Piezoelectricity in uniaxially stretched and plasticized nylon 11 films

The combined effect of uniaxial stretching and plasticization of nylon 11 films on the resulting piezoelectric response was studied. Three different kinds of samples were studied for nylon 11 α′-form films: (1) uniaxially stretched at 150°C, (2) samples uniaxially stretched at 150°C and then plasticized by immersion in 2-ethyl 1,3-hexanediol, and (3) samples plasticized and then uniaxially stretched. The largest piezoelectric response was obtained from the samples which were plasticized prior to uniaxial stretching under identical poling conditions. For the case of nylon 11 δ′-form films, two different kinds of experiments were performed: (1) samples uniaxially stretched at room temperature were subsequently plasticized by immersion in the plasticizer and a comparison of their piezoelectric response made with that of the unplasticized samples as a function of poling field; (2) the plasticizer content dependence of the piezoelectric response from these samples was studied. In both cases, d₃₁ was observed to be higher for the plasticized films compared with the unplasticized films. The piezoelectric stress constant e₃₁ showed a small decrease with plasticization. X-ray diffraction studies indicated a small conversion of δ′-phase to α′-phase with plasticization. No significant changes were observed in the x-ray diffraction scans taken before and after poling.