Recent Developments in the Usa in the Application of Pvf2 Polymer in Underwater Transducers

1'2 particularly polyvinylidene fluoride (PVFz), show considerabl e promise for hydrophone application s.PVFa offers the advantages of a characteris tic impedance that closely matches water, low mass density, mechanical flexibility , and it can be manufacture d in large dimensions as a single piece.The development of thick film PVFa with large values for the hydrostatic piezoelectri c constant makes it suitable for hydrostatic drive hydrophones, with their associated simplicity of fabrication and virtually unlimited depth capability.These advantages and the unique properties of polymer, with applications to novel hydrophone designs, are reviewed in this paper.Presently piezoelectri c polymers are commercially available in experimental quantities from at least three sources: Thorn EMI Central Research Laboratories , Pennwalt Corporation, and Raychem.Because of difficulties in polarizing the material, the maximum thickness is limited to about one millimeter. Piezoelect ric polymers,Current interest in the 0.5. is focused on thick film PVFZ, particularl y for use in large area passive arrays.Considerabl e effort is underway in the devel opment of large area hydrostatic drive hydrophones.Strictly speaking, we mean