Abstract

It has been shown that the use of a polarized attenuated total reflectance (ATR) infrared technique affords a means to study structure/frequency relationships and orientational behavior in partially oriented nylon (PON) yarns. In continuing studies, efforts have been directed toward the study of orientational development in the high-speed spinning of high-viscosity (HV) and low-viscosity (LV) Nylon 66 yarns. Infrared dichroism was used to study fiber orientation, and a relationship between infrared dichroism and orientation factor has been developed. The relationship between orientation measured by infrared and by x-ray diffraction is also shown. These are used to obtain the transition moment direction of a molecular vibration, which would otherwise be impossible to obtain by a single technique. Transition moment angles determined for crystalline vibrations were 39° and 41° with respect to the molecular chain axis for high- and low-viscosity PONs, respectively. Crystalline orientation factors obtained with these values are in excellent agreement with x-ray results. Infrared data indicate a sharp increase in crystalline orientation at slower spinning speeds up to a point (transition point); then orientation increases monotonically with increasing speeds. Beyond the transition point, high-viscosity yarn showed less orientation; below this point it showed higher orientation than lower-viscosity yarn. This transition is interpreted to be related to the molecular relaxation phenomenon. Amorphous orientation was also estimated from the <i>f</i>_IR and birefringence data, following the relationship proposed by Samuels. It was found that amorphous orientation was less than crystalline orientation at all speeds and practically insignificant at slower speeds, which leads us to the conclusion that, at low-to-moderate spinning speed, crystalline orientation predominates.

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