Cytonix Corporation (Beltsville, MD) inventor James F. Brown reveals compositions for extremely hydrophobic coatings which are durable, weatherable, scratch- and erosion-resistant in U.S. Patent 7,579,056. The coatings can be used on a signal transmitter or receiver such as a microwave, infra-red, light, radar, electromagnetic emitter or receiver such as a radome. The coatings do not adversely affect signal reception or transmission and help maintain the signal during rainy and stormy weather. The coating helps prevent satellite television interruption due to heavy rains.
The compositions consists of a fluorinated component and an adhesion promoter compound. The adhesion promoter compound can include an alkoxy group, a furfuryl-containing ring structure, and a reactive group.
The composition includes a hardenable resin, hydrophobic microparticles having an average particle size diameter of from about 1 nanometer to about 100 microns, and a substantially nonvolatile mobile fluorinated compound that is a liquid in a temperature range from about -30.degree. C. to about 30.degree. C. The fluorinated compound is a perfluorinated compound, for example, a perfluoroether or a fluoro-chloro compound.. The fluorinated compounds are resistant to degradation by sunlight. The fluorinated compound produces a surface comprising at least fifteen percent trifluoromethyl groups.
Hydrophobic coatings are used on antennas and radomes. Microwave signals are significantly, and in some cases about equally, attenuated by atmospheric precipitation and by water films on antennas and radomes. Higher microwave frequencies have resulted in greater communication bandwidth, but the shorter wavelengths are even more susceptible to rain attenuation. Airports report losses of vital satellite links during heavy precipitation, and most home viewers of satellite TV are familiar with programming disruption during even light rain. As bandwidths expand commercial and private use of microwave links, the problem of rain attenuation will become even more critical.
Numerous companies have addressed the problem of water filming on microwave radomes and dishes by using hydrophobic coatings to shed water as small, microwave-transparent beads. The smooth silicones and fluoropolymer coatings allow formation of large beads that can form rivulets and films during moderate to heavy rain. As these coatings degrade over time due to sunlight and pollution, they become less hydrophobic and their effectiveness is diminished.
Several companies, notably Vellox (Salisbury, Mass.) and Boyd (Hudson, Mass.), have addressed the problem of rain fade using hydrophobic coatings that comprise micropowders of Teflon.TM. or fumed silica dispersed in a hardenable resin, such as an alkyd or diisocyanate. These composite coatings have good performance initially but begin to form water films in an hour or less of moderate to heavy rain. After months or just weeks of exposure to mid-latitude summer sunlight these types of coatings wet out even more quickly.
Numerous companies have addressed the problem of water filming on microwave radomes and dishes by using hydrophobic coatings to shed water as small, microwave-transparent beads. The smooth silicones and fluoropolymer coatings allow formation of large beads that can form rivulets and films during moderate to heavy rain. As these coatings degrade over time due to sunlight and pollution, they become less hydrophobic and their effectiveness is diminished.
Several companies, notably Vellox (Salisbury, Mass.) and Boyd (Hudson, Mass.), have addressed the problem of rain fade using hydrophobic coatings that comprise micropowders of Teflon.TM. or fumed silica dispersed in a hardenable resin, such as an alkyd or diisocyanate. These composite coatings have good performance initially but begin to form water films in an hour or less of moderate to heavy rain. After months or just weeks of exposure to mid-latitude summer sunlight these types of coatings wet out even more quickly.
Mid-latitude summer sunlight is defined as average mid-day uv radiation during the summer months in regions of the United States from a latitude of 25.degree. to a latitude of 40.degree., and moderate to heavy rain is defined as 1 to 6 inches per hour. Drying fully after being swamped, the Boyd Teflon.TM. dispersion coating CRC6040 recovers most of its previous performance, but the hydrophobic performance of the Vellox LC-410 fumed silicate coating is permanently lost. Both coatings must be reapplied every year or two.
It is believed that sunlight damages at least the surfaces of all solid polymers to some degree. Generally, unsaturated materials degrade faster than aliphatics, and aliphatics degrade faster than some fluoropolymers. But all hydrocarbon resins suffer at least superficial changes that render them more wettable; and this is also true for most fluoropolymers.
It is believed that sunlight damages at least the surfaces of all solid polymers to some degree. Generally, unsaturated materials degrade faster than aliphatics, and aliphatics degrade faster than some fluoropolymers. But all hydrocarbon resins suffer at least superficial changes that render them more wettable; and this is also true for most fluoropolymers.
The fluoropolymer exceptions are those that degrade to hydrophobic by-products, such as PTFE; but even the exceptions can be rendered somewhat more hydrophilic and receptive to adhesives by ionizing radiation treatment. Once surface damage has taken place, the new surface is a permanent feature of the solid. Tests of all common fluorinated and non-fluorinated plastics show increases in surface wettability after exposure to the equivalent of months in mid-latitude summer sunlight.
The Cytonix coating fills the need for extremely hydrophobic coatings that are durable, for coatings for articles such as windshields, rainshields, and satellite and/or radar dishes, other signal receivers and transmitters, and radomes that does not interfere with signal transmission or reception.
The composition that forms a hydrophobic surface is useful as a surface for other articles which could benefit from hydrophobic properties such as radomes and antennas, vehicular surfaces, architectural surfaces, outdoor furniture, household goods, and kitchen and bath articles.
The Cytonix coating fills the need for extremely hydrophobic coatings that are durable, for coatings for articles such as windshields, rainshields, and satellite and/or radar dishes, other signal receivers and transmitters, and radomes that does not interfere with signal transmission or reception.
The composition that forms a hydrophobic surface is useful as a surface for other articles which could benefit from hydrophobic properties such as radomes and antennas, vehicular surfaces, architectural surfaces, outdoor furniture, household goods, and kitchen and bath articles.
