Ferroelectric nylon-5 and nylon-7 dielectric and electromechanical properties and ultrasonic transducer performance

Ferroelectric (odd-numbered) nylons have gained recent interest for their electromechanical properties which are competitive with PVDF and its copolymers for some sensor applications. Nylon films were prepared by melt quenching and cold drawing to impart three-dimensional molecular orientation. Their thickness-mode high frequency dielectric and electromechanical properties were characterized over a temperature range of 0-160°C using a piezoelectric resonance technique. These tests yielded electromechanical coupling coefficients of 0.10-0.15 and mechanical quality factors of 8-12, which are competitive with PVDF and its copolymers. Measurements of the ultrasonic pulse-echo performance of ferroelectric nylon-7 were conducted and compared with PVDF and P(VDF-TrFE) copolymer with the use of a simple contact transducer test fixture. Comparisons were also made of the pulse-echo insertion loss, pulse-width, and bandwidth performance. The effects of water absorption on the nylon film properties and ultrasonic transducer performance are also reported