Fibre to fabric manufacturing process of wool

Prof. R.N. Narkhedkar and Parag Bali share the details on wool, a natural, animal hair fibre.

Woolis a natural fibre composed of proteins, as it comes from the fleece of sheep.Each sheep has various grades of fleece found in their coat with the highestgrade fibers being found on the sides, shoulders, and back, while the lowestgrade are found on the lower legs.

Wool couldbe sourced from the fleece of sheep and other animals. These include cashmerefrom goats, mohair from rabbits and other types of wool from camellias, musk ox,Angora rabbit, vicuna, guanaco, pashmina and alpaca. Wool has some specialqualities which distinguish it from hair or fur. The best quality wool comes frommerino sheep, found in Australia.

The surface scales of the fibres are also responsible for the unique felting and shrinking properties of wet wool. The scales also cause water to form beads and roll off. This helps wool fabric to repel moderate rain and spills.

Fibre to fabric process flow chart:-

To source wool, sheep are sheared of their woollen fleece by a shearer. Typically, each adult sheep is shorn or sheared once each year. The annual shearing often occurs in a shearing shed, a facility designed to process hundreds and sometimes more than 3,000 sheep per day. The fleece can be removed using scissors or mechanical fleece removers (see pic).

Sorting: After shearing, the wool is sorted. Wool from ewes, rams, and lambs must be sorted from each other and kept separately. Different quality of wool is used for wefts, warps, and piles. Therefore, while sorting wool, factors such as the length of fibres and wool's ability of absorbing dyes should be considered. Wool which is going to be the source of the yarns for pile should be supple, resilient, and soft. The quality of wool varies not only due to the different type of breeds, but it also depends on the geographic location of animals, climatic conditions of the region, the season of shearing, the quality, and composition of fodder.

Wool scouring: - The main purpose of scouring is to remove the impurities in wool like dust, dirt, perspiration, and natural oily matter. Without this, further processes are impossible. The process of sequence is carried out in a large machine called the scouring train. This process is carried out in different ways.

1. Emulsion scouring

2. Solvent scouring (normally uses petroleum ether or carbon tetrachloride)

Wool Scouring

Drying: While using heavy weight squeeze rollers for final delivery of wash bowls, the wool has 50 per cent moisture, which must be removed before further processing. Wool must have only 15 per cent moisture before heading to next process.

Wool drying                                            burr -picking

Burr picking: The primary object of burr picking is to remove all the burrs and vegetable matter possible before the stock is passed to the carding machine. Under the head of burrs, particles of vegetable matter that become attached to the fleece during the life of sheep are included, although a burr is really a vegetable seed or husk covered with sharp spines, or prickles. If the burrs are not removed from the wool, they are broken into innumerable small particles during the operation of carding.

Carbonising: Carbonising removes cellulosic impurities from the wool by treating it with acid or acid-producing salts. Carbonising may be carried out in loose wool or on piece goods after scouring. However, it is common practice to carbonise worsted piece goods as well as woollens. The process begins by immersing wool in a solution of sulphuric acid (H2SO4) that reacts with the cellulose impurities in the wool.

Neutralising: After carbonising, wool is dropped into a cold water rinse bowl and is passed through a pair of squeezing rollers. Then it passes into a soda bath of 100^oF followed by an ionic wash. After that, it is put into a bowl of cold water of ph-6.5. It takes 12 minutes to neutralise. Then, the wool passes into the dryer and is dried at approximately 140 ^o F.

Carding: Wool that is free from fat, suint and dirt is subjected to a process called carding to produce the most staple yarn. In worsted industries, the wool is always carded in the un-dyed or dope-dyed state. If the ultimate fabric is to be coloured, then dyeing can be done after combing, spinning or weaving.

Backwashing: After carding, the wool, in sliver form, is given additional scour or "backwashing." This removes surface dirt picked up during the mechanical operation of carding and finally cleans the fibres.

Backwashing                                          Combing

Gilling: This makes fibres straight, uniform, and unidirectional and ultimately makes the sliver finer by reducing weight per unit length.

Drawing: The drawing out of fibre tops into the thickness of one, to thoroughly blend the wool and ensure evenness or regularity of the resulting roving material. Drawing involves passing the top through rollers and reducing slivers to a suitable thickness ready for spinning. The process is repeated several times to ensure regularity or evenness in the finishing, the final stage of the drawing process. A small amount of twist is also added to the sliver at this stage to increase strength. This reduced sliver is called a 'roving.' Drawing simply blends and reduces the wool to a suitable thickness for spinning. 

Spinning: This involves drawing the thick rove and making it thinner with sufficient twist, to impart strength. The process ensures a uniform yarn of desired thickness, twist, strength, surface handle and appearance. It is wound on convenient packages such as bobbins, spooks or cops to be used for knitting and weaving. The objective of spinning is to produce yarn with specific linear density, of good quality at reduced cost.

Spinning                                                          AutoWinding

Auto winding: Winding is the most important process in the spinning system. The main objective of winding is to remove objectionable faults from single yarn, to prepare fault-free yarn with the help of electronic yarn clearers, and to transfer yarn from small packages to bigger packages.

Steaming:-

Steaming is done to set the twist which is imparted in the ring frame and to eliminate snarling. After the yarn is steamed lot-wise, single ring yarn doffs are stored for at least eight hours to cool and condition. Then, it is to be taken for winding. The time between steaming and winding is important so that yarn can retain moisture and get stabilised so that it can be suitable for winding.

TFO: Twisting of parallel wound double yarn can be done by the method of inserting two twists for one revolution of the spindle. It is done to give twist as per requirement of direction for imparting strength to double yarns.

Weaving:-

The main objective of the weaving department is to weave fault-free fabric of required length by keeping required production rate and maximum level of efficiency. The fabric is woven as per quality, specifications, weave, design effect etc. specified by the customer. After weaving, the fabric is dyed as per requirements. During the whole manufacturing process, the fabric acquires stains and stress. Therefore, it is essential to give the fabric a finishing effect.

References:-

1. Proc. Seminar. Specification of Australian wool and its Implications for marketing and processing, CSIRO Division of Wool Technology and International Wool Secretariat (No. 1994), Sydney, Australia.

2. D.Stevens, Handle: Specification and effects, in Proceedings of the Wool spec 94, Seminar 'Specification of Australian Wool and its Implication for Marketing and Processing', CSIRO Division of Wool Technology and International Wool Secretariat, Sydney, Australia, November 1994, pp. H1-H10.

3. K.J.Whitely and D.Charlton, Proc. Obj. Meas. Wool Aust. Paper No. 9, 1973.

4. R.A. O'Connel and H.P.Lundgren, Text. Res.J.24 (7) (1954) pp. 677-685. [938] R.M.W. Sumner and M.P. Up dell, Wool Technol. Sheep Breed. 49(1) (2001) pp. 29-41.

5. P.G. Swan, Fibre specification and staple structure, in Proceedings of the 'Woolspec 94' Seminar 'Specification of Australian Wool and its Implication for Marketing and Processing', CSIRO Division of Wool Technology and International Wool Secretariat, Sydney, Australia, 1994, pp. G1-G12.

6. Anonymous, Method for the determination of wool base and vegetable matter base, of core samples of raw wool (original version), IWTO 1930 DFT, IWTO-19-85(E), March 1985

7. D.W.Crowe and D.Stevens, Style and processing effects, in Proceedings of the Woolspec 94 , Seminar 'Specification of Australian Wool and its Implication for Marketing and Processing', CSIRO Division of Wool Technology, Sydney, Australia, November 1994, pp. F1-F11.