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Leather technology

I hope u will get as possible as more INFORMATION to understand THE LEATHER TECHNOLOGY

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Leather technology

  1. 1. Leather Technology Name : Parth M. Ka.patel Sem. : 3rd Roll no.: 12 Department of Materials science Date : 12/9/2014
  2. 2. Outline  Introduction  Production of leather 1. Preparatory stages 2. Tanning 3. Crusting  Forms of leather  Types of leather  Less-common leathers  Leather Products  Environmental impact  References
  3. 3. Introduction  Leather is a durable and flexible material created by the tanning of animal rawhide and skin, often cattle hide. It can be produced through manufacturing processes ranging from cottage industry to heavy industry.
  4. 4. Production of Leather  The leather manufacturing process is divided into three fundamental sub-processes: 1. Preparatory stages 2. Tanning 3. Crusting
  5. 5. 1. Preparatory stages  In the preparatory stages the raw hide/skin is cleaned and sterilized, under this process all the unwanted matter like Flesh and blood stains are removed.  Preparatory stages may includes : (A) Soaking : under which the raw hide is washed and is put in water temporarily. (B) Unhairing : Just includes removal of hair (C) Splitting : It includes cutting the raw hide into many pieces of horizontal layers.
  6. 6. (D) Degreasing : Under this, non-chemically most of the fats and oil are removed. (E) Bleaching : Chemical modification of dark pigments and stains to yield lighter colored raw hide. (F)Saline treatment : under this, all the harmful bacterias are neutralized with the help of salt solution.
  7. 7. 2. Tanning  Tanning is the process that converts the raw hide into more stable form.  In this process the proteins and fibers of the raw hide is reacted with certain chemicals(Ex. Chromium, formic acid) which changes the property of the materials and makes it more stable for the longer usability  In this process leather is treated with chromium which tanns the leather and change the color to Light Blue for this the product is commercial called “Wet Blue”.  Tanning increases the hydrothermal stability and also resistance to the abrasion.
  8. 8. 3. Crusting  Crusting is the process by which the hide/skin is thinned, retanned, lubricated, soften and simultaneously coloured by the use of chemical.  The precautions which are to be taken by crusting are as below : (A) Amount of chemicals used (B) Temperature & Pressure (C) pH i.e. Maintain between 4.5 to 6.5 (D) Drying : The leather is dried to various moisture levels Removal of moisture i.e. 40% to 55% water is squeezed out of leather
  9. 9.  For some leathers, a surface coating is applied  Surface coating is one of the most important process which includes the final toning of the finished leather.  It includes treatments like  Oiling  Brushing  Buffing : It is the mechanical rubbing of the final leather with soft material which smoothens the surfaces.  Polishing  Ironing : it is done to remove the wrinkles.
  10. 10. Forms of Leather  Several tanning processes transform hides and skins into leather: 1. Vegetable-tanned leather is tanned using tannins and other ingredients found in different vegetable matter, such as tree bark prepared in bark mills, wood, leaves, fruits and roots and other similar sources. It is supple and brown in color, with the exact shade depending on the mix of chemicals and the color of the skin. It is the only form of leather suitable for use in leather carving or stamping.
  11. 11. 2. Chrome-tanned leather is tanned using chromium sulphate and other salts of chromium. It is more flexible and pliable than vegetable-tanned leather and does not discolor or lose shape as drastically in water as vegetable-tanned. 3. Brain tanned leathers are made by a labor-intensive process which uses emulsified oils, often those of animal brains. They are known for their exceptional softness and their ability to be washed. 4. Alum-tawed leather is transformed using aluminium salts mixed with a variety of binders and protein sources, such as flour and egg yolk. 5. Rawhide is made by scraping the skin thin, soaking it in lime, and then stretching it while it
  12. 12. Types of Leather  Full-grain leather refers to the leather which has not had the upper “top grain” and “split” layers separated.  Top-grain leather is the second highest quality and has had the “split” layers separated away, making it thinner and more pliable than full grain.
  13. 13.  Corrected-grain leather is any leather that has had an artificial grain applied to its surface.  Split leather is leather created from the fibrous part of the hide left once the top-grain of the rawhide has been separated from the hide.
  14. 14. Schematic of types of leather
  15. 15. Less-common leathers  Buckskin or brained leather is manufactured by tanning process that uses animal brains or other fatty materials to alter the leather.  Patent leather is leather that has been given a high-gloss finish.  Vachetta leather is used in the trimmings of luggage and handbags. The leather is left untreated and is therefore susceptible to water and stains.  Slink is leather made from the skin of unborn calves. It is particularly soft and is valued for use in making gloves.  Deerskin is a tough leather, possibly due to the animal's adaptations to its thorny and thicket-filled habitats.  Nubuck is top-grain cattle hide leather that has been sanded or buffed on the grain side, or outside, to give a slight nap of short protein fibers, producing a velvet-like surface.
  16. 16. Leather used in specialty products, such as briefcases, wallets, and luggage  Belting leather is a full-grain leather that was originally used in driving pulley belts and other machinery. It is found on the surface of briefcases, portfolios, and wallets, and can be identified by its thick, firm feel and smooth finish. Belting leather is generally a heavy-weight of full-grain, vegetable-tanned leather. Ex.
  17. 17.  Napa leather is chrome-tanned and is soft and supple. It is commonly found in wallets, toiletry kits, and other personal leather goods.  Bycast leather is a split leather with a layer of polyurethane applied to the surface and then embossed. Bycast was originally made for the shoe industry and it was also adopted by the furniture industry.
  18. 18. Examples of Napa leather Ladies Pouch Mobile cover Examples Of Bycast leather Tronchetto boots
  19. 19. Leather Products Product group Description Handbags Handbags with or without shoulder strap Pocket or small leather goods Wallet, purses, key pouches, credit-card cases, pen cases and other small articles Travel goods Suitcases, casual travel bags, beauty cases, sports bags and other travel articles Stationary articles and special cases Writing pads, book covers, camera cases, spectacles cases, jewel cases, mobile phone holsters etc. Military equipments Various holsters for fire arms Belts Women's and Men's belts Watch straps Watch straps made of leather and synthetics Sports articles Balls for football, rugby
  20. 20. Environmental impact  Addition to the environmental impact of leather, the production processes have a high environmental impact, most notably due to:  The heavy use of chemicals in the tanning process (e.g. chromium, formic acid, mercury and solvents etc.)  Air pollution due to the transformation process (hydrogen sulphide during dehairing and ammonia during deliming, solvent vapours)
  21. 21. References  Introduction to the principles of leather Manufacture By-S. S. Dutta, 4th edition, I.L.T.A., Calcutta  Theory and practice of leather manufacture By- K. T. Sarkar, Macmillan Indian Press, Madras.  Google Images

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