Deformation properties of the long period structure of oriented PM polyimide

Abstract

A study was made of the supermolecular structure of oriented rigid-chain polymer-PM polyimide, the effect of longitudinal elastic deformation on this structure and micro-deformation (relative deformation of crystallites) was compared with macrodeformation (relative deformation of the entire specimen), using large and small angle X-ray diffraction. A small-angle X-ray reflex is typical of the fibres studied, which proves the existence along the axis of orientation of a more or less regular alternation of regions of different densities (long periods). A study was made of the effect of elastic tension of specimens on small and large-angle X-ray diffraction patterns. The small-angle reflex increases in intensity and is displaced to smaller angles, i.e. the long periods are deformed. Long periods in PM arimide are examined using these results. The relative deformation of the crystalline lattice appeared abnormally high for polymers with a molecule in the crystallite shaped as a plane zigzag by up to 3%, which is ∼60% of the relative deformation of the entire specimen, i.e. crystallites have a considerable effect on the overall deformation of fibres. However, in PM arimide there are places which are “weaker” from a deformation point of view than crystallites—these are intercrystallite layers which together with crystallites evidently constitute the long periods observed.