Effect of water content on the piezoelectric properties of nylon 11 and nylon 7

A study of the effect of absorbed water on the piezoelectric properties of Nylon 11 and Nylon 7 films has been carried out. Films were prepared by slow cooling from the melt or by quenching rapidly into ice water. Poled films were soaked in distilledde-ionized water and the piezoelectric strain coefficientd ₃₁, piezoelectric stress coefficiente ₃₁, dielectric constant, and elastic modulusc measured continuously as the films dried out in a stream of dry nitrogen gas. The results obtained show that the piezoelectric response of poled Nylon 11 and Nylon 7 films is sensitive to adsorbed water, the sensitivity being greater for Nylon 7 than for Nylon 11. These observations are discussed in terms of the effect of water on molecular relaxation of these polymers.