Electromechanical properties of poly-L-lactic acid

The electromechanical coupling coefficient, the piezoelectric constant, the elastic compliance constant and the mechanical quality factor for a poly-L-lactic acid (PLLA) plate elongated to 4 times the original length were determined by a self-resonant method. k(14) = 0.064, d(14) = 9.82 x 10(-12) C/N, s(44)(E) = 9.28 x 10(-10) m(2)/N and Q(m) = 30.3 were obtained at room temperature for a 0 degrees X-cut square plate. It is noted that elongated PLLA films have no spontaneous polarization, unlike poled polymers such as poly(vinylidene fluoride) (PVDF), but still have a large shear piezoelectric constant.