FERROELECTRIC AND PIEZOELECTRIC PROPERTIES OF NYLON-11 POLY(VINYLIDENE FLUORIDE) BILAMINATE FILMS

The ferroelectric and piezoelectric properties of a new class of polymer ferroelectric and piezoelectric materials, nylon 11/polyvinylidene fluoride (PVF2) bilaminate films, prepared by a co-melt-pressing method, is presented. The bilaminate films exhibit typical ferroelectric D-E hysteresis behavior with a remanent polarization, P(r), of about 75 mC/m2, which is higher than the value of 52 mC/m2 observed for PVF2 or nylon 11 films measured under the same conditions. The coercive field, E(c), of the bilaminate films is approximately 78 MV/m, which is higher than that of either PVF2 or nylon 11 films. Measurements of the temperature dependence of the piezoelectric strain coefficient, d31, and the piezoelectric stress coefficient, e31, were also carried out. The bilaminate films exhibit a piezoelectric strain coefficient, d31, of 41 pC/N at room temperature, which is significantly higher than the PVF2 films (25 pC/N) and the nylon 11 films (3.1 pC/N). When the temperature is increased to 110-degrees-C, d31 of the bilaminate films reaches a maximum value of 63 pC/N, more than five times that of PVF2 (11 pC/N) and more than four times that of nylon 11 (14 pC/N) at the same temperature. The piezoelectric stress coefficient, e31, of the bilaminate films shows a value of 109 mC/m2 at room temperature, almost twice that of the PVF2 films (59 mC/m2) and about 18 times that of the nylon 11 films (6.2 mC/m2). Measurement of the temperature dependence of the hydrostatic piezoelectric coefficient, d(h), of the bilaminate films also shows an enhancement with respect to the individual components, PVF2 and nylon 11. (C) 1995 John Wiley & Sons, Inc.