Structure–property relationships of high-performance polyethylene fibres

The morphology of surface grown polythylene fibres before and after zone-drawing is studied by electron microscopy using various preparation techniques, mainly chlorsulfonation staining and ultra-thin sectioning. Computer processing is applied in order improve the detectability of image details. Image analysis is carried out by digital or optical diffraction. It is found that, to a first approximation, the average lateral core size of the fibrils (≈ 4 nm) remains nearly constant during drawing. This is consistent with a successive “reeling in” process of chain segments from the molten shish kebab overgrowth and from the interfibriller matrix into the extended-chain backbone fibrils. The structural data derived by electron microscopy enable us to calculate the Young's moduli of the fibres within the scope of an unidirectional fibre composite model. Comparing these estimates with the results of mechanical testing yields quite a good agreement. On the other hand, the existance of gross morphological defects like kink bands, disordered boundary regions, voids, and distortions and terminations of fibril bundles, prove to cause a considerable deterioration of the fibre properties.