Dielectric relaxation in the odd‐numbered polyamides: Nylon 7‐7 and nylon 11

Abstract

AbstractOdd‐numbered polyamides have dipoles with components that point in the same direction in the planar zigzag conformation (rather than alternating as in the even‐numbered polyamides). An investigation of the dielectric properties of two odd nylons was undertaken here to see if dipole correlation resulting from this effect could be detected. It was found that the dielectric constant and relaxation strength associated with the α loss process (amorphous phase glass–rubber relaxation) when normalized for dipole concentration was indeed markedly higher in the odd nylons. The effect of uniaxial orientation induced by solid‐state extrusion on the isotropy of the dielectric properties was also studied. A previous study on nylon 6–10 found a reduction in relaxation strength of the α process in both the parallel and perpendicular directions but with the perpendicular direction being much stronger than the parallel. A similar result was found here for the odd polyamides. Thus the reduction in intensity appears to be due to effective reduction in the amount of amorphous material and not due to any change in dipole correlation induced by orientation. The anisotropy in relaxation strength can be explained by a composite material effect resulting from parallel stacking of crystal lamellas and interlamellar amorphous material and without invoking any anisotropy in the amorphous‐phase dielectric strength. Thus there is no reason to conclude that the amorphous phase undergoes orientation as a result of the crystal‐phase orientation.