Polymer Sci. Group, Naval Surface Warfare Ctr., 10901 New Hampshire Ave., Silver Spring, MD 20903-5640
Recognizing a long-standing need for standard materials to calibrate acoustic measurement equipment, Wayne Reader initiated a Working Group with the title ``Characterization of the Dynamic Properties of Viscoelastic Polymers.'' The Working Group was organized under Standards Committee S2 of the Acoustical Society of America and was given the designation S2-79. The desirable qualities for the materials were: Ready availability, wide range of acoustic properties, stable with time, reproducible from lot to lot, and thermorheologically simple. He drew Group members from government, private industry, and universities, both in this country and abroad. Under his leadership, the Working Group progressed to the point that its work is nearly complete. This presentation will give an overview of the results from various laboratories on the most promising candidates. Emphasis will be given to a high loss polyurethane, for which the most data is available. In contrast, data for a low loss polyurethane will be presented to illustrate the reasons it was eliminated as a standard.