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Mercerisation

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  • 1. Mercerization Aravin Prince PeriyasamyDKTE’S Textile Engineering Institute
  • 2. MercerisationDefinition: Treatment of cellulosic materials with higher concentrated alkali for short period at lower temperature.
  • 3. Objectives To improve lustre of cotton materials To improve strength and mechanical properties To improve dyeability and moisture absorbancy To improve dimensional stability of materials Improving elasticity
  • 4. Action Of Alkali Cotton have resistance to alkali solutions. Mild alkalis like sodium carbonate have no action on cotton. Strong alkalis with higher concentration induce structural and physical changes in cotton fiber.
  • 5. Penetration of alkali For small concentration of alkali i.e., less than 5% no penetration. As the concentration of alkali increases, penetration will increase, then automatically fiber swells.
  • 6. What Happens To Cotton During Mercerization ? Swelling of the fiber takes place Cellulosic chains gets rearranged and become parallel De-convolution Cross sectional bean shape to ~ circular shape
  • 7. When Mercerization Can Be Carried Out?  At Grey stage  After Desizing  After Scouring  After Scouring and bleaching
  • 8. Physical Changes Improvement in strength Improvement in luster (under tension) Change in cross section from bean shape to almost circular Change in longitudinal view convoluted to cylindrical
  • 9. Chemical Changes Formation of cellulose- II. Improvement in moisture regain (more hydroxyl group). Improvement in dye uptake.
  • 10. Structural ChangesCellulose-I Cellulose-II
  • 11. Absorption of the alkali and swelling
  • 12. Conditions Application of caustic soda solution around at a Room temperature. A dwell period of 55 sec on an average. Tension at both directions Finally, washing-off of alkali from the treated fabrics/ yarn.
  • 13. What Are The Parameters Concentration of NaOH Time of Treatment Tension applied Temperature Impurities of NaOH
  • 14. Mercerization machinesTension Mercerization ( treatment under tension/ Control)Slack mercerization ( Treatment without tension/ Control) Yarn mercerization Fabric mercerizationFabric mercerization machinesWoven fabric Pad chain type Pad chainless type Padless chainless typeKnitted fabric
  • 15. Hot mercerizationDrawbacks with cold mercerization•Penetration of grey cotton becomes more difficult(high viscosity)•Swelling only in surface (heavy fabrics)•Poor mercerization at the core and lack of uniformity
  • 16. Recipe Na OH = 26 – 30 % Wetting agent =1% Temp = 60 Degree C Time = 20 to 60 sec
  • 17. Advantages of hot mercerization•Rapid alkali penetration•Improved core mercerization•More uniform treatment•Dwell time can be reduced from 50 sec. to 20-30 sec.
  • 18. Dis- Advantages of Hot Mercerisation Less luster (Lower swelling) Higher energy consumption Costlier
  • 19. Hot Mercerizing Machine
  • 20. Liquid Ammonia Mercerization Treatment of cotton fiber with liquid Ammonia (NH3) produces similar effect that of Mercerization. The liquid ammonia treatment is widely accepted for yarns used in Sewing Threads, and special fabrics like Denims, Corduroys, Pillow material, linen, Jute and blends of cellulose with PET and/ or Nylon.
  • 21. Advantages of Ammonia Mercerization Less pollution Higher productivity Jute and linen can be mercerized Evenness and uniformity of swelling is comparatively better.
  • 22. Dis Advantages of Ammonia Mercerization Very costly equipments Ammonia recovery problem, leakages will do great harm to the personnel working.
  • 23. Comparison of mercerization processesProperty Conv. Merc. Hot Merc. NH3/Dry-steamSwelling speed Low Fast V. FastEvenness uneven Good GoodLuster Good Good Very goodDye uptake Good Not quite high GoodDimensional Good Good Goodstability
  • 24. Test Method:- Determination of BAN

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