Hava-jetli Tekstüre İşleminde Hacimlilik (bulk) İncelenmesi

Abstract

Hava-jetli tekstüre, paralel bir düzende bir arada bulunan sentetik filament iplikleri kesmeksizin veya koparmaksızın bu liflerin tekstil amaçlı kullanılabilirliğini arttırmak amacıyla daha hacimli bir yapı kazandırma tekniği olan iplik tekstüre işlemlerinden biridir. Hava-jetli tekstüre tek mekanik iplik tekstüre yöntemidir ve bu yöntemle üretilen tekstüre iplik özelliklerinin kesikli elyaftan yün veya pamuk eğirme sistemlerine göre eğrilmiş iplik özelliklerine olan yakın benzerliği hava-jetli tekstüreyi diğer iplik tekstüre yöntemlerine göre avantajlı konuma getirmektedir. Bu yöntem ekonomik açıdan da düşük yatırım ve işletim maliyetleri ile dikkat çekmektedir ve pazar payını gittikçe artırmaktadır. Ayrıca yeni bir fikir olarak bu çalışmada gündeme getirilen hava-jetli tekstüre ipliğin işlem esnasında on-line olarak boyanmasının da sistemin esneklik avantajını daha da öne çıkaracağına inanılmaktadır. Hava-jetli tekstüre ipliklerin özellikleri numara ve mukavemet değerleri ile beraber ilmik boyutu, ilmik sıklığı, hacimlilik ve dolaşıklık derecesi gibi yapısal özellikleri tarafından belirlenir. Hava-jetli tekstüre ipliğin özelliklerini hava basıncı, aşın besleme, tekstüre hızı, mekanik kararlılık kazandırma gerilimi, ıslak ya da kuru tekstüre ve çarpma elemanın kullanılıp kullanılmaması gibi çeşitli işlem parametreleri ve iplik içindeki filament sayısı, filament numarası, filametin kesit şekli, ipliğin malzemesi gibi besleme ipliği özellikleri etkilemektedir. İşlem parametrelerinden aşın beslemenin ve besleme ipliği özelliklerinden iplik içindeki filament sayısı ve filament numarasının sonuçta hava-jetli tekstüre iplik özelliklerini nasıl etkilediği numara, mukavemet ve tüylülük deneyleri kullanılarak araştınldı. Tekstüre ipliklerin mikroskopta incelenerek çekilen fotoğrafları da bu araştırmaya görsel destek sağladı. Hava-jetli tekstüre makinası ile on-line çalışabilecek bir boyama ünitesini gerçekleştirme imkanlarını aramak ve tasanmını yapabilmek için bu çalışmaya konu olan hava-jetli tekstüre ipliklerin de malzemesi olan polyester elyafının yapısı, boyanma özellikleri ve pratikte kullanılmakta olan boyama yöntemleri ile ilgili araştırmalar yapıldı.

"Texture" is a concept describing the most important properties of a textiles product, which are appearance and hand. Originating from the surface characteristics of the product and the structure in which the filaments are arranged this concept describes the feeling of warmth and bulkiness of yarns, fabrics as well as apparel products. Warmth, hand and natural texture are the main demands from a textiles product. Although natural fibres, with their natural structure, comply well with these demands, continuous filaments which resemble glass rods, are far away from fulfilling these expectations them. Yet, they posses much better characteristics in terms of strength and uniformity, compared to natural fibres. Hence, the main objective of a synthetic yarn production processes is to produce yarn, imitating the desirable characteristics of natural fibre yarns, while maintaining the superior mechanical characteristics of synthetic filament yarns. A way to do this has been to first crimp continuous bundle of filaments, then cut ör break them apart into little pieces, and make yarn out of them with traditional spinning methods that are used for cotton and wool. Yarn can also be made out of continuous filaments, without having to cut them, by utilizing specific texturing methods. Yet, the results of these operations are not as satisfactory as those of spinning operations, in terms of imitating natural fibre yarns. Generally speaking, "Yarn Texturing Processes" can be defined as the techniques employed to enhance bulkiness and textiles applicability of closely packed parallel arrangements of continuous filaments. Using these techniques, it is possible to modify the compact structure of synthetic yarns without having to cut ör break the filaments. Yarn texturing methods may be grouped as thermo-mechanical and mechanical methods. Thermo-mechanical methods consist of heating thermo-plastic filament yarn up to its semi-plastic temperature limit, mechanically deforming it there and then cooling it back to ambient temperature while retaining the deformations, leaving permanent crimps on the yarn. Techniques exist relying on this principle such as false twist, stuffer box, knit-de-knit process, gear crimping, and edge crimping. False trvvist, among these techniques, is the most commonly used öne, as 75% of the total texturing production accomplished so far. The second most commonly used texturing technique coming after false twist is bulked continuous filament (BCF) texturing, which is realized with the aid of a höt fluid. xi The method of texturing with the aid of a cold fluid, which is also known as air-jet texturing is the only method which is purely mechanical and does not depend upon any thermoplastic properties of fılaments, rather than that, it relies on the application of the principle of overfeed. Yarn texture obtained by thermo-mechanical methods is generally lost under increasing load conditions. On the other hand, texture obtained by the air-jet texturing process is retained similar to the natural spun fibre yarns. Furthermore, the air trapped vvithin the fixed and flexible loops on the surface of air-jet textured yara constitutes a thermal insulation layer, in a similar manner to the hairs sticking out from the surface of spun yaraş. Hence, air-jet textured yarn is very close to imitating both the physical and visual properties of spun yarn. Photographs of an air-jet textured yara and a cotton yara are presented in the below figüre for comparison. ^^^^^^^^m^^jSfat Figüre 1. Visual comparison of a cotton yarn with an air-jet textured yara The topic of the work carried out is the investigation of bulkiness in air-jet textured yaraş. These types of yaraş can be classified into three groups in terms of their production processes: 1. Single End Textured Yara 2. Parallel End Textured Yarn 3. Core-Effect Textured Yara Single End Texturing is referred to texturing process of feeding a single supply yarn into an air-jet at a certain overfeed ratio. Parallel End Texturing is referred to the texturing process of rwo of more yaraş of the same ör different type at the same speed. Core-Effect Texturing, on the other hand, is referred to the process of texturing two ör more yaraş of the same ör different type using at least two of more different texturing speeds by the assistance of separate feeding cylinders to enhance blending properties. Air-jet texturing is a technique that converts continuous filament yaraş into a yara which posesses properties closest to those of natural fibre yaraş and staple spun yaraş. in order to be able to produce air-jet yaraş of desired characteristics at optimum producîion configurations, it is essential that the structures of such yaraş are well understood and the influences of process parameters on the production are closely identified. xii The properties of air-jet textured filament yarns are identified in terms of loop size, loop frequency, bulkiness, and degree of entanglement in addition to yarn linear density and yarn strength. On the other hand, the factors affecting the properties of air-jet yarns can be listed as the air pressure used, overfeed ratio, texturing speed, stabilizing extension, the use of water, the use of an impact element as process factors, and the number of filaments, filament linear density, shape of filament cross- section, and spin finish, as factors arising from the supply yarn. Until now, although extensive studies have been conducted on single end and parallel end texturing processes, such a study on core-effect texturing has not been come across. in this work, to constitute a foundation from previous research work, single and parallel end texturing worked out first. Then, the influence of process and supply yarn parameters of core-effect texturing on product properties were investigated. As part of experimental studies carried out, a set of 40 yarns, each possessing different properties, were designed and produced, using two selected types of partially oriented (POY) polyester yarn having a final linear density of 150 den. with 34 and 68 filaments. Using the 150/34 and 150/68 yarns as core and effect yarns in the core- effect processes respectively, air-jet texturing with the following supply yarn combinations were realized, 34f, 68f, 34f+34f, 34f/34f, 34f768f, 34f+34f/68f, 34f+34f/68f+68f, 34f+34f/68f+68f+34f Overfeed ratios in the single and parallel end texturing processes were varied within the range of 5% to 25% by 5% increments. For the core-effect texturing process, the overfeed ratio of the core yarn was kept constant at 5% while the overfeed ratio of the surface yarn was varied within the range of 10% to 50% by 10% increments. The air-jet textured yarns produced were given numbers from l to 40 according to their supply yarn properties, texturing method and overfeed ratios. The properties of these yarns are presented in the following table. Table l. Air-jet textured yarns %50 l %40 l %30 l %20 l %10 l Effect l Core l %5 l %10 l %15 l %20 l %25 34f İ 2 3 4 5~ 68f6 7 8 9 ÎÖ~ 34f+34f İl 12 13 14 ı5~~ 20 l 19 l 18 l 17 l 1634f34f ~25 24 23 22 21 68f34f ~~3Ö29 28 27 26 68f 34f+34f ~3534 33 32 31 68f+68f 34f+34f ~4Ö 39 38 37~ 36 68f+68f+34f 34f+34f xiü Influences of the overfeed ratio and supply yarn filament number and filament linear density, on the product properties were investigated by inspections and tests for yarn linear density, tenacity, and hairiness. The investigations were also accompanied by the visual assistance of microscopic images of produced yarns. By the application of air-jet texturing process to continuous filament yarn, textured yarn closely resembling the characteristics of spun yarn was obtained, eliminating the prolonged operations required to reshape cut filaments into natural looking yarn. In addition to the above mentioned work, a technique of on-line dyeing of yarn was also proposed to be integrated into the air-jet texturing process, which should enable dyeing flexibility and quality that cannot normally be achieved by means of any other conventional dyeing method in only one operation. The idea behind this technique is as follows: Yarn coming out of the air-jet that has passed the mechanical and thermal stabilizing regions is to enter a tube where it is to absorb the prepared dye mixture being sprayed on it. The dye on the yarn is to be set by means of subjecting the yarn to a temperature, a little lower than that of the dimensional stabilizing region which is 240°C. Once the dye is set, excess dye is to be washed off along with other impurities by a cleansing solution sprayed on the yarn as it passes through a channell. After leaving the channel, the yarn is to be wound at the take-up unit. The described on-line dyeing system has been designed with appropriate dimensions, taking into account the associated process parameters. Yet due to time considerations, the design was not verified by building a prototype and testing it in actual production circumstances. Hence this issue has been left for future work. In the context of this work, the results of the studies carried out on air-jet textured yarns and their dyeing operations are summarized below: Yarn linear density for single end, parallel end and core-effect textured yarns have been observed to increase with increasing overfeed ratios, in an unproportional manner. This is believed to originate from the stabilizing extension applied in the mechanical stabilizing region and also the tension preceeding the take-up unit. On the other hand, the increase in the number filaments, while linear density is kept constant for supply yarn seems to have no effect on the linear density of the textured yarn, whereas the linear density of the product yarn seems to increase in a proportional manner to the increase in the total number of filaments resulting from the addition of identical supply yarns. The strength and elongation values obtained from tenacity tests conducted on the textured yarns provide a good insight about the amount of texturing that the yarn has undergone and its resulting bulkiness and structure. Observing the drop in strength values with increasing overfeed ratios, it can be said that yarns with low strength values have undergone more texturing compared to yarns with higher strength values. In addition to that, it can also be said that texturing ability improves with the xiv decreasing linear density and the increasing number of filaments in the supply yarn. The decrease in the strength of core-effect textured yarns after exceeding and overfeeding ratio of 30% becomes less observable. This is related to the phenomenon that after this overfeed ratio, the effective texturable length in the air-jet is exceeded. On the other hand, the drop in specific strength of yarns produced from a core yarn larger than 34f+34f and an effect yarn larger than 68f can be related to exceeding the total number of filaments that the air-jet can handle at once. Observing the microscopic images of the produced yarns, it was seen that the number and dimensions of loops formed on the yarn surface increase with increasing overfeed ratios. For core-effect textured yarns produced in overfeed ratios exceeding 30%, slack loops were spotted on the yarn surface, not completely attached to the core, justifying the fact that the effective texturing length of filaments for the given air-jet. Such yarns might be considered for some special applications. Increase in the number and size of loops, and thus bulkiness was recognised with the increase in the filament linear density of supply yarn. Also, the existence of loose loops on the surface of yarns produced over the limit of the number of filaments that the jet can handle, is in agreement with the drop in the specific strength of such yarns. The overfeed ratio and the optimum number of filaments to be used in the air-jet, should be determined in a precise manner, depending on the desired properties of the product. The hairiness tests conducted, considering the resemblance between the loops on the surface of air-jet textured yarns and the hairs on the surface of spun yarns have proven to be unsatisfactory in providing information about the structure and bulkiness of air- jet textured yarns. The filament bundles sticking out of poorly textured yarns are considered to have a negative effect on the hairiness measurements. Yet, for core- effect textured yarns produced at overfeed ratios of 30%, 40% and 50%, the hairiness index has been observed to increase with increasing number of filaments in the supply yarn. Hence, hairiness indexes obtained for core-effect yarns produced at high overfeed ratios can be considered to give an insight about the bulkiness of such yarns. After having analyzed the structure of air-jet textured yarns, a theory of integrating an on-line dyeing operation into the air-jet texturing process has been developed, considering current methods employed for dyeing polyester and the principles they rely on. The necessary apparatus required for the implementation of this theory was designed considering the technological parameters of a typical air-jet texturing process. Yet, due to time considerations, a prototype was not built to test and verify the theory, which is left for future work.