Orientation and structure development in melt-spun Nylon-6 fibres

A network model is applied to describe the deformation behaviour of melt-spun Nylon-6 fibres obtained at different spinning and drawing conditions. The network draw ratio is determined from analysis of true stress–strain curves and correlated with fibre orientation. From this analysis it appears that the deformation behaviour of Nylon-6 fibres adheres to a pseudo-affine mechanism. The results are discussed in terms of the semicrystalline nature of Nylon-6 fibres. By means of on-line birefringence measurements, wide angle X-ray scattering (WAXS) and solid-state NMR, it is shown that the crystalline and amorphous phases in Nylon-6 respond in a different way to network deformation. In the spin line, an affine (rubber-like) deformation mechanism is observed and this rubber-like network behaviour is transferred to the amorphous phase. After winding and conditioning of the spun fibres, a crystalline phase with relatively high orientation is formed which deforms according to a pseudo-affine mechanism upon further stretching.