Structure-property relationships in polymer interpenetrating networks for use as broad band damping materials

In the search for broadband damping materials, it is desirable to have polymers with a broad and high loss region in shear or extension, covering the entire temperature and frequency range of interest. Interpenetrating networks, IPN’s, are materials composed of two or more crosslinked polymers intimately and irrevocably intertwined. The resulting distribution of microenvironments can result in a material with a high mechanical loss broadened over that of either polymer component alone. Several series of polyurethane/epoxy IPN’s have been prepared for possible use as broadband damping materials. All IPN’s showed apparent true IPN behavior with no or very small scale phase separation. Dynamic mechanical analysis revealed that the temperature of the loss peak may be varied over a wide temperature range with formulation. Further work has focused on incorporating a more flexible epoxy component and/or a plasticizer, and comparison of viscoelastic behavior to observed damping in constrained layer structures. [Work supported by ONR.]