Abstract: An extruded, coalesced foam strand propylene polymer material that is either open-celled and useful for sound insulation applications or close celled and useful for thermal insulation applications. An apparatus suitable for preparing such foams with an expanded cross-section.

Abstract: Thermoplastic foams with an average cell size of greater than one and one-half millimeters and an average noise reduction coefficient in excess of 0.3 have improved sound attenuating properties when they include a Helmholtz resonator, a quarter-wave attenuator or both.

Abstract: An extruded, coalesced foam strand propylene polymer material that is either open-celled and useful for sound insulation applications or close celled and useful for thermal insulation applications.

Abstract: An inverted Cassegrain antenna utilizing polarization rotation. The polarizer-reflector or mirror utilized comprises two or more polarizer-reflector elements joined together around hinges perpendicular to the widening direction required. A sheet comprising parallel metal wires covers the whole of the elements. For each element, a metal film is separated from the sheet by a first dielectric layer. Each hinge is formed, on one side, by the flexible sheet of metal wires which straddles the gap between elements. The other side of the hinge includes a second dielectric layer backed by a rigid metal strip, also straddling the gap. One end of the metal strip is fixed to the metal film of one adjacent element while the other end of the metal strip is in moveable electrical contact with the metal strip of the other adjacent element. The antenna is particularly applicable to multiple function radars.