Ultraviolet protection of knitwear fabrics

Abstract

The alarming increase of incidence of skin cancer has hastened the development and research of ultraviolet (UV) protective clothing. Although various fabric parameters that affect the ultraviolet radiation (UVR) transmission were studied by researchers, most of them focused on woven fabrics and chemical approaches for enhancing UV protection. Knitwear is an indispensable clothing in summer but there were few studies concerning knitted fabrics, in particular the influence of fabric constructions on ultraviolet protection factor (UPF) and structural properties. This thesis aimed at studying the UV protective property of knitted fabrics at a fundamental level by investigating the influence of different knit structures upon UPF with the three main knit stitches incorporated in the cotton knitted fabric constructions, namely, knit, tuck and miss stitches. The impacts of yarn characteristics, fabric constructions, coloration, end-use conditions including stretching, wetting and laundering, on UV protection were comprehensively studied. A metallic biaxial stretching equipment was specially developed for the evaluation of UV protection of fabrics in stretched condition. The results showed that fabrics with different knit structures have distinct performances in UV protection. A fabric with miss stitches offered remarkable UV protection whereas a fabric with tuck stitches exhibited poor UV protection. The colored knitted fabric with miss stitches imparted relatively better UV protection in a lighter color depth than the fabric with tuck stitches that were dyed in a darker shade. It infers the potential for reducing usage of dyestuffs and chemical auxiliaries in manufacturing UV protective clothing. Besides, knitted fabrics with miss stitches retained good UV protection under the stretched and wet conditions that simulating the daily wearing conditions of knitwear. The results of this study would provide value-added information to textile designers, manufacturers, and consumers for the enhancement of UV protection and selection of UV protective knitwear.