Clothing comfort is very important feature which is considered as a result of different process of heat exchange between human body, clothing and environment. The purpose of this paper is to analyse the impact of clothing insulation on the heat transfer. The measurements were carried out on commercially 1x1 RIB knitted fabrics used for the production of next-to-skin shirts. The one group of samples are made from 100% cotton yarn and another with 96% cotton and 4%lycra. It is noticed that knitted material composition affected the change in heat resistance. Also, this paper presents and verifies the correlation between the measured values of thermal resistance (Rct) and the knitwear thickness (dpl), the covering factor (K), the porosity of the twists (e) and the surface coefficient (dp). Based on these results, a mathematical model for calculating thermal resistance is proposed. Comparing the results obtained with the proposed equation and the measured results, we can see that the deviations are minimal. The highest deviation for sample C4 is 0.05%,while the largest deviation for sample CL4 is 4.6%.

An analysis of the mechanical properties of textured PES yarns shows that the texturing speed has a significant effect on these properties. The results showed that with the increase in the texturing speed, a decreasing trend was observed in the breaking forces of the analyzed textured PES yarns at stretching degrees of 1.665 and 1.685. Some deviations of the results were found in the textured PES yarns with the applied stretching degree of 1.675. Also, the results showed that at a stretching degree of 1.685, the analyzed yarns generally have higher values of breaking forces. Applying a higher degree of stretching of PES filament yarns improves the orientation of molecular chains in the direction of the stretching force, which contributes to better mechanical characteristics of textured PES yarn. In addition, the results of the analysis of the influence of the first heater temperature show that, at higher temperatures, the textured PES yarns with higher values of breaking forces are produced. The results obtained were used to suggest the equations for predicting the yield points and breaking forces of textured PES filament yarns depending on the process parameters of production.

The properties of textured POY PES multifilament yarns are conditioned by texturing temperature, texturing speed, stretching degree and by the ratio of disc peripheral speed and yarn speed. In the paper attention is focused on crimping of yarns. New method for defining crimping limits is proposed. The method is based on the flow analysis of the force-elongation function. POY multifilament polyester yarns, having the fineness of 167f36x1 dtex were analyzed. The texturing of PES multifilament yarns was performed using different first heater temperatures (350 oC, 400 oC, 450 oC) and maintaining the constant temperature of the second heater (180 oC), then with different texturing speeds (500 m/min, 600 m/min, 700 m/min, 900 m/min, 1000 m/min, 1100 m/min), using different ratio of the disc circumferential speed to yarn speed (2.15, 2.20, 2.25) and at the extension degree of 1.665.