Woven soft shell fabrics such as microfiber polyester and ultralight ripstop nylons suffer from poor DWR finishes that make their utility in the rain very limited. Perseverance Mills of the UK addresses this concern with the introduction of Pertex Shield.
Pertex Shield is the culmination of extensive research to develop a new process for applying and bonding durable water repellency to breathable fabrics. The net result is a fabric that has the breathability of a typical microfiber with the water repellency approaching more traditional waterproof-breathable fabrics.
Based on the concept of moisture vapor “venting” (convective, rather than diffusive movement of moisture, a process on which eVent fabrics are based), Pertex Shield is poised to add significant water resistance to Perseverance Mills’ already extensive line of highly breathable performance fabrics.
One of the most remarkable features of Pertex Shield is the contact angle of water droplets in contact with the surface (see photograph). Steep contact angles (and they are 90 degrees or greater in this image) mean that there is less water to come into contact with the fabric; as a result, there is a (2) higher probability that water will roll off the fabric rather than stick to it, and thus, (2) a lower probability that water molecules will diffuse through the fabric via capillary action. Even more important, as can be seen in the photograph, is that this contact angle appears to be consistent across drop sizes, which means that even large water drop aggregates, like those that form on fabrics in heavy rain, are more likely to disperse in response to very low surface adsorption between the water and the fabric.
So what does this really mean for the lightweight backpacker? Fabrics that have a higher water resistance without compromising breathability, and the opportunity to achieve a level of water resistance in ultralight fabrics that was once only attainable in heavier fabrics.
We will be reporting more details about Pertex Shield soon, as it will be formally launched at the Outdoor Retailer show in Salt Lake City on August 15. In addition, we are looking forward to formal testing of Pertex Shield and evaluation of ultralight Shield-treated Pertex fabrics and garments this fall.