Abstract: Radiation resistant composites made of adjacent layers of a microporous hydrophobic polytetrafluoroethylene layer and one or more supporting layers made of woven metal material or woven synthetic organic polymeric material and a microporous hydrophobic polytetrafluoroethylene membrane are described. Filtration devices containing the composite are described.

Abstract: The present invention provides a two component polyurethane system with excellent wetting properties for casting a supported or unsupported, expanded polytetrafluoroethylene structure. It consists essentially of a polyisocyanate component having an isocyanate functionality of 2.2 or less and a polyol blend having an overall hydroxyl functionality of 2.2 or less and a viscosity of less than 500 cps., preferably 200 cps. or less. The polyol blend consists essentially of (i) a linear polyether or polyester (about 200-2500 molecular weight), (ii) a diol or triol (less than 200 molecular weight), and (iii) a catalyst in an amount sufficient to provide gelling at greater than 2 minutes and less than 10 minutes. The isocyanate to hydroxyl ratio is between 0.95:1 and 1.10:1. In some cases, it is desirable to include selected siloxane surfactants when polyol blends with the higher viscosities, i.e., about 200-500 cps., are used. The casting system is useful for making membrane filters.