2.1.2. Influence of Fabric Structure, with PBT Weft, on the Properties of Fabrics

We continued with an investigation of the influence of different yarn densities, the sequence of insertion of PBT yarn in the weft direction and different weaves on the properties of fabrics with PBT yarn.

Nine samples of fabrics, differing in the structure of the PBT-containing yarn, the weave and sequence of PBT in the weft, were all produced on the laboratory rapier weaving machine (Minifaber, Seriate (BG), Italy), with the warp of 100% cotton (8 × 2 tex) at on-loom density of 20 ends/cm. Three of them, containing PBT in every fifth weft (sequence: four cotton yarns, one yarn containing PBT), were designed and produced in three different twill weaves, (rows 2, 3, and 4 in Table 1, Figure 3). By using different twill weaves, we also wanted to evaluate the influence of float length on fabric properties before and after thermal treatment. Figure 4, first row, shows three weaves used and simulations of woven fabrics [28] with well depicted weft sequence.

Simulations of woven fabrics shows the weave, linear density of the PBT yarns, and different weft sequence used.

Pictures of samples produced with untreated Co/PBT yarn in weft, before and after thermal treatment of fabrics.

Characteristics of samples to evaluate the effects of different float lengths and weft sequences.

We also studied the changes in elastic properties of woven fabrics and cotton series with the addition of two different sequences of viscose/PBT yarn in the weft direction and different weaves to achieve better elastic properties. Viscose/PBT core yarn was 10 × 2 tex (50/2 Nm) with PBT 5.6 tex in the core, where the PBT contributes 28% of yarn mass. Six samples were designed and produced, with different sequences of viscose/PBT combinations in every fourth and fifth weft and in three different weaves (rows 5, 6, and 7 rows in Table 1, Figure 3). After weaving, all fabrics were thermally treated—boiled in distilled water for 30 min and dried for 24 h in a state of free tension [5,17].

In this study, the following properties of all woven samples were investigated: physical properties (mass per unit area SIST EN 12127:1999, number of threads per unit length SIST EN 1049-2:1993, thickness of textiles SIST EN ISO 5084:1996), tensile properties of fabrics (SIST EN ISO 13934-1), air permeability (ISO 9237:1995), and for samples from 4 to 6 (Table 1) the abrasion resistance by Martindale method (SIST EN ISO 12945-2) was also measured. The results of shrinkage after thermal treatment and physical properties of samples are shown in Appendix B Table A6 and Table A7.

The study was further extended by investigating the influence of the use of PBT on the properties of complex fabrics, such as terry fabrics. The range of applications of terry fabrics with increased elasticity is much wider than the classical one. They would also be suitable for sportswear and children’s clothing, blankets, bedding, technical applications or as innovative products (universal fitted sheet/bedding/towel for inflatable pillows).

In this work the influences of different constructions of the fabrics on the elastic and other usage properties of terry were investigated. To study the influence of constructional parameters on terry properties, six different terry samples were used, which were industrially produced on terry weaving machine (Vamatex, Deinze, Belgium). They differed in warp yarns (OE cotton yarn, 74 tex and carded ring spun yarn, 60 tex) and weft yarns (OE cotton yarn, two core spun yarns with cotton sheet—one with PBT core and the other with Lycra core, PBT multifilament), as far as the pile yarn was the same for all samples (OE cotton, 37 tex). The face-side three-pick terry, with base weave mixed rip 2/3, and the same warp sequence were used for all six terry fabrics, but last two terry fabrics had different weft sequences, as shown in Table 2.

Basic constructional parameters of face-side three-pick terry (base weave: mixed rip 2/3).

After thermal treatment, boiling in water for 30 min to impart elasticity, basic properties of treated and untreated terry fabrics were investigated: crimp of yarn in fabric (ISO 7211-3:1984), mass per unit area (SIST EN 12127:1999), tensile properties of fabrics (SIST EN ISO 13934-1:2013), bursting properties of fabrics (ISO 13938-2:1999), vertical wicking (measures the distance in mm at a given time; (AATCC Test Method 197), dimensional changes of treated samples (ISO 3759:2011). The results of physical mechanical properties of the samples before (b.t.) and after (a.t.) treatment are shown in Table 3.

Properties of terry samples before (b.t.) and after (a.t.) treatment.