Navy

Omniphobic moisture-curable paints and coatings

Water and oil wicking coatings provide enhanced corrosion resistance and repellency of hydrocarbons

Materials Other

Polysiloxane topside coating on the USS Gunston Hall.

Polyurethane-based topcoats are used to provide visual camouflage, hydrocarbon resistance, flexibility, first-line corrosion resistance, and a host of other properties for military assets. The majority of polyurethane topcoats utilized by the Army, Marine Corps, Navy, and Air Force are qualified under MIL-DTL-53039E (Coating, Aliphatic Polyurethane, Single Component, Chemical Agent Resistant), MIL-DTL-64159B (Camouflage Coating, Water Dispersible Aliphatic Polyurethane, Chemical Agent Resistant) or MIL-PRF-85285E (Coating, Polyurethane, Aircraft and Support Equipment), and these topcoats are found on tanks, vehicles, aircraft (fixed and rotary wing) or ground support equipment. Unfortunately, these polyurethane coatings contain hydrophilic (i.e., water-loving) urethane linkages, which can lead to the uptake of water into the matrix and subsequent hydrolysis of polymer chains, blistering, and cracking of the coating. Furthermore, the penetration of moisture through the topcoats, and eventually the underlying primer, leads to substrate corrosion that can render an asset inoperable. And, while these polyurethanes provide resistance to hydrocarbons, such as lubricating oils and jet-fuels,  resistance is narrowly defined as not significantly softening, whitening, or dulling of the coating, as opposed to preventing the chemicals from entering the matrix where they can off-gas for days after contact.

To address the above drawbacks of current coatings, Navy researchers have recently developed novel omniphobic moisture-curable coating formulations for enhanced corrosion resistance and hydrocarbon repellency.

The tested formulations are made with 2-5 wt. % of fluorosilane, which imparts omniphobic properties. The use of alternative fluorinated silanes, fluorinated silica particles, fluoropolymers, and other fluorinated additives also generate omniphobic coatings when utilized in these moisture-curable formulations. Furthermore, the addition of alkylsilanes, such as isooctyl silane, has been found to increase their olephobicity.

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