Makina Halılarının Yapısal Özellikleri İle Mekanik Etkiler Karşısındaki Davranış Özellikleri Üzerine Bir Araştırma

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Tarih
1997
Yazarlar
Berkalp, Ömer Berk
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Özet
Halı ve halı lifi üreticileri ürünlerini satış noktasında cazip şekilde sunmak ve görünüm ile konforlarının yıllar sonra kullanımda bile aynı kalmasını temin etmek için bir rekabet içine girmişlerdir. Birçok üretici için uzun süreli dayanımdan bile çok daha önemli olan görünüm korunması, halıların performanslarında göze alınan en önemli ve tercih edilen özelliğidir. Görünüm ve konforun hangi şartlarda temin edildiğini belirlemek açısından halıların temel yapısal özelliklerini değiştirerek incelemelerin yapıldığı çok sayıda çalışma sözkonusudur. Bu tezin hazırlanmasındaki amaç da makina halılarının yapısal özellikleri ile mekanik etkiler karşısındaki davranış özellikleri üzerine bir araştırma yapmaktır. Bunun için halılarda bilhassa kalite kontrolde önemli olan aşınma dayanımı, hekzapot sonrası kalınlık azalması ile görünüm değerlendirmesi ve ender olarak araştırılmış tutam mukavemeti üzerine çalışmalar yapılmıştır. Gümüşsüyü halı fabrikasından temin edilen 12 farklı yapısal özelliğe sahip Wilton yüz-yüze dokunmuş "3-shot" halıların aşınma, görünüm ve tutam mukavemeti özellikleri test edilmiştir. Fabrikanın kalite kontrol laboratuarında, her deney için standard boyutlarda kesilen halılar sırasıyla ilk önce WIRA aşındırma cihazında halılar son noktaya kadar aşındırılmış; daha sonra hekzapot yürüyücü ile 1500 devir kısa test ile 8000 devir uzun test yapılmış; hekzapot sonrası kalınlık tayini WRONZ halı kalınlık ölçer ile ölçülmüş ve görünüm değerlendirmesi göz ile yapılmıştır. En son olarak toplanan numunelerle İ.T.Ü Tekstil laboratuarında tutam mukavemeti değerleri saptanmıştır. Elde edilen deney sonuçları istatiksel metotlarla değerlendirilmiş ve bu sonuçlar çerçevesinde yapısal özellikler ile bağlantılı olan halı davranışları yorumlanmıştır. Bu yorumlar sonucunda daha iyi kalitelere ulaşılabilmek için hammaddenin, ilme yüksekliğinin, ve atkı sıklığının özellikle ana ve bunun yanısıra ikili etkilerinin önem kazandığı belirlenmiş ve bu konudaki öneriler ortaya konmuştur.
Carpetmaking is rich in tradition and reflects the customs, religions and aspirations of more than one civilization. In its highest form the carpet or rug is a work of art seldom equaled in other crafts and its important to the world in both utility and elegance. In the last fifty years, carpets become a necessity more than luxury. Everyone connected with the carpet industry must agree with a statement made in 1962 in the Journal of Textile Industry: " For practically half a century, the craft of carpet making remained almost stationary. Then, a few years ago, impelled by the demand created by the rising standards of living, the manufacture of carpets became the focus for a fantastic burst of technological activity. New processes and machines were devised; novel fibers yarns (novel, that is, for carpets) were engineered to take advantage of an expanding outlet; older textile processes, previously confined flat cloths were developed to capture a share of the increased market for pile fabrics; and conventional carpet looms were re-designed to step up production to hitherto unthought-of speeds." Manufacturers of traditional Wilton and Axminister carpets all over the world are watching and following the pattern of trade in the United States of America where the tufting process, that offspring of the sewing machine, has since 1951 mushroomed to supply over 85% of the domestic output. Another process with potentialities is knitting, which has been taught to make loop pile materials but has not quite overcome some of the technical troubles involved in the production of cut-pile fabrics for floorcoverings. Both tufting and knitting enjoy the economic advantages of high-speed production, which make them of special interest for the low price-range trade. This has been assisted by the use of inexpensive rayon yarns, which unfortunately, however lack that resilience which makes wool so desirable a carpet fiber. Moreover, the variety and richness of pattern obtainable in the woven carpet is not yet as readily available in these new processes. XV And in this work woven carpets are chosen, since they are used very widely at houses, hotels, theaters and contract work. Also Turkey is one of the leading woven carpet manufacturer in the world and seems to have a bigger role in the market at the future. The classification of woven carpet looms are as follows: 1) Wilton weaving a) Wire Wilton b) Face-to-face Wilton - Single shed weaving - Double shed weaving 2) Axminister a) Gripper Axminister b) Royal or Spool Axminister c) Chenille Axminister The Wilton loom, or more specially, the Brussels loom, represents the first breakaway from the older system of tying-in tufts by hand. At the old handloom type of weaving each separate tuft of pile yarn was knotted, usually round a pair of warp ends, and later trimmed to exact length. When a bigger market came to catered for, a faster means of production was necessary. In the method of weaving, the weft was made to hold the pile yarn, and there were no knots in tufting but merely the catching of the pile yarn under the pick of weft. This method persists to-day in all types of carpet manufacture. A slight exception is in chenille weaving, where the "fur" or weft pile yarn is bound into the carpet under a special warp though here again there is no knotting. The method by which Wilton carpet is made allows for great density of fabric, and the tuft, particularly in the 3-shot, is very secure. In its best qualities, because of its closeness of pile, sturdy backing and general hard-wearing properties, it is in high demand, particularly for hotels, liners, theaters and contract work in general. In the modern world, more and more production speeds are necessary in order to supply the high demands of the market. And face-to-face weaving represents the most productive method currently available for the manufacture of woven floorcoverings, and much modem technology has been applied to the machinery on which such carpets are produced. Unlike other systems of carpet weaving, the face-to-face system has gained in popularity in recent years. XVI The technique is not new, however. It was first used by Jean-Baptiste Dans of St. Etienne, Belgium in 1798. The basic principles of the technique have not change since those early years. The disadvantages of the system arise mainly from the fact that there is no possibility of producing loop-pile carpets, so that scope is limited to the production of floorcoverings containing variations in texture. Furthermore it is not possible to produce multi-pile-height effects, so that any texture variations must be introduced via the use of effect yarns. Face-to-face machinery is therefore employed exclusively in the production of level cut-pile carpets, the bulk of which are jacquard-patterned. Intricate and beautiful designs can be achieved by using fine wool yarns produced on the worsted and semi-worsted systems. Coarser woolen-spun yarns are also woven into plain and patterned carpets particularly for wall-to-wall use. There are two methods of producing face-to-face carpets:. on machinery with one shed and single weft insertion. on machinery with two shed, one above the other, and double weft insertion. Whichever methods is used, the underlying principles are the same: Two fabrics are woven one above the other under strong tension and pile warps are interlaced between the two so that a "sandwich" is formed. Following the beat-up of the loom, the pile warps are cut by a reciprocating knife mechanism which separates the fabric to give two carpets. The distance between the top and bottom cloths, which can be regulated on the loom, determines the pile height of the two carpets. From these principles it can be seen that face-to-face is only suitable for the production of cut-pile carpets. The ground warps which form the backing are always drawn into the loom via heald shafts which are moved by cams or other devices on the side of the loom. The pile warps may also be draw into heald shafts, but this gives only limited design possibilities, so that usually the pile warps are controlled by one ore more jacquard machines. The pile warps are divided into colour groups, generally four or five but in certain cases up to seven, each of which corresponds to a harness on the jacquard. Designs on the loom are set up in such a way that only one harness at a time is lifted to form the pile. The end which are not lifted are known as dead pile. This takes various form according to the weave structure:. floating underneath the bottom carpet and requiring scraping off during finishing xvu . floating between the top and bottom carpets, requiring removal with suitable shearing equipment. woven into the backing, usually evenly between the top and bottom carpets. In this work, the physical properties of face-to face woven carpets, such as appearance retention after hexapod tumbler testing, abrasion resistance and tuft withdrawal force, are examined. Good appearance retention is one of the most important and desirable attributes of overall carpet performance, and is often regarded as being more critical than even long term durability, especially in commercial and contract carpets. The affects of wear can be characterized in terms of texture and colour differences, most notably phenomena such as pile flattening, reduction in tuft clarity, shading, soiling and loss of colour. The ability to resist these changes varies between carpets due to the vast number of manufacturing variables, for instance, fibre composition, yarn processing route, carpet structure, tuft morphology and pile dimensions. A carpet need not retain its original appearance to be acceptable in use, but the nature and rate of any apparent change has an important influence on the assessment of wear performance. Appearance retention is the only element of total carpet performance which cannot be measured objectively. Current standardized tests involve the use of subjective panels to grade the extent of change in tested samples from the original. These subjective means of grading do, however, have their short comings: they can be open to bias, time consuming and inconsistent. The subjective grade given according to British standard, for the degree of change in surface structure contributes up to 30% towards overall performance rating of a carpet, as detailed in BS7131, Part 1, 1989. This performance rating forms the basis of the grading scheme adopted by the British Carpet Manufacturers Association (BCMA) for the classification of carpets according to their suitability for different applications, ranging from domestic to heavy contract applications. It is crucial, therefore, that subjective results are both accurate and truly indicative of the wear to be expected in a carpet. A reliable, reproducible method of rating would ultimately require all subjective elements to be measured objectively. To meet the demands for objective measurement of carpet appearance characteristics, many instrumental methods have been developed over the past decades, including microscopy, photography, densitometry, goniophotometry, photogrammetry, glass bead filling, and image analysis. Of these methods image analysis has shown great potential as an automated approach for quantitative and comprehensive evaluation of carpet appearance. Different image analysis techniques have been applied for various carpet appearance characteristics. Some of them are as follows : for tuft definition : local intensity variation and image moments; for tuft geometry: XVUl size measurement and shape analysis; for tuft placement: tuft evenness, distance measure and spatial density; for periodicity: two dimensional Fourier transform, auto-correlation function, image covariance co-occurence matrix etc. The mechanical properties of carpets have been the subject of research for many years. Emphasis on these researches are firstly on the compression and recovery of pile. The compression properties of carpets, particularly their dynamic response, are especially relevant to a carpet's mechanical performance. The dynamic-compression properties of carpets are characterized by several unique features: the stress/strain compression curve is non-linear; there is hysterisis, i.e. energy dissipation, during a compression release cycle, and the compression modulus and energy dissipation per cycle are affected by the magnitudes of the pressures or displacement involved. This study covers the following main methods of appearance retention: - To develop an understanding of important appearance parameters, in human judgement, by means of subjective assessment. - To develop an understanding of important appearance parameters by means of pile thickness variations. For the purpose of measuring the appearance retention of carpets two testers are used: The Hexapod tumbler tester and WRONZ pile thickness probe. The Hexapod tumbler tester is known to produce realistic changes in surface structure and colour, but it cannot used to predict pilling. The principle is: a cylindrical drum lined with textile floor covering specimens and containing a hexapod is rotated for a specified number of revolutions. Hexapod tumbler tester has the following technical specifications: (a) PVC drum of : internal diameter 305 + 1 mm : wall thickness 8 mm (approx.) : internal depths 200 ± 1 mm The drum speed is 35 ± 2 rpm, and the direction of rotation is reversed every 15 minutes. The drum system incorporates a revolution counter, and the drum base and lid have a locating groove to hold the specimen backing sheet flat to the inner wall of the drum. (b) Polyethylene specimen backing sheet of size 950 * 215 mm and 2 mm thick XIX (c) Hexapod tumbler comprising a mild steel cube (with sides of 50 mm) with 25 mm thick plates welded to each side. The outside corners are rounded such that when the studs are fitted and the hexapod placed on a flat surface, no metal touches the flat surface. A replaceable poly urethane stud is screwed centrally in each face. There are two testing terms: Short-term testing (1 500 revolutions) and long- term testing (8000 revolutions) First carpet specimens are cut according to the standard. Three samples can be tested at the same time. They are mounted at the drum allowing 5 mm gap at each side. After preparing and mounting the specimens in the drum, hexapod is placed into drum. If short-term testing will be done, the counter is adjusted to 1500 revolutions. After the test, the specimen is cleaned and evaluated. If long term testing will be done, the counter is adjusted to 2000 revolutions. In every 2000 revolutions, the specimens are cleaned by a vacuum cleaner. Testing is finished after 8000 revolutions. After hexapod tumbler tester, specimens must be assessed under good lighting conditions. The draft BS conditions require daylight equivalent D65, vertical lighting giving 1500 lux at the carpet surface. The specimens are viewed at an angle of 45° from 1.5 metres distance, judging from all directions. As far as possible these conditions should be used but it is often informative also to view specimens more closely. The fatigued specimen is placed alongside a similar sized original specimen of the carpet ensuring that it lies in the same direction and that, if the carpet is patterned, a similar pattern area is compared. a) The change in surface structure is assessed on the following scale: 5 = no or very slight change 4 = slight change 3 = moderate change 2 = large change 1 = severe change b) The change in colour (tone, depth, brightness) is assessed against the standard large grey scales. Also to determine the appearance retention, the change of the pile thickness after tumbler testing is measured. To measure the pile thickness of the unworn and worn carpet specimens, WRONZ Pile-thickness probe is used. It has been found that in all of the commonly available carpets and carpet types the backing structure is far more dense than the pile, even in worn XX carpets in which the pile has been severely flattened and compressed. The pile can be easily penetrated by a needle like probe. It is thus possible to use a needle-probe of appropriate design to detect the upper surface of the backing and to use the tip of this probe as a reference point against which the thickness of the pile can be measured. The WRONZ pile-thickness probe consists essentially of two probes, one to sense the position of the upper surface of the backing as described, and a second (flat) probe to sense the upper surface of the carpet pile. These two probes are inter connected via an engineer's standard dial gauge, the spacing between the planes of the two probes being displayed on the dial gauge is the thickness of the carpet pile. The abrasion resistance of carpets does not necessarily relate to actual wear where other factors may be involved. In particular, it is known that the ranking of different pile fibres or widely different constructions does not always reflect the floor life. The test is preliminary intended for quality control and care should be taken in assessing any new pile blend or construction. The average rate of weight loss is an objective method and reasonably independent of pile height, density or weave. It is therefore an estimate of the quality of the pile and can be used, for instance, to assess any chemical damage, efficiency of blend, with greater accuracy. However, adequate conditions and conditioning time are very important since a fairly small weight loss is obtained by the difference from two much greater weights and any small error in conditioned weight may show as a proportionately large effect on weight loss. The number of rubs to end point also takes into account the available weight of pile and is more an estimate of the quality of the carpet. The main difficulty is that this is a subjective assessment and personal differences may occur apart from random variation. Specimens are judged in the holder immediately after releasing the pressure since some recovery takes place in time after release of the load, and could affect judgement. In order to determine the abrasion resistance of carpets, WIRA carpet abrasion machine is used. The machine consists of a circular specimen holder rotating approximately the same speed and in the same direction as the circular abradant holder but with the axes of rotation offset. The technical specifications of the machine is as follows: Rotational speed of specimen holder and abradant holder = 1 56 ± 3 rpm Exposed area of specimen = 645 mm2 Exposed area of abradant = 1 1000 mm2 (approx.) XXI Distance between axes of specimen holder and abradant holder = 25.4 mm Abradant pressure = 0.54 kgcm"2 Circular specimens of carpet are abraded against a specified worsted crossbred fabric for various number of rubs. The abrasion resistance is then estimated by the number of rubs required to reveal the backing. The withdrawal force to remove tufts or pile from textile floor coverings is determined by a tensile testing machine with a 500 N load cell having an accuracy of 5 per cent. A loop, or one end of a tuft, is gripped and pulled upwards out of the structure of the floorcovering. The force required to break the bond between the tuft and the backing structure is recorded. In this work, the carpet specimens are provided from Gümüşsüyü Carpet Manufacture. All of them are face-to face woven carpets. Three different pile materials are used: Wool, Polypropilen and Acrylic. Pile height (7mm and 9mm) and weft density (500 and 600 weft/m) are also the other variables. After the tests, the test results are evaluated statistically. Variance analysis, regression analysis and the mean value graphics are used to determine the effective properties of carpets. According to the analysis, the material type, pile thickness and the number of revolutions of the hexapod tumbler is the main effect on appearance retention and the thickness loss. The flattening effect of Polypropilen fibres is clearly observed after the tests. Because of the resilience of the wool and acrylics fibres, wool and acrylic carpets have showed good appearance retention. Material type, pile thickness and weft density played an important role on the abrasion resistance of carpets. Wool showed lack of mechanical abrasion. But acrylic and polypropilen showed resistance to abrasion. Pile thickness was the most important effect on the withdrawal force to remove the tufts. But there become an inconsistent relation between the force and the weft density. It will be necessary to carry out more extensive work on this subject. If Turkey want to play an important role in the world carpet market, Turkish carpet manufacturers should develop better qualities. So they should give support to researchers for studying on the instrumental techniques and analysis so as to have a detailed understanding of factors effecting on carpet appearance retention.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1997
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1997
Anahtar kelimeler
Makine halısı, Yapısal özellikler, Machine carpet, Structural properties
Alıntı