The following may explain some of the failures reported elsewhere -- leakage when the (probably contaminated) fabric is constrained under a pack strap or similar. >From the Sci.chem FAQ. 31.4 What is Goretex?. Goretex is a dispersion-polymerised PTFE that is patented by W.L.Gore and Associates [5]. It is classed as a stretched semi-crystalline film, and is produced by extrusion under stress ( faster take-up rate than extrusion rate ). The extrudate is stretched below the melting temperature, often in the presence of an aromatic hydrocarbon that swells the amorphous region, creating porosity. The hydrophobic nature of the PTFE means that liquid water is repelled from the pores, whereas water vapour can pass through. It is important to realise that once the PTFE pores are filled with liquid water, the fabric can allow liquid water to pass though until it is dry again. Thus Goretex-containing fabrics ( such as Nomex/Goretex - which consists of an outer aramid fabric, a central Goretex layer, and a cotton backing ) should never be used as protection from chemicals as many will pass straight through. Any water-miscible solvent ( eg alcohol ) can fill the pores, and then liquid water can displace it and continue to rapidly pass through until the fabric is fully dried out. [5] Goretex patent U.S. Pat. 3,962,153 (8 June 1976) R.W.Gore (to W.L.Gore and Associates) -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Sat Nov 21 1998 - 02:03:16 PST
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