Piezoelectric properties and ferroelectric hysteresis effects in uniaxially stretched nylon-11 films

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Abstract
Oriented nylon‐11 films [initially quenched (δ′ form) or slow cooled (α′ form) from the melt] subjected to a series of static positive and negative poling fields were found to show a hysteresislike behavior of the piezoelectric strain constant d31 and the piezoelectric stress constant e31. This behavior was very similar to that observed in poly(vinylidene fluoride) (PVF2) and attributed to ferroelectric dipole switching, in a previous study. No change in the x‐ray diffraction patterns of the δ′‐form films was observed after poling. Changes in the x‐ray diffraction patterns of the α′‐form films after poling were consistent with dipole reorientation in the crystalline regions. In both cases the magnitude of the piezoelectric response of the oriented films was considerably higher than that of the unoriented films. The melting points of the poled films increased significant ly relative to that of the unpoled films with the same thermal history, which may suggest field‐induced annealing effects.

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