Observations of trimodal crystal texture in polypropylene blended with nylon 11

Abstract

AbstractX‐ray diffraction techniques, optical microscopy, and scanning electron microscopy have been used to study a series of melt‐spun bi‐constituent fibers containing isotactic polypropylene and nylon 11. The addition of small amounts of nylon 11 produces bimodal crystal texture in polypropylene with most crystallites having either their c‐axes or a‐axes oriented nearly parallel to the fiber axis. In blends containing about 50% nylon 11 a third polypropylene crystallite orientation is observed in which the [101] directions are oriented nearly parallel to the fiber axis. The polypropylene chain axes make an angle of about 50° to the fiber axis, and an additional set of layer lines is produced. In blends containing more than 50% nylon 11, most of the polypropylene crystallites adopt the third orientation. It is suggested that this third orientation of polypropylene crystallites is the result of epitaxy on portions of nylon 11 fold surface at the interface between the two components.