Knitted fabrics and products are subjected to a variety of stresses and loads/deformation during their usage. The loads are different by value, by direction, and by duration. The alternations of loading and unloading or resting processes affect the knitted structure and could bring about changes in the linear dimensions of the fabric or result in the deformation of the knitted items and ultimately the loss of product appearance or its functional properties. A wide range of textile materials resistant to multiply loads was produced by using elastomeric yarn that has an elongation of more than 95% and is able to attain full recovery after relaxation due to its chemical composition. This case study examines two existing test methods for evaluating the stretch properties of textile materials produced with the elastomeric yarns with emphasis on warp knitted abdominal binder-type fabrics. It was found that the linear density of the weft in-laying threads and the preliminary tension of the ground yarn which formed pillar stitch affect stretch properties of elastic warp knitted fabric: the full deformation and its constituent parts. The change in the preliminary elongation of the bare spandex in the 210%-270% range does not have a significant effect.
The demand for medical textile products is increasing with awareness regarding better healthcare services and efficient medical treatments. Compared to other textiles, elastic warp knitted materials, which have elastomer threads in each wale have been widely used in producing medical and preventive products. Thus, in order to decrease the weight and cost of these products without effect on fabric’s stretchability, in this study, various elastic warp knitted fabrics were produced using different raw materials and elastomer threading arrangements, and their properties were investigated. The fabrics were produced on a crochet knitting machine with five different arrangements of elastomer threading and four different laid-in yarn materials as polyester, cotton, and linen. Then the dimensional properties and elastic behaviors of the samples were determined and evaluated comparatively. Statistical analysis showed that all studied elastic warp knitted fabrics have high provide elasticity at a higher than 95% level. On the other hand, the mass per unit area of the fabric is reduced, with the use of linen yarn as weft yarn, or when the total linear density of the weft yarn and the amount of elastomer threads decrease. Finally, the obtained results revealed the possibility to reduce elastomer consumption to decrease weight for elastic medical products, which were developed, without effect on fabric’s stretchability and elasticity as well as replacing synthetic threads with natural yarns in order to improve product comfort.
Two main methods employed in designing knitted fabrics for production rely on a given surface density or on the basis weight (grams per square meter). The actual value of these parameters may differ. Normally, the actual basis weight of knitted fabrics is determined by weighing a sample of a certain width and length and subsequently performing the relevant conversion (ISO 3801:1977). This method involves a destruction or wasting of the material. A non-destructive ultrasonic method for determining the basis weight of textile materials was developed, which is based on a determination of the amplitude ratio of ultrasonic waves falling on the fabric and the waves passing through it. However, this method has limitations in determining the basis weight of textile materials with variable porosity, such as knitted fabrics. To improve the developed method, it is proposed to continue the measuring of an amplitude of the reflected wave from the fabric surface. In this case, it is possible to monitor the fabric porosity changes. If the distance and pore size of the controlled fabric have increased or decreased relative to the control sample, the amplitude and magnitude of the reflected wave (part of the reflected ultrasonic signal) changes and the ultrasonic device will be adapted to the fabric structure. Our studies have demonstrated the possibility of determining the fabric porosity by using an amplitude of the reflected ultrasonic wave from the fabric surface, which allows adaptively to determine the basis weight using an amplitude of transmitted ultrasonic wave. Further development of ultrasonic non-contact methods and relative devises is very important for production control.
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