Water-based pressure-sensitive paints (PSPs) have been invented as alternatives conventional organic- solvent-based pressure-sensitive paints, which are used primarily for indicating distributions of air pressure on wind-tunnel models. Typically, PSPs are sprayed onto aerodynamic models after they have been mounted in wind tunnels. When conventional organic- solvent- based PSPs are used, this practice creates a problem of removing toxic fumes from inside the wind tunnels. The use of water-based PSPs eliminates this problem. The water-based PSPs offer high performance as pressure indicators, plus all the advantages of common water-based paints low toxicity, low concentrations of volatile organic compounds, and easy cleanup by use of water).
A typical PSP (whether conventional of the present innovative type) contains the following:
- A luminescent compound, the luminescence of which is quenched by oxygen;
- An oxygen-permeable polymeric binder;
- Pigment materials to hide the painted surface and to increase reflectance of the light emitted from the luminescent compound; and
The paint is applied to a surface of interest on a model and allowed to dry. During a subsequent wind-tunnel test, under the appropriate illumination, the intensity of luminescence emitted by the PSP is inversely proportional to the concentration of oxygen, hence, to the air pressure at the painted surface.
A water-based PSP contains all the basic ingredients of a conventional PSP (see table), except that the organic-solvent content (if any) is much smaller and the basic ingredients are incorporated in a water matrix. The oxygen-permeable polymer is prepared as a water-borne emulsion. This is blended with the necessary coalescing agents, coupling solvents, luminophore, and pigments. The resulting water-based PSP can be applied by spraying to obtain a single coat, which cures to touch in less than one hour and cures for use in 12 hours at room temperature. The cured paint is smooth and has good adhesion to most metal and plastic substrates.
This work was done by Jeffrey D. Jordan and A. Neal Watkins of Langley Research Center and Donald M. Oglesby and JoAnne L. Ingram of Swales Aerospace. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Materials category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
LaRC On-Site Offices
1224T11 N. Wright Street, MS186A
Hampton, VA 23681-9668
Phone: (757) 864-9857
Refer to LAR-16603-1, volume and number of this NASA Tech Briefs issue, and the page number.