Use of a composition comprising a polytetrafluoroethylene resin and a fine inorganic powder for a gasket, said composition being characterized in that the polytetrafluoroethylene resin is at least 5% by weight and the fine inorganic powder is at least 40% by weight, based on the total amount of the polytetrafluoroethylene resin and the fine inorganic powder; the total amount of the polytetrafluoroethylene resin and the fine inorganic powder is at least 80% by weight based on the entire amount of the composition; and the polytetrafluoroethylene resin and the fine inorganic powder are mutually uniformly dispersed and mixed with each other.
This invention provides porous electrically-conductive gasket materials having thin porous coating layers that provide good release properties from clamping surfaces and that provide good electrical conductivity.
A cylinder head gasket of the present invention includes a main gasket body and a metallic generally U-shaped flange which engages the inner periphery of a combustion bore opening formed in the main gasket body. A coating including tetrafluoroethylene and a high temperature resin binder such as either a polyimide or a polyamide-imide polymer are applied to at least the flange after it is formed and the entire gasket then cured at high temperatures in a series of steps including sintering to securely bond the coating to the flange. An optional plating layer disposed between the coating and the base material of the flange further improves bonding.
A ceramic filled fluoropolymer composite coaxial cable insulation and the coaxial cable made therefrom is presented. In accordance with the present invention, the coaxial cable insulation is comprised of 60-25% fluoropolymer that is fibrillatable, 40-75% ceramic filler and a void content which is effective to provide a dielectric constant of approximately less than 2.30. In a preferred embodiment of the present invention, the coaxial cable insulative composite comprises approximately 40 weight percent PTFE, 60 weight percent fused amorphus silica and a void volume percent of between 30 and 60. Also in certain preferred embodiemnts, the composite may include 1-4% by weight of microfiberglass filler and the ceramic filler may be coated with a silane coating. The provision of the void volume is an important feature of the present invention and acts to substantially lower the overall dielectric constant of the insulative composite. Still another important feature of this invention is the provision of an effective amount of ceramic filler (silica) so as to reduce the coefficient of thermal expansion (CTE) to a CTE approximating that of copper. This results in a coaxial cable having electrical properties which are more temperature stable than the prior art; and coaxial cable assemblies having improved thermomechanical stability relative to the prior art.
