In this paper, the ultraviolet protection factor (UPF) of weft knitted fabrics made from 20Ne cotton yarn, Coolmax yarn and their blends in dry, relaxed and stretched states were studied. According to the fibre composition, samples were divided into three groups: Group I (single cotton yarn); Group II (cotton/cotton combination); and Group III (Coolmax/cotton combination) for discussion. In addition, yarn and fabric properties such as yarn tenacity, yarn strength, fibre combination and water vapour transmission that affect the corresponding UPF values are used for formulating a prediction model in order to determine UPF. Generally speaking, when samples are measured under stretched conditions in a dry state, they exhibit a remarkable reduction in ultraviolet protective power, as pores are opened up and UV radiation can easily penetrate through these pores. In addition, greater stretch percentage came along with greater reduction in UPF. This can be explained by the fact that the amount and the size of pores increase when samples are subjected to greater tension.

In this paper, the ultraviolet protection factor (UPF) of plain knitted fabrics made from 20Ne cotton yarns, Coolmax yarn and their combinations in wet, relaxed and stretched states were studied. According to the fiber composition, fabric samples are divided into three groups including Group I (single cotton yarn), Group II (cotton/cotton combination) and Group III (Coolmax/cotton combination) for discussion. In order to study the effect of wet condition on the UPF of different plain knitted fabrics, five wetting solutions, namely: (i) chlorinated pool water; (ii) sea water, (iii) acidic perspiration; (iv) alkaline perspiration and (v) deionized water (DI water) were prepared and the fabrics were wetted with different percentages of 50%, 75% and 100%. The UPF of the plain knitted fabrics in wet, relaxed and stretched states was measured and the results were discussed. In addition, yarn and fabric properties such as yarn tenacity, yarn strength, fiber combination and water vapor transmission, which affect the corresponding UPF values, were used for generating a prediction model in order to determine UPF. Verification of the prediction model was also conducted.