Piezoelectric relaxations in collagen gelatin systems

Abstract

Films consisting of three joined layers of gelatin, oriented collagen, and gelatin were prepared. The temperature dependence of piezoelectric constants (d=d′–id″) and e=e′–ie″ was determined at 10 Hz for the combined films with different hydrations. At a moisture content above 30 wt ∧#x0025;, d′ and e′ decreased with increasing temperature just above −100°C, and their signs reversed around −30°C, and approached zero around room temperature. The temperature dependence of the piezoelectric current induced by static stress was also determined for a film with a moisture content of about 33 wt∧#x0025;. The sign reversal of the decaying current was observed at intermediate temperatures in accord with the sign reversal of d′ in a.c. measurements. The theoretical explanation for this was given on the basis of the Maxwell—Wagner type dielectric relaxation in a two phase system and the decay of piezoelectric polarization in collagen layer. The same explanation may be applied for the temperature dependence of the piezoelectric constant of bone, which consists of collagen fibers and hydroxyapatite. © 1979, The Society of Polymer Science, Japan. All rights reserved.