PHYSICO-MECHANICAL PROPERTIES OF DOUBLE-LAYER KNITTED FABRICS

ABSTRACT

In our research, studies were conducted on the physico-mechanical properties of newly structured double-layer knitted fabrics made from polyacrylonitrile yarn, with the aim of efficiently utilizing locally available raw materials. In this work, new structural designs of double-layer knitted fabrics based on rib knitting were proposed in order to expand the assortment of knitted fabrics and improve their quality indicators. Ten variants of the proposed samples were produced using yarn with a linear density of 31×2 tex, and knitted on the “LONG-XING” LXA-252 flatbed knitting machine at the laboratory of the Department of Textile Fabric Technology, Tashkent Institute of Textile and Light Industry. The physico-mechanical properties of the obtained samples were analyzed.

АННОТАЦИЯ

В нашей научной работе с целью эффективного использования местного сырья были проведены исследования физико-механических свойств двухслойного трикотажа новой структуры из полиакрилонитрильной пряжи. В данной работе с целью расширения ассортимента трикотажных полотен и улучшения их качественных показателей были предложены двухслойные трикотажные полотенца новой структуры на основе резинового переплетения. Предлагаемые образцы двухслойного трикотажа, полученные из нити с линейной плотностью 31*2 текс, были выработаны на плосковязальной машине "LONG-XING" ЛХА-252 в лаборатории кафедры "Технология текстильных тканей" ТТЭСИ. Проанализированы физико-механические свойства полученных образцов.

Keywords: raw material, polyacrylonitrile, knitwear, flatbed knitting machine, double-layer, air permeability, deformation.

Ключевые слова: сырье, полиакрилонитрил, трикотаж, плоскофанговая машина, двухслойная, воздухопроницаемость, деформация.

Introduction.

In our republic, one of the main challenges faced by enterprises specializing in the production of knitted products is to increase the country's export potential, expand the range of products in domestic and foreign markets, improve their quality, and manufacture high physico-mechanical performance knitwear from local raw materials that can substitute imported goods. One of the pressing issues today is to expand the production of consumer goods by efficiently utilizing the technological capabilities of the installed knitting machines and the available local raw materials, and to produce competitive, high-quality knitted products that meet the demands of both domestic and international markets, thereby replacing imported goods. This scientific research contributes, to a certain extent, to the implementation of the tasks set out in the Presidential Decree of the Republic of Uzbekistan No. PF-60 dated January 28, 2022, "On the Development Strategy of New Uzbekistan for 2022–2026," the Presidential Decree No. PF-53 dated January 21, 2022, "On Measures to Encourage Deep Processing and Production of High Value-Added Finished Products in Textile and Knitwear Enterprises and Promote Their Export," as well as other relevant regulatory and legal documents related to this field [1–2]. In order to utilize raw materials more efficiently, I.I. Shalov [3] proposed several approaches in the production of knitted fabrics, including the replacement of double-layer fabrics with single-layer ones, the use of yarns with reduced linear density, and the application of partial (incomplete) knitted structures. In this scientific study, in order to improve the shape retention properties of knitted products, Prof. V.A. Zinovyeva and M.A. Popova [4] proposed a method for producing double-layer knitted fabric based on productive rib knitting. In this method, both sides of the fabric consist of extended front-side loops, with each course shifted by one needle pitch, and the layers are interconnected using not fewer than two yarns.

Materials and methods. In our research, new structural designs of double-layer knitted fabrics based on rib knitting were proposed in order to expand the range of knitted fabrics and improve their quality characteristics. Ten sample variants of the proposed double-layer knitted fabrics were produced from yarn with a linear density of 31×2 tex using the “LONG-XING” LXA-252 flatbed knitting machine at the laboratory of the Department of Textile Fabric Technology, Tashkent Institute of Textile and Light Industry. In order to study the physico-mechanical properties of the 10 variants of double-layer knitted fabric samples, experimental tests were carried out using modern equipment installed at the “SENTEX-UZ” certification laboratory under the Tashkent Institute of Textile and Light Industry. The analysis results are presented in Table 1.

Table 1.

Physical and mechanical properties of double-layer knitted fabrics

Results and discussion. Air permeability refers to the ability of a material to allow air to pass through it. It is characterized by the air permeability coefficient, which indicates the amount of air passing through 1 cm² of fabric per second under a given pressure difference across both sides of the material. The air permeability coefficient is denoted as B and expressed in cm³/cm²·s [5-6].

In the production of knitted products, the air permeability coefficient of knitted fabrics varies (expressed in cm³/cm²·s) depending on the type of knit structure, fabric thickness, and density.

One of the most important characteristics of knitted products is their hygienic property, particularly air permeability. The air permeability of the base sample (Variant 1), produced from double-layer PAN yarn, was found to be 34% higher than that of Variant 2, 14% lower than Variant 3, 16% higher than Variant 4, 12% lower than Variant 5, 16% lower than Variant 6, 52% lower than Variant 7, 14% lower than Variant 8, 64% lower than Variant 9, and 51% lower than Variant 10.

The study shows that the air permeability characteristics of the double-layer knitted fabrics made from PAN yarn in Variants 2 and 5 exhibit higher hygienic properties compared to the base Variant 1 and other sample variants, as illustrated in Figure 1.

Figure 1. Variation in Air Permeability of Double-Layer Knitted Fabrics

The durability of knitted fabrics is determined by their resistance to abrasion and tensile strength. The analysis of abrasion resistance across the studied knitted fabric samples indicates that the base sample (Variant 1) made from PAN yarn, along with Variants 2, 3, 4, 5, and 7, exhibited lower abrasion resistance compared to the other variants.

Variant 6 showed 6% higher abrasion resistance than the base sample made from PAN yarn; Variant 8 was 5% lower, Variant 9 was 12% higher, and Variant 10 demonstrated 15% higher abrasion resistance than the base sample made from polyacrylonitrile yarn, as illustrated in Figure 2.

Figure 2. Change in the abrasion resistance of double-layer knitted fabrics

The tensile strength of the double-layer knitted fabrics varied across the samples. The tensile strength of the base sample (Variant 1) made from PAN yarn was found to be 23% lower than that of Variant 2. The tensile strength of Variant 3 was 9% lower than the base sample, while Variant 4 was 6% higher. Variant 5 showed a 31% increase, Variant 6 was 12% lower, Variant 7 was 30% higher, Variant 8 was 7% higher, Variant 9 was 9% higher, and Variant 10 was 20% lower than the base sample made from polyacrylonitrile yarn. The variation in residual deformation of the double-layer knitted fabrics showed distinctive characteristics in the samples made from PAN yarn.
The residual deformation of Variant 2, produced from PAN yarn, was found to be 10% higher in lengthwise direction compared to the base sample (Variant 1).
The deformation of Variant 1 was 18% higher than that of Variant 3. Compared to Variants 4, 5, and 6, the deformation of the base sample was 10% lower.
Variant 1 showed 18% lower residual deformation than Variant 7, and 11% higher than Variants 8, 9, and 10. The recoverable (elastic) deformation of Variant 1, made from PAN yarn, was found to be 3% higher in the longitudinal (lengthwise) direction compared to Variants 2, 4, 5, 6, and 7. In comparison with Variant 3, the recoverable deformation of Variant 1 was 4% lower, and it was also 2% lower than that of Variants 8, 9, and 10.

Conclusion

1. It was established that the air permeability properties of the proposed two-layer knitted fabric samples in Variants 2, 4 are lower than in the 1st basic option, which indicates that these Variants have higher heat-insulating properties.
2. In samples of two-layer knitted fabrics of Variants 8, 9, 10, the property of abrasion resistance has a higher indicator compared to other samples and base sample 1, these Variants reflect that they are stronger compared to other option samples.
3. The features of reversible deformation of two-layer knitted fabrics of the proposed new structure in Variants 2, 4, 5, 6, 7 showed that these Variants have high shape-preserving properties.
4. Scientific research of two-layer knitted fabrics of a new structure from Pan yarn allows for the widespread use of local raw materials.
5. The production of two-layer knitted fabrics on flat knitting machines increases the technological capabilities of the machine and expands the range of fabrics and products.
6. Two-layer knitted fabrics of a new structure are recommended for outer knitted products.

References:

1. Decree of the President of the Republic of Uzbekistan "On Measures to Raise the Development of the Textile and Sewing and Knitwear Industry to a New Level" (No. UP-71, 01.05.2024) https://kknews.uz
2. Presidential Decree of the Republic of Uzbekistan dated February 12, 2019, No. UP-4947
3. Resolution of the President of the Republic of Uzbekistan No. PP-4186 "On Measures for Further Deepening the Reform of the Textile and Garment and Knitwear Industry and Expanding its Export Potential." https://lex.uz/docs/4199423
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