Effect of polyester fibre fineness and cross‐sectional shape on physical characteristics of yarns

Polyester fibres with different geometrical features such as fineness, length and cross-sectional shapes were spun on a ring frame in all-polyester and 67:33 polyester:viscose (P:V) blended schemes using viscose fibres of same lengths. Along with circular fibres, three other non-circular fibres, namely trilobal, scalloped oval and tetrakelion, were investigated. Yarn physical parameters such as diameter, diameter variation, fibre packing fraction, surface twist angle variation, unevenness and imperfections were observed. It was found that an increase in the fibre linear density increases the yarn diameter, diameter percent coefficient of variation (CV%), mass CV% and surface twist angle CV%. It was observed that non-circular fibres all have their yarn CV% higher than the corresponding circular ones. The trend of the yarn packing fraction decreased with the linear density of the constituent fibre. The degree of yarn packing in non-circular fibres was observed to be lower than that in the corresponding circular fibres but the behaviour in respect of their yarn unevenness and imperfections was the other way round. Also, it was observed that the addition of viscose fibres to polyester improved the uniformity but deteriorated the imperfection level of the yarn. Trilobal fibres exhibited a higher number of neps in comparison with their circular counterparts but a reversal was seen in the case of scalloped oval and tetrakelion fibres.