MEMBRANE

The industry's lightest, most breathable, most sustainable waterproof membrane

Based on both our own testing and the feedback of materials professionals given the chance to preview Intrepid fabrics, we believe them to be the lightest and most breathable on the market. Of course we invite brands to do their own testing and see for themselves. But to gain some appreciation for how such a bold claim might actually be borne out, it may be helpful to first understand how Celgard’s new PP membrane works. The key is its pores, their size, their shape, their uniformity, the materials that they're made out of, and ultimately, the fact that they contribute roughly 74% of the membrane by volume.

The membrane's pores are created through a patented process which leverages polypropylene's unique molecular properties – properties which make possible the creation of very smooth, spherical pores. Beyond just making tidy pores though, polypropylene is an ideal material for a waterproof-breathable membrane because it is highly hydrophobic, the result of its low surface energy. Liquid water is thus repelled by the matrix structure of polypropylene. Where water is pressed against a pore though, it intrudes slightly but is held contiguous in the form hemispherical lumps by surface tension,  thus preventing the water from permeating the membrane. 

PTFE is also naturally hydrophobic – even more so than than polypropylene in fact, with a surface energy roughly 20% lower. However, the ability of a porous, hydrophobic membrane to repel water is a function of not only hydrophobicity, but also of the size and shape of its pores. Not surprisingly, round pores are much more effective, as water in ball form maintains its integrity more easily than in triangular or trapezoidal shapes. This is where PTFE and electro-spun PU membranes are challenged. Jagged, triangular voids do a poor job of creating surface tension. This is the same reason why Loofah sponges are not much good at soaking up spills.

In addition to being of a preferred shape, the Intrepid membrane's pores are also of a preferred size – smaller. Much smaller. Whereas the leading maker of ePTFE membranes puts their mean pore size at roughly 200 nanometers, Intrepid's pores are roughly a tenth that size. While this makes no difference to water vapor, it makes a huge difference to water droplets. That is why the leading PTFE membrane manufacturer has tried to engineer smaller pores, by experimenting with progressively less expansion. But while created in smaller pores, the resulting membrane's void ratio (the ratio of pore volume to total volume) fell as low as 30%.  

By contrast, the membrane in Intrepid fabrics boasts a void ratio of approximately 74%, meaning that it consists of far more air than material. Combined with it's 18 micron thickness, this high void ratio makes Intrepid remarkably light, at just four grams per square meter. We believe this to be the lightest weight of any waterproof-breathable membrane. In actual usage, this weight advantage over polyurethane membranes is even greater as these hydrophilic films can easily absorb up to double their weight when saturated with the athlete's perspiration. Ironically, it is when these osmotic membranes are fully saturated that they are most breathable. This is obviously sub-optimal. 

One of the other great things about the Intrepid membrane is that it's made of polypropylene, one of the most environmentally sustainable plastics. Based on Higg Index values, the manufacture of polypropylene is 22% less toxic than polyurethane, and 93% less toxic than PTFE. Moreover, the Intrepid membrane can be laminated to polypropylene fabrics and paired with polypropylene trim to make garments that are 100% recyclable, use no water in dyeing, and require far less DWR, due to polypropylene's strong inherent hydrophobia. 

As Greenpeace has done an excellent job of highlighting, the issue of PFCs is neither abstract nor benign. These compounds have been found in elevated levels near various production sites, in both the surrounding groundwater and the blood of residents. These same global hotspots have shown elevated levels of various different cancers, birth defects, and reproductive issues. When PTFE-based garments are incinerated, the PTFE emerges as fine particulate matter that never breaks down. We feel that it's high time we moved beyond this 40 year-old technology.