In the name of ALLAH, the beneficent the merciful

Wool

Wool A natural fiber from animal origin which is obtained from skin hair of domesticated sheep. It is a protein fiber containing keratin linked through amino acids It has scales as well as crimps on its surface.

Scales on woolen surface

Crimps on woolen surface

Physical properties of wool fiber Climate, nutrition and breed of sheep has primary influence on fiber properties of wool. Fineness, length and crimp are closely correlated to each other. Longer fiber are coarser and less crimped, and shorter fibers are finer and more crimped. Fineness of wool is measured in micrometers.(18-60 µm) The average length fluctuates between 55 and 300 mm. The color of the wool fiber could be white, near white, brown and black. Standard moisture regain is 16%-18%. The density of wool fiber is 1.32 g/cm3 The wool decomposes under the action of sun light, fiber become discolored and develop a harsh feel. The elastic recovery of wool fiber is good.

Chemical properties of wool fiber Effect of Acids: Wool is attacked by hot concentrated sulphuric acid and decomposes completely. It is in general resistant to mineral acids of all strength even at high temperature though nitric acids tend to cause damage by oxidation. Effects of Alkalis: Wool will dissolve in caustic soda solutions that would have little effects on cotton. Strong alkaline affect on wool fiber but weak alkaline does not affect wool. Effect of Organic Solvent: Wool does not affect in organic solvents. Effects of Insects: Wool affected by insects. Effect of Micro Organism: It affected by mildew if it remains wet for long time. Dyeing ability: Wool fiber could be dyed by basic dye, direct dye and acid dye.

Sheep population around the world

Wool production by country

Impurities in wool Contains 40% or more by weight of impurities in the form of waxes, suint, cellulosic material such as straw and dried grass, dirt, and proteinaceous material. Besides, during spinning and weaving other impurities are added. 

Verities of wool 100 of verities of sheep exist in the world depending on the environment and breed. Classification of wool is done as follows 1. Fine wool or merino wool 2. Cross breed or medium wool A. Fine cross breed B. Medium cross breed C. coarse cross breed 3. Long wool or carpet wool

Wool shearing The removal of wool from the animal body is called wool shearing It is normally done twice a year. Two methods of wool shearing 1. Manual It is normally done in subcontinent and a person can shear wool from around 30 sheep a day 2. Mechanical It is normally done in advance countries and almost 300 sheep can be sheared in one day.

Wool shearing Best wool is sheared from sheep shoulders. Medium wool is sheared from head and back Poor quality wool is sheared from leg, tail and belly

Classing and sorting Classing of wool means separation of wool fleece on basis of staple length, fineness, dust and impurities Sorting is separation of wool obtained from different body parts of the animal

Wool impurities The impurities present in the wool are of three different types. Natural Oil, fats and perspiration from animal body usually it’s a mixture of fatty acids and fatty alcohols Acquired impurities These impurities are added to the wool fiber by interaction of the animal with the environment. They can be removed by the mechanical dusting process but due to fats they need to be scoured. Applied impurities The applied paints, medicine , tar etc. are added to the wool manually for specific purposes.

Woolen and worsted yarns Woolen yarns are made from ordinary wool and its has relatively rough structure and it is low grade quality wise. The processing of this yarn is relatively simple and low cost process. Worsted yarns are made from finest wool and short fibers are removed during it processing. It is a bit more complicated and costly process to spin worsted yarn as well as its raw material is costly.

Wool Process Flow Chart

Wool processing steps

Scouring It is a chemical process which removes the impurities of wool. Wool has grease like fatty acids, oils and perspiration salts. Due to this phenomena dirt, sand particles and other impurities are likely to cling to the wool fiber surface.

Scouring The most widely used scouring method is emulsion scouring method. In this method a combination of soap and alkali or a synthetic detergent is used. The wool scouring is done in bowls usually 3-6 in number. These are separated from each other by means of a squeezing roller. Finally the wool is washed with warm water that removes the detergent from the material.

Scouring

Scouring of wool Alkali is composed of sodium carbonate and soda ash. PH of the scouring solution is maintained around 10. These chemicals are used because they are not enough costly Temperature is maintained around 105- 130 Fahrenheit

Wool drying Wool leaving the squeezing rollers of scouring bowl contain too much moisture Moisture present is to be removed to ensure the easy processing Too much moisture can cause mildew, rusting of machinery and may contribute to the excessive nep formation. So excessive moisture must be removed Hot air drying is used to remove moisture and a drum drying machine is used.

Wool drying Hot air drying machine consist of a chamber with 2 – 4 revolving drums Surface of drum is perforated and each drum is nearly half covered with a damper Dia of drum is usually 4 ft. First roller has damper on upper side and second roller has damper on lower side and so on. Feed rollers are used to feed the wool. Heated air is moved through the drums Hot air temperature is about 80 – 82 degree C.

Wool drying Wool drying ball Reduced the time of drying process 30-50 %

Wool drying The speed and efficiency of drying depends upon the following factors Air temperature Rate of air circulation in m3/min Time for which wool is exposed to the drying air The state of material to be dried e.g. wool quality, thickness and packing density

Wool drying Purpose of drying Minimize the chances of poor carding Avoid rusting Minimize chances for microbiological attack Enable the material for perfect processing in the next machine

Wool carbonizing: Wool contains 3 – 20% of vegetable impurities which are not removed during scouring Two methods are there to remove these impurities Mechanical method Chemical method Mechanical method is used for worsted industry In worsted industry these impurities are removed during carding and combing process While in woolen industry chemical method of removing vegetable matter is used Treated with certain mineral acids, vegetable matter is cellulosic so converted in brittle hydro-cellulose

Chemical Method: After scouring wool passed through two more tanks containing cold dil. H2SO4 Tank made up of stainless steal Drying Crushing is done in pair of fluted crushing rollers Shaking Treated with soda ash to neutralize the acidic wool Rinsed and than dried again

Wool spinning There are mainly two methods of spinning Mule spinning Ring spinning Mule spinning is an intermittent process Ring spinning is a continuous process

Wool spinning: Mule spinning Older method of spinning Best method as far as quality is concerned Low production Complicated process Occupy more space Spinning, twisting, drafting and package formation is not done simultaneously But one function is done at a time Spindle drafting method is used Spindle revolves in a carriage which move forward and backward to impart draft Twisting is done due to rotation of spindle

Mule spinning

Wool spinning Ring spinning A continuous process it is Drafting twisting and package formation simultaneously More production

Ring spinning

Difference in cotton and wool ring spinning Range of drafts For cotton range is 10 – 60 For wool only 1.5 – 3.5 Length of drafting zone Wool drafting zone is much wide No aprons in case of wool drafting Woolen ring dia is much more than for cotton Traveller is much more heavier than in case of wool Bobbin length is more in case of wool

Worsted Carding After The wool has been thoroughly washed, dried, luibbricated and otherwise prepared, it is subjected to carding. Objectives of Worsted Carding 1. To straighten, separate and make the long fibers parallel. 2. To clean the fibers i.e., removal of vegetable impurities such as burs, shives and other extraneous vegetable matter and dust. 3. To blend, distribute and mix different lengths and qualities harmoniously into one quality 4. To arrange the fibers into a continuous slivers of definite weight and thickness.

Carding Action Carding action is basically result of relative motion of two interacting rollers which are covered with specially shaped hooks of fine steel wires.

Gilling or Prepairing Gilling is a process of aligning the wool fibres so they are parallel to one another. This is done using a coarse comb. At this stage, the sliver still contains particles of vegetable matter as well as short fibres. The gilled sliver is is either delievered in the form of a ball or coiled into a suitable can in preparation.

Back Washing After long wool (generally employed in the bradford system) have been carded they are usually subjected to a backwashing. This process is necessary, especially after solvent scouring , as large amount of sand and dust are still present in the card sliver. In French or continental system comber, back washing is primarly concerned with straightening and crimp removal of the fibers. The main object is through wetting of the individual fibers to make them pliable and adaptable for stretching when dried under tension. Silvers are backwashed after combing on French system, while they are washed before combing on Bradford system

Combing Worsted combing has three distinct functions to perform: To remove the “short wool” fibers below a predetermined length. To straighten and to make the retained long fibers as parallel as possible. To remove foreign impurities, such as burs(a rough, prickly husk around the seed or fruit of some plant),straw, shievs, kemps, neps and dust. The long fiber are retained and made into combed sliver and latter into “worsted top” while short fibers are rejected as “Noils” which from a raw material used in the manufacturing of woolen yarns.

Worsted yarns are made from the long and straightened wool fibers obtained from the worsted combing process. Machines: There are four types of comb available for worsted combing: 1). Circular, (2) nip-motion, (3)rectilinear, (4)square motion. They are also known by the name of their inventors: The noble or circular comb, the Lister or nip-motion comb, the Heilmann, French or rectilinear comb, and the Holden or square-motion comb. Bradford Worsted Combing For Bredford System the only combs in consideration are the circular or Nobel Comb, and the nip or Lister comb.

The Noble comb is one of the most comprehensive machine of worsted industry and accommodate all qualities and wide range of wool types. Its Production is greater than any other comb, and the quality of noil and the top is usually satisfactory. An overview of Noble comb The nip or Lister comb can be used only on long wool and hairs.

French Worsted Combing In the French system the rectilinear or Heilmann comb is standard machine. It is generally called french or continental comb and was originally invented for cotton. The machine is known for making good sliver of very short and fine wool. It can comb wools which are far too short for any other comb.

Worsted Drawing During drawing the actual reduction in sliver weight takes place. Drawing is an advanced operation which doubles and redoubles slivers of wool fibers. The amount of draft at any stage is restricted to the degree of fiber control during drafting and varies from 4 to as much as 25 according to the type of drafting system in use. Thus, it is necessary to employ several successive drafting operations between the top and the roving.

Worsted Spinning The worsted spinning process is carried out in three separate steps as follows: Drawing out or Drafting Insertion of twist Winding on or Packaging These operations takes place in spinning irrespective of the particular system employed.

Objectives of Worsted Spinning The production of very uniform yarn of desired thickness, twist,strength, surface, handle and appearance. It must be put up in convenient form such as bobbins, spools,cops,or packages for later use in knitting or weaving. Methods of Spinning Worsted yarn are normally spun by four different methods. Flyer Spinning Cap Spinning Ring Spinning Mule Spinning Note: In first three methods, drafting, twisting, and winding are continuous operations. In mule spinning they are carried out intermittently, self acting.

Kemp is generally a chalky-white, brittle, weak fibre which may be mixed with normal fibers in a sheep's wool fleece. Kemp fibres are often detached from the skin. This hair is not desirable in a fleece, as it does not accept dye, minimising both the quality and the value of the wool