Aspects of the microfibrillar structure of highly oriented polyamide-6 and its behaviour on deformation☆

The dependence of the large period on the macrostrain of a commercial polyfilament of PA-6 proved to be stepped. The steep portions of this dependence are associated with uncoiling of the through segments in the intrafibrillar amorphous layer to a trans-conformation and the sloping with the stretching of the trans-isomers. Such an interpretation is confirmed by the dependence of the mean length of the coherently scattering portion on the macrostrain which has marked maxima for the same strains when growth of the large period slows. The presence of several of inhibited growth of the large period is linked with the non-simultaneity of straightening of various through segments apparently caused by shifts of the planes of the hydrogen bonds in the crystallites.