Although compression therapy is a key factor in the successful treatment of some circulatory problems in lower limbs, this form of therapy includes some risks if used inappropriately. Based on deliberate application of pressure to a lower limb, using a variety of textile materials, elastic or rigid in order to produce a desired clinical effects, modern compression therapy presents a good sample of successful penetration of textile technology into the phlebology field of medicine. However, although compression therapy has been in use for over 150 years, there exists a low awareness among practitioners and patients on the product usage, application techniques and benefit of appropriate selection of bandages for determined types of leg venous diseases. Also, not all manufacturers for compression textile materials seem to be conscious of end-users need. simultaneously, impressive developments in the field of elastic fibers and modern knitting and weaving technologies, offer chances for realization of completely new types of compressed bandages, capable of making an important contribution to the management of venous disease. In this review, starting from brief account of pathogenesis and the presentation of compression therapy principle, an account of the contribution of all sectors in the textile technology chain to a modern compression therapy is given.
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Cukurova University, Faculty of Fine Arts, Department of Textile Design,
This is a digital age, dominated by information, communication and technology-based entertainment. This age is a result of rapid visual information-sharing. In this age, technology enables video sharing, saving every moment as visual data, and it is a result of rapid visual and information sharing. Today, artists use digital technologies as a means of expressing concepts. Woven textiles are also affected by the technological advances. Textiles have been essential for people from ancient times to now, for covering and protecting themselves from heat and cold. Weaving is a fine art form and a product of labor, including Coptic textiles and European tapestries; it can also utilize the speed, selection and color options of digital technologies that result from the mechanization and technological advances in the 20th century. Computerized Jacquard looms are one of the benefits of digital technologies that enable the weaving of complex imagery by allowing individual warp threads to be lifted.
Today, working with digital cameras, scanners and jacquard looms the textile artist becomes a designer and technology becomes a medium serving the artist’s creativity. In this study, the works of textile artists will be examined in view of time, technology and communication.
Keywords: Weaving, digital technology, jacquard loom
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The technologies embedded in wearables influence the comfort, wearability and aesthetics. According to Tao (2005) (Figure 1) a typical system configuration of a wearables includes several basic functions such as: interface, communication, data management, energy management and integrated circuits. This classification is based on general purpose wearable computers.
A similar classification is presented by Seymour (2009) with focus on fashionable wearables, a combination of aesthetic as well as functional pieces . Thus most common technological components used to develop fashionable wearables are: interfaces (connectors, wires, and antennas), microcontrollers, inputs (sensors), outputs (actuators), software, energy (batteries, solar panels), and materials (interactive or reactive materials, enhanced textiles).
Both classifications are overlapping each other, but for the purpose of this thesis they will be combined and all the concepts explained, with emphases on e-textiles. The project examples used in this section, supporting the theory are related to wearable textile technology already available on the market or projects currently being developed in research labs around the world showing promising results in becoming future technologies. The diversification of the project concepts goes from being very functional and practical towards more expressive and artistic.
To obtain information for wearable devices components such as sensors are often used, for instance, environmental sensors, antennas, global positioning system receivers, sound sensors and cameras. Such sensors can be divided on active and passive(Langenhove & Hertleer, 2004)(Seymour, 2009). Active inputs are controlled by a user via a tactile or acoustic feedback system, which provides an intuitive interaction with the garment. Passive inputs collect biometric data from the human body as well as environmental data collected via wireless transmission system. The data is captured and further processed usually using a microprocessor. The table below provides suggestions for the type of inputs wearable systems can collect from a person or the environment.
The most common way for a user to interact with a device these days, involves the use of buttons, keyboards and screens, as they are proven to be easy to learn, implement and use with few mistakes. Fabric- based interfaces using keyboards and buttons are most common for wearables. They are usually designed from either multilayered woven circuits or polymer systems (Tao, 2005). At the dawn of ubiquitous computing environments, people will need to engage with many different devices with built-in microprocessors and sensors. As wearable devices become more complex, a need for more complex interfaces arises. People want more options on their devices, they want everything, but they also want them with the maximum of easy, freedom and comfort. This requires new ways of interaction, such as user engagement through voice, touch and gestures. The devices of the future will have no faces(Saffer, 2007). They will implement more intuitive ways of interaction.
Figure 1 – Suggestions types of inputs that a wearable system can collect
Voice recognition – Voice-controlled interfaces are currently most common on phones. However there are few drawbacks in the technology. It is difficult to create voice-controlled interfaces in public spaces, from both technical and design perspective, when the system should always listen for a command. In this case, incorrect processing of information is possible due to large influence of background noise. How will the system know to differentiate between a command and a background noise is a design challenge that yet needs to be answered. Furthermore, the current voice recognition technology has a problem distinguishing between different people’s voice and additionally, it requires more processing power then previous technologies. Leading researchers believe these obstacles will be overcome as technology advances, predicting that in a very near future we will interact with voice – controlled devices and environments.
Gesture recognition – As devices gain better awareness of the movement of the human body through technologies such as Global Positioning System (GPS) sensors and sudden – motion sensors (SMSs), gesture recognition as a way of human interaction with devices is becoming even more achievable. Indeed, there are devices such as mobile phones equipped with tilt motion sensors, so that users can, for example, “pour” media data from their phone to another device (Dachselt & Buchholz, 2009). Donneaud (2007) created a large textile interface for playing electronic music. Figure 2 illustrates the textile interface that is constructed of two conductive fabrics which are fixed on a frame each one weaved with conductive threads in a different direction.
Figure 2: Textile XY: interface for playing music
When the performer presses any point of this textile, the two fabrics connect and the current electrical value is sent to the computer. This textile interface is flexibility and transparency, involving the whole body through choreographic movements in the musical interpretation, thus allowing the performer to explore the textile interface by look, touch and gesture.
Presence recognition – Person’s presence is another way of interaction with a system. Present- activated systems are one of the central research points for ambient intelligent environments. The main design and technical challenge here is what determines if the system should react to the presence of a person, how it should react and how fast this reaction should be after a change has been detected.
There are a variety of output devices or materials which activate in wearables as a result of computation triggered by input data. Many outputs can stimulate any of the five the senses of the wearer or his audience. For example, shape memory alloy can change the silhouette of a fabric presenting a visual experience for an audience and a tactile experience for the wearer. The table below provides an overview of possible outputs to address specific senses.
LEDs, EL wires, displays, photochromic ink, thermocromic ink, E-ink
Figure 3 – Overview of possible outputs that address specific senses
For electronic components to truly become part of bigger interactive systems they need to be connected in order to exchange information. Wires, cables, antennas and connectors are most common physical components used to connect electronics together. Wired connections are secure and practical in many cases, but they can cause inflexibility and add to the weight of the system. On the other hand, wireless connections increase flexibility and the lightness of the system, but increase its complexity.
The advances in wireless technologies have played a significant role in the development of wearables and e-textiles, reducing the number of devices attached to a system, simplifying its construction as well as minimizing the size. According to Seymour(2009) some of the most common wireless communication and location based systems are: UMTS (Universal Mobil Telecommunication System), GPRS (General Packet Radio Service), GSM (Global System for Mobile Communication), GPS (Global Positioning System), Cell Triangulation, WIFI, Bluetooth, IR (Infrared) and PAN (Personal Area Network). These communication systems can be further subdivided to long- range or short range communications(Tao, 2005), if the transfer of information is between two or more users via the internet or a network protocol or between two or more wearable devices worn by a user, respectfully.
The long-range communication technologies advanced during the mobile revolution. All portable devices such as mobile phones, PDAs, MP3 players use radio frequencies to enable communication. From the list above the following communication systems: UMTS, GPRS, GSM, GPS, cell triangulation, WIFI are long-range. GSM is the communication system currently most suitable for voice transmission, as well as for data and files transmission at 9.6 kbps. For transfer of pictures and video a third-generation (3G) wireless system is also available, with the capacity of 384 kbps. GPS and cell triangulation is suitable for navigation purposes. The variety of communication systems opens many possibilities for wearable devices and the exchange of information.
Short-range communication for wearables is a research area that still needs to be developed. Some of the approaches considered for implementation in wearables are wiring, infrared, Bluetooth technology, WIFI, Personal Area Network (PAN) and Fabric Area Network (FAN). Even though they have some disadvantages, they show promising results as future technologies embedded in devices and textiles.
Embedding wires in garments is cumbersome and constrictive, and therefore not adequate. For infrared to be effective it requires direct lines of sight, which is not practical and difficult to implement on different devices worn on the body. Bluetooth technology is widely used, with an open wireless communication protocol which ensures connection between several devices within a short communication range (10 m), overcoming problems of synchronization. This technology is embedded in a range of products (such as smart phones, headsets, mouse, keyboards, printers and game consoles) and has many applications in situations where low-bandwidth communication is required. Bluetooth devices can interact independently of the user, as well as advertise services they provide, thus making this network more secure than other types, as more of the security, network address and permission configuration can be automated. This also provides an easier access to services for the users. WIFI (also called “wireless Ethernet”) uses the same radio frequency as the Bluetooth, but with higher power, resulting with a stronger connection. The users have the advantage to move around within a broad coverage area and still be connected to the network, through a variety of WIFI enabled devices such as laptops, smart phones, PDAs.
From a collaboration research project in 1996 between MIT Media Lab and IBM Almaden Research Center a new wireless technology emerged called the Personal Area Network (PAN) also referred to it as Body Area Network. The technology is considered the backbone of wearable technology, allowing exchange of digital information, power and control signals within the user’s personal space. PAN takes advantage of the natural electrical conductivity of the human body combined with a transmitter embedded with a microchip, to create an external electric field that passes an incredibly tiny current (1 billionth of an amp- 1 nanoamp) through the body, used to transmit data (IBM, 1996). As a comparison, the electrical field created by running a comb through hair is more than 1000 times greater than the current required for PAN technology to be functional. The technology is still being refined but researchers see great potential in PAN, as an effective and cost-efficient communication network. Passing of simple data between electronic devices carried by two people would be easier than ever, such as exchanging business cards via a handshake. This scenario as fascinating as it sounds also imposes many security issues, because touching a person with a PAN is like tapping a phone line (Tao, 2005).
In 2001 Hum proposed a wireless communication infrastructure to enable networking and sensing on clothing called the Fabric Area Network (FAN). The technology promises to solve some of the problems Bluetooth and GSM are facing, regarding the public concern of health hazards from the increased amount of emissions in the body from these sources of radiation. The new and innovative method, in which the technology architecture is designed, uses radio frequency (RF) fields for data communication and powering, restricted only to the surface of the clothing thus eliminating radiation into the body. More specifically, the technology uses multiple radio frequency identification FRID links, which have been used in the industry for years for tagging and tracking products. Even though the technology is being promoted as emission-save, low-cost and easy to maintain, it still has much more development it needs to undergo before such networking and sensing clothing can be considered for mass production.
The technologies described above such as GSM, GPS, WIFI and Bluetooth are already widely used as part of wearable devices. Since, they have been proven to be stable communicational systems and well developed; attempts have been made in the research community for their implementation in computational and smart textiles. However, these technologies were not initially designed for integration in clothing and accessories and thus researchers are modifying and perfecting these wireless networks to meet the requirements that currently established communication systems, cannot fulfill. For that reason, wireless networks such as PAN and FAN were originally designed and are still investigated.
Data management technologies and integrated circuits
The storing and processing of data in wearables is carried out in integrated circuits (IC), microprocessors or microcontroller. Integrated circuits are miniaturized electronic circuits which are mostly manufactured from silicon because of its superior semi conductive properties. However silicon is not flexible and therefore ICs are not very suitable for incorporating them on clothing. Developing ICs from conductive or semi-conductive polymeric Having the properties of a polymermaterials can be of great importance for wearable electronics since these materials are flexible, lightweight, and strong and of low production cost (Rossi, Capri, Lorussi, Scilingo, Tognetti, & Paradiso, 2005). Their down side is that they are not as efficient as silicon, and thus scientists are looking into developing electronics in the near future that will be a combination of both silicon and conductive polymers which will be complimenting each other.
Among the most advanced integrated circuits there are the microprocessors which are the heart of any normal computer. Also known as the CPUs (Central Processing Units), they present complete computation engines fabricated on single chips. The microprocessor performs many functions some of which are executing a stored set of instructions carrying out user defined tasks as well as carrying the ability to access external memory chips to both read and write data from and to the memory. From the architecture of the microprocessors, more specialized processing devices were developed, such as microcontrollers.
A microcontroller is a single-chip computer, which is embedded in many everyday products and therefore it is also called “embedded controller”. If a product has buttons and a digital display, most likely it also has a programmable microcontroller that provides a real-time response to events in the embedded system they are controlling. Such automatically controlled devices, often consumer products, are remote controls, cell phones, office machines, appliances, toys and many more.
Even though microcontrollers are “small computers”, they still have many things in common to desktop computers or large mainframe computers. All computers have a CPU which executes many different programs. In the case of microcontrollers the CPU executes a single program and thus they are known as “single purpose computers”. Also microcontrollers have a hard disk, a RAM (random-access memory) and inputs and outputs, which are all combined on a single microchip. Other characteristics common for a majority of microcontrollers, besides being embedded inside other devices dedicated to run specific single task programs, are that they come as low-power devices, small and at low cost, which is of great importance for wearable e-textiles. While some embedded systems are very sophisticated, many of those implemented in wearable e-textiles have minimal requirements for memory and program length, with no operating system and low software complexity. The actual processor used in the microcontrollers can vary widely, where ones choice when designing interactive applications depends on the context in which the embedded system will be used. The programs running on the microcontrollers can be stand-alone or can communicate with the software running on other external devices, preferably through a wireless network.
Energy management technologies
One of the biggest problems in wearable and integrated electronic technology is power and the quest for alternative energy sources is essential. Today batteries in the form of AA batteries or lithium batteries are the most common source of energy utilized for running embedded systems and processing of captured data through a microcontroller. However their life span is limited and designers of wearables will have to find new and improved solutions to acquire the needed energy, either making it long lasting or easy to recharge on the move. At the same time the energy source must become light and discreet, which currently is the heaviest part of wearables.
The need for alternative sources of power is rising as the demand for greater design freedom in creating light, flexible and reliable wearable e-textile is increasing. Researchers see a potential in an alternative source of power based on the miniaturization of fuel cell technology. The way fuel cells generate electrical power is similar to batteries, as they convert the chemical energy of a given type of fuel (e.g. hydrogen and oxygen) into electrical energy. They have longer lives than batteries of similar size since oxygen does not need to be stored, only hydrogen in metal hydrides (Larminie & Dicks, 2003). Before 2010 Toshiba is planning to launch the first commercial direct methanol fuel cell-based (DMFC) batteries for cell phones and laptops.
In the beginning of 2009 researchers from the University of Illinois claimed they have developed the smallest working fuel cell, with dimensions 3 mm x 3 mm x 1 mm and it is made from four layers: a water reservoir, a thin membrane, a chamber of metal hydride, and an assembly of electrodes (Heine, 2009). Scientists claim that with the capacity of 0.7 volts and a 0.1 milliamp current for about 30 hours the mini battery can be used to run simple electronics. Researches see a great potential in fuel cell technology as it is considered to be a clean, efficient and silent technology, nevertheless the main hurdles preventing commercial introduction is high cost, lack of durability, high system complexity and lack of fuel infrastructure (Bruijn, 2005).
Another interesting alternative energy source for intelligent clothing is to harvest the kinetic energy from the human movement or the fluctuations in body temperature. Even though this energy is very minimal to drive wearable technology and can only be measured in microwatts, it is still a research field that attracts attention. Some research has been done in piezoelectric materials, which creates charge when mechanically stressed, thus inserting them on shoes, walking power can be harnessed (Tao, 2005).
Other forms of power supply are utilizing photovoltaic cells which are gathering the energy of the sun, allowing a sustainable approach to wearable technology. There are many examples of products that are incorporating solar panels onto the surface of wearable e-textiles, using thin film printed on flexible surfaces such as plastics; however the efficiency of this alternative energy source still needs to be improved.
Responsive materials represent a new generation of fibers, fabrics and articles, which are able to react in a predetermined way when exposed to stimuli, such as mechanical, electrical, chemical, thermal, magnetic and optical. They are reactive and dynamic and they have the ability to change color, shape and size in response to their environment. For many years researchers have devoted their work in developing responsive materials such as shape memory materials, chromic materials, micro and nanomaterial and piezoelectric materials.
By constantly improving and incorporating responsive materials in the development of light and flexible electronic components, conductive and semi-conductive materials, such as conductive polymers, conductive threads, yarns, coatings and inks, are receiving widespread attention. They are less dynamic then smart textiles but equally important in realizing fashionable, desirable, lightweight, soft and wireless computational textiles.
The following section gives an overview of conductive and responsive materials that are currently most used in wearable computational textiles.
Conductive fabrics and textiles are plated or woven with metallic elements such as silver, nickel, tin, copper, and aluminum. There are many different fabrics with various textures, looks and conductivity and few samples are illustrated in Figure 4 (left), those are: electronylon, electronylon nickel, clearmesh, softmesh, electrolycra and steelcloth. All these textiles show amazing electrical properties, with low surface resistance15, which can be used for making flexible and soft electrical circuits within garments or other products, pressure and position-sensing systems. They are lightweight, flexible, durable, soft and washable (some) and can be sewn like traditional textiles, which makes them a great replacement for wires in computational garments.
Figure 4 : conductive fabrics (left) and Different types of conductive threads (Middle and right)
Conductive threads and yarns have a similar purpose to wires and that is to create conductive paths from one point to another. However, unlike wires they are flexible and can be sewn, woven or embroidered onto textile, allowing for soft circuits to be created. They contain metallic elements such as stainless steel or silver, with nylon or polyester as base fiber. Commercially available conductive threads usually vary in the resistance and the thickness of the thread. Figure 5 (middle and right) illustrates few commercially available threads. Since they are conductive when working with them, one has to take all the precautions as when using uncoated electric wire or a metallic surface without insulation. Conductive threads and yarns offer alternative ways of connecting electronics on soft and flexible textiles medium as well offering traditional textile manufacturing techniques for creating computational garments.
Conductive coatings are used to convert traditional textiles into electrically conductive materials. The coatings can be applied to different types of traditional fibers, yarns and fabrics, without changing their flexibility, density and handling.
Conductive ink is an ink that conducts electricity, providing new ways of printing or drawing circuits. This special ink can be applied to textile and other substrates. Since wearable e–textiles require great flexibility, conductive inks are become more interesting for designers and developers in this area. Conductive inks contain powdered metals such as carbon, copper or silver mixed with traditional inks.
Shape memory alloys (SMA or muscle wire) are composed of two or more metals usually nickel and titanium, combination also known as Nitinol. These wires, usually of very small diameter, have the capacity to actuate when heated and to return to their original shape when cooled. Their capacity to flex or contract is up to 5% and it is a result of dynamic changes in their internal structure generated by an electric current. Some SMA wires can be “programmed” (heated at a transition temperature) into a particular shape for ex. zigzag or coiled. They can remember the form, to which they return when cooled. SMAs are used for triggering movement, have been woven in textiles or can make fabrics shrink or curl in wearable e-textiles applications. Long before SMAs were introduced to wearable e-textile projects, they have been used in many different areas, like electronics, robotics, medicine, automotive industry and appliances. SMAs are more and more becoming an interesting material for designers working on interdisciplinary projects across the fields of computation, technology, science, design and art. They explore how new ways of combining SMAs with computation can aid the design of responsive garments, objects and spaces and provide more meaningful interfaces.
Piezoelectric materials have the ability to generate electrical charge when exposed to mechanical stress (sound, vibration, force or motion). Piezoelectric materials exhibit reversible effect because they can produce electrical charge when subjected to stress and also they can generate stress when an electrical field is applied. Therefore the materials can be used both as sensors and actuators. Piezoelectric materials can serve as excellent environmental sensors, but the number of interesting applications in wearable e-textiles is even greater if they are coupled with other sensors, for ex. solar cells where they can be used to convert light to sound, motion or vibration.
Chromic materials are those that radiate, erase or just change the color based on the induction caused by external stimuli. They are also known as non- emissive “active materials” (Berzowska & Bromley, Soft computation through conductive materials , 2007). The classification of chromic materials depends on the stimuli affecting them. Some of the most know are photochromic and thermochromic materials. Most of the color changing phenomena (photochromism, thermochromism, electrochromism, piezochromism etc.) are reversible.
Photochromic (inks and dyes) are materials that react to light as an external stimulus. They are typically available in powdered crystals of ultraviolet (UV) sensitive pigments that need to be dissolved in an ink for application. Once the material is exposed to sunlight, blacklight or other UV source it will change from clear to colored state. When the UV source is removed they revert to their original state. They can be applied on various media, including textile, paper, plastic, wood and glass and can be used to create dynamic patterns that change in accordance to light variations in their surroundings.
Thermochromic inks are heat sensitive materials. They are made from various compounds that need to dissolve in the appropriate ink type for application. When exposed to a specific temperature they change from one color to another of from color to translucent. Thermochromic inks can be classified to three types, low – react to cold, body – react to body heat, touch and breath and high – react to hot liquids and air. They have the ability to infinitely shift color and with that create dynamic patterns on various substrates, including textiles.
Nanomaterials and microfibers have been the subject of enormous interest, over the past decades. They are materials fabricated on a molecular level. The technology is aimed at manipulating the structure of materials on atomic, molecular and nano16 level in a precise and controlled manner to create products or byproducts with specially engineered characteristics. Scientists use the prefix nano to denote a factor of 10-9 or one-billionth. One nanometer is one-billionth meter which is about 100,000 times smaller than the diameter of a single human hair (Qian & Hinestroza, 2004).
Many believe that the future development of many areas of our lives lie in nanotechnology, which fundamentals are based on the fact that properties of substances can change when their size is reduces to the nanometer range. The technology will be used in fabricating nanomachies, nanelectronics and other nanodevices to improve existing products and to create many new ones. Nanotechnology will also
have a great impact on textiles, being able to transform the molecular structure of the fibers and create fabrics that offer unsurpassed performance and comfort. The technology is likely to revolutionize wearable e-textiles, by not only developing very small and flexible electronic devices embedded in textile substrates, but it will go even further, ultimately having the electronic devices and system becoming the fabric itself. Researchers have already started to develop transistors in yarn form and to make conductive, carbon nanotube.
Refrance : E-textiles: The intersection of computation and traditional textiles (Interactive Sample Book by Marija Andonovska)
PET is a polymer that possesses great importance in the contemporary world of plastics. Being a thermoplastic i.e. recyclable polymer made it the number one choice for numerous applications which satisfies the world need for a greener and more ecological alternative to commonly used plastics such as polyethylene and others.
Nowadays, Two PET grades dominate the global market fiber-grade PET and bottle-grade PET. They differ mainly in the end product properties such as optical appearance and production technologies where these properties can be controlled by molecular weight, intrinsic viscosity, and additives specific to each process or application. Other uses include film production and specialty nylons .
The scope of this report will focus on bottle-grade PET because of its high demand especially in the Egyptian market. The report discusses the historical development of PET, its importance, properties and material handling considerations.
Ever since its discovery in the beginning of 20th century several companies were interested n providing production technologies to supply the increasing need for large amounts of PET. Technologies and their current licensors are discussed in detail with their flow sheets, chemistry and specific properties.
The report splits the PET production processes into two main parts; monomer preparation and polymerization. Each of the technologies uses different raw materials, solvents, catalysts and reaction conditions with their advantages and disadvantages. After the detailed market study which has put into account both global and local markets’ considerations, a thorough evaluation study is constructed in the report to evaluate each technology according to standard evaluation techniques displayed in the evaluation section.
The carefully studied numbers and statistics in the market section led us to suggest a suitable capacity for the PET production plant based on many factors listed in the same place. The summation of the work done in this project is shown in the recommendation part where a justified process is selected to produce PET and TPA in Egypt. Further desired information about the report as a whole and any given part is attached to this report in the form of an appendix where much more detailed data can be found.
Both natural and man-made fibres are mainly composed of the compounds belonging to high polymers or macromolecules. Macromolecular structure is necessary for the production of materials of high mechanical strength and high melting point. The natural fibres are found to consist chain molecules of linear molecular type. Further, the chain molecules are oriented into the parallel bundles in the process of growth. Based on these investigations, it is assumed that polymers must satisfy the minimum requirements, if it is to serve as a fibre. These requirements are as mentioned follows:
The polymer must be linear flexible macromolecule with a high degree of symmetry the effect of cross sectional diameter should be less than 15Å. The polymer should not contain any bulky side groups or chains.
The testing of fibres was always of importance to the spinner. It has been known for a long time that the fibre characteristics have a decisive impact on the running behaviour of the production machines, as well as on the yarn quality and manufacturing costs. In spite of the fact that fibre characteristics are very important for yarn production, the sample size for testing fibre characteristics is not big enough. This is due to the following
The labour and time involvement for the testing of a representative sample was too expensive. The results were often available much too late to take corrective action.
The results often depended on the operator and / or the instrument, and could therefore not be considered objective
One failed in trying to rationally administer the flood of the raw material data, to evaluate such data and to introduce the necessary corrective measures.
Only recently technical achievements have made possible the development of automatic computer-controlled testing equipment. With their use, it is possible to quickly determine the more important fibre characteristics.
Recent developments in HVI technology are the result of requests made by textile manufacturers for additional and more precise fibre property information. Worldwide competitive pressure on product price and product quality dictates close control of all resources used in the manufacturing process.
Conventionally measurement of the fibre properties was mainly carried out using manual method and it included the maximum chance of getting errors involved in it due to manual errors and was also a time consuming job. Thus there was a need for development of an instrument capable of measuring all properties in minimum time for better cotton classification.
PCCA (plans cotton cooperative association) played a key role in the development of High Volume Instrument (HVI) testing to determine the fibre properties of cotton which revolutionized the cotton and textile industries. As its name implies, HVI determines the fibre properties of a bale of cotton more quickly and more accurately than the previous method of evaluating some of those properties by hand classing. The HVI system provides more information about a bale of cotton than the subjective hand classing method.
In 1960, PCCA and Motion Control, Inc., an instrument manufacturer in Dallas, Texas, began pioneering the development of a system to eliminate the potential for human error that existed with hand classing and expand the number of fibre properties that could rapidly be determined for each bale of cotton. The goal was to be able to provide seven fibre quality characteristics for every bale produced by PCCA’s farmer-owners. Laboratory instruments were available for determining most of the fibre properties, but they required up to 15 minutes or longer to determine each of the properties. The PCCA theory was based on economics: the faster cotton could be classed, the faster it could be marketed; and, the more accurate measurements of quality could result in a more adequate supply of cotton with fibre properties to meet the specific needs of textile mills.
By the mid-1960s, the United States Department of Agricultural (USDA) and the Cotton Producers Institute (now called Cotton, Incorporated) also became involved in the research required to bring this concept to the marketplace.
In 1968 three of the first five HVI lines were in operation in Lubbock, Texas. One line was at Texas Tech University’s International Textile Center and two at PCCA. These lines were the very earliest versions to have all seven-fibre properties combined into a single testing line and measure them in less than 20 seconds per test.
In 1980, USDA built a new classing office in Lamesa, Texas, (about 60 miles south of Lubbock) specifically designed only for instrument testing all of the cotton samples received at that office using the latest version of the HVI equipment. This was a daring step but was based on data collected and analysed and improvements made in the HVI system during the previous 20 years. Although met with scepticism in the initial years by many in the cotton and textile industries, the HVI system prevailed, and USDA continued to install the instrument testing lines in all government cotton classing offices. In 1991, USDA used the HVI system on all the cotton provided to the department for classing. Today, HVI class data is accepted throughout the world and is the foundation on which cotton is traded.
In total, there are five companies manufacturing rapid instrument testing machines in the world,
i. Uster technologies, Inc.,
ii. Premier Evolvics Pvt. Ltd.,
iii. Lintronics (China, Mainland)
iv. Changing Technologies (China, Mainland)
v. Statex Engineering (India).
High volume instrument (HVI) is the most common rapid instrument testing machine made by Uster Technologies, Inc. The only other company that has over 100 machines installed in the world, mostly in Asia, is Premier Evolvics Pvt. Ltd. based in India. It is estimated that close to 2,000 rapid instruments testing machines have already been stalled in the world, mostly from Uster Technologies, Inc. Not only do the machines from each company differ, but various models from each company also differ among themselves. The full fledge models of both the manufacturers are capable of measuring measure micronaire, length, length uniformity, strength, colour, trash, maturity, sugar content etc.
High volume instrument systems are based on the fibre bundle testing, i.e., many fibres are checked at the same time and their average values determined. Traditional testing using micronaire, pressley, stelometre, and fibro graph are designed to determine average value for a large number of fibres, the so called fibre bundle tests. In HVI, the bundle testing method is automated.
CONCEPTS IN BALE MANAGEMENT
This is based on the categorising of cotton bales according to their fibre quality characteristics. It includes the measurement of the fibre characteristics with reference to each individual bale, separation of bales into classes and lying down of balanced bale mixes based on these classes. The reason for undertaking this work lies in the fact that there is sometimes a considerable variation in the fibre characteristics from one bale to another, even within the same delivery. This variation will result in the yarn quality variation if the bales are mixed in an uncontrolled manner.
The bale management software, normally embedded with an HVI, helps in selection of bales for a particular mix from the available stock. Once the data are received from HVI in the software, classification of bales in groups are done with user defined criteria.
· Manual calculation errors and the tedious task of day to day manual planning of mix are avoided.
· The storage of large number of data enables for tracking long period records or results thereby helping in clear analysis.
· More cost effective mix can be made since cost factor is also included. It also helps in planning for further requirements or purchase.
· Additional details such as party name, weighment details, and rejection details can be printed along with the test results which will be useful for the mill personnel for better analysis.
· Separate range criteria shall be selected for basic samples , lot samples and mixing
· Flexible intervals in grouping of bales with reference to the selected category.
· Basic sample results and results checked after lot arrival shall be compared graphically or numerically for easy decision making of approval or rejection.
The instruments are calibrated to read in staple length. Length measurements obtained from the instrument are considerably more repeatable than the staple length determination by the classer. In one experiment the instrument repeated the same staple length determination 44% of the time while the classer repeated this determination only 29% of the time. Similarly, the instrument repeated to 1/32″ on 76% of the samples, while the classer agreed on 71% of the samples to within 1/31″.
The precision of the HVI length measurement has been improved over the last few years. If we take the same bale of cotton used in the earlier example and repeatedly measure length with an HVI system, over two-thirds of measurements will be in a range of only about 1/32 nd of an inch: 95% of the individual readings will be within 1/32nd of an inch of the bale average. In the 77000 bales tested, the length readings were repeated within 0.02″ on 71% of the bales between laboratories.
Ø Length uniformity
The HVI system gives an indication of the fibre length distribution in the bale by use of a length uniformity index. This uniformity index is obtained by dividing the mean fibre length by the upper-half-mean length and expressing the ratio as a percent. A reading of 80% is considered average length uniformity. Higher numbers mean better length uniformity and lower numbers poorer length uniformity. Cotton with a length uniformity index of 83 and above is considered to have good length uniformity, a length uniformity index below 78 is considered to show poor length uniformity.
Ø Short fibre index
The measure of short-fibre content (SFC) in Motion Control’s HVI systems is based on the fibre length distribution throughout the test specimen. It is not the staple length that is so important but the short fibre content which is important. It is better to prefer a lower commercial staple, but with much lower short-fibre content.
The following data were taken on yarns produced under identical conditions and whose cotton fibres were identical in all properties except for short-fibre content. The effects on ends down and several aspects of yarn quality are shown below.
LOT -A, (8.6% SFC)
LOT-B (11.6% SFC)
Ends down / 1000 hrs
Skein strength (lb)
Single end strength g/tex
These results show that an increase of short-fibre content in cotton is detrimental to process efficiency and product quality. HVI systems measure length parameters of cotton samples by the fibrogram technique. The following assumptions describe the fibro gram sampling process:
· The fibrogram sample is taken from some population of fibres.
· The probability of sampling a particular fibre is proportional to its length
· A sampled fibre will be held at a random point along its length
· A sampled fibre will project two ends away from the holding point, such that all of the ends will be parallel and aligned at the holding point.
· All fibres have the same uniform density
The High Volume Instruments also provide empirical equations of short fibre content based on the results of cotton produced in the United States in a particular year.
Short Fibre Index = 122.56 – (12.87 x UHM) – (1.22 x UI)
where UHM – Upper Half Mean Length (inches)
UI – Uniformity Index
Short Fibre Index = 90.34 – (37.47 x SL2) – (0.90 x UR)
Where SL2 – 2.5% Span length (inches)
UR – Uniformity Ratio
In typical fibrogram curve, the horizontal axis represents the lengths of the ends of sampled fibres. The vertical axis represents the percent of fibre ends in the fibrogram having that length or greater.
1. Strength and elongation:-
Ø Principle of measurement
HVI uses the “Constant rate of elongation” principle while testing the fibre sample. The available conventional methods of strength measurement are slow and are not compatible to be used with the HVI. The main hindering factor is the measurement of weight of the test specimen, which is necessary to estimate the tenacity of the sample. Expression of the breaking strength in terms of tenacity is important to make easy comparison between specimens of varying fineness.
The strength measurement made by the HVI systems is unlike the traditional laboratory measurements of Pressley and Stelometer in several important ways. First of all the test specimens are prepared in a very different manner. In the laboratory method the fibres are selected, combed and carefully prepared to align them in the jaw clamps. Each and every fibre spans the entire distance across the jaw surfaces and the space between the jaws.
Strength is measured physically by clamping a fibre bundle between 2 pairs of clamps at known distance. The second pair of clamps pulls away from the first pair at a constant speed until the fibre bundle breaks. The distance it travels, extending the fibre bundle before breakage, is reported as elongation.
In the HVI instruments the fibres are randomly selected and automatically prepared for testing. They are combed to remove loose fibres and to straighten the clamped fibres, also brushed to remove crimp before testing. The mechanization of the specimen preparation techniques has resulted in a “tapered” specimen where fibre ends are found in the jaw clamp surfaces as well as in the space between the jaws.
A second important difference between traditional laboratory strength measurements and HVI strength measurements is that in the laboratory measurements the mass of the broken fibres is determined by weighing the test specimen. In the HVI systems the mass is determined by the less direct methods of light absorption and resistance to air flow. The HVI strength mass measurement is further complicated by having to measure the mass at the exact point of breaks on the tapered specimen.
A third significant difference between laboratory and HVI strength measurements is the rate or speed at which the fibres are broken. The HVI systems break the fibres about 10 times faster than the laboratory methods.
Generally HVI grams per Tex readings are 1 to 2 units (3 to 5%) higher in numerical value. In some individual cases that seem to be related to variety, the differences can be as much as 6 to 8% higher. This has not caused a great deal of problems in the US, perhaps because a precedent was set many years ago when we began adjusting our Stelometer strength values about 27% to put them on Presley level.
Relative to the other HVI measurements, the strength measurement is less precise. Going back to our single bale of cotton and doing repeated measurements on the bale we shall find that 68% of the readings will be within 1 g/Tex of the bale average. So if the bale has an average strength of 25 g.tex, 68% of the individual readings will be between 24 and 26 g/Tex, and 95% between 23 and 27 g/Tex
Because of this range in the readings within a single bale, almost all HVI users make either 2 or 4 tests per bale and average the readings. When the average readings are repeated within a laboratory, the averages are repeated to within one strength unit about 80% of the time. However, when comparisons are made between laboratories the agreement on individual bales to within plus or minus 1 g/tex decreases to 55%.
This decrease in strength agreement between laboratories is probably related to the difficulty of holding a constant relative humidity in the test labs. Test data indicate that 1% shift in relative humidity will shift the strength level about 1%. For example, if the relative humidity in the laboratory changes 3% (from 63 to 66%), the strength would change about 1 g/tex (from 24 to 25 g/Tex)
2. Fibre fineness:-
Ø Principle of measurement
Fibre fineness is normally expressed as a micronaire value (microgram per inch). It is measured by relating airflow resistance to the specific surface of fibres and maturity ration is calculated using a sophisticated algorithm based on several HVI™ measurements.
The micronaire reading given by the HVI systems is the same as has been used in the commercial marketing of cotton for almost 25 years. The repeatability of the data and the operator ease of performing the test have been improved slightly in the HVI micronaire measurement over the original instruments by elimination of the requirement of exactly weighing the test specimen. The micronaire instruments available today use microcomputers to adjust the reading for a range of test specimen sizes.
The micronaire reading is considered both precise and referable. For example, if we have a bale of cotton that has an average micronaire of 4.2 and repeatedly test samples from that bale, over two-thirds of that micronaire readings will be between 4.1 and 4.3 and 95 %of the readings between and 4.0 and 4.4. Thus, with only one or two tests per bale we can get a very precise measure of the average micronaire of the bale.
This reading is also very repeatable from laboratory to laboratory. In USDA approx. 77000 bales were tested per day in each laboratory, micronaire measurements made in different laboratories agreed with each other within 0.1 micronaire units on 77% of the bales.
The reading is influenced by both fibre maturity and fibre fineness. For a given growing area, the cotton variety generally sets the fibre fineness, and the environmental factors control or influence the fibre maturity. Thus, within a growing area the micronaire value is usually highly related to the maturity value. However, on an international scale, it cannot be known from the micronaire readings alone if cottons with different micronaire are of different fineness or if they have different maturity levels.
Ø Principle of measurement
Moisture content of the cotton sample at the time of testing, using conductive moisture probe and the main principle involved in the measurement is based on the measurement of the dielectric constant of a material.
Ø Principle of measurement
Rd (Whiteness), +b (Yellowness), Colour Grade
Measured optically by different colour filters, converted to USDA Upland or Pima Colour Grades or regional customized colour chart.
Ø Other information
The measurement of cotton colour predates the measurement of micronaire, but because colour has always been an important component of classer’s grade it has not received attention as an independent fibre property. However the measurement of colour was incorporated into the very early HVI systems as one of the primary fibre properties.
Determination of cotton colour requires the measurement of two properties, the grayness and yellowness of the fibres. The grayness is a measure of the amount of light reflected from the mass of the fibre. We call this the reflectance or Rd value. The yellowness is measured on what we call Hunter’s +b scale after the man who developed it. The other scales that describe colour space (blue, red, green) are not measured becasue they are considered relatively constant for cotton.
Returning once again to the measurements on our single bale, we see that repeated measurements of colour are in good agreement. For greyness or reflectance readings, 68% of the readings will be within 0.5 Rd units of the bale average, and 95% within one Rd unit for the average.
As for yellowness, over two-thirds of these readings will be within one-fourth of one +b unit of the average, and 95% within one-half of one +b unit. The greyness (Rd) and yellowness (+b) measurements are related to grade through a colour chart which was developed by a USDA researcher. The USDA test of 77000 bales showed the colour readings to be the most repeatable of all data between laboratories; 87% of the bales repeated within one greyness(Rd) unit, and 85% repeated within one-half of one yellowness(+b) unit.
5. Trash content
Ø Principle of measurement
Particle Count, % Surface Area Covered by Trash, Trash Code
Measured optically by utilizing a digital camera, and converted to USDA trash grades or customized regional trash standards.
Ø Other information
The HVI systems measure trash or non-lint content by use of video camera to determine the amount of surface area of the sample that is covered with dark spots. As the camera scans the surface of the sample, the video output drops when a dark spot (presumed to be trash) is encountered. The video signal is processed by a microcomputer to determine the number of dark spots encountered (COUNT) and the per cent of the surface area covered by the dark spots (AREA). The area and count data are used in an equation to predict the amount of visible non-lint content as measured on the Shirley Analyser. The HVI trash data output is a two-digit number which gives the predicted non-lint content for that bale. For example, a trash reading of 28 would mean that the predicted Shirley Analyser visible non-lint content of that bale would be 2.8%.
While the video trash instruments have been around for several years, but the data suggest that the prediction of non-lint content is accurate to about 0.75% non-lint, and that the measurements are repeatable 95% of the time to within 1% non-lint content.
6. Maturity and stickiness
Ø Principle of measurement
Calculated using a sophisticated algorithm based on several HVI™ measurements.
Ø Other information
Near infrared analysis provides a fast, safe and easy means to measure cotton maturity, fineness and sugar content at HVI speed without the need for time consuming sample preparation or fiber blending.
This technology is based on the near infrared reflectance spectroscopy principle in the wavelength range of 750 to 2500 nanometres. Differences of maturity in cotton fibres are recognized through distinctly different NIR absorbance spectra. NIR technology also allows for the measurement of sugar content by separating the absorbance characteristics of various sugars from the absorbance of cotton material.
Cotton maturity is the best indicator of potential dyeing problems in cotton products. Immature fibres do not absorb dye as well as mature fibres. This results in a variety of dye-related appearance problems such as barre, reduced colour yield, and white specks. Barre is an unwanted striped appearance in fabric, and is often a result of using yarns containing fibres of different maturity levels. For dyed yarn, colour yield is diminished when immature fibres are used. White specks are small spots in the yarn or fabric which do not dye at all. These specks are usually attributed to neps (tangled clusters of very immature fibres)
NIR maturity and dye uptake in cotton yarns have been shown to correlate highly with maturity as measured by NIR. A correlation of R=0.96 was obtained for a set of 15 cottons.
In a joint study by ITT and a European research organization, 45 cottons from four continents were tested for maturity using the NIR method and the SHIRLEY Development Fineness/ Maturity tester (FMT). For these samples, NIR and FMT maturity correlated very highly (R=0.94).
On 15 cottons from different growth areas of the USA, NIR maturity was found to correlate with r2 = 0.9 through a method developed by the United States Department of Agriculture (USDA). In this method, fibres are cross-sectioned and microscopically evaluated.
Sugar Content is a valid indicator of potential processing problems. Near infrared analysis, because of its adaptability to HVI, allows for screening of bales prior to use. The information serves to selected bales to avoid preparation of cotton mixes of bales with excessive sugar content. Cotton stickiness consists of two major causes- honeydew form white flies and aphids and high level of natural plant sugars. Both are periodic problems which cause efficiency losses in yarn manufacturing.
The problems with the randomly distributed honeydew contamination often results in costly production interruptions and requires immediate action often as severe as discontinuing the use of contaminated cottons.
Natural plant sugars are more evenly distributed and cause problems of residue build-up, lint accumulation and roll laps. Quality problems created by plant sugar stickiness are often more critical in the spinning process than the honeydew stickiness. Lint residues which accumulate on machine parts in various processes will break loose and become part of the fibre mass resulting in yarn imperfections. An effective way to control cotton stickiness in processing is to blend sticky and non-stick cottons. Knowing the sugar content of each bale of cotton used in each mix minimizes day-to-day variations in processing efficiency and products more consistent yarn quality. Screening the bale inventory for sugar content prior to processing will allow the selection of mixes with good processing characteristics while also utilizing the entire bale inventory.
The relationship between percent sugar content by NIR analysis and the Perkins method shows an excellent correlation of r2=0.95. The amount of reducing material on cotton fibre in the Perkins method is determined by comparing the reducing ability of the water extract of the fibre to that of a standard reducing substance. Using the NIR method, the amount of reducing sugar in cotton is measured.
Merits of HVI testing:-
· The results are practically independent of the operator.
· The results are based on large volume samples, and are therefore more significant.
· The time for testing per sample is 0.3 minutes. The respective fibre data are immediately available.
· About 180 samples per hour can be tested and that too with only 2 operators.
· The data are clearly arranged in summarised reports.
· They make possible the best utilisation of raw material data.
· It is best applied to instituting optimum condition for raw material.
· Problems as a result of fibre material can be predicted, and corrective measures instituted before such problems can occur.
· The classing of cotton and the laying down of a mix in the spinning mill. This HVI testing is suitable for the extensive quality control of all the bales processed in a spinning mill.
· The mill is in a position to determine its own quality level within a certain operating range.
Standardized process for hvi testing:-
· Pre-season precision and accuracy tests for all HVIs:-
All offices are required to select known-value cotton samples and perform stringent and consistent performance evaluations, before machines can be placed into production.
· Instrument calibration
Strict calibration procedures used by all offices and Quality Assurance Branch Known-value cottons and tiles used for calibration, Periodic calibration checks, Data is collected, analysed and corrective actions taken when necessary
· Quality Assurance Branch,Check lot Program
Approximately 1% of entire crop is selected from each field office for retest in “QA” as Check lots. Check lot data is returned to classing offices quickly for review. Check lot system assists in monitoring office performance and ensuring proper testing levels.
· Laboratory Atmospheric Conditions:-
Testing laboratories are required to maintain conditions of 70°±1° F and 65%±2% RH. All cotton must stabilize at moisture content level of 6.75%-8.25% prior to HVI testing.
Various HVI models available in market in present date are:-
We know that nonwoven fabrics are one of the oldest and simplest textile fabrics. Its classic example is felt. The first well documented discovery of felt dates back 3500-3000 BC. It was made from hairs of various animals. The term “Nonwoven fabrics” was applied to new modern techniques, which were totally based on new principles, by U.S.A. in 1965. “Non woven fabrics” is being defined into different ways by different literatures; the term defined by “Textile oregano” in 1965 is as follows:
“Nonwoven fabrics are products made of parallel laid, cross laid or randomly laid webs bonded with application of adhesive or thermoplastic fibres under application of heat and pressure.”
In other words nonwoven fabric can be simply defined as a fabric those can be produced by a variety of processes other than weaving and knitting.
The nonwoven fabric properties depends on following particulars to an great extent,
1. The choice of fibres.
2. Technology which determines how the fibres are to be arranged.
3. The bonding process and the bonding agent.
Fabric properties of nonwovens range from crisp to that soft-to-the –touch to harsh, impossible-to-tear to extremely weak. This leads to a wide range of end products such as nappies, filters, teabags, geotextiles, etc. some of which are durable and others are disposable.
The first stage in the manufacturing process of nonwoven fabrics is “production of web” and another is “bonding of web by using several methods”. Some of those (binding methods) are felting, adhesive bonding, thermal bonding, stitch bonding, needle punching, hydro-entanglement and spin laying.