The Role of Physical Acoustics in the Development of Specialty Polymers for Underwater Acoustical Applications

Physical acoustical measurements provide valuable means for studying dynamic mechanical relaxation mechanisms in high polymers. Knowledge of acoustical behavior is desirable both from a fundamental point of view as to how specific relaxation processes depend upon the structural characteristics of molecules, and for design purposes in engineering applications. For special applications such as underwater acoustics, the combination of an often hostile service environment and constraints on desired physical and acoustical properties poses a difficult problem in polymer physics and chemistry. This paper discusses the role of physical acoustics in elucidating the correspondence between chemical composition of elastomeric materials and their acoustical properties, and illustrates this with examples from studies involving reinforcing fillers, variations in base polymers, and crosslinking systems. The theory and operation of automated systems for the measurement of the dynamic Young's modulus and bulk longitudinal modulus of polymers are also described.