The encyclopedia · Engineering & Operations · Technical decision · 1969–1976
Gore's ePTFE let a jacket block rain while still breathing out sweat.
Bob Gore yanked a heated PTFE rod and it stretched 800% into a microporous membrane that keeps liquid rain out and lets water vapor pass.
W.L. Gore & Associates
the move
Waterproof rainwear meant a non-breathable polyurethane or plastic coating, so a wearer stayed dry from outside but soaked in sweat from inside.
The obvious fix was a more breathable but leaky fabric, or yet another coating that trapped moisture.
In October 1969 Bob Gore was trying to stretch heated PTFE by about 10%; a sudden, accelerating yank stretched it roughly 800% into a microporous structure that was about 70% air, which became expanded PTFE or ePTFE, patented in 1976.
Because the pores reject liquid water but let vapor escape, Gore-Tex became a shell that was dry from outside and breathable from inside at once.
why it works
- Pores smaller than droplets but bigger than vapor molecules separate rain from sweat on a size basis.
- The roughly 70% air structure gives the breathability a solid film cannot.
- A counterintuitive process, a fast yank instead of a slow stretch, was the discovery that unlocked it.
what transfers
Size the pores to the molecule, not the thing you want to keep out: let vapor through and reject liquid on a size basis, and remember the right conditions can be counterintuitive.
what came after
Gore-Tex became a benchmark for outerwear, medical implants, cable insulation and filters, and W.L. Gore chose to supply the membrane and license rather than make garments, keeping the material business broad. Bob Gore secured nine fluoropolymer patents and was inducted into the National Inventors Hall of Fame, and the ePTFE discovery turned a small basement firm into a global materials company.
references
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