UV radiation (UV-R) can be divided into UV-A, UV-B and UV-C radiation. UV-C radiation get absorbed by atmosphere, but diminishing of the ozone layer results with the reaching of UV-B and UV-A rays on the Earths surface. Even though the UV-A rays are necessary for vitamin D synthesis, longer exposure to UV-A and UV-B rays can cause acute and chronic reactions and damages such as erythema (sunburn), sun tanning, photocarcinogenesis and photoaging, as well as known skin aging and recently the formation of skin malignant neoplasm. Garment provides some UV protection, but in most cases there are not enough its sun screening properties. This protection, among other large number of factors, highly depends on fabric surface and construction, especially for longer pending in the sun. Therefore, in last few years different protective finishes and material modification were developed. This paper deals with the influence of yarn linear density of cotton knitted fabric on its ultraviolet skin protection expressed as ultraviolet protection factor (UPF). The effects of yarn linear density on UPF using knitted fabrics from the same cotton fibers were discussed. Raw, pretreated and zeolite treated cotton fabrics were used. UV-A and UV-B transmissions were measured on transmission spectrophotometer Cary 50 Solarscreen (Varian) according to AATCC Test Method 183-2000. On the base of these values Ultraviolet protection factor (UPF) was calculated.
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