LOW DIELECTRIC, LOW LOSS RADOMES, MATERIALS AND METHODS FOR MAKING LOW DIELECTRIC, LOW LOSS RADOMES

1 . A material for a low dielectric, low loss radome, the material comprising a foamed thermoplastic having a dielectric constant less than 2.3 at frequencies up to 90 gigahertz and a plurality of closed pores including gas entrapped within at least some of the closed pores.

2 . The material of claim 1 , wherein the foamed thermoplastic includes nitrogen or carbon dioxide entrapped within at least some of the closed pores of the foamed thermoplastic.

3 . The material of claim 1 , wherein:

the gas entrapped within at least some of the closed pores of the foamed thermoplastic provides a weight reduction of the foamed thermoplastic within a range from about 10% to about 25%; and/or

the gas entrapped within at least some of the closed pores of the foamed thermoplastic provides a dielectric constant reduction of at least about 10%.

4 . The material of claim 1 , wherein:

the foamed thermoplastic has a lower dielectric constant due to the gas entrapped within at least some of the closed pores of the foamed thermoplastic;

the foamed thermoplastic has a pore density within a range from about 20% to about 50%; and

the foamed thermoplastic has a closed porosity.

5 . The material of claim 1 , wherein the foamed thermoplastic comprises a microcellular polymer foam.

6 . The material of claim 1 , wherein the foamed thermoplastic comprises polypropylene and/or polyolefin.

7 . The material of claim 1 , wherein the foamed thermoplastic comprises cyclic olefin copolymer.

8 . The material of claim 1 , wherein the foamed thermoplastic comprises a blend of polypropylene and cyclic olefin copolymer.

9 . The material of claim 8 , wherein the blend of the polypropylene and the cyclic olefin copolymer includes at least about 5 weight percentage to about 50 weight percentage of the cyclic olefin copolymer.

10 . The material of claim 9 , wherein the blend of the polypropylene and the cyclic olefin copolymer includes about 80 weight percentage of the polypropylene and about 20 weight percentage of the cyclic olefin copolymer.

11 . The material of claim 8 , wherein:

the blend of the polypropylene and the cyclic olefin copolymer has an average dielectric constant of about 2.2 for frequencies from 18 gigahertz to 40 gigahertz; and

the gas entrapped within at least some of the closed pores of the foamed thermoplastic reduces dielectric constant such that the foamed thermoplastic has an average dielectric constant less than 2 for frequencies from 18 gigahertz to 40 gigahertz.

12 . The material of claim 1 , wherein the foamed thermoplastic includes one or more open pores in addition to the plurality of closed pores having the gas entrapped within at least some of the closed pores of the foamed thermoplastic.

13 . The material of claim 1 , wherein the material includes fibers within the material that comprise polytetrafluoroethylene.

14 . The material of claim 1 , wherein the material includes one or more impact modifiers within the material that comprise one or more of acrylic styrene acrylonitrile, methacrylate butadiene styrene terpolymer, acrylate polymethacrylate copolymer, chlorinated polyethylene, ethylene vinyl acetate copolymer, acrylonitrile butadiene styrene terpolymer, and/or polyacrylate.

15 . The material of claim 1 , wherein:

the material has a dielectric constant less than 2.1 at frequencies up to 90 gigahertz; and

the material further comprises flame retardant within the material whereby the material has a UL94 flame rating of V0; and

the material is configured to have a loss tangent less than 0.01 for frequencies up to 90 gigahertz.

16 . The material of claim 1 , wherein:

the material is injection moldable; and/or

the material comprises thermoplastic injection moldable pellets.

17 . A radome injection molded from the material of claim 1 , wherein:

the radome has a dielectric constant less than 2.1 for frequencies up to 90 gigahertz;

the radome has a loss tangent less than 0.01 at frequencies up to 90 GHz; and

the radome has a UL94 flame rating of V0.

18 . A method of making a low dielectric, low loss radome, the method comprising:

injecting a fluid into a thermoplastic to thereby provide a foamed thermoplastic having a dielectric constant less than 2.3 at frequencies up to 90 gigahertz; and

injection molding the foamed thermoplastic to thereby provide at least a portion of the radome that is injection molded from the foamed thermoplastic.

19 . The method of claim 18 , wherein injecting a fluid comprises injecting a supercritical fluid into the thermoplastic such that the injected supercritical fluid transitions to a gas phase, which gas is entrapped within at least some closed pores of the foamed thermoplastic.

20 . The method of claim 18 , wherein:

the fluid comprises nitrogen or carbon dioxide; and/or

the foamed thermoplastic comprises a blend of polypropylene and cyclic olefin copolymer; and/or

the foamed thermoplastic includes fibers within the foamed thermoplastic that comprise polytetrafluoroethylene.

21 . A material for a low dielectric, low loss radome, the material comprising low dielectric constant, low loss filler within a resin matrix, the low dielectric constant, low loss filler reducing overall dielectric constant, wherein the resin matrix comprises cyclic olefin copolymer.

22 . The material of claim 21 , wherein:

the resin matrix comprises a blend of polypropylene and the cyclic olefin copolymer; and

low dielectric constant, low loss filler is within the blend of the polypropylene and the cyclic olefin copolymer.

23 . The material of claim 22 , wherein:

the blend of the polypropylene and the cyclic olefin copolymer includes about 80 weight percentage of the polypropylene and about 20 weight percentage of the cyclic olefin copolymer; and/or

the material has a dielectric constant of less than 2.1 for frequencies from 18 gigahertz to 40 gigahertz; and/or

the material includes fibers within the material that comprise polytetrafluoroethylene.

24 . The material of claim 21 , wherein:

the low dielectric constant, low loss filler comprises microspheres within the resin matrix; and/or

the resin matrix includes a plurality of closed pores, and the low dielectric constant, low loss filler comprises gas entrapped within at least some the closed pores of the resin matrix.

25 . The material of claim 21 , wherein the low dielectric constant, low loss filler comprises one or more of hollow glass microspheres, hollow plastic microspheres, hollow ceramic microspheres, microballoons, and/or bubbles within the resin matrix.