Two piezoelectric constants (polarization per unit stress, d=d'-id'', and polarization per unit strain, e=e'-ie''), the elastic constant, and dielectric constant are determined for oriented collagen at different hydration levels at 10 Hz from -150 to 50 degrees C. With no hydration (approximately 0% H2O), d' increases slightly with higher temperatures, while e' decreases slightly. Near 11 wt% H2O, both d' and e' increase then decrease around 0 degrees C, and is probably caused by an increase of the dielectric constant and the ionic conductivity in the nonpiezoelectric phase. Hydration greater than 25 wt%, d' and e' decrease above -50 degrees C which is considered to be due to a greater ionic conductivity surrounding the piezoelectric phase.

SynopsisThe complex piezoelectric constant (d = d'id"), elastic constant (c = c' + ic"), and dielectric constant (6 = E'if") were measured at a frequency of 10 Hz over the temperature range from -150 to 50°C and for a range of hydration up to 0.26 g/g for decalcified bone and up to 0.084 g/g for bone. For decalcified bone, t' and t " increased with increasing hydration with a deflection at the critical hydration h, = 0.08 g/g; d' at -150°C increased below h, but decreased above h, with increasing hydration; c' increased below -60°C but decreased above -60°C with increasing hydration; and the peak temperatures oft", d " , and c" below -50°C agree with each other and decreased with increasing hydration with a deflection at h,. For bone, similar hydration and temperature dependences were observed for t and c. However, the dependence of d on hydration and temperature was different from that of decalcified bone, reflecting a two-phase structure consisting of collagen fibers and mineral hydroxyapatite. The critical hydration for bone was 0.04 g/g.

synopaisAn apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d' -i d ' for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (e + K)/G, where t is the dielectric constant, K is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field-induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95OC followed by cooling to room temperature, maintaining a constant d.c. bias on a poly(viny1 chloride) film, piezoelect.ricity is observed a t null d.c. field, which suggests the introduction of a residual polarization in the film.

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