has described it as a lightweight material with a high level of stretch, and a recycled face and back, with newly developed membrane technology in between. It is 100% free from per- and polyfluoroalkyl substances (PFAS).
The company says a combination of air permeability and its new proprietary, hydrophobic nano-fibre membrane can keep wearers dry while maintaining windproof and water-repellency functionality without PFAS-containing materials. Air comes through the fabric from the outside, returning moisture and air to the outside from the wearer’s body.
Business manager for Polartec and senior vice-president at parent group Milliken & Company, Ramesh Kesh, says traditional waterproof-breathable membranes rely on moisture vapour diffusion. This can only happen, he explains, if there is “a vapour pressure differential” between the outside environment and the microclimate that the wearer creates between a garment and the skin. In contrast, AirCore uses “highly engineered nanofibre membrane technology to control airflow”.
This component, Dr Kesh says, is “the main driver” of the solution it believes it has found, working with launch partner, cycling apparel brand Castelli. “As long as air can get in, it will pull out condensate that is accumulating,” he says, “and the wearer will have a better chance of staying dry than with anything else we have seen in the past.”
Brain behind the membrane
To produce the membrane, Polartec has put a hydrophobic polyurethane solution through electro-spinning at high voltage. It extrudes the solution through multiple spinnerets, resulting in stretch polymer nanofibres. It is these nano-fibres that form the membrane, with a pore structure that, the manufacturer insists, delivers better levels of air permeability than clothing brands have been able to achieve before, while maintaining, without PFAS-containing materials, water- repellency and windproofing properties.
“We have engineered a nanofibre-based membrane that can be precisely tuned for end-use performance,” Dr Kesh tells Sportstextiles. “By controlling more than a dozen process variables, we create a microporous scaffold that allows us to adjust fibre diameter, pore size, and other critical parameters to shape the balance of breathability, protection and durability.”
Polartec’s director of product management, Karen Beattie, explains the mechanism this way. The AirCore fabric makes possible “a continuous moisture vapour exchange”, harnessing airflow from the outside and allowing that air to come in through the fabric and return, carrying moisture, to the outside. The result is faster drying times, reduced clamminess and increased levels of comfort, even during peak exertion.
Polartec has calculated the fabric’s moisture vapour transmission rate (MVTR) at more than 25,000 grammes per square-metre per 24 hours. It has air permeability ranging from 0.4 to 1 cubic-feet per minute (CFM). It has an average water-column of 5,000 millimetres. “This represents a bold step forward in breathable, weather protection,” Karen Beattie adds, “and is a concrete example of our commitment to creating performance fabrics that enable excellence while staying true to our values of environmental stewardship. We are empowering people to embrace their most ambitious adventures.”
Cycling will never be the same again
Cycling presents an ideal example of this, not least because Italian brand Castelli is the inspiration and a launch partner for the fabric, having used it in a new jacket, the Perfetto RoS 3. RoS stands for ‘rain or shine’.
Head of cycling at Castelli’s parent company, MVC Group, Steve Smith, says he is excited about the new jacket precisely because it has this “huge innovation in technology”, AirCore, behind it. His view is that garments such as the new version of the Perfetto jacket will keep wearers “drier than ever when they are riding”. He goes further, claiming that performance cycling “will never be the same again”.
Mr Smith says the original idea came from Castelli, which led to Dr Kesh and him working on it together. “We sat round a table and dreamed up something that had never been done before,” he says. He explains that the impetus for this came from “a hard look” at what cyclists in the 2020s really need, following an industry-wide pledge to stop using PFAS.
Textile chemicals certification body Bluesign said no new chemicals containing PFAS could be included on its approved list from July 2022. By July 2023, it confirmed that it had removed all chemicals containing PFAS from the list. There were some exemptions, but these will lift in January 2026.
A different world
Steve Smith and his colleagues see a major change in the way cyclists are riding in cold and wet conditions these days, partly driven by technology, but also partly driven by climate change. It is, he suggests, a different world, even compared to a few years ago.
This is what he means: “How often are we riding in the rain? I could talk to 300 cyclists and count on the fingers of one hand the people who go out on their bikes, intentionally, when it is raining.” Reasons include the rise and rise of indoor training tools. These, Steve Smith says, have completely changed the game. He claims there are keen cyclists who stick to a static bike hooked up to a screen in a gym or in their homes even on days with good weather. This is because the quality of the technology that controls the detail of each session and captures detailed performance data is so good now.
Secondly, when we do venture out, smartphones make up-to-the minute weather information available to us at the touch of button. If you know when it is going to start raining, you can, and probably do, adjust the time and the length of your bike-ride to be all-but sure of staying rain-free.
In a similar vein, global-warming data (from NASA and other sources) suggests that, even in years with a similar total amount of rainfall, there are fewer rainy days. When it does rain, it rains more intensely, but there are more days without rain. This gives cyclists more dry days to choose from in deciding when to hit the road.
“Most cyclists are riding in the rain less often,” Mr Smith continues. “And when it does rain, cyclists usually reach for a rain shell-jacket. Those jackets can handle hard rain. Most of our rides, even in autumn, winter and spring conditions, are going to be in the dry.”
Breathability unleashed
This is significant. It led him to conclude that if an apparel brand and its fabric partners no longer have to “worry about water”, they must be free to see how far they can push breathability. And if they can push breathability further, they can, he suggests, keep cyclists drier on the inside, across a wider range of temperature and intensity levels. “Breathability has been constrained until now because we have been saying that we need to start with water protection,” he says, “and then add in a bit of breathability.”
Castelli’s idea, with the Perfetto RoS 3, was to turn these priorities around, to make an ideal jacket for dry conditions, pushing the breathability “off the charts”, and then see how much water protection it was possible to add.
Steve Smith admits that the Veneto-based brand lacks the capability to develop in house a fabric that would fulfil these requirements, but initial conversations about the idea with suppliers met only with “blank stares”, until its discussion with Polartec.
Plastic films and PFAS
The view of Ramesh Kesh is that the entire sports and outdoor sector had become used to using shell materials that were waterproof because of plastic films and PFAS. “You can make anything waterproof that way,” he says. Making fabric breathable as well is what he calls “the biggest challenge”, especially since the industry’s move away from PFAS.
AirCore’s non-PFAS-containing recycled face, back and nano-fibre membrane means the partners have ended up with a better product, Dr Kesh insists. He describes it as a technology that “takes advantage of the air”. Sticking with cycling as an example, he mentions the contrast between building up high levels of heat when a rider climbs a steep hill and the need for protection from the wind on the descent. The new fabric can achieve this without letting condensation accumulate between the body and the garment. Warm air next to the body holds more moisture than most people realise, he suggests. In high-aerobic activity, he says that for every one degree Celsius your body temperature rises, you accumulate 7% more moisture and that such a build-up of condensation can be “more uncomfortable than being in the rain”.
Picking up this point, Steve Smith says the key is that AirCore lets enough air come in to keep the wearer dry, but imperceptibly, so that the cyclist descending the hill will feel no wind chill. He describes this as “a small amount of air coming in, grabbing the moisture and taking it out”, and doing so before it forms a noticeable level of condensation. This mechanism can work like the demister in a car, removing moisture before it fogs up the windscreen.
Column conundrum
Mr Smith sees an average water-column of 5,000 millimetres as more than adequate. He knows that there was a push from some prominent players in the outdoor industry to present 10,000 millimetres as the minimum for being able to call a fabric or a garment waterproof. He thinks this was unnecessary. In fact, he thinks this insistence has done a disservice to the industry. “Normal rain falls at a pressure equivalent to a water column of 800 millimetres,” he says. “If the rain is heavy, it will fall at a pressure equivalent to 2,000 millimetres. This means 10,000 millimetres is way more than you need, and it comes at the expense of breathability.”
He is adamant that the Perfetto RoS 3 jacket has “an excellent level of water protection”. The shoulder seams are taped because Castelli’s experience of riding in the rain suggests to it that this is where a cyclist will feel the effect of driving rain. Seams at the side of the jacket and the back of the sleeve have no seal. The jacket is not made to stop every drop of rain from coming in, but to keep the rider as comfortable possible, he insists. Plus, a simpler construction has helped keep the level of stretch high.
Castelli will have exclusive access to AirCore for the cycling market and is already preparing a version of its Alpha 150 winter jacket that uses the fabric. Away from cycling, Polartec says there will certainly be applications in the wider outdoor apparel market. This comes as no surprise to Steve Smith. “With the stretch and breathability AirCore offers, you don’t feel like you are closed into a plastic shell,” he observes. “It is easy to imagine the fabric working well in running, ski-mountaineering, downhill skiing and even in hiking, unless you are hiking in an absolute downpour for hours on end. I can see this becoming our generation’s reference product for outdoor.”
Castelli claims AirCore fabric can help keep cyclists drier than ever.
Credit: Castelli/Polartec
