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Properties of Air Covered Yarn as Influenced by Air Pressure and Delivery Speed: A study for the Extension of Textile Technology.


Summary: Air covered yarn was produced from thermoplastic, cellulosic or non organic filament yarns using compressed air. Loops were formed on the surface of the filament yarn, giving it a voluminous character. Depending on the material used, the loop structure results in a yarn with characteristics resembling those of conventional staple fibre yarn. The present study was planned to explore, "Properties of air covered yarn as influenced by air pressure and delivery speed". Following parameters of covered yarn such as delivery speed; air pressure of air nozzle and denier of spandex were studied. The present study should be discussed with the textile experts in the textile industries to find out the solution of the problems they faced, where as the results of the said study must be shared to improve the quality not only but also for eco-friendly in the sense of financial matters.


Air intermingling is a process where the elastane core and multi filament yarn are fed through a pressurized air jet which blows the filaments of the covering yarn apart causing them to partially intermingle around the core. Air covered yarn are produced from thermoplastic, cellulosic or non- organic filament yarns using compressed air. Loops are formed on the surface of filament yarn, giving it a voluminous character. Depending on the material used, the loop structure results in yarn with characteristics resembling those of conventional staple-fibre yarn. The resulting yarn used for sewing, thread application, apparel fabrics, fancy yarn articles, automotive interior fittings and home furnishing fabrics, carpets, fire blankets and a wide range of other applications [1].

A core-spun yarn is "a structure composed of a separable core surrounded by fiber and suitable for use as a yarn". Core-spun yarns are produced with a continuous filament core such as polyester, nylon, polyurethane, carbon, etc. The manufacturing process mainly consists of feeding filament to the spinning unit, where it is covered by staple fibers. Elastic core- spun yarns use spandex as the core and are covered with staple fibers. Spandex fibers that are made of long chain polymer fibers containing at least 85% segmented polyurethane have superior stretch and elastic recovery ability. Core-spun yarns containing spandex provide fabric producers with broad possibilities, because such stretchable yarns can be produced with a wide range of properties using virtually any kind of staple fiber as the cover material. The basic requirement to produce an elastic core-spun yarn is to stretch a spandex thread before it enters the spinning unit.

This action provides elasticity in the final yarn by retraction of the spandex core when stress is removed, thus compacting and bulking the spun yarn cover. The core spun yarn can be extended to the point where the non-elastic cover yarn is stretched to its limit, thus resisting further extension of the core-spun yarn [2].

The process uses an air-jet delivered by a nozzle to entangle/interlace the constituent filaments of a continuous yarn, producing intermittent nodes, i.e., entangled sections (usually known as nips) at reasonably regular intervals with undisturbed (un- entangled) sections between them. This technique is widely used in industry owing to its low cost compared to alternatives such as sizing and twisting. The first patent for an intermingling nozzle was acquired by DuPont in 1961, but much of the published scientific work is relatively recent. The simplest intermingling nozzle consists of a yarn channel with an air inlet hole in the middle. A jet of air emerging from this inlet hole usually impinges at right angles onto the yarn traveling through the channel [3].

In core-and-effect texturing, two or three yarns are fed at different overfeed levels, and the effect end forms most of the loops and entangles with the core end. The effect yarn gives the desired bulk to the textured yarn. Normal textured yarns are the least expensive and are preferred where nominal bulk is required. Core-and-effect yarns are expensive and preferred for applications where spun aesthetic, compressibility, drape, and fullness are important. In the case of single end texturing, there should be a minimum number of filaments to produce a stable structure. Textured yarns made from finer filaments have more and smaller loops. The physical bulk of air-jet textured yarns improve when more ends are fed into the jet. Core-and-effect textured yarns have a lower tenacity than normal textured yarns [4].

In the present study air covered yarn made of spandex in the core and nylon as covering element was made and the physical properties of the air covered yarn were tested and given in detail according to their use in fabric.

Results and Discussion

The statistical analysis of variance and comparison of individual means for yarn count are given. The results indicate that the effect of Denier (D), Delivery speed (S) and air pressure (P) is significant while the effect of nylon brands (N) is non-significant. While all other interactions have non-significant effect on yarn count. The mean values for different Denier of Spandex D1 (20 dtex) and D2 (40 dtex) recorded as 19.458 and 18.477 respectively. These results showed significant effect of Spandex denier on yarn count. This indicates that as the filament denier in the core increases the yarn count decreases. The covered yarn has the same number of turns; its mechanical properties vary, depending on the denier of the core and draft ratio [5].

These results show that the elongation increased with the increasing delivery speed. The maximum value was 36.669 at 800 m/min speed and minimum value obtained was 36.432 when the delivery speed was 500 m/min. The fibre elongation correlates closely with yarn elongation, however, the degree of correlation is influenced by twist, yarn number and fibre length.

Fig. 3 indicates the mean values for different nylon types N1 (Pakistani), N2 (China), N3 (Taiwan), N4 (Indonesia) recorded as 72.133, 72.130, 72.140 and 72.136 respectively. These result showed non-significant effect on yarn stretch recovery of the air covered yarn. The mean values for different delivery speeds S1 (500), S2 (600), S3 (700) and S4 (800) recorded as 71.447, 71.678, 72.612, and 72.802 showed a significant effect on stretch recovery the air covered yarn. These results show that the yarn stretch recovery increased with the increasing delivery speed. The maximum value was 72.802 at 800 m/min speed and minimum value obtained was 71.447 when the delivery speed was 500 m/min. Similarly, under repeated stretching, high-twist elastomeric yarns had a lower elastic recovery percentage than core-spun yarns with a lower twist factor [6].


The details of the material used and methods applied to test the raw material, processing proce- dures and to measure various quality characteristics of the yarn and fabric are briefly described. The nylon filament which was taken from the running stock of the mill, was subjected to following tests. Nylon filament yarn linear density (denier) was checked through skein method by [7] on digital Uster Autosorter III that give direct reading. Tenacity of the yarn is expressed in grams force per Tex. Tenacity was determined by dividing breaking load with corresponding denier/titer and was determined by Uster Tensojet. Elongation Percentage is measured simultaneously along with breaking load on an automatic strength testing apparatus Uster Tensojet.

The method was adopted as given in [7]. The following variables are selected for the production of nylon covered spandex air covered yarn as shown in Table-1.

Table-1: variables selected for the production of nylon covered spandex air covered yarn.

Spandex(D)###Nylon(N)###Delivery Speed(S)###Air Pressure(P)





Yarn Count

Yarn number (count) was estimated through "Skein method" according to [7] with the help of Uster Auto Sorter, a direct reading instrument. A program of count determination for 120 yards lea was fed to the computer to determine English count. The yarn count was noted from its automatic digital display.

Yarn Elongation

Yarn elongation was determines by uster Tensorapid, which applies a constant rate of extension (CRE) principle of testing. CRE describes the simple fact that the moving clamp is displaced at a constant velocity.

Yarn Stretch Recovery

To measure the elastic recovery percentage of the elastic complex yarns, the yarns were wound eight times each on a wrap reel. Each sample was first hung with 50 g counterweights for I minute, then the length (Lo) of the sample was measured.

Analysis of Data

The data thus obtained have been analyzed statistically by applying analysis of variance technique, while DMR test was applied for individual comparisons as suggested by [8] using SPSS (Statistical program for social science) micro- computer statistical program.


On the basis of present investigations, it was concluded that the quality of air covered yarn depends upon the no of nips or loop length in the yarn. The yarn count decreases with increase in filament denier and air pressure and decreases with decrease in delivery speed. The nip frequency generally increases with increasing air pressure in the nozzle and decreased with the increasing delivery speed. The nylon type did not show any significant effect on no of nips per meter. The percentage of spandex in the core of air covered yarn increases with increase in filament denier. The air covered yarn showed better stretch and elongation at higher speed and low air pressure in the nozzle. The different nylon types used in the experiment did not have a significant effect on the stretch and elongation properties of the air covered yarn.


It is suggested that the present work may be extended to another textile industry with different material of different location, so as to find out the more results for further improvement of the study.


1. K. W. Y. Ng, M. P. Millman, D. R. Whitby and M. Acar. Mechatronic On-line Stability Tester for Air-jet Textured Yarns. Innovations in Manufacturing Control through Mechatronics, IEE. 22, 5 (1995).

2. G. H. Ortlek and S. Ulku, Textile Research Journal, 77, 432. (2007).

3. H. K. Versteeg, M. Acar and S. Bilgin. Textile Research Journal, 69, 545 (1999).

4. R. S. Rengasamy, V. K. Kothari and A. Patnaik, Textile Research Journal. 74, 259 (2004).

5. G. N. Yoshimura, S. Iwaki, S. Shintaku and T. Takayama. Journal. Textile Machinery Society of Japan. 22, 77 (1969).

6. C. Su and H. Yang, Textile Research Journal. 74, 1041 (2004).

7. ASTM, Committee, Standard method for measurement of yarn properties. ASTM

8. Designation D-1907-97, D-1578-93, D-1425-96. American. Society. for testing and material. Philadelphia, U. S. A (2008).

9. D. C. Montgomery, Design and analysis of experiments. Arizona stat university ISBN: 978-0-470-12866-4 (2009).

1Department of Fibre Technology, University of Agriculture, Faisalabad, Punjab, Pakistan., 2 Institute of Agricultural Extension and rural Development, University of Agriculture, Faisalabad. Punjab, Pakistan.,*
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Author:Iftikhar, Muhammad; Shahbaz, Babar; Zaheer, Ehsan Elahi
Publication:Journal of the Chemical Society of Pakistan
Article Type:Report
Geographic Code:9PAKI
Date:Oct 31, 2012
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