Plasticizer loading in acoustic encapsulants

Abstract

Acoustically transparent elastomers are the windows through which the United States Navy views the ocean. For acoustic clarity and sensitivity, it is important that the elastomer operates well outside damping conditions as dictated by the temperatures and frequencies of interest. Damping behavior is characterized by a peak in the loss tangent. However, the temperature and frequency location of this peak can shift in response to absorbed plasticizing fluids. This material characteristic is under investigation using dynamic mechanical analysis (DMA) to assess its dependence on the plasticizer and polyurethane component chemistry. In this first stage of the research, a temperature range from −100 to 100 °C and samples saturated with fluid were explored by DMA to determine the limiting behavior of the samples, enabling more detailed investigation in future work. Association of absorbed plasticizers with polyurethane components by polarity was demonstrated in the results by the shifting of the appropriate hard and soft block loss tangent peak.