MORPHOLOGY OF COMPACTED POLYETHYLENE FIBERS

The microstructure of aggregates of parallel high-modulus polyethylene fibres, compacted at 138-degrees-C to give a composite with good mechanical properties, has been examined. Detail of transverse and longitudinal cross-sections has been revealed by permanganic etching and studied electron microscopically. The fibres pack together irregularly with coordination numbers typically between 4 and 7 and fibre diameters in the range 10-20 mum. Misalignment of fibres is generally close to zero but does occur incrementally, by 10-degrees and more, between successive rows of fibres. A substantial proportion of fibres has deformed, often by shear, during treatment producing a broadening of interfibrillar contacts. A lamellar component of texture is present both between and within fibres. It is inferred to form by melting of those parts of the fibres where there is least constraint on the melt, followed by recrystallization on the fibres as nuclei. The lamellae therefore share the axial orientation of the fibres, while the crystallographic fibre/lamellar contact promotes good transverse properties.