The document discusses various preparatory processes that cotton fabric undergoes before dyeing or other chemical processing. It describes how cotton contains natural impurities like fats, waxes, pectins, proteins and colouring matter that need to be removed. The preparatory processes involve mechanical operations like brushing to remove loose threads, shearing to cut attached threads, and singeing to burn protruding fibers. This is followed by inspection of grey fabric for defects and stamping with a lot number for identification during processing.

1. PREPARATORY PROCESSES R.B.CHAVAN Dept. of Textile Technology Indian Institute of Technology Hauz-Khas, New Delhi 110016

2. CLASSIFICATION OF TEXTILE FIBRES Minor Classifiction Natural Synthetic Regenerated Vegetable Animal Polyester Viscose Rayon Cotton Silk Nylon Jute Wool Acrylic

3. CLASSIFICATION OF TEXTILE FIBRES Major Basis Textile fibre product identification act 1960 Considerations: Principal origin of fibre (Natural or man-made) Generic term (Seed, hair, rayon) Common names (cotton, viscose, nylon etc.)

4. Natural fibres Cellulosic fibres Seed hairs: Cotton, Kapok Bast fibres: Flax, Ramie, Hemp, Jute, Sunn, Kenaf Leaf fibres: Abaca, Pineapple, Sisal (Agave), Palm Fruit: Coir Mineral: Asbestos

5. Natural Protein fibres Animal hair fibres Wool (Sheep) Speciality hair fibres: Alpaca, Camel, Cashmere, Mohair (Angora Goat), Fur fibres: Mink, Muskrat, Rabbit Animal Secretion Silk fibre: Mulberry, Tussar, Moga, Erie Spider silk

6. Regenerated natural fibres Rayon Cuprammonium Viscose: Regular, high tenacity, high wet modulus, hollow fibres, polynosic, lyocell Acetate: Secondary acetate, Tri acetate Regenerated Protein: Casein, Zein, Peanut, Soyabean Miscellaneous: alginate

7. Synthetic fibres Condensation polymers Polyamide Nylon 6, 66, 11 Aramide : Quiana, Kevlar, Nomex Polyester Aromatic: Polyethylene terephthalate (PET) Aliphatic Poly lactic acid (PLA) Addition polymers Acrylic, modacrylic Olehene fibres: Polyethylene, polypropelene Saran Vinal Vinyon

8. Synthetic fibres Elastomers Spandex Synthetic Rubber Lastrile Man-made (Mineral) Glass Metallic

9. Chemical processing Give value addition Can be carried out in Fibre Yarn Fabric Garment or other ready made forms.

10. Chemical processing operations Preparatory Dyeing Printing Finishing

11. Preparatory Processes Purpose To remove Natural and added impurities To improve the appearance of fabric To impart certain desirable properties To make it suitable for subsequent processes like dyeing, printing finishing

12. Fabric manufacturing Fibre  Yarn  Fabric  Fabric for sale Spinning: Fibre to yarn Weaving: Yarn to fabric by interlacement of yarn in length direction and width direction Length direction yarn Warp Weft direction yarn: Weft Grey fabric for sale or chemiccal processing

13. Operations before Preparatory Processes Weaving: Conversion of yarn to fabric Machine used: Loom Fabric known as Loom state fabric or Grey fabric Grey fabric length: 80

14. Grey fabric inspection Major fabric defects Oil stains: formed accidentally during weaving and handling Holes Thick places due to yarn defect Warp or weft thread breaks Long thread of fabric surface others Chemical processing step

15. Fabric faults Stains Thick place Missing end or pick Hole

16. Grey fabric inspection machines Individual piece inspection (Mannual)

17. Grey fabric inspection machine (Continuous length (Manual)

18. Grey fabric inspection machine

19. fabric inspection machine Digital cameras, computerized

20. Stamping Lot card Lot Number Placing the code mark in the form of lot No. with marking ink Ink should withstand chemical processing operations Lot No. mark helps to identify the fabric lot at any stage of processing. Stitching of individual non-defective pieces

21. Lot card Lot No. Yarn count Fabric construction details such as Ends and Picks per inch or per cm. Fabric weight g/sq.m (gsm) Processing sequence Date and time on which the lot has been received Date and time of subjecting the lot to different processing sequence along with signature of supervisor The information helps in knowing the status of lot at any time and analysis of processing problems if there are any.

22. Mechanical operations Brushing Shearing/Cropping Singeing

23. Brushing Purpose To remove short loose threads from fabric surface Operation Fabric moves in contact with Cylinders (2-4) covered with fine bristles (Brush Roller). The loose threads are picked up by the brush rollers. Removed by vacuum. In this operation only loose threads are removed Threads attached to the fabric surface removed by shearing/cropping operation.

24. Shearing/Cropping Purpose To cut the loose threads attached to the fabric surface Achieved by raising the loose thread with the help of brush roller and cutting it close to the fabric surface with the help of spiral blades.

25. Four cutter shearing machine

26. Singeing Purpose To burn the protruding fibres present on the fabric surface. Impart smooth appearance to the fabric. Improve the appearnce of dyed and printed fabric. Principle Burning of protruding fibres by means of gas flame. Passage of fabric at high speed (180 m/min) Contact time with flame: Fraction of seconds Fabric is quenched immediately when it comes out of machine

27. Gas singeing machine

28. Composition of cotton Natural impurities Constituent % Cellulose 88 Oils and Waxes 0.5 Pectins 0.7 Proteins 1.1 Colouring matter 0.5 Mineral Matter 1.0 Moisture 8.0

29. Fats and Waxes These are Readily saponifiable triglycerides of fatty acids Waxes which are saponified with difficulty Free fatty acids Traces of soaps Free fatty acids and fatty alcohols identified in cotton are

30. Fats and Waxes Fatty acids Stearic acid Palmitic acid Oleic acid Fatty alcohols Gossipyl alcohol (C30H61OH) Ceryl alcohol (C26H53OH) Montanyl alcohol (C28H57OH)

31. Reactions Fat 3 C17H35COOH + OH-CH2 OH-CH OH-CH2 = (C17H35COO) 3 C3H5 + 3H2O Wax C17H35COOH + OHC28H57 = C17H35COOC28H57

32. Pectins Derivatives of pectic acid Polymer of high molecular weight Composed of Galactouronic acid Some COOH groups are present as Ca and Mg salts Free acid and Ca and Mg salts are insoluble in water

33. Proteins Nitrogenous compounds Present in primary wall and Lumen Some of the amino acids identified are Leucine Valine Proline, Alanine etc. Yellowish (Creamish) colour of cotton is related to Proteins and Colouring matter

34. Colouring matter Colour pigments present are 3,5,7,2’, 4’ Penta hydroxy flavone (Morrin) 3,5,7,8,3’,4’ Hexa hydroxy flavone (Gossypetine)

35. Mineral Matter Depends on soil composition Can be determined by ash analysis Potassium carbonate 44.8 Potassium chloride 9.9 Potassium sulphate 9.3 Calcium sulphate 9.0 Calcium carbonte 10.3 Magnesium sulphate 8.4 Ferric oxide 3.0 Aluminium oxide 5.0