Low-Permeability Coating for Nitrile Rubber

Researchers have tried for years to make low water vapor transmission rate (WVTR) elastomers without success. Developing low WVTR coatings for the Tomahawk missile fly-through nitrile covers requires a breakthrough technology in barrier materials. A nanocomposite elastomer is proposed that exploits tortuous path and constrained polymer (TP/CP) effects that accrue with high aspect ratio clays such as vermiculite. A “brick wall” like structure is formed that resists water vapor permeation. Permeation improvements to factors of 100-500 compared to the pure polymer are possible with well formed nanocomposites. The result is a barrier material as impermeable as any known polymer - but still elastomeric. Candidate resin/clay combinations will form nanocomposite coatings to be tested for WVTR and elastic properties. WVTRs are projected in the range of 10e-3 gm/100 in.e-2/day/mil, which – based on a ROM model of missile tube relative humidity – is enough for a 33 year barrier life. Physical properties will be tested for each barrier/cover combination before and after accelerated aging exposures. In Phase I Option an OEM elastomer lamination company will help develop a manufacturing strategy and produce pre-prototype fly-through cover bi-laminates for proof testing. Raw material and processing costs are low, netting at least a 40% part cost reduction.