For outdoor enthusiasts, having the right clothing is essential to maintain thermal comfort outdoors, especially in a wet, windy and cold environment. Water resistance is a fundamental function of any outdoor or sportswear garment to ensure the body stays dry.

For a person to feel comfortable in outdoor environments, it is vital that the energy produced and exchanged with the environment is evenly balanced. The human body must maintain its core body temperature of 37°C, to ensure the body feels comfortable and maintains well-being. The body maintains a comfortable temperature during different levels of exertion and environmental conditions, through changes in blood flow and evaporation of perspiration from the skin’s surface as it naturally tries to cool itself down [1]. However, as the body has a limited ability to cope with the outdoor climate, functional materials are selected and engineered for use in outdoor apparel to provide comfort and protection from otherwise uncomfortable environments.

Clothing designed to keep a wearer dry is typically made from either permeable (breathable) or impermeable (non-breathable) textile materials. Impermeable water-resistant materials are notorious for being excellent at blocking water molecules from entering through the membrane. However, it is this same mechanism that often makes these materials uncomfortable to the wearer. This is because excellent resistance to water molecules from the outside environment means that water vapour molecules produced from the body’s perspiration cannot escape from inside the microclimate between the skin and the clothing. Therefore, because perspiration can’t escape, wearing impermeable waterproof textiles commonly causes the wearer to become stuffy and wet with sweat, and subsequently can cause the wearer to experience cold chills.

Permeable textiles, also referred to as waterproof-breathable membranes, prevent liquid water permeating the material. However, they allow water vapour and sometimes air to pass through, maximising comfort and dryness during outdoor activities [2].

Breathability in outdoor garments is extremely important to prevent the wearer overheating, as well as for keeping both the wearer comfortable and the textile fresh by avoiding the build-up of lingering odour. Therefore, a breathable protective garment will aid to enhance sports performance by enabling the athlete to pursue outdoor physical activity of any intensity, while remaining comfortable and protected [2].

Moreover, achieving water resistance in textiles has often resulted in the use of perfluorinated chemicals (PFCs) due to their superior water, oil and soil repellent abilities. PFASs – polyfluoroalkyl substances – are also used as this group of chemicals is closely related to PFCs, with both containing fluorine and carbon atoms. However, despite their great repellent properties, both PFCs and PFASs are part of the DWR discussion that refers to concerning compounds, and they have been the subjects of severe criticism in recent years. Specifically, longer chain PFC materials, depending on their functional groups, can be very hazardous due to their harmful by-products; although it is generally understood that not all PFCs/PFASs are hazardous [3].

PFCs and PFASs can be both environmentally and physiologically hazardous. They are highly persistent molecules in nature, meaning that some of them will degrade extremely slowly or not at all, and many are also bioaccumulating. However, ironically, those who treasure the environment often wear garments that are damaging it. The majority of breathable outdoor outerwear is created with PFASs because they are extremely good at providing water and oil repellence. And although there are still no obvious alternatives to PFAS membranes for deterring oil, developments are being made for fending off water.

In this innovation profile, WTiN reports on a textile material discovered by researchers from Aalto University School of Chemical Engineering, Finland, who have developed a non-toxic, water-resistant and breathable coating solution with wax obtained from Brazilian palm tree leaves [4].

Additionally, WTiN compares the research outcome from Aalto University with a commercially available PFC and PFAS-free, water-resistant and breathable membrane technology from the company Dimpora. Dr Mario Stucki, CEO and co-founder of Dimpora, talks to Laura Solomon about the technology used within the company’s environmentally-friendly membranes for outdoor clothing.