Textile manufacturing


Textile manufacturing is a major industry. It is based on the conversion of fibre into yarn, yarn into fabric. These are then dyed or printed, fabricated into clothes. Different types of fibres are used to produce yarn. Cotton remains the most important natural fibre, so is treated in depth. There are many variable processes available at the spinning and fabric-forming stages coupled with the complexities of the finishing and colouration processes to the production of a wide range of products.

History

Processing of cotton

Cotton is the world's most important natural fibre. In the year 2007, the global yield was 25 million tons from 35 million hectares cultivated in more than 50 countries.
There are six stages:
is grown anywhere with long, hot dry summers with plenty of sunshine and low humidity. Indian cotton, Gossypium arboreum, is finer but the staple is only suitable for hand processing. American cotton, Gossypium hirsutum, produces the longer staple needed for machine production. Planting is from September to mid-November and the crop is harvested between March and June. The cotton bolls are harvested by stripper harvesters and spindle pickers that remove the entire boll from the plant. The cotton boll is the seed pod of the cotton plant; attached to each of the thousands of seeds are fibres about 2.5 cm long.
Scutching refers to the process of cleaning cotton of its seeds and other impurities. The first scutching machine was invented in 1797, but did not come into further mainstream use until after 1808 or 1809, when it was introduced and used in Manchester, England. By 1816, it had become generally adopted. The scutching machine worked by passing the cotton through a pair of rollers, and then striking it with iron or steel bars called beater bars or beaters. The beaters, which turn very quickly, strike the cotton hard and knock the seeds out. This process is done over a series of parallel bars so as to allow the seeds to fall through. At the same time, air is blown across the bars, which carries the cotton into a cotton chamber.


Measurements

The weaving process uses a loom. The lengthway threads are known as the warp, and the cross way threads are known as the weft. The warp, which must be strong, needs to be presented to loom on a warp beam. The weft passes across the loom in a shuttle, that carries the yarn on a pirn. These pirns are automatically changed by the loom. Thus, the yarn needs to be wrapped onto a beam, and onto pirns before weaving can commence.

Measurements

When a hand loom was located in the home, children helped with the weaving process from an early age. Piecing needs dexterity, and a child can be as productive as an adult. When weaving moves from the home to the mill, children are often allowed to help their older sisters, and laws have to be made to prevent child labour becoming established.

Knitting – fabric manufacture

by machine is done in two different ways; warp and weft. Weft knitting is similar in method to hand knitting with stitches all connected to each other horizontally. Various weft machines can be configured to produce textiles from a single spool of yarn or multiple spools depending on the size of the machine cylinder. In a warp knit there are many pieces of yarn and there are vertical chains, zigzagged together by crossing the cotton yarn.
Warp knits do not stretch as much as a weft knit, and it is run-resistant. A weft knit is not run-resistant, but stretches more. This is especially true if spools of spandex are processed from separate spool containers and interwoven through the cylinder with cotton yarn, giving the finished product more flexibility and making it less prone to having a 'baggy' appearance. The average t-shirt is a weft knit.

Finishing – processing of textiles

The woven cotton fabric in its loom-state not only contains impurities, including warp size, but requires further treatment in order to develop its full textile potential. Furthermore, it may receive considerable added value by applying one or more finishing processes.
Production of cotton requires arable land.
In addition, cotton is farmed intensively and uses large amounts of fertilizer and 25% of the world's insecticides. Native Indian varieties of cotton were rainwater fed, but modern hybrids used for the mills need irrigation, which spreads pests. The 5% of cotton-bearing land in India uses 55% of all pesticides used in India.
The consumption of energy in form of water and electricity is relatively high, especially in processes like washing, de-sizing, bleaching, rinsing, dyeing, printing, coating and finishing. Processing is time consuming. The major portion of water in textile industry is used for wet processing of textile. Approximately 25 per cent of energy in the total textile production like fibre production, spinning, twisting, weaving, knitting, clothing manufacturing etc. is used in dyeing. About 34 per cent of energy is consumed in spinning, 23 per cent in weaving, 38 per cent in chemical wet processing and five per cent in miscellaneous processes. Power dominates consumption pattern in spinning and weaving, while thermal energy is the major factor for chemical wet processing.
Cotton acts as a carbon sink as it contains cellulose and this contains 44,44% carbon. However, due to carbon emissions from fertiliser application, use of mechanized tools to harvest the cotton,... cotton manufacture tends to emit more CO2 than what it stores in the form of cellulose.
The growth of cotton is divided into two segments i.e. organic and genetically modified. Cotton crop provides livelihood to millions of people but its production is becoming expensive because of high water consumption, use of expensive pesticides, insecticides and fertiliser. Genetically modified products aim to increase disease resistance and reduce the water required. The organic sector was worth $583 million. Genetically modified cotton, in 2007, occupied 43% of cotton growing areas.
Before mechanisation, cotton was harvested manually by farmers in India and by African slaves in America. In 2012 Uzbekistan was a major exporter of cotton and uses manual labour during the harvest. Human rights groups claim that health care professionals and children are forced to pick cotton.

Processing of other vegetable fibres

Flax

Flax is a bast fibre, which means it comes in bundles under the bark of the Linum usitatissimum plant. The plant flowers and is harvested.
It is now treated like cotton.

Jute

Jute is a bast fibre, which comes from the inner bark of the plants of the Corchorus genus. It is retted like flax, sundried and baled. When spinning a small amount of oil must be added to the fibre. It can be bleached and dyed. It was used for sacks and bags but is now used for the backing for carpets. Jute can be blended with other fibres to make composite fabrics and work continues in Bangladesh to refine the processes and extend the range of usage possible. In the 1970s, jute-cotton composite fabrics were known as jutton fabrics.

Hemp

Hemp is a bast fibre from the inner bark of Cannabis sativa. It is difficult to bleach, and is used for making cord and rope.

Other bast fibres

These bast fibres can also be used: kenaf, urena, ramie, nettle.

Other leaf fibres

is the main leaf fibre used; others are: abacá and henequen.

Processing of animal and insect fibres

Wool

Wool comes from domesticated sheep. It forms two products, woolens and worsteds. The sheep has two sorts of wool and it is the inner coat that is used. This can be mixed with wool that has been recovered from rags. Shoddy is the term for recovered wool that is not matted, while mungo comes from felted wool. Extract is recovered chemically from mixed cotton/wool fabrics.
The fleece is cut in one piece from the sheep. This is then skirted to remove the soiled wool, and baled. It is graded into long wool where the fibres can be up to 15 in, but anything over 2.5 inches is suitable for combing into worsteds. Fibres less than that form short wool and are described as clothing or carding wool.
At the mill the wool is scoured in a detergent to remove grease and impurities. This is done mechanically in the opening machine. Vegetable matter can be removed chemically using sulphuric acid. Washing uses a solution of soap and sodium carbonate. The wool is oiled before carding or combing.

Silk

The processes in silk production are similar to those of cotton but take account that reeled silk is a continuous fibre. The terms used are different.
Both wool and silk require farmland. Whereas silkworms require mulberry leaves, sheep eat grass, clover, forbs and other pasture plants. Sheep, like all ruminants emit CO2 via their digestive system. Also, their pastures may sometimes be fertilised which further increases emissions.

Discussion of types of synthetic fibres

Synthetic fibres are the result of extensive development by scientists to improve upon the naturally occurring animal and plant fibres. In general, synthetic fibres are created by forcing, or extruding, fibre forming materials through holes into the air, thus forming a thread. Before synthetic fibres were developed, cellulose fibres were made from natural cellulose, which comes from plants.
The first artificial fibre, known as art silk from 1799 onwards, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibres, but not truly synthetic, being made from wood. Although these artificial fibres were discovered in the mid-nineteenth century, successful modern manufacture began much later in the 1930s. Nylon, the first synthetic fibre, made its debut in the United States as a replacement for silk, and was used for parachutes and other military uses.
The techniques used to process these fibres in yarn are essentially the same as with natural fibres, modifications have to be made as these fibres are of great length, and have no texture such as the scales in cotton and wool that aid meshing.
Unlike natural fibres, produced by plants, animals or insects, synthetic fibres are made from fossil fuels, and thus require no farmland.