A porous composite laminate material comprises a layer (4) of expanded polytetrafluoroethylene (PTFE) membrane, and a layer (2) of non-expanded porous PTFE attached thereto. The non-expanded porous PTFE layer may be a sintered porous PTFE produced by sintering granular-type PTFE particles to form a porous integral network of interconnected particles; and may be produced in situ by spray application onto the membrane followed by baking. Modifiers including unsintered fine powder PTFE, thermoplastic fluorinated organic polymer, a low molecular weight PTFE and mixtures thereof may be included. The expanded PTFE membrane can be in sheet form or in the form of expanded PTFE fibres woven into a fabric. The laminate may be used for oiling and cleaning high temperature fuser rolls in a photocopying machine, or as a filter.
The present invention discloses discloses a composite PTFE membrane comprising an expanded PTFE membrane as substrate and a sintered porous PTFE membrane on top of it. The porous PTFE membrane on top has porous structure with interconnected channels formed with a sintering process that fuses the PTFE fine powders coated on the ePTFE membrane. Furthermore, the present invention discloses a method for forming the composite PTFE membrane.
A method of manufacturing a filter medium that has a PF value that exceeds 32, the PF value calculated from the pressure loss and the collection efficiency of the filter medium according to the following formula: PF=[-log(permeability (%)/100)/(pressure loss (Pa)].times.1000[Formula 1] in which permeability (%)=100-collection efficiency (%). In this method, 380 ml or more of a liquid lubricant at 20.degree. C. is added per 1 kg of a PTFE fine powder, this compound is processed into a tape shape and elongated to obtain a PTFE porous film, and an air permeable support member is heat laminated to at least one surface of the PTFE porous film.
A composite expanded polytetrafluoroethylene (ePTFE) article includes at least two different component layers. At least one of the layers includes a node-fibril structure presenting nodes that are connected together by a first plurality of relatively short fibrils. At least one additional layer of the article includes a plurality of aggregates connected together by a plurality of relatively long fibrils having an average length of greater than about 100 microns. In addition, each of the aggregates are formed of ePTFE, including nodes that are connected together by a second plurality of relatively short fibrils. Preferably, the short fibrils have a length of 10-100 microns, and the nodes found in the article have a density of about 2.0-2.2 grams per cubic centimeter. A method of producing the article includes the steps of extruding a first polytetrafluoroethylene (PTFE) material to form a first extrudate, and extruding a second PTFE material to form a second extrudate, wherein the first PTFE material is more expandable than the second PTFE material. A stack is formed from at least one layer of the first extrudate and at least one layer of the second extrudate, and the stack is expanded and sintered to form the article.
A toner supply roller comprises a metallic core shaft and an electrically conductive elastic layer formed to surround the outer surface of the shaft. The conductive elastic layer is formed of open-cell polyurethane foam. The polyurethane foam is impregnated with an electrically conductive polymer and a binder.
A method of producing a polytetrafluoroethylene (PTFE) material including the steps of extruding a first material to form a first extrudate, and extruding a second PTFE material to form a second extrudate, wherein the first PTFE material is more expandable than the second PTFE material. A stack is formed from at least one layer of the first extrudate and at least one layer of the second extrudate, and the stack is expanded and sintered to form the article.
