Physical-Mechanical Properties of PES Fibres after Blind Dyeing in Acid and Alkali Media

Abstract

Some characteristic physical-mechanical, viscoelastic, structural and morphological properties of polyester filaments (A) are investigated and compared to the properties after a blind high-temperature dyeing in alkali (B) and acid (C) medium. The results obtained indicate that dyeing in either acid or alkali medium does not influence filament yarn properties in such a degree as to cause crucial changes in fibre properties. The changes in viscoelastic properties of the filaments are statistically random and have no impact on end-use properties. The module is reduced after dyeing in both alkali and acid medium, which results in higher bending elasticity of both the filament and end-product. Melting enthalpy is somewhat increased, due to crystallisation that occurs at dyeing temperature. Scanning electron microscopy (SEM) confirms high degree of oligomer migration onto the filament surface after dyeing in an acid medium, and their saponification when dyeing in an alkali medium. The investigations presented have confirmed that the problem of oligomer diffusion onto the surface of PES filament yarn can be successfully solved by dyeing PES in an alkali medium, with no significant change of their physical-mechanical and processing properties.