Comfort is an important quality criterion, especially for sportswear. It influences well-being, performance and efficiency. The necessary dissipation of heat and air flow, at high metabolic rates, must be designed and planned in advance. The influence of structure, density, mass and thickness of fabric were considered as well as yarn material composition, yarn linear density, yarn evenness and yarn hairiness. The influence of the mentioned parameters on thermal properties and air permeability was calculated. From the correlation analysis, it can be concluded that yarn’s linear density, yarn short fibers hairiness, and mass per unit area of knitted fabric has the greatest impact on heat resistance. The yarn linear density, the yarn hairiness of the longer protruding fibers, and the thickness of the knitted fabric have the greatest impact on air permeability. A statistically significant model of multiple linear regression equations was offered to predict the thermal comfort of knitted fabric.

A double-bed circular knitting machine with a gauge of E17 and a needle bar diameter of 200 mm (8 in) was used to make three groups of plain weft knitted Tencel fabrics and three groups of modal knitted fabrics. The yarns were spun using three spinning methods: ring, rotor, and air-jet system. Their count was 20 tex. All the knitted fabric samples were manufactured under the same conditions. One-half of each knitted fabric sample remained unfinished, while the other half was finished. Structure parameters of all finished and unfinished knitted fabrics were analyzed, and the most significant parameters were compared. Tensile properties of the knitted fabrics in wale and course directions were measured. The difference in the elasticity of the knitted fabric was analyzed in particular, and the portions of knitted fabric stretch are given. The basic conclusion is that using equal yarn fineness, but different raw material composition and structure, the produced knitted fabrics had substantially different fabric masses per unit area. The raw material composition and construction of the yarn, that is, the yarn manufacturing process and the spinning process produce yarns of different structures and properties that are manifested in the structure and properties of the knitted fabric. Thus, the finishing process must be specific for each raw material composition and yarn structure.

The research was carried out on five double jersey knitted fabrics, knitted from cotton, Viscose®, Tencel®, Modal® and polyester ring spun yarns finesses of 20 tex. A circular double bed knitting machine gauge of E17 with the same production parameters was used for knitting all the fabrics. A change in all knitted fabric structure parameters was reflected through fabric mass per unit area, which ranged from 142 g m−2 to 165 g m−2. The minimum and maximum knitted fabric mass per unit area difference is up to 16 %. The lowest thermal resistance have polyester, while the largest have cotton knitted fabric. Thermal resistance of cotton fabric is higher for 36.7 % related to polyester knitted fabric. Considering basic knitted fabric parameters, knitting with same constructional parameters but different yarn raw materials doesn’t provide knitted fabric with same mass per unit area or thickness, i.e. thickness factor. It can be concluded that beside basic knitted fabric parameters, yarn raw material influence on thermal resistance.