Tài liệu Introduction of finishing and resin finishing

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Introduction Of Finishing And Resin Finishing aravinprince@gmail.com By Aravin prince I M.Tech ( Textile Technology) INTRODUCTION& IMPORTANCE OF FINISHING The ultimate aim of a finishing process is to develop and or modify the fibers or finishes for conventional synthetic fibers so that they give the comfort of natural fibers , the richness of animal fibers  A finishing process in which a desired quality or qualities are imparted to fabric in order to improve the appearance, to affect stiffness, weight, elasticity, or softness, to facilitate care, or to protect the wearer.  Examples include calendaring, durable press finishing, water and oil repellency, and softening aravinprince@gmail.com  CONTD… As the name implies, it is the last step or the process in the method of conversion of fiber into fabric which is in the marketable or useable form.  After finishing only the steps of inspection and packing are left to make the fabric ready for shipment or marketing. aravinprince@gmail.com  FINISHING GIVES THE FOLLOWING ADVANTAGES: Improved appearance – luster ,whiteness etc.,  Improved feel which depends on the handle of the fabric and its softness, suppleness, fullness etc.,  It improves the wearing qualities – Non soiling anticrease.  It gives special properties required for particulars uses – water proofing, Flame proofing etc.,  It covers the faults of the original cloth  It increases the weight of the fabric  It increases the sale value of the material.  It improves the serviceability of the fabric. Hence finishing is essential for a textile good before they are put on the market.  aravinprince@gmail.com CLASSIFICATION TEXTILE FINISHING CHEMICAL DEPOSITION TYPE OF FINISH Parchementising TEMPORARY (Stiff& Transparent) Starch Chlorination of wool China clay (Antishrink) Mercerizing Velan Pf (Flame retardant) Ethylene oxideFormaldehyde (Soil release) Phosphorous& Nitrogen compounds (Flame retardant) All are permanent (Stiff) Oils, Fats & waxes (soft) Optical brightening TEMPORARY PERMANENT E.g. Calendaring Eg.Raising, Sanforising PERMANENT E.g., Synthetic resin (Crease resistance, Wash & wear Durable press) China clay (Stiff) Rubber coating (water proof) Cellulose Acetate cellulose ether (stiff) aravinprince@gmail.com REACTIVE TYPE OF FINISH MECHANICAL Finishing Is Commonly Divided Into Two Categories Chemical aravinprince@gmail.com Mechanical. Chemical Finishing In chemical finishing, water is used as the medium for applying the Chemicals. Heat is used to drive off the water and to activate the chemicals.  Resin treatment  Softener treatment  Powder Coating  Soil/Stain Resist  Fire/Flame retarding  Special Purpose aravinprince@gmail.com Mechanical Finishing It is considered a dry operation even though moisture and chemicals are often needed to successfully process the fabric. Calendaring  Pitching/Raising  Sanforising  Heat setting Type Of Finish (Durability)  Finishing mainly falls into three groups;  1. Temporary finish  2. Permanent finish  3. Semi-permanent finish RESIN FINISHING Cotton is mainly selected for apparel purpose because of its durability, ability to withstand the rough laundering treatments especially under alkaline conditions, good perspiration absorption characteristics, and comfort during wear and ability to take up a wide range of dyestuffs.  However, proneness to creasing under slight crushing and retention of the crease for a long time give cotton garments a poor rating during actual wear.  aravinprince@gmail.com The ability of a fabric to resist the formation of crease or wrinkle when slightly squeezed is termed as crease resistance.  The ability of a fabric to recover to a definite degree is called crease recovery of the fabric.  Contd… Obviously Resin Finishing is the process of bringing out a special property of „crease recovery‟ to Cotton.  Resin finishing often known by various fancy terminology is an important process of textile processing.  Resin finishing quite often called “ Wash & wear finish” “Anti crease finish” “Crease resistant finish” “Durable press finish” And “ wrinkle free finish” is gaining importance today aravinprince@gmail.com  Contd… aravinprince@gmail.com  Resins are cross linking agents, which form covalent bond on reaction with –OH groups of cellulosic materials in acidic medium at a pH of 3-4. RESINS MAINLY FALL INTO TWO GROUPS aravinprince@gmail.com Deposition type of resins Cross linking type of resins Deposition type of resins This type of resins is deposited on the fabric as surface coating. No reaction will take place between the fiber and resin. They include Phenol-Formaldehyde resins Urea formaldehyde resin Alkyd resins Ketone resins Vinyl resins Cross Linking Type Of Resins o These types of resins chemically react with the fiber and aravinprince@gmail.com cross link the fibre molecules. o The type of finish obtained is durable and much better than deposition type. o They are also known as N – Methylol compounds as the Methylol groups (-CH2 OH) are attached to the nitrogen. The cross linking compounds are commonly called resins, but the term pre condensate is correct. The pre condensates further polymerize to form resins. The following are some of the cross liking agents mostly used for crease resistant finishing. DMU (Dimethylol Urea ) DMEU (Dimethylol Ethylene Urea) DMDHEU (Dimethylol Dihydroxy Ethylene Urea) DMPU (Dimethylol Propylene Urea) TMM ( Trimethylol melamine/ Melamine formaldehyde Objective The main objective of resin finish Keep the fabric flat and smooth and Free from undesirable creases aravinprince@gmail.com Advantages  It improves the Crease Resistance and Crease Recovery property  It reduces the shrinkage of the fabric during laundering  It imparts a smooth and quick drying property  It improves Resilience, Handle and Draping quality  It improves the weight and Dimensional stability  It increases the strength of RAYONS in both wet and dry state  It gives resistance to degradation by light and laundering  It improves the fastness to Light and Washing of many dyestuffs  It prevents the Inter molecular slippage in the fiber core  It becomes partially water proof and Rot proof Disadvantages aravinprince@gmail.com It decreases the Tensile strength and Tear strength  It decreases the Abrasion resistance  It gives an unpleasant odor  It gives unwanted Harsh and Stiff feel  It turns the fabric yellow after chlorine bleaching  WHY COTTON FORMS CREASES ? We also understand that Elastic materials like rubber do not form creases.  We know that rigid materials like metals do not form creases. Cotton is not * RIGID and therefore bends and the deformation results in as CREASE * ELASTIC and therefore can not regain its original shape and position after deformation. * It is clear that when a load is applied on cotton material, since it is not rigid will bend and deformation that takes place results in as CREASE and since cotton is not a elastic material it can not regain its original shape and position and hence the deformation that resulted remains as SET CREASE.  aravinprince@gmail.com MECHANISM OF CREASING Why do some fabrics wrinkle and others don't?  Close examination of this question reveals a relationship between moisture absorption and wrinkling. Wool and cotton fabrics wrinkle, both fibers absorb water. Polyester and nylon fabrics are more resistive to wrinkling, they absorb much less than the other two.  To understand wrinkling of cellulose fibers, consider the stress and strain forces within the cellulosic chain.  The stretching stresses a t the outer reaches of the bend provide lateral forces to adjacent polymer chains which can cause them to move. aravinprince@gmail.com  MECHANISM OF CREASING  Under stress, the hydrogen bonds between adjacent cellulose chains can break allowing the chains to slip past each other. aravinprince@gmail.com  The inner polymer chains are under compressive stresses – also providing lateral forces. New H-bonds can form as the hydroxyl groups reassociate with different partners.  Having done so, there are no forces to pull the neighboring chains back to their former position.   The stressed shape of the fiber is just as stable now as was the original shape. THEN HOW TO MAKE COTTON CREASE RESISTANT ? It is clear now that the weak Hydrogen bonds gets disturbed during the course of washing and on drying they try to rearrange and reform giving rise to creases. aravinprince@gmail.com From the mechanism of creasing either we have to Prevent disortion of hydrogen bonds. Make cotton rigid- which for obvious reasons not recommended. Make cotton Elastic- which for obvious reasons not feasible. Therefore the only way left out will be to prevent disortion of Hydrogen bonds which is being perfectly carried out by means of BLOCKING the Hydrogen bonds forming groups by means of cross linking of –OH groups of cellulosic chains. CATALYSTS Various Catalysts have been suggested and reported in literature which exhibits their own influence on the fixation of resin and in turn on the CRA.  The catalysts mainly are Acid liberating agents which liberates the required acid by decomposition during curing process and thus maintains the pH. Of the various catalysts, Magnesium Chloride, DiSodium Hydrogen Phosphate, Di-Sodium DiHydrogen Phosphate, etc are popular. For commercial purposes Magnesium Chloride is only used from the cost point of view. Even though differences in the CRA obtained are reported with different catalysts usage in the padding liquor, commercially they are not much important.  aravinprince@gmail.com RESIN CONCENTRATION  As the concentration of resin increases in the pad bath the CRA of the resultant product increases. aravinprince@gmail.com Dry Crease Recover y (w+d) Degress Reagent Concentration (Mole x 102 / 100G Fabric)
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