Intrinsic Birefringence of γ‐Form Crystal of Nylon 6: Application to Orientation Development in High‐Speed Spun Fibers of Nylon 6

The intrinsic birefringences of the α‐ and the γ‐form crystals of nylon 6 were calculated from the atomic coordinates and the bond polarizabilities using the Lorentz‐Lorenz equation. The intrinsic birefringence of the γ‐form crystal was found to be significantly smaller than that of the α‐form crystal. Those values were applied to the evaluation of the orientation function of the amorphous phase of the nylon 6 fibers produced by the high‐speed spinning process. The molecular orientation in the amorphous phase increased to the maximum point and then decreased with the spinning speed. These results suggested that an inhomogeneous structure in the fiber was formed for the higher take‐up speed.