Eco – friendly in textile wet processing

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  • 1.Eco Friendly in Textile Wet ProcessingBy Aravin Prince Periyasamy., M.Tech (Textiles) Lecturer, Dept of Apparel Technology,S.S.M. Institute of Textile Technology & Polytechnic College, Komarapalayam, Namakkal. Mobile #:+91-97 90 08 03 02 E-mail: aravinprince@gmail.comABSTRACTEnvironmental considerations are now becoming vital factors during the selection ofconsumer goods including textiles all over the world. However due to increased awareness ofthe polluting nature of textiles effluents, social pressures are increasing on textile processingunits. Awareness about eco-friendliness in textiles is one of the important issues in recenttimes since textiles are used next to skin and is called second skin. Owing to the demand ofglobal consumer the researchers are being carried out for new eco-friendly technology.Plasma, biotechnology, ultrasonic, super critical carbon dioxide and laser is quite newtechnology for the textile industry. It offers many advantages against wet techniques. Thereare no harmful chemicals, wet processes, waste water and mechanical hazards to textiles, etc.It has specific action on the all types of fibres and textiles.INTRODUCTION:Increasing environment consciousness in textile processing has forced research anddevelopment efforts to search the safe methods for textile processing. The textile chemicalprocessing plays an important role in controlling the pollution load for environment. Becausethe textile industry has long recognized that, for a large number of process and applications,the surface properties are a key aspect of the product and often need to be quite different fromthose of the fabric bulk. New applications and improved applicability of the many fibre usedfor clothing, as industrial materials and for interior decoration requires the provisions of newproperties in such areas as dyeability, static resistance, and current control, stain resistance,water absorption, hydrophilicity, water repellency, adhesive ability and so on. There aresurface treatment methods that additionally increase the value of textile materials. The methods can be classified as chemical treatment (wet) methods and physicaltreatment (dry) methods. Chemical treatment methods are most often used in actual practice.Because of the large amount of energy involved and the high consumption of water andconsequently increase of pollution, these techniques are costly and not eco-friendly. Inaddition, these processes treat the fabric in bulk, something which is unnecessary and mayadversely affect overall product performance. Problems related to toxicity and other healthhazards have resulted in the replacement of chemical processing by more eco-friendlyphysical methods. The physical treatment processes are dry, which makes it possible topreserve certain properties intrinsic to textile materials; they are likely to affect the surface ofthe materials. Therefore the researchers are extensively studying the possibilities of physicalsurface treatments as alternatives to the chemical treatments.

2. At the beginning, studies initially focused on electron beam irradiation and ultravioletlight irradiation, but electron beam irradiation required too much energy and as a result,properties deteriorated and graft polymerization sometimes occurred. In the latter case it wasnecessary to find a means of reducing the efficiency of grafting. Ultraviolet light irradiationwas tried as a method of resin hardening, but never went beyond the scope of studies onmethods of treating fiber surface. In all probability, this was because it offered no specificfeatures superior to what could be obtained with chemical treatment. The industry is,therefore, strongly motivated to seek alternative surface engineering processes which couldoffer lower cost, environmentally-friendly manufacturing and routes to new products, withimproved lifetime, quality and performance. Research is going on worldwide with the focuson new quality requirements that include maintaining the intrinsic functionality of the productthrough an eco-friendly production process. Therefore, an attempt has been made to reviewthe physical methods for processing of textile materials by plasma, laser and supercriticalcarbon dioxide to enhance the specific properties.PLASMA TECHNOLOGYThe physical definition of plasma (glow-discharge) is an ionized gas with anessentially equal density of positive and negatives charges. It can exist over an extremelywide range of temperature and pressure. Plasma treatment usually practiced in textile industryto enhance the functional finishing. High-pressure glow discharge plasma, modifying theactive surface characteristics of the polymer so it contains polar functional groups. A treatedfibre will comprise a hydrophobic core and a receptive pouter sheath which consists ofhydrophilic functional groups, resulting from the active species interacting with the surface ofpolymer during treatment.Fig 1 Plasma TechnologyPlasma technology has been shown to improve fibre surface properties withoutaffecting desirable bulk properties. It also offers environmental advantages. Therefore, thereare increasing uses of plasma treatment of synthetic fibres such as polyethylene terephthalate,nylon, and polypropylene. A general effect is in improvement in their hydrophilic properties. Fig 2: Plasma Technology in TextilesHow does the Plasma treatment affects the textile material? According to requirements the textile materials to be processed processing will betreated for seconds or some minutes with the plasma. The following are the propertiesimprovements with plasma treatment:1. The cleaning effect is mostly combined with changes in the wettability and the surface texture. This leads to an increase of quality printing, dye-uptake, adhesion and so forth.2. Increase of micro-roughness: this effect an anti-pilling finishing of wool. 3. 3. Generation of radicals: The presence of free radicals induces secondary reactions such as cross linking. Furthermore, graft polymerisation can be carried out as well as reaction with oxygen to generate hydrophilic surfaces in hydrophobic fibres such as polyester or polypropylene.4. Plasma polymerization: It enables the deposition of solid polymeric materials with desired properties onto the substrates.The advantage of plasma treatment is that the modification is restricted to theuppermost layers of the substrate, thus not affecting the overall desirable bulk properties ofthe treated substrate. Functional groups are introduced in the treated textile materials which would playprominent role in improving the dyeability of hydrophobic fibres such as poly (tetraetylene)(PET) and polypropylene (PP). The plasma treated PP and PET could be easily dyed bywater soluble acid dye which is more environmentally friendly plasma is advantageous information of hydroxyl groups on the PET surfaces. To improve the deep colouring effect ofpolyethylene terephthalate (PET) fabrics, anti-reflective coating layers have been depositedon the surface of the fabrics with two different organo-silicon compounds such as HMDS,TTMSVS using atmospheric pressure plasma. Oxygen promoted the decomposition oforganic monomers and contributed to the enhancement of the colour intensity on the PETsurface. Plasma treatment can also be used for grafting of textile fiber with other polymer toenhance specific properties. For example, Poly (ethylene terephthalate) (PET) would beexposed to oxygen plasma glow discharge to produced peroxides on its surfaces. Theseperoxides were then used as catalysts for the polymerization of acrylic acid (AA) in order toprepare a PET introduced by a carboxylic acid group(PET-A). Chitosan and quaternizedchitosan (QC) were then coupled with the carboxyl groups and the PET-A to obtain chitosangrafted PET (PET-A-C) and QC-grafted PET (PET-A-QC), respectively. After the launderingthe inhibition of the growth of the bacteria was maintained in the range of 48 58%, showingthe fastness of the grafted PET textures against laundering. Not only the hydrophobic fibres but also the natural fibres treatment such as in wooldyeing, plasma could be employed. The kinetics of dyeing of wool with acid dyes aftertreatment with low temperature plasma was investigated researcher. It shown the plasmatreated wool can be dyed at 80c at high rates and dye fixing was improved. Modification ofthe wool with low temperature plasma enables the dyeing temperature to be reduced, thushelping to reduce fibre damage. Colour fastness of a wool fabric that was low-temperatureair-plasma treated and dyed with an acid dye has been evaluated. Colour fading of the plasmatreated fabric by carbon arc light irradiation was lesser at initial stage than that of the fabricwithout plasma treatment. The oxidized substrate through the plasma treatment may inhibitthe photo reduction reaction of the dye. The colour fastness of the plasma treated fabric tolaundering was poorer than that of untreated fabric. The phenomena may be attributed to an 4. enhancement of dye diffusion in wool substrate by relaxation of inter cellular material ofwool by the plasma treatment. Wool and nylon 6 fibres treated with oxygen low-temperature plasma were dyed withacid and basic dyes. Despite the increase of electro negativity of the fibre surface caused bythe plasma treatment, the rate of the dyeing of wool was increased with both dyes, while thatof nylon 6 was decreased with the acid dye and increased with the basic dye. After a lowtemperature glow discharge treatment on wool, reduced dyeing times are possible, reducedcost of maintenance and possibilities of recycling are also possible due to reduced dischargesof toxic components. The process is also more environmentally friendly and introduces costsavings by reducing the amount of dyestuffs and auxiliaries required.Marino wool can be treated with low temperature plasma based onoxygen/helium/argon/tetrafluromethane for 30 180 sec before dyeing with acid or directdyes. The pretreatment not only increases the dyeing rate, but also the saturation of dyeexhaustion. The barrier effect is reduced by plasma treatment. The surface of the endocuticleor the adhesive filler in the wool scales is relaxed by the plasma treatment, thereby improvingthe dyeing of wool with direct dyes. Time of half-dyeing is reduced by oxygen andtetrafluoromethane plasma treatment. Although the dyeing rate in short periods increasedindependently of dyes and plasma gases, the helium/argon, plasma was especially effective. Itwas found that there is no relationship to wettability with water and the dyeing rate of plasmatreated wool. Dye penetration is accelerated as a result of the plasma pretreatment.LASER TREATMENT:Another physical surface treatment method to create the hydrophilic groups onhydrophobic fibres and enhance the dyeing process is laser treatment. Extensive research hasbeen carried out into the possibility of surface finishing of synthetic fibre fabrics by laserirradiation. A laser type must be selected which irradiates in a strongly absorbing spectralregion of the high polymers. It is possible to obtain surface structuring without affecting thethermal and mechanical properties of the body of the fibre. Surface properties affectedinclude particle adhesion, wettability and optical properties. Poly (ethylene terephthalate)(PET)modified by a 248 nm KrF excimer laser withhigh(above ablation threshold) and low (below ablation threshold)energy irradiation .ThePET surface develops a well-oriented periodic structure of hills and grooves or a ripplestructure with high energy treatment. However, the ripple size can be reduced to submicronlevel by irradiation of the sample below the ablation threshold. Chemical surface changes ofthe material can be characterized by X-ray photoelectron spectroscopy (XPS) and contactangles. PET modified by high energy will normally exhibit the deposition of some yellow toblack ionized, carbon rich debris on the treated surface, resulting in a reduction of the O/Cratio. In contrast, a PET surface modified by low energy leads to oxidation and almost noablation. The increased oxygen concentration on low energy modified surfaces is probablydue to a subsequent reaction with atmospheric O2 during irradiation. Polar oxidized groupslike carboxyl are also included .Contact angle measurements are in good agreement with 5. these findings .Changes in surface morphology of PET fibres were found in relation to laserenergy applied . The mean roll to roll distance increased with increasing laser energy.Merging of ripples was observed and believed to be a major reason of increased roll to rolldistance. With approximately 50 to 200 pulses, ripple almost approached parallelism. Nofurther change of PET surface was observed with more laser pulses applied since the fibrehas disintegrated into ellipsoidal segments. In the study of morphological modification of laser-ablated PET fabrics, it wasobserved that after laser treatment the ratio of carboxylic acid groups to ester groupsincreased, the relative size if the amorphous regions increased and the ratio of oxygen tocarbon increased. A greater depth of shade was achieved on treated fabrics compared withuntreated fabrics dyed with the same amount of disperse dye. This is due to the scattering oflight caused by ripples on the fibre surface, and greater dye uptake by the amorphous regionson the surface of laser irradiated PET fabrics. The same depth of shade can be obtained onlaser treated fabric with less dye than is needed on untreated fabric.Polyamide (nylon 6) fabrics were irradiated with a 193nm argon fluoride excimerlaser and the effects on the dyeing properties of the fabrics were investigated. Chemicalanalysis indicated that carbonisation occurred in the laser irradiated samples. The lasertreatment breaks the long chain molecules of nylon, increasing the number of amine endgroups which change the dyeing properties with acid and disperse dyes. The results suggestedthat laser treatment could be used to improve the dyeing properties of nylon fabric with adisperse dye. Ablation products must be removed to achieve better bonding at laser treatedsurfaces. Carboxyl group formation at surface of nylon or polyester is stimulated leading tobetter dye ability. Anomalous surface structure of nylon and polyester fibres and yarns werestudied .ultraviolet laser radiation causes less damage to nylon yarn than to polyester yarn,which absorbs more radiation and heats to higher temperatures. The higher temperatures areproduced in a pulse-like action in microscopic areas, resulting in a short-time pyrolysis whichgenerates changes in the surface structure.SUPER CRITICAL CARBON DIOXIDE:Hydrophobic textile materials require creating pores, so that the non-ionic dyeparticles would be entered into the textile materials at high temperature and pressure duringdyeing process. After dyeing when the temperature of the dyed materials goes down to theroom temperature, the dye particles wo...