Abstract: The present invention provides porous polytetrafluoroethylene ("PTFE") products having fine pores and high porosity, the pore diameter being less than about 1,500A, generally ranging from about 100A to 1,000A. The process for the manufacture of these products comprises: (a) shaping of a lubricated PTFE mixture, by extrusion and/or rolling; (b) a first stretching of the shaped mass while in an unsintered state; (c) free sintering of the stretched mass at a temperature above 327.degree. C; and (d) a second stretching of the sintered mass. These porous PTFE products are suitable for use as gas separators, diaphragms, filters, and other applications.
Abstract: In this process metal ions such as Ag.sup.+, Pb.sup.2+, Co.sup.2+, Cu.sup. 2+, Fe.sup.3+, etc., are extracted through a porous membrane impregnated with the first extractant containing chelating agents. The membrane contacts with an extraction feed on one side, and with the second extractant on the other side, and the objective metal ions are transferred from the feed to the second extractant. Throughout the extraction process, the pH values of the extraction feed, the impregnated extractant solution, and the second extractant are kept in decreasing order.An apparatus used for the above objective is also provided by this invention.
Abstract: The present invention provides an effective process for an enzymatic reaction which utilizes the enzyme membrane of the invention. The enzyme membrane consists of an enzyme strongly entrapped in a membrane base, said base being porous, fibrous, or roughened material which is permanently self-polarized or maintained polarized under an electric field. This enzyme membrane catalytically reacts with a substrate solution without loss of enzyme. The most preferred material for the membrane substrate is expanded porous polytetrafluoroethylene.
Abstract: The product of the present invention is a fabric woven from oriented polytetrafluoroethylene (PTFE) strands, in which the strands of the weave are interconnected by a multiplicity of fine PTFE fibrils. To produce this fabric, consisting entirely of PTFE, a woven PTFE fabric is heated substantially unrestrained to a temperature above the crystalline melt point of PTFE and stretched. Alternatively, a woven PTFE fabric may be impregnated with other fluorocarbon polymers, heated substantially unrestrained to a temperature above the crystalline melt point of PTFE, and subsequently stretched, thereby generating a multiplicity of fine fibrils interconnecting the weave.
Abstract: In the method for detecting liquid leak of the present invention, the inventive cable, i.e., a parallel pair or a coaxial cable insulated with porous polymer material, is placed along or under a storage and/or transport means for conveying chemicals. If leakage occurs, the leaked liquid permeates into fine pores in the porous insulation material separating two conductors from each other, and varies the characteristic impedance of the cable to some detectable extent. The variation of impedance is electrically measured by a pulse reflection method (TDR). The inventive method comprises; sending pulse waves from one end of the cable, sensing the reflected and deformed pulse shape, and thus detecting and locating the liquid leak.
Abstract: This invention provides a tetrafluoroethylene polymer in a porous form which has an amorphous content exceeding about 5% and which has a micro-structure characterized by nodes interconnected by fibrils. The material has high porosity and high strength. It can be used to produce all kinds of shaped articles such as films, tubes, rods, and continuous filaments. Laminations can be employed and impregnation and bonding can readily be used to produce a large variety of articles. Compressed articles of very high strength can also be produced from these porous forms.