Wool is possibly the oldest fiber known to humans. It was one of the first fibers to be spun into yarn and woven into the fabric.
Of the major apparel fibres, wool is the most reusable and recyclable fibre on the planet. The eco-credentials of wool are enhanced by its long service life and suitability to be recycled to new textiles for clothing, resilient upholstery or products that call on its natural resistance to fire and temperature extremes. Aside from premium next-to-skin apparel, wool can be used in industrial applications such as thermal and acoustic insulation or in pads to soak up oil spills.
At the disposal stage, natural fibres such as wool reduce the impact of the textile industry on pollution and landfill build-up. In warm, moist conditions such as in soil, wool biodegrades rapidly through the action of fungi and bacteria to essential elements (i.e. Nitrogen and Sulphur) for the growth of organisms as part of natural carbon and nutrient cycles.
Growth
Wool is possibly the oldest fibre known to humans. It was one of the first fibres to be spun into yarn and woven into a fabric. Wool mostly comes from sheep but also from alpacas, camels, and goats. Australia, Eastern Europe, New Zealand, and China are major wool producers. The American woollen industry began in the Massachusetts settlements in 1630, where each household was required by law to produce wool cloth.
Harvesting
Then, they need a haircut. The process is called sheering. A sheering specialist can sheer 200 sheep in a day. A ewe, or female sheep, can produce up to 15 pounds of wool. A ram, or male sheep, can 20 pounds of wool. The sheared wool is called raw wool and since sheep don’t take showers, it must first be cleaned.
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Next, the wool is carded – that means brushing the wool to straighten the fibres. Once done by hand, these days a carding machine passes the wool through a series of rollers covered with wire bristles. The carded fibres are gently scraped into strands called roving. The roving is spun into yarn that is then woven into cloth. In the past, the task of spinning usually was the job of unmarried females – they became spinsters.
Fleece is a ball of wool taken from a single animal in a shearing. But not all wool is equal – even when it comes from the same animal. The highest quality wool comes from the sides, shoulders, and back. The lowest quality comes from the lower legs.
Grading of Wool Fibers
Wool is graded for fineness and length. The length varies from place to place on the animal, but it mostly varies amongst sheep breeds. Australian Merino wool is 3-5 inches long. Breeds found in Texas and California produce fibres 2.5 inches long. Wool from other breeds and other animals may be as long as 15 inches.
Properties of Wool Fibers
This microscopic view shows us why wool is special. The surface is a series of overlapping scales of protein, pointing toward the tip. On the animal, this enables the foreign matter to work its way out of the fleece. In a strand of yarn, it enables the fibres to lock with one another. This is the key to wool’s strength.
Wool’s surface repels water. Since moisture does not remain on the surface, woollen fabrics tend to feel dry and comfortable even in damp weather. The inner core does absorb moisture – so much so that wool can absorb almost double its own weight in water and still feel reasonably dry. This absorbency also gives wool its natural resistance to wrinkles. The absorbed moisture also holds down static electricity. And because of the inner moisture, wool is naturally flame resistant.
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Moisture in wool
The amount of water absorbed by wool is usually referred to as ‘regain’. Regain is the ratio of the mass of water to dry wool expressed as a percentage.
Another term also used by the textile industry, predominately for cotton, is ‘moisture content’. Moisture content is the ratio of the mass of water to the mass of water plus wool expressed as a percentage.
Wool, along with cotton and to a lesser extent nylon, is a fibre that absorbs moisture from the surrounding air to reach an equilibrium, which depends on the relative humidity of the environment. At ambient humidity, wool will contain 10 to 15% by weight of water and up to 35% water at high relative humidity, which is more than most other fibres. This water is incorporated in the internal structure of the fibre and, therefore, is hardly noticed by the wearer. Wool garments do not feel damp or clammy. This property enables wool to act as a buffer against sudden environmental changes, for example, excessive perspiration during exercise or changes in climatic conditions such as going outside from an air-conditioned room.
Although the wool fibre can readily absorb water vapour from the air, a garment made from wool will be water repellent to some extent. This is because the surface of the fibre has a very thin, waxy, lipid coating chemically bonded to the surface that cannot be easily removed. Scouring, washing or processing will not remove this layer. The only way to
remove this layer, if required, is by chemical treatment.
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Source: Textile School
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The commonly used, time-tested spinning technique, ring spinning is one of oldest machine oriented spinning techniques used for staple fiber spinning. The staple fiber such as cotton and wool has to go through a series of processes until reaching the finished product or the yarn package.
The ring spinning system is the oldest spinning system that remains dominant because of the high-quality yarns it produces. Ring spinning has various advantages besides disadvantages.It is the most flexible system from the viewpoints of fibers which can be used and the extent of the yarn counts which can be produced.
Before talking about Ring Spinning Pros and Cons, let's understand what the Ring Spinning Process is with the Yarn Fair.
Ring Spinning Process
l Roving bobbins are creeled in appropriate holders
l Guide rods leave the roving into the drafting arrangements
l Drafting arrangements attenuate the roving to the final count
l The drafting arrangements are inclined at an angle of 45 degrees to 60 degrees.
l Upon leaving the front rollers the fiber strand is twisted to impart strength
l Each rotation of the spindle imparts one twist to the strand
l The twist is generated by the spindle which is rotating at high speed
l The directions of the twist are either “S” or “Z”
l This completes the spinning of the yarn
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l The amount of twist inserted in the yarn is controlled by the front roll or the delivery speed and traveler rational speed
l Traveler Speed Formula
l In practice, spindle speed(n spindle) is used instead of traveler speed in the above equation, the spindle speed is slightly higher than traveler speed
l Yarn Winding is performed simultaneously with Twisting
l The difference in the speed between traveler and spindle causes the yarn to wind on the package
l The size of the yarn package is limited by the ring diameter, which has to be small to increase the spindle rotation at the same traveler speed
l The draft is the ration between the delivery speed and the feeding speed.
l The twist is the ratio between spindle speed and the delivery speed
l Winding speed is directly proportional to the delivery speed
l Contraction occurs in yarn by increasing twists
The metal ring is the origin of the name of the ring spinning machine. The twist creates friction between the fibers by which the strength of the fiber mass increases. In this state, the fiber mass is now called yarn. The yarn is wound on to a bobbin attached to the spindle. The speed of the spindles amounts to 10,000 to 14,000 r/min for wool and about 18,000 to 25,000 r/min for cotton. Thus one meter of yarn contains between 300 and 2,000 twists. The weighting arm is required to allow different loads to be set on the top rollers. Normally this is achieved by helical springs which can be adjusted mechanically in steps.
Also, the distances between the rollers have to be adjustable. The distance has to be larger than the length of the longest fibers to avoid the situation where single fibers are torn between the clamping points of top rollers and bottom cylinders.
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Advantages of Ring Spinning
The Ring Spinning System allows various types and lengths of fibers (natural, man-made) to spin on a wide count range from 6 tex to 118 tex.
whereas this range is between 17 and 118 tex in rotor spinning. By combing option, the high quality combed yarns which are smoother, brighter and more compact can be produced using the ring system. On the other hand, the ring spinning system has two main problems. The first is low production speed because of frictional contact of ring and traveler, and the yarn tension caused, and the second is high energy consumption that causes high production costs.
Following are the advantages of Ring Spinning Process:
l Production of high strength yarns.
l The spinning of fine count yarns.
l Proper for special yarns.
l It is universally applicable (any material can be spun).
l The know-how for the operation of a machine is well established accessible to everyone.
l It is flexible as regards quantities (blend and lot size).
l Since the speeds in drawing section are best controlled, yarn evenness is excellent. But if short fibers are too much, yarn unevenness occurs.
l Fine yarns can be produced as compared to the open-end system
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Disadvantages of Ring Spinning
Following are the disadvantages of choosing Ring Spinning Process:
l Process stages are more numerous. Roving stage exists as an extra process compared to the other systems.
l Yarn breakages are more numerous as a result of ring traveler friction and yarn air friction. Interruptions, broken ends and piecing up problems exist because of the yarn breakages.
l The high speed of the traveler damages the fibers.
l The capacity of the cops is limited.
l Energy cost is very high.
l Low production rate.
l New spinning processes have difficulty in gaining widespread acceptance. Owing to their individual limitations, the new spinning processes are confined to restricted sectors of the market.
l The ring frame can only survive in the longer term if further success is achieved in automation of the ring spinning process. Also, spinning costs must be markedly reduced since this machine is significant cost factor in a spinning mill.
l The cost structure in ring spinning mill is shown in the graph.
Source: Textile School
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