GB821250A - Dielectric walls for transmission of centimetric radiation - Google Patents

Abstract

821,250. Laminates. McMILLAN, E. B., and REDHEFFER, R. M. June 1, 1956, No. 17069/56. Drawings to Specification. Class 140. [Also in Group XL (c)] The Specification gives a number of examples of laminated dielectric material, the various layers in laminate having differing dielectric constants and controlled thicknesses so that the material is suitable for the construction of a radiation-transmissive housing for a radio aerial. The material has a core of relatively high dielectric constant and an outer layer or layers on each side of the core of lower dielectric constant. In one example the core layer is a polyester resin, fibre glass cloth laminate loaded with rutile titanium dioxide and to each side of this is attached a sheet of butyl rubber composition. In a modification of this the same core layer is used but on one side of it a layer of rigid polymethyl methacrylate is attached and, on the other, a layer of plasticized polyvinyl formal. In another example the core layer comprises plasticized polyvinyl formal loaded with rutile titanium dioxide and both outer lamina of rigid polymethyl methacrylate. In a further example the core layer consists of fibreglass cloth impregnated with polyester-styrene resin and loaded with fine aluminium powder and both outer layers of nylon. A similar core layer to that last described is used in another example and is laminated with a resin-impregnated fibre-glass mat on each side. An extra erosionresistant layer is added on the side intended to be outermost and consists of a vulcanized rubber loaded with zinc and magnesium oxides. In an example having a high strength to weight ratio the core layer is of fibreglass impregnated with polyester-styrene resin and loaded with aluminium powder. On either side of this is a cellular resin foam layer loaded with a small amount of aluminium powder. On the outer sides of these layers are layers consisting of parallel warps of glass fibres bonded with polyester styrene resin. Finally there is an erosionresistant layer of vulcanized synthetic rubber compound on one side only of the material. An example of a heat-resistant laminate comprises a porcelain core with outer layers of polytetrafluoroethylene. In another construction described the core layer is of a glass containing 96% silica and the outer layers of mahogany wood veneer. In a final example the core is made of a ceramic of mica, glass, and titanium dioxide, the outer layer intended to be on the outside of the housing is a solid dispersion of polyvinyl chloride-acetate resin in alkyd resin and the other outer layer of poly-N-vinyl carbazole.