Yalancı büküm tekstüre işleminde hava jeti ile tork (Büküm canlılığı) gidermenin iplik yapısı üzerine etkileri

Abstract

Bu çalışmada tekstüre ve tekstüre iplik özellikleri tanıtıldı. Yalancı büküm tekstüre işleminin ana prensipleri tanımlandı. Daha sonra büküm canlılığının oluşma sebebleri üzerinde duruldu. Avantaj ve dezavantajları dikkatle incelendi. Büküm canlılığım gidermek için kullanılan alışılagelmiş yöntemler tanıtıldıktan sonra işlem sırasında büküm canlılığını gideren tork giderme jeti anlatıldı. Bu jetlerin ipliğe etkisini araştırmak üzere mukavemet, mukavemet değişim değeri, kopma uzaması, kopma uzaması değişim değeri, kaynama çekmesi, tekstüre özellikleri, büküm canlılığı miktarı, yağ miktarı tayin edildi. X ışınlan difraksiyon testi yapıldı. Elektron mikroskobunda moleküler yapının değişip değişmediği incelendi. Tork giderme jetlerinin kullanımı çok yeni olmasına rağmen ileride yaygın bir halde kullanılması beklenmektedir. Bu jetlerin en iyi bir biçimde kullanılabilmesi için iplik özelliklerine etkisinin tüm detaylarıyla anlaşılması gerekmektedir.

Synthetic filament yarns are now accepted like wool, cotton, flax and silk as everyday textile material. Until the 1930's synthetic filament yaraş were in experimental stage. With a high growth, the production of synthetic filaments was nearly equal to the production of cotton in 1994 (17 718 000 tons of synthetic fibers against 18 600 000 tons of cotton). Synthetic filament yarns when they are forced through spinneret, they take smooth rod-like structure. in this form the textile qualities of such yarns are not suitable for human sense. The textile qualities of such yarns should be improved by a further process. To achieve this, various texturing techniques are used such as false twist texturing, air texturing ete. By texturing we change structural properties of yara like lustre, handle. Texturing increases the bulk of the yara by changing the geometrical configuration of the filaments. Also during texturing the yara is also drawn, so the strenght of the yara is increased. False twist texturing method is most dominant öne at present. The basic principles involved in the production of false tvvist method are as follovvs: 1- If a stationary multifilament yara is held at both ends and twisted in the center by a spindle, equal amounts of twist with opposite directions will be imparted on each side of spindle (Figüre 2.1.a.). 2- Although if either hah0 of the yara were considered separetely, it would be observed that the tvvist was real and number of tvvist at both sides are equal. With the false tvvist spindle rotating continously and yara moving through the spindle continuously, the tvvist on the output side of the false tvvist spindle is carried avvay to the wind up and tvvist from the input side moves through the false tvvist spindle. When the yara moves through the false tvvist spindle, the yara is tvvisted at opposite side, so the yara is untvvisted (Figüre 2. l.b). ifa heater is added on the input side of the false tvvist spindle, vvith enough space left for cooling before the spindle, then three basic steps of tvvisting, heat setting and untvvisting can be carried out continuously on the nıachine (Figüre 2.1.c). [5] After the false tvvist spindle the basic texturing operation is completed, the textured yara at this stage has a high bulk and high stretch. Besides these properties the false tvvist textured yara has high snarling tendency which is called tvvist liveliness. Sometimes tvvist liveliness of the yara creates problems in later processes. Where the high bulk, high stretch and high tvvist liveliness is not essential, another heater is used after the basic false tvvist texturing process. By this way tvvist liveliness of the yara is reduced. ix The tvvist liveliness especially causes different problems in warp knitting machines. in this knitting system the yarn wind off speed is too low so the tension of the yarn is as low as 3-5 cN. in this stage the false tvvist textured yara which has high tvvist liveliness tends to turn. So in the fiırther stages the yam may not be fully opened, so this makes faults in the fabric. in some positions these faults causes yara breakages. Different kinds of methods are used for reducing the tvvist liveliness of the yara. Conventional methods are as follovvs: -SET Texturing The setting operation is applied to the yara after the basic false tvvist texturing process and reduces the tvvist liveliness together with the bulk and stretch of the yara. When the second heater temperatures are setted to the levels that are near, equal to ör more than first heater temperatures, a new geometrical configuration is inserted to the filament in which the pitch of the helix is increased. By this way interaal stresses can be released and the internal torque can be eliminated. But the speed of the yara effects the elimination of the torque. in high speed levels the elimination of the yam torque can not be achieved completely. So another system which is less effected from the yara speed should be found. -Doubling When the two ends textured by S and Z tvvists in texturing zone are brought together before ör after the the second heater. The opposite torque directions eliminates each others torque. The doubling of the two ends require a coherence imparting medium betvveen these oppositiy torqued filaments. This coherence is usually imparted by a co-mingling jet. But by using this method the machine capacity is halved which renders itself to be a costly operation. -Double and single end tvvisting If we tvvist the two ends slightly on a tvvisting machine, the final yara is regarded as torque free yara. it is obvious that such second operations are cost, intensive and used only for very specific applications. If we tvvist the single end opposite direction of the texturing operation the torque inserted in texturing machine will be eüminated. Both the second step processing and the tvvisting operation itself are costly operation. -Single end sizing By using heavy sizes the internal torque could be eüminated. This sizing metarial is applied to the extended textured yam on a separate machinery. This sizing x «, material should be later dried. Both applying and removing of the sizing material is an expensive and enviromently unfiiendly process. -Steam setting Yarns are inserted through a steam autoclave. By this way the twist liveliness of the yarn is reduced. This is also a slow and costly operation. -Torque elimination by an air jet For this operation the detorque jet is used. The detorque jet is placed between the second heater and third feed roller, it requires very little air pressure. The supply air pressure to the detorque jet ranges betvveen 0,4 to 1,5 bar. [8] The working pririciple of the detorque jet is to turn the yarn in the opposite direction of the texturing operation so the filaments take torque free configuration in the second heater and the new form is inserted to the filaments in the second heater by heating. in this method another operation is not required so this is very economic method. in the experimental of part of the study by changing the second heater temperature and detorque jet pressure, 12 samples of false tvvist textured yams are obtained. Also in the experimental study the raw material POY is also used. Samples' tensile, texture, molecular and chemical structures were analysed. The test results are given in Table 4.1. The molecular structures of torque free yarn and torqued yara were analysed by taking the SEM photograhs. Again for analysing the molecular structure X-Ray diffraction test is applied to the samples. As a result of these experiments, the CV% of tenacity and breaking elongation seemed to be increased in torque free yaraş. This has been indicated that the molecular structure was changed. Also SEM photo-micrographs have also indicated that the oriented molecular structure has been changed because by using detorquejet.