The process and efficiency of sizing aramid yarns before the weaving process was studied. The sizing was carried out under different conditions, with and without the pre-wetting of the threads before the actual sizing process. Two groups of yarns were tested. The first group consisted of five yarn samples that were blended with 95% meta-aramid and 5% para-aramid in counts of 20 × 2, 17 × 2, 14 × 2 and 12.5 × 2 tex. The second group of yarns consisted of three yarn samples that were blended with 93% meta-aramid, 5% para-aramid and 2% carbon in counts of 20, 20 × 2 and 17 × 2 tex. The inlet moisture of the yarn before sizing was 40% (with pre-wetting) and 4% (without pre-wetting), and the outlet moisture after drying was 4%. In order to carry out such tests to reproduce them, the sizing was carried out on a laboratory-sizing machine with the possibility of adapting to industrial conditions. According to the obtained results related to the properties of yarn before and after sizing, it can be concluded that sizing of aramid yarns is justified. When sizing the yarn without pre-wetting, the mechanical properties improved, especially breaking force, strength and abrasion resistance. Irregularity and hairiness were also reduced, especially when sizing with pre-wetting. Yarn hairiness or the frequency of protruding fibres also decreased with sizing in almost all samples and sizing conditions. The second group of yarns with a carbon fibre content mostly showed better mechanical properties before sizing, which continued after sizing. In general, the aramid yarn sized with pre-wetting showed certain deformations caused by stretching in the wet state and thus reduced the size pick-up, which caused less breaking forces and strength. Sizing with pre-wetting resulted in a slightly better smoothness of the thread and its higher evenness. It can be concluded that the aramid yarn should be sized with a lower size percentage (up to 4.5%), i.e., without pre-wetting in order to minimise the deformation of the yarn during sizing and thus improve the mechanical properties in the weaving process.

The physical and mechanical properties of knitted fabrics for sports swimsuits are analysed in this paper. The knitted fabrics were experimentally aged in seawater and exposed to the sun continuously for 100 hours. Data were processed for nine knitted fabrics with the same raw material composition, polyamide and elastane in different proportions. The physical-mechanical properties of all nine samples before and after aging, as well as the drying rate and water absorption capacity, were examined. The results show that the properties of the knitted fabric changed in all samples. The sample with a higher elastane content (59% PA and 41% EL) is less sensitive to changes in mass per unit area and thickness after aging (−0.89% and 0.40%). The results of maximum wetted radius absorption water on the top and bottom of the knitted fabric, spreading speed absorption and drying time are shown. The results show that the values of the maximum wetted radius of absorbed water and the spreading speed increase for all samples, while the drying time for the knitted fabrics show different results.

Understanding the factors that affect how materials age is essential for creating a durable product with long-lasting properties. It is also important to prioritize defining aging parameters that reflect the real-world conditions the materials will encounter. For this study, a range of swimwear materials were selected consisting of a blend of polymer (polyamide/polyester) and elastane in varying ratios. In order to simulate aging conditions, materials were immersed in chlorinated outdoor pool water during the summer season, either in shade or the sun, for 200 and 300 h. The materials were tested for mass per unit area, thickness, tensile properties, and moisture management. A slight mass per unit area increase was observed, rising from 1.0% after 200 h of chlorine and sunlight exposure to 3.7% after 300 h. Thickness increased by 1.7% after 200 h and 3.2% after 300 h of chlorine exposure, with no significant effect of sunlight. Breaking force dropped by 12.4% after 200 h in chlorine and 8.2% in chlorine and sunlight, becoming more pronounced after 300 h (65.7% in chlorine and 65.1% in chlorine and sunlight). The overall moisture management capability declined from 0.4888 to 0.3457 after 200 h in chlorine and 0.3393 with sunlight, dropping further after 300 h to 0.3838 and 0.3253, respectively.