Micro-computed tomography analysis of ring, rotor, and air jet yarn structures and their impact on fragmented fibres release from polyester textiles

The structural arrangements of fibres in a yarn (bundle of fibres) are critical to its properties. X-ray micro-computed tomography (μCT), an advanced non-destructive technique, was employed to investigate the internal structure of 100% staple PET (polyethylene terephthalate) yarns produced by ring, rotor, and airjet spinning. Commercially relevant yarns of the same linear density were scanned 9 times along their length using µCT to generate stitched 3D reconstructions to analyse fibre arrangements along the yarn length and cross-section. Image-J and Avizo software processed the data, revealing distinct structural differences among yarn types. Ring-spun yarns exhibited rounder profiles, higher fibre packing density, and greater fibre migration, followed by air jet and rotor yarns. A direct relationship between fibre migration (mean fibre position, RMS deviation) and mean packing density with the yarn tensile strength was observed with ring-spun yarn showing the highest values, followed by air jet and rotor yarns. The fragmented fibres (FFs) mass release is explained in terms of structural features of yarns. The yarn hairiness and radial packing density near the yarn periphery were attributed to the release of FFs. This study presents a novel μCT approach, compared to traditional tracer fibre techniques and cross-sectional microtomy, to analyse staple spun yarn structures.