Orientation in nylon spherulites: A study by X‐ray diffraction

A microbeam x‐ray diffraction method has been used to study orientation in spherulites grown from the melt of nylon 66 and in one case of nylon 610. It is concluded that in positively birefringent spherulites the crystallographic a axis is parallel to the spherulite radius. The zigzag extinction pattern shown by such spherulites in a polarizing microscope can be understood in terms of this orientation. The results on negatively birefringent spherulites are not in agreement with earlier results of Keller and it is suggested that further work on such spherulites is desirable. Evidence is cited which shows that zero birefringent spherulites have random orientation. The spheruloids or spheruloidal aggregates which grow at the same time as negatively birefringent spherulites are found to have well defined optical properties when grown in thin films and confused optical properties when grown in thick film. This difference is reflected in differences in the x‐ray diagrams. In thin films a unique orientation exists in which a direction close to the crystallographic b axis lies parallel to the radius while the (002) plane lies near the surface of the film. This orientation provides an explanation of the observed optical properties. In thick film the (002) plane again tends to lie near the surface of the film, but orientation relative to the radius varies from place to place, thus causing confused optical properties.