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July 2017


ABSTRACT:


Today, data acquisition, automatic monitoring and display of trends can be performed with personal computers. This allows us to quickly identify and systematically eliminate weak points in the production process. There is need for quality product, which gives high standard, which is possible by use of automation in textiles. The automation has done a drastic change in textiles by the use of electronics and computers in it. Since the use of it has given economically feasible for many mills, a major part of the new plants will be equipped with such systems. Electronics & computers has given some the benefits in the textile industry, Such as high production rates, consistency in quality, and ease in monitoring, reduced maintenance, flexibility, reduction in man power, etc. Now day’s modern weaving machines are equipped with the various control systems like electronic take up and let off, permanent insertion control (PIC), slim through-light sensor, electronic color selector, ECOWEAVE /RTC, automatic picks finding, electronic yarn tension control, automatic pre winder switch off, automatic start-mark prevention, E-shed, CAN-bus , etc. Some of them are discussed briefly in this paper.

1. INTRODUCTION


The world is bright & cheerful, full of color, constantly changing fashion demands and rapid response in the industry, has given a new image to it. There is need for quality product, which gives high standard; same applies for all textile products with new fields of application. Which is possible by use of automation in textiles? The automation has done a drastic change in textiles by the use of electronics and computers in it.


1.1 Why Electronics and Control Systems in Textiles?


Electronics & computer control systems in the textile industry include primarily the machine panels, the systems for regulating, controlling and the data recording. Productivity, quality, operational profit of the industry and therefore the competitiveness depends on the technology. Due to the increase in performance of electronic systems in recent years, it is now possible to realize solutions, which in the past had to be rejected for cost reasons. Today, data acquisition, automatic monitoring and display of trends can be performed with personal computers. This allows us to quickly identify and systematically eliminate weak points in the production process. Since the use of it has given economically feasible for many mills, a major part of the new plants will be equipped with such systems. Electronics & computers has given some the following benefits in the textile industry,

1.1.1 High Production Rates:


A better utilization of the production equipment will result in cash profit. But without a data system, this would be a laborious, error prone and costly undertaking. An operator-oriented way of data preparation makes it possible to quickly identify problems, recognize trends and then take the appropriate measures.

1.1.2 Consistency in Quality:


The production of the finest quality product with a consistency is a demand of a modern era. Quality and reliability plays a major role in the textile industry, if they have to compete in the market. The involvement of it gives the on-line monitoring & controlling of the quality.

1.1.3 Reduced Maintenance:


The uses of mechanical operating parts are unable to get high speed. The worn out of the parts is a major problem & so the machine stoppage for the maintenance is a critical & time-consuming job. It is reduced in the modern automated textile machines.

1.1.4 Flexibility:


The supplied functions leave almost nothing to be desired, demanding customers can create their own applications by accessing the database. In addition, the data can be transferred to spreadsheet programs in a very simple way. In a similar simple way, the PCs can be interconnected to a network. Via the Windows functions and commercial components, can be operated in a network, even via modem and cellular telephone systems.

1.1.5 Reduction in Man Power:


The applications were realized when a higher quantity and a better quality was produced with the reduction in personnel. On the other side, it must be noted that the personnel definitely reacts to the presence of data systems and that its efforts and attentiveness increases. The automated work has given the reduction in manpower.
Following are the some of the applications of electronics and control systems in weaving machines.

2. Modern Electronic Control Systems in Weaving Machines:

2.1 Electronic Take Up and Let Off:


The take-up is used to keep the required thread density in the fabric and wind the fabric on the cloth roll and let off release the required amount of warp. The electronic system provides important time saving the required pick density is electronically set (no pick wheels are required to change pick density). The accuracy of settings makes it easy to adjust the pick density of the fabric for optimum fabric weight and minimum yarn consumption. The take up and let off are driven by separate motors.

Let-off and take-up motions are identical in construction, each motion utilizes a resolver as the measuring system, connected together with the sensor to a control circuit. Electronic fabric take-up and warp let-off is not only controlling and reacting, but also acting with regard to the future. Absolute sensors measure the warp tension – independently of the position of back-rest roller and mechanical element motion – keeping it constant, even when weaving with splitted warp beams. The accuracy of warp beam settings on the display amounts to 1 cN/end with a filling density resolution of 0.01 picks/cm. Exactly reproducible values for filling density, machine speed, warp tension and contraction support start-mark prevention. 


Figure 2.1 Electronic Take Up and Let Off
Figure 2.1 Electronic Take Up and Let Off
2.2 Permanent Insertion Control (PIC®) with Servo Control®


PIC®-system of DORNIER permanently monitors the most important electrical filling insertion elements. It recognizes imprecise operation of filling insertion elements. It sets new standards for process reliability and quality consistency. Feeders with reliable layer separation activated via CAN interface, support exact feed length measuring for insertion. 

Flow optimized main and relay nozzles as well as short reaction times and low pressure volumes in the regulation circuit of ServoControl® provide gentle, low tension force application on filling threads. This allows higher speeds with a lower thread break figure combined with less yarn napping and therefore better final fabric quality. 

Figure 2.2 Permanent Insertion Control (PIC®) System
Figure 2.2 Permanent Insertion Control (PIC®) System
Combined with electronic controlled switching times and nozzle timing, these devices guarantee high flexibility with lower air consumption. The modular, patented Triple Weft Sensor with deflection and stretching nozzles opens up a new dimension in reliable filling monitoring.

The permanent control of the relay nozzle jetting sequence with a continuous standard value comparison (PIC®) assures weaving quality and precludes machine downtime. Defective or worn magnets are indicated immediately. Yarn-, speed- and width-related parameters for the control of the nozzles pick and pick are supplied from a data library. The timing of the electronically controlled filling scissor can be set on the display with the machine running.


Figure 2.3 ServoControl® unit
The new ServoControl® unit regulates the pressure in one control circuit for all main and tandem nozzles depending on the specified thread arrival time. This raises the machine automation level. For processing of new, unknown yarns only a few settings are still required and can be attained fast and reproducible. Absolute pressure values are shown as digital values on the machine display for the first time. A precisely dimensioned air supply unit serves the main, tandem, relay and stretching nozzles.

2.3 Slim Through-Light Sensor (STS)


The new, patented filling stop sensor DORNIER STS (Slim Through light Sensor) is based on the through light principle. It provides highest functional and quality reliability for dark filling colors and finest threads up to 20den. It can be easily positioned anywhere on the reed with a clip-on attachment according to filling insertion width. The compact design prevents damage to reed teeth.


Figure 2.4 Slim Through-light Sensor
Figure 2.4 Slim Through-light Sensor
2.4 Electronic Color Selector (ECS)


During weaving various colors are used in the fabric in warp & weft direction. In this system the weft colors are changed electronically instead of mechanical slow speed system. The electronic filling tensioner maintains optimum tension on the weft throughout the weaving.

Figure 2.5 Electronic Color Selectors (ECS)
Figure 2.5 Electronic Color Selectors (ECS)
The electronic color selector, ECS, and the electronic filling tension EFT device with integrated filling stop motion, is based on a new type of stepping motor distinguished by its sturdy construction, extremely small control increment of 0.9o and high torque Setting and function relative to the weaving process are precisely programmable on the machine display. Due to the modular concept individual modules can be added or removed easily. In this way, a single color machine can be inexpensively upgraded to handle 12 colors. The powerful stepping motors are of a very compact design and permit very small graduated increments which in turn help to perfect sequence in the weaving process. The motors are controlled via a microprocessor. Needle position can be set individually on the color selector via the display.

The needle´s smoothly controlled movement allows gentle yarn presentation with reduced yarn tension peaks. Low tensile strength yarns and also heavy yarns with high yarn tension, like 2400 Tex glass for example, can be processed without difficulty.


2.5 Energy Consumption Optimized Weaving with Real Time Control (ECOWEAVE /RTC)

Figure 2.6 ECOWEAVE /RTC
Figure 2.6 ECOWEAVE /RTC
2.5.1 Technical Information


  1. Optimized Valve Timing: shorter blowing times for relay nozzles due to patented real time controlled valve timing. 
  2. Advanced Design: new dedicated micro-controller design for high speed valve timing corrections; continuously actuated during weft insertion. Based on changing weft speed and actual weft tip position. 
  3. Self-Adjusting: no more tedious setting of relay nozzle timing – most settings are adjusted automatically during auto tune procedure. 
  4. Failure Detection: hardware failures (missing pulses, valve failure) are immediately detected. 
  5. Patent: based on previously approved L5500 patent with improved reliability and precise weft insertion. 

2.5.2 Advantages


  1. Cost Savings: up to € 500 - € 2’000/year depending on weft yarn and machine width. 
  2. Reduced Air Consumption: less CO² emissions and 10% - 20% less air consumption provides immediate energy cost reduction.
  3. Reduced Weft Stops: weft stops due to improper valve timing and variation in arrival time are eliminated by precise & continuous adjustment of the relay nozzles and specific control of the weft tip. 
  4. Ease of Use: simplified system with few parameters allows easy integration for weavers. 
  5. Energy Consumption Optimized Weaving with Real Time Control.

2.6 Prewinder Switch off (PSO)


GamMax has a Piezo-electric filling detector that stops the machine in case of a filling break. With its Prewinder Switch off (PSO) system, the machine continues weaving even if a filling break occurs on the packages or the Prewinder. The Prewinder signals the filling breaks and simply switches to single-channel operation instead of weaving with two channels. PSO is a patented Picanol development.

At a filling break the machine stops and only the harnesses are moved automatically to free the broken pick for removal by the weaver. The automatic pick finder and the slow motion movements are not driven by a separate motor; instead, the pick finding is simply done by the Sumo at slow speed. The required pick finding position is reached with a minimum of reed movements through the beat-up line.

2.7 Automatic Picks Finding


The GTX plus machine is equipped with an automatic pick finding device and with slow forward and backward motion. In case of a filling stop, the pick finder opens the shed on the broken pick for removal by the operator. The microprocessor synchronizes all mechanisms in this process. The automatic pick finding system makes repairing a filling break much easier for the operator and it shortens the time lost by filling stops.


2.8 Electronic Yarn Tension Control


Each pre-winder can be equipped with a new type of Programmable Filling Tensioner. This PFT is microprocessor controlled and ensures optimum yarn tension during the complete insertion cycle. Reducing the basic tension is an important advantage when picking up weak yarns, while adding tension is an advantage at transfer of the yarns and avoids the formation of loops. The tension control enables you to weave strong or weak yarns at even higher speeds. It also drastically reduces the amount of filling stops, and enables you to set an individual waste length per channel and reduce the waste length for some channels.

The Yarn Tension Meter is a portable and precise sensor between Prewinder and filling detector to measure and display the filling tension on the microprocessor quickly. Thanks to the immediate feedback, the sensor allows very easy fine-tuning of the yarn tension, which is very helpful when sensitive yarns need to be woven, such as wool. Instead of “trial and error”, you can “measure and act”. This has a direct impact on the productivity and the quality.


2.9 Automatic Start-mark Prevention (ASP)


ASP: Preventing start-marks at the source. The simple functionality of automatic start-mark prevention saves time and significantly contributes toward quality improvement. All the functions outlined in the illustration can be simply called up on the machine display and changed as required, including the patented AE-function (dynamic start-up) and automatic single pick mode. All settings are reproducible.

Figure 2.7 Automatic Start-mark Prevention
Figure 2.7 Automatic Start-mark Prevention


2.10 Mobile, Multi-functional Axis Control


The new mobile warp change key pad significantly facilitates the warp changing process. It can even be carried out by one person on double width weaving machines. The operator can control warp and fabric take-up with it from any point around the weaving machine. 


Figure 2.8 Mobile Warp Change Key Pad
Figure 2.8 Mobile Warp Change Key Pad
2.11 E-SHED


Toyoda's electronics technology has created the E-shed, yet another breakthrough in the weaving industry. Its ultimate shedding motion makes weaving easy, even with textile fabrics difficult to weave with conventional shedding motions. Based on the settings from the function panel, the E-shed's main 32-bit CPU controls independent servo-motors that drive individual shedding frames with perfect ease. This flexible system enables not only shedding patterns but also cross-timing and dwell angle to beset from the function panel. All of which leads to greater efficiency, easier operation and higher fabric quality.


Figure 2.8 Schematic of E-Shed
Figure 2.8 Schematic of E-Shed
2.11.1 Ultimate Flexibility


The E-shed combines the optimum cross-timing and dwell angle for each shedding curve, making It easy to weave various kinds of fabrics such as high density fabrics traditionally woven by cam shedding,
Complex fabrics with a dobby and even fabrics difficult to weave with conventional shedding motions because of loose warp yarn or incomplete shedding.

2.11.2 Greater Fabric Quality


Unlike existing shedding devices, the E-shed allows separate upper and lower dwell angles to be set, which improves beating-up performance and fabric quality. Meanwhile, combined variations in cross-timing prevent warp entanglement and minimize problems caused by warp yarn. And since the shedding and beating motions are not synchronized, there are fewer stop marks during start-up. High Efficiency freely controllable warp leads to increased warp shedding ability and minimal miss picks in weft insertion. And this means greater efficiency.

2.11.3 Easy Operation


Settings can be changed by a touch of the function panel. This makes it much quicker and easier to be flexible when manufacturing many different kinds of articles in small quantities. 

2.11.4 Not Affected by Upper/Lower Frame Imbalance


The E-shed is not affected by any difference between the numbers of upper and lower heaId frames unlike in dobby shedding, which enables wider range of patterns to be woven with great ease.

2.11.5 Pick Finding with Shedding Motion Only


Shedding and beating are not synchronized, which enables pick finding while moving the heald frame and keeping the reed fixed. The result is higher quality fabric with fewer stop marks. (With the Optional electronic take up motion installed).

2.12 CAN-Bus – The Backbone Weaving Machine Control


Electronic Control Technology the electronics of modern weaving machine are based on multiprocessor architecture with 32-bit technology. Data transfer between the various sub units of the machine is via a CAN- BUS, permitting fast and reliable exchange of data both internally and externally. The terminal has a graphic display in which various functions of the warp let-off, cloth take-up, weft feeder, etc. can be programmed easily and clearly. The modern CAN-Bus System gives the following advantages: 
  1. Ease of operation. 
  2. High fabric quality irrespective of speed. 
  3. Pick density alterable while the machine is in operation. 
  4. Immediate help trouble-shooting problem. 
  5. Self-adjusting stop position of the machine. 
  6. Microprocessor controlled central forced lubrication system. 
  7. Storage and monitoring of all the production data, efficiently. 
  8. Machine function control, pattern weave, warps tension, pick density. 
  9. Pick finding control and the elimination of stop marks by means of preset programs. 
  10. Control and report of style change timing. 
  11. Quick control of the electronic functions (self-diagnostics and auto checkup) and monitoring of the machinery functions for protection. 
  12. Bi-directional communication between the weaving machine and the central production computer. 
  13. Speed set-up. 
  14. Electronic weaving speed variation depending on the characteristic of the yarn being used. 
  15. Control of warp let-off and fabric take-up. 
  16. Electronic control of the filling tension. 
  17. Transfer of setting and production parameters of a fabric style, to other machine with the help of memory cards. 
In Picanol GamMax, most of the machine functions are digitally controlled. All the machine settings can be digitally stored and transferred. The electronic terminal on GamMax monitors and controls all machine functions. Its LCD screen has self-explanatory menus and enables the weaver to set the weaving parameters in a very user-friendly way. GamMax is also Internet- enabled. The GamMax terminal features wireless communication through a USB memory stick or key tag, permitting robust, flexible, handy and reliable operation. Sulzer G6500 offers "Smart Weave" - intelligent pattern data programming. "Smart Weave" offers fabric designer intelligent support in the preparation of weaves design and picks repeats. The G6500 control interface is a user-friendly, Internet-ready touch screen terminals. The logical structuring with self-explanatory Pictogram guides the operators to the desired function simply and with a minimum of keying. In Leonardo, the computer system is based on the CAN-BUS system. This drives and controls all the main textile and mechanical function. With the CAN-BUS in mind, a new controller has been developed, called the FULLTRONIC. This co-ordinate all loom functions instant by instant, from the operating conditions of the various mechanisms to each individual response: heald movement, color to be selected, warp tension, density of the weft in the fabric, plus the messages describing the status of the lubrication circuit. Monitoring takes place at a frequency of more than 700 messages/sec. The Dornier rapier-weaving machine, type PS, has control cabinet with integrated CANBUS and various modules for start, stop, warp let-off and fabric take-up as well as start mark prevention. The Dornier Customer Service Department can directly access machine displays - trouble shooting online. The DoNet Global Communication Network offers quick location and transportation of setting instructions, remote diagnostics.


Figure 2.9 CAN-BUS Connections
Figure 2.9 CAN-BUS Connections

2.12.1 DISPLAY


Evidence of how advanced electronics high quality and perfect repeatability can be found in the many functions accessed via the microprocessor. These include integrated setting screens with preset ranges for shedding, filling insertion, pick density and warp tension values. Pre-programmed procedures to prevent starting marks in sensitive fabrics are included as a standard feature.

Standard – color-graphic display. Ergonomic navigation through only a few menu levels has been drastically simplified. Shortcut keys support rapid, direct access to important menus and data for machine control. Weaving parameters such as speed, filling density and warp tension can be freely selected and stored as style data. The electronic terminal monitors and controls all machine functions. Its LCD screen has self-explanatory menus and enables the weaver to set the weaving parameters in a very user-friendly way. The display advises which action to take when a stop occurs. Pre-programmed procedures to prevent starting marks are standard. 

Figure-2.10 Display of modern weaving machine
Figure-2.10 Display of modern weaving machine

Important settings normally done by the fixer under difficult conditions, such as setting the selvedge crossing time or the shed crossing, are now done by simply typing in the required values. The settings are accurate and easily transferable to other machines, and the result of slight adjustments can be checked immediately in the fabric. For the weaver, all this means great ease of operation and higher weaving productivity.

CONCLUSION


Many times in the past it was argued that projectile and Rapier systems have attained maximum speed limit. However, these machines continue to enhance the speed limit and are not far behind Airjet machines. Most of the developments are in the area of attaining better fabric quality, gentle treatment to warp and weft and reduced breakages. Another interesting trend is in the type of selvedge formation and waste reduction. Weft waste has been reduced to zero even in Rapier and Airjet machines. The future trend in developments would, probably, be in similar lines.

REFERENCES


1. Model development; Textile Magazine; Issue4; 2008; pp36-39
2. Amit A Jadhav, Modern development in weaving; The Indian Textile Journal; July 2007; pp22-25
3. Yueyang Guo, Ruiqi C, A new type of microprocessor con-trolled positive dobby, Indian Journal of Fibre and Textile Research, vol. 28, pp. 275, (2003).
4. Subhankar Maity, Kunal Singha, Mrinal Singha, Recent Developments in Rapier Weaving Machines in Textiles, American Journal of Systems Science, 1(1): pp7-16, 2012
5. DORNIER Machinery Brochures
a) Air-Jet AS type
b) Air-Jet A1 Type 
c) Air-Jet Tire Cord
d) Rapier P1Type 
6. Picanol Machinery Brochures
a) GTXplus
b) GamMax
7. TOYODA E-SHED Brochures

ACETATE


Cellulosic-based, from wood pulp or cotton linters.

Characteristics:


Luxurious appearance Crisp or soft hand Wide range of colors; dyes and prints well Excellent drape ability and softness Shrink, moth, and mildew resistant Low moisture absorbency, relatively fast drying No pilling problem, little static problem Most acetate garments require dry-cleaning.

Major End Uses:


Apparel- Blouses, dresses, linings, special occasion apparel, Home Fashion - Draperies, upholstery, curtains, bedspreads.

TRIACETATE


Man-made.

Characteristics:


Luxurious hand Excellent drape ability Resilient Excellent pleat retention Washable or dry-cleanable No pilling problem Can have static problem.

Major End Uses:


Apparel - dresses, skirts, sportswear, robes, particularly where pleat retention is important.

LYOCELL


Man-made, cellulosic-based.

Characteristics:

Excellent strength Washable Shrink- and wrinkle-resistant Soft hand Excellent drape Absorbent Dyes and prints well.

Major End Uses:


Apparel - dresses, suits, sportswear, pants, jackets, blouses, skirts.

ACRYLIC


Man-made.

Characteristics:


Light-weight, soft, warm for winter wearing Fine, soft, lightweight, cotton-like fabrics, which are cool in hot weather Dyes to bright colors with excellent fastness Outstanding wick ability Machine washable, quick drying Resilient; retains shape; resists shrinkage, & wrinkles Flexible aesthetics for wool-like, cotton-like or blended appearance Excellent pleat retention Resistant to moths, oil and chemicals Superior resistance to sunlight degradation Static and pilling can be a problem.

Major End Uses:


Apparel - sweaters, socks, fleece, circular knit apparel, sportswear, children's wear Home Fashion - Blankets, throws, upholstery, awnings, outdoor furniture, rugs/floor coverings.

Fibres
Fibres


SPANDEX


Man-made.

Characteristics:


Lightweight Can be stretched over 500% without breaking Able to be stretched repetitively and still recover original length Abrasion resistant Stronger, more durable than rubber Soft, smooth and supple Resistant to body oils, perspiration, lotions or detergents No static or pilling problems.

Major End Uses:


Apparel - articles where stretch is desired: athletic apparel, bathing suits, foundation garments, ski pants, slacks, hosiery, socks, belts.

NYLON


Man-made.

Characteristics:


Lightweight Exceptional strength Good drape ability Abrasion resistant Easy to wash Resists shrinkage and wrinkling resilient, pleat retentive Fast drying, low moisture absorbency. Can be pre-colored or dyed in a wide range of colors Resistant to damage from oil and many chemicals Static and pilling can be a problem Poor resistance to continuous sunlight.

Major End Uses:


Apparel - swimwear, activewear, intimate apparel, foundation garments, hosiery, blouses, dresses, sportswear, pants, jackets, skirts, raincoats, ski and snow apparel, windbreakers, children's wear. Home Fashion - carpets, rugs, curtains, upholstery, draperies, bedspreads Other - Luggage, back packets, life vests, umbrellas, sleeping bags, tents.

POLYESTER


Man-made.

Characteristics:


Strong Crisp, soft hand Resistant to stretching and shrinkage Washable or dry-cleanable Quick drying Resilient, wrinkle resistant, excellent pleat retention (if heat set) Abrasion resistant Resistant to most chemicals Because of its low absorbency, stain removal can be a problem Static and pilling problems.

Major End Uses:


Apparel - essential every form of clothing, dresses, blouses, jackets, separates, sportswear, suits, shirts, pants, rainwear, lingerie, children's wear Home Fashion - curtains, draperies, floor coverings, fiber fill, upholstery, bedding.

RAYON


Man-made, cellulosic-based from wood pulp.

Characteristics:


Soft and comfortable Drapes well Highly absorbent Dyes and prints well No static, no pilling problems Fabric can shrink appreciably if washing dry clean only rayon Washable or dry cleanable.

Major End Uses:


Apparel - Blouses, dresses, jackets, lingerie, linings, millinery, slacks, sport shirts, sportswear, suits, ties, work clothes Home Fashion - bedspreads, blankets, curtains, draperies, sheets, slip covers, table cloths, upholstery.

Raw wool contains seeds and other pieces of vegetable matter. Much of this may be removed in scouring and in combing. Combing is not used in woolen system and vegetable matter is only partially removed in carding. Even in some worsted processes, small amount of residual vegetable material is present in the fabric and in such cases carbonizing is essential to remove the residues.

Sheep
Sheep
The scoured wool fabric is padded, either in the rope form or in open width, with liquor containing dilute sulfuric acid (5 to 7 % by wt.) at approximately 65% wet pick up. And dried at 65 -90 degree celsius to concentrate the acid. Baking at 125 degree celsius for one minute chars the cellulosic material. The charred vegetable material is brittle and easily crushed on passing the rollers. it can be removed as dust during subsequent mechanical working. After carbonizing the wool fabric should rinsed and neutralized by washing. Such neutralization should be carried out immediately after baking; otherwise fabric damage will occur during storage of wool in such as acidic state. It is convenient to neutralize prior to dyeing but uneven neutralization leads to uneven dyeing’s.

Physical Properties of Polyester:

The moisture regain of polyester is 0.2 to 0.8 and specific gravity is 1.38 or 1.22 depending on the type of polyester fibres is moderate. The melting point of polyester is 250-300°C. A wide of polyester fibres properties is possible depending on the method of manufacture. Generally as the degree of stretch is increased, which yields higher crystallinity and greater molecular orientation, so are the properties e.g. tensile strength and initial Young’s modulus. Shrinkage of the fibres also varies with the mode of treatment. If relaxation of stress and strain in the oriented fibre occurs, shrinkage decreases but the initial modulus may be also reduced.


Polyester
Polyester

Miscellaneous Properties of Polyester:

Polyester fibres exhibit good resistant to sunlight and it also resists abrasion very well. Soaps, synthetic detergents and other laundry aids do not damage it. One of the most serious faults with polyester is its oleophilic quality. It absorbs oily material easily and holds the oil tenacity.

Chemical Properties of Polyester:

Effect of Alkalies on Polyester:

Polyester fibres have good resistance to weak alkalies high temperatures. It exhibits only moderate resistance to strong alkalies at room temperature and is degraded at elevated temperatures.

Effect of Acids on Polyester:

Weak acids, even at the boiling point, have no effect on polyester fibres unless the fibres are exposed for several days. Polyester fibres have good resistance to strong acids at room temperature. Prolonged exposure to boiling hydrochloric acid destroys the fibres, and 96% sulfuric acid and causes disintegration of the fibres.

Effect of Solvents on Polyester:

Polyester fibres are generally resistant to organic solvents. Chemicals used in cleaning and stain removal do not damage it, but hot m-cresol destroys the fibres, and certain mixtures of phenol with trichloromethane dissolve polyester fibres. Oxidizing agents and bleachers do not damage polyester fibres.
Polyester fibres have taken the major position in textiles all over the world although they have many drawbacks e.g.,
  • Low moisture regain (0.4%),
  • The fibres has a tendency to accumulate static electricity,
  • The cloth made up of polyester fibres picks up more soil during wear and it also difficult to clean during washing
  • The polyester garments from pills and thus, the appearance of a garment is spoiled,
  • The polyester fibres is flammable.
Thus, it has been suggested that surface modifications can have an effect on hand, thermal properties, permeability, and hydrophobicity. Polyester fabrics have been widely accepted by consumers for their easy care properties, versatility and long life, In spite of such acceptance, complaints concerning their hand, thermal properties and moisture absorbency have been cited improved moisture absorbency of polyester fibres can be achieved by introducing hydrophilic block copolymers. However, this modification can lead to problems of longer drying time, excessive wrinkling and wet cling. In addition, penetration of water into the interior of the fibres has not been clearly shown to improve perceived comfort Polyester fibres are susceptible to the action of bases depending on their ionic character. Ionizable bases like caustic soda, caustic potash and lime water only affect the outer surface of polyester filaments. Primary and secondary bases and ammonia, on the other hand, can diffuse into polyester fibre and attack in depth resulting in breaking of polyester chain molecules by amide formation.

COTTON FIBER QUALITY OR COTTON FIBER YIELD?

Like all agricultural commodities, the value of cotton lint responds to fluctuations in the supply-and-demand forces of the marketplace.  In addition, pressure toward specific improvements in cotton fiber quality - for example, the higher fiber strength needed for today's high-speed spinning - has been intensified as a result of technological advances in textile production and imposition of increasingly stringent quality standards for finished cotton products.

Changes in fiber-quality requirements and increases in economic competition on the domestic and international levels have resulted in fiber quality becoming a value determinant equal to fiber yield. Indeed, it is the quality, not the quantity, of fibers ginned from the cotton seeds that decides the end use and economic value of a cotton crop and, consequently, determines the profit returned to both the producers and processors.

Cotton
Cotton
Field-production and breeding researchers, for various reasons, have failed to take full advantage of the fiber-quality quantitation methods developed for the textile industry. Most field and genetic improvement studies still focus on yield improvement while devoting little attention to fiber quality beyond obtaining bulk fiber length, strength, and micronaire averages for each treatment . Indeed, cotton crop simulation and mapping models of the effects of growth environment on cotton have been limited almost entirely to yield prediction and cultural-input management.

Plant physiological studies and textile-processing models suggest that bulk fiber-property averages at the bale, module, or crop level do not describe fiber quality with sufficient precision for use in a vertical integration of cotton production and processing. More importantly, bulk fiber-property means do not adequately and quantitatively describe the variation in the fiber populations or plant metabolic responses to environmental factors during the growing season. Such pooled or averaged descriptors cannot accurately predict how the highly variable fiber populations might perform during processing.

Meaningful descriptors of the effects of environment on cotton fiber quality await high-resolution examinations of the variability, induced and natural, in fiber-quality averages. Only then can the genetic and environmental sources of fiber-quality variability be quantified, predicted, and modulated to produce the high-quality cotton lint demanded by today's textile industry and, ultimately, the consumer.

Increased understanding of the physiological responses to the environment that interactively determine cotton fiber quality is essential. Only with such knowledge can real progress be made toward producing high yields of cotton fibers that are white as snow, as strong as steel, as fine as silk, and as uniform as genotypic responses to the environment will allow.


Estimating Cotton Fiber Fineness:

Fiber fineness has long been recognized as an important factor in yarn strength and uniformity, properties that depend largely on the average number of fibers in the yarn cross section. Spinning larger numbers of finer fibers together results in stronger, more uniform yarns than if they had been made up of fewer, thicker fibers. However, direct determinations of biological fineness in terms of fiber or lumen diameter and cell-wall thickness are precluded by the high costs in time and labor, the noncircular cross sections of dry cotton fibers, and the high degree of variation in fiber fineness.

Advances in image analysis have improved determinations of fiber biological fineness and maturity, but fiber image analyses remain too slow and limited with respect to sample size for inclusion in the HVI-based cotton-classing process.

Originally, the textile industry adopted gravimetric fiber fineness or linear density as an indicator of the fiber-spinning properties that depend on fiber fineness and maturity combined. This gravimetric fineness testing method was discontinued in 1989, but the textile linear density unit of Tex persists. Tex is measured as grams per kilometer of fiber or yarn, and fiber fineness is usually expressed as millitex or micrograms per meter. Earlier, direct measurements of fiber fineness (either biological or gravimetric) subsequently were replaced by indirect fineness measurements based on the resistance of a bundle of fibers to airflow.

The first indirect test method approved by ASTM for measurement of fiber maturity, linear density, and maturity index was the causticaire method. In that test, the resistance of a plug of cotton to airflow was measured before and after a cell-wall swelling treatment with an 18% (4.5 M) solution of NaOH (ASTM, 1991, D 2480-82). The ratio between the rate of airflow through an untreated and then treated fiber plug was taken as indication of the degree of fiber wall development. The airflow reading for the treated sample was squared and corrected for maturity to serve as an indirect estimate of linear density. Causticaire method results were found to be highly variable among laboratories, and the method never was recommended for acceptance testing before it was discontinued in 1992.

The arealometer was the first dual-compression airflow instrument for estimating both fiber fineness and fiber maturity from airflow rates through untreated raw cotton (ASTM, 1976, D 1449-58; Lord and Heap, 1988). The arealometer provides an indirect measurement of the specific surface area of loose cotton fibers, that is, the external area of fibers per unit volume (approximately 200-mg samples in four to five replicates). Empirical formulae were developed for calculating the approximate maturity ratio and the average perimeter, wall thickness, and weight per inch from the specific surface area data. The precision and accuracy of arealometer determinations were sensitive to variations in sample preparation, to repeated sample handling, and to previous mechanical treatment of the fibers, e.g., conditions during harvesting, blending, and opening. The arealometer was never approved for acceptance testing, and the ASTM method was withdrawn in 1977 without replacement.

The variations in biological fineness and relative maturity of cotton fibers that were described earlier cause the porous plugs used in air-compression measurements to respond differently to compression and, consequently, to airflow . The IIC-Shirley Fineness/Maturity Tester (Shirley FMT), a dual-compression instrument, was developed to compensate for this plug-variation effect (ASTM, 1994, D 3818-92). The Shirley FMT is considered suitable for research, but is not used for acceptance testing due to low precision and accuracy. Instead, micronaire has become the standard estimate of both fineness and maturity in the USDA-AMS classing offices.

Cotton
Cotton

Cotton Fiber Maturity and Environment:

Whatever the direct or indirect method used for estimating fiber maturity, the fiber property being as sayed remains the thickness of the cell wall. The primary cell wall and cuticle (together »0.1 µm thick) make up about 2.4% of the total wall thickness (»4.1 µm of the cotton fiber thickness at harvest). The rest of the fiber cell wall (»98%) is the cellulosic secondary wall, which thickens significantly as polymerized photosynthate is deposited during fiber maturation. Therefore, any environmental factor that affects photosynthetic C fixation and cellulose synthesis will also modulate cotton fiber wall thickening and, consequently, fiber physiological maturation  

Cotton Fiber Maturity and Temperature and Planting Date:

The dilution, on a weight basis, of the chemically complex primary cell wall by secondary-wall cellulose has been followed with X-ray fluorescence spectroscopy. This technique determines the decrease, with time, in the relative weight ratio of the Ca associated with the pectin-rich primary wall. Growth-environment differences between the two years of the studies cited significantly altered maturation rates, which were quantified as rate of Ca weight-dilution, of both upland and Pima genotypes. The rates of secondary wall deposition in both upland and Pima genotypes were closely correlated with growth temperature; that is, heat-unit accumulation.

Micronaire (micron AFIS) also was found to increase linearly with time for upland and Pima genotypes. The rates of micronaire increase were correlated with heat-unit accumulations. Rates of increase in fiber cross-sectional area were less linear than the corresponding micronaire-increase rates, and rates of upland and pima fiber cell-wall thickening  were linear and without significant genotypic effect .

Environmental modulation of fiber maturity (micronaire) by temperature was most often identified in planting- and flowering-date studies. The effects of planting date on micronaire, Shirley FMT fiber maturity ratio, and fiber fineness (in millitex) were highly significant in a South African study (Greef and Human, 1983). Although genotypic differences were detected among the three years of that study, delayed planting generally resulted in lower micronaire. The effect on fiber maturity of late planting was repeated in the Shirley FMT maturity ratio and fiber fineness data.

Harvest dates in this study also were staggered so that the length of the growing season was held constant within each year. Therefore, season-length should not have been an important factor in the relationships found between planting date and fiber maturity.

Variations in fiber maturity were linked with source-sink modulations related to flowering date, and seed position within the bolls. However, manipulation of source-sink relationships by early-season square (floral bud) removal had no consistently significant effect on upland cotton micronaire in one study. However, selective square removal at the first, second, and third fruiting sites along the branches increased micronaire, compared with controls from which no squares had been removed beyond natural square shedding. The increases in micronaire after selective square removals were associated with increased fiber wall thickness, but not with increased strength of elongation percent. Early-season square removal did not affect fiber perimeter or wall thickness (measured by arealometer). Partial defruiting increased micronaire and had no consistent effect on upland fiber perimeter in bolls from August flowers.

Cotton Fiber Maturity and Water:

Generous water availability can delay fiber maturation (cellulose deposition) by stimulating competition for assimilates between early-season bolls and vegetative growth. Adequate water also can increase the maturity of fibers from mid-season flowers by supporting photosynthetic C fixation. In a year with insufficient rainfall, initiating irrigation when the first-set bolls were 20-d old increased micronaire, but irrigation initiation at first bloom had no effect on fiber maturity. Irrigation and water-conservation effects on fiber fineness (millitex) were inconsistent between years, but both added water and mulching tended to increase fiber fineness. Aberrations in cell-wall synthesis that were correlated with drought stress have been detected and characterized by glycoconjugate analysis.

An adequate water supply during the growing season allowed maturation of more bolls at upper and outer fruiting positions, but the mote counts tended to be higher in those extra bolls and the fibers within those bolls tended to be less mature. Rainfall and the associated reduction in insolation levels during the blooming period resulted in reduced fiber maturity. Irrigation method also modified micronaire levels and distributions among fruiting sites.

Early-season drought resulted in fibers of greater maturity and higher micronaire in bolls at branch positions 1 and 2 on the lower branches of rained plants. However, reduced insolation and heavy rain reduced micronaire and increased immature fiber fractions in bolls from flowers that opened during the prolonged rain incident. Soil water deficit as well as excess may reduce micronaire if the water stress is severe or prolonged.

Micronaire or maturity data now appear in most cotton improvement reports. In a five-parent half-diallel mating design, environment had no effect on HVI micronaire. However, a significant genotypic effect was found to be associated with differences between parents and the F1 generation and with differences among the F1 generation. The micronaire means for the parents were not significantly different, although HVI micronaire means were significantly different for the F1 generation as a group. The HVI was judged to be insufficiently sensitive for detection of the small difference in fiber maturity resulting from the crosses.

In another study, F2 hybrids had finer fibers (lower micronaire) than did the parents, but the improvements were deemed too small to be of commercial value.  Unlike the effects of environment on the genetic components of other fiber properties, variance in micronaire due to the genotype-by-environment interaction can reach levels expected for genetic variance in length and strength. Significant interactions were found between genetic additive variance and environmental variability for micronaire, strength, and span length in a study of 64 F2 hybrids.

FIBER STRENGTH:

The inherent breaking strength of individual cotton fibers is considered to be the most important factor in determining the strength of the yarn spun from those fibers. Recent developments in high-speed yarn spinning technology, specifically open-end rotor spinning systems, have shifted the fiber-quality requirements of the textile industry toward higher-strength fibers that can compensate for the decrease in yarn strength associated with open-end rotor spinning techniques.

Compared with conventional ring spinning, open-end rotor-spun yarn production capacity is five times greater and, consequently, more economical. Rotor-spun yarn is more even than the ring-spun, but is 15 to 20% weaker than ring-spun yarn of the same thickness. Thus, mills using open-end rotor and friction spinning have given improved fiber strength highest priority. Length and length uniformity, followed by fiber strength and fineness, remain the most important fiber properties in determining ring-spun yarn strength.

Historically, two instruments have been used to measure fiber tensile strength, the Pressley apparatus and the Stelometer. In both of these flat-bundle methods, a bundle of fibers is combed parallel and secured between two clamps. A force to try to separate the clamps is applied and gradually increased until the fiber bundle breaks. Fiber tensile strength is calculated from the ratio of the breaking load to bundle mass. Due to the natural lack of homogeneity within a population of cotton fibers, bundle fiber selection, bundle construction and, therefore, bundle mass measurements, are subject to considerable experimental error.

Fiber strength, that is, the force required to break a fiber, varies along the length of the fiber, as does fiber fineness measured as perimeter, diameter, or cross section further, the inherent variability within and among cotton fibers ensures that two fiber bundles of the same weight will not contain the same number of fibers. Also, the within-sample variability guarantees that the clamps of the strength testing apparatus will not grasp the various fibers in the bundle at precisely equivalent positions along the lengths. Thus, a normalizing length-weight factor is included in bundle strength calculations.

Cotton
Cotton
In the textile literature, fiber strength is reported as breaking tenacity or grams of breaking load per Tex, where Tex is the fiber linear density in grams per kilometer. Both Pressley and stelometer breaking tenacities are reported as 1/8 in. gauge tests, the 1/8 in. (or 3.2 mm) referring to the distance between the two Pressley clamps. Flat-bundle measurements of fiber strength are considered satisfactory for acceptance testing and for research studies of the influence of genotype, environment, and processing on fiber (bundle) strength and elongation.

The relationships between fiber strength and elongation and processing success also have been examined using flat-bundle strength testing methods. However cotton fiber testing today requires that procedures be rapid, reproducible, automated, and without significant operator bias.  Consequently, the HVI systems used for length measurements in USDA-AMS classing offices are also used to measure the breaking strength of the same fiber bundles (beards) formed during length measurement.

The HVI bundle-strength and elongation-percent testing methods are satisfactory for acceptance testing and research studies when 3.0 to 3.3 g of blended fibers are available and the relative humidity of the testing room is adequately controlled. A 1% increase in relative humidity and the accompanying increase in fiber moisture content will increase the strength value by 0.2 to 0.3 g tex-1, depending on the fiber genotype and maturity.

Further, classing-office HVI measurements of fiber strength do not adequately describe the variations of fiber strength along the length of the individual fibers or within the test bundle. Thus, predictions of yarn strength based on HVI bundle-strength data can be inadequate and misleading. The problem of fiber-strength variability is being addressed by improved HVI calibration methods and by computer simulations of bundle-break tests in which the simulations are based on large single-fiber strength databases of more than 20 000 single fiber long-elongation curves obtained with MANTIS.

Reports of stelometer measurements of fiber bundle strength are relatively rare in the refereed agronomic literature. Consequently, the interactions of environment and genotype in determining fiber strength are not as well documented as the corresponding interactions that modulate fiber length. Growth environment, and genotype response to that environment, play a part in determining fiber strength and strength variability.

Early studies showed fiber strength to be significantly and positively correlated with maximum or mean growth temperature, maximum minus minimum growth temperature, and potential insolation. Increased strength was correlated with a decrease in precipitation. Minimum temperature did not affect fiber strength. All environmental variables were interrelated, and a close general association between fiber strength and environment was interpreted as indicating that fiber strength is more responsive to the growth environment than are fiber length and fineness. Other investigators reported that fiber strength was correlated with genotype only.

Square removal did not affect either fiber elongation or fiber strength. Shading, leaf-pruning, and partial fruit removal decreased fiber strength. Selective square removal had no effect on fiber strength in bolls at the first, second, or third position on a fruiting branch. Fiber strength was slightly greater in bolls from the first 4 to 6 wk of flowering, compared with fibers from bolls produced by flowers opening during the last 2 wk of the flowering period.

In that study, fiber strength was positively correlated with heat unit accumulation during boll development, but genotype, competition among bolls, assimilatory capacity, and variations in light environment also helped determine fiber strength. Early defoliation, at 20% open bolls, increased fiber strength and length, but the yield loss due to earlier defoliation offset any potential improvement in fiber quality.

Of the fiber properties reported by USDA-AMS classing offices for use by the textile industry, fiber maturity is probably the least well-defined and most misunderstood. The term, fiber maturity, used in cotton marketing and processing is not an estimate of the time elapsed between floral anthesis and fiber harvest. However, such chronological maturity can be a useful concept in studies that follow fiber development and maturation with time. On the physiological and the physical bases, fiber maturity is generally accepted to be the degree (amount) of fiber cell-wall thickening relative to the diameter or fineness of the fiber.

Classically, a mature fiber is a fiber in which two times the cell wall thickness equals or exceeds the diameter of the fiber cell lumen, the space enclosed by the fiber cell walls. However, this simple definition of fiber maturity is complicated by the fact that the cross section of a cotton fiber is never a perfect circle; the fiber diameter is primarily a genetic characteristic.

Further, both the fiber diameter and the cell-wall thickness vary significantly along the length of the fiber. Thus, attempting to differentiate, on the basis of wall thickness, between naturally thin-walled or genetically fine fibers and truly immature fibers with thin walls greatly complicates maturity comparisons among and within genotypes.

Within a single fiber sample examined by image analysis, cell-wall thickness ranged from 3.4 to 4.9 µm when lumen diameters ranged from 2.4 to 5.2 µm. Based on the cited definition of a mature fiber having a cell-wall thickness two times the lumen diameter, 90% of the 40 fibers in that sample were mature, assuming that here had been no fiber-selection bias in the measurements.

Unfortunately, none of the available methods for quantifying cell-wall thickness is sufficiently rapid and reproducible to be used by agronomists, the classing offices, or fiber processors. Fiber diameter can be quantified, but diameter data are of limited use in determining fiber maturity without estimates of the relationship between lumen width and wall thickness. Instead, processors have attempted to relate fiber fineness to processing outcome.

Ashish Hulle

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