Sunday, December 30, 2007

Carbonizing of wool

Raw wool contains seeds and other pieces of vegetable matter. Much of this may be removed in scouring and in combing. Combing is not used in woolen system and vegetable matter is only partially removed in carding. Even in some worsted processes, small amount of residual vegetable material is present in the fabric and in such cases carbonizing is essential to remove the residues.

The scoured wool fabric is padded, either in the rope form or in open width, with liquor containing dilute sulfuric acid (5 to 7 % by wt.) at approximately 65% wet pick up. And dried at 65 -90 C to concentrate the acid. Baking at 125 C for one minute chars the cellulosic material. The charred vegetable material is brittle and easily crushed on passing the rollers. it can be removed as dust during subsequent mechanical working. After carbonizing the wool fabric should rinsed and neutralized by washing. Such neutralization should be carried out immediately after baking, otherwise fabric damage will occur during storage of wool in such as acidic state. It is convenient to neutralize prior to dyeing but uneven neutralization leads to uneven dyeings.

Friday, December 21, 2007

Polynosics fibres

“A manufactured cellulose fibre with a fine and stable micro fibrillar structure which is resistant to the action of 8% sodium hydroxide solution down to zero degree Celsius., which structure results in a minimum wet strength of 2.2 grams per denier and a wet elongation of less than 3.5% at a stress of 0.5 grams per denier”.

The word polynosic has no connection with, or similarity of meaning to, such words as polymer, polyamide, and polyester, polyvinyl and so on. It is said to mean multifibrillar.

There are 4 main ways in which the polynosic differ from ordinary rayon

1) Dimensional stability in fabric form
2) Ability to withstand mercerizing. Their alkali solubility is much less than that of ordinary rayon
3) Crisper, loftier handle more like cotton than rayon. Luster is also more like that of sea-island cotton, sometimes like that of spun silk
4) Swelling in water and imbibition of water are much lower.

Tuesday, December 18, 2007

Methods of mordanting for natural dyeing

The three methods used for mordanting are: -

- Pre-mordanting: - The substrate is treated with the mordant and then dyed.
- Meta - mordanting: - The mordant is added in the dye bath itself.
- Post-mordanting: - The dyed material is treated with a mordant.
The methods have different effects on the shade obtained after dyeing and also on the fastness properties. It also depends upon the dye and the substrate. It is therefore necessary to choose a proper method to get the required shade and fastness by optimisation of parameters.

Since metallic mordants are soluble in water and are loosely held by the cotton fibres, these mordants have to be precipitated on the fabric by converting them into insoluble form, or by first treating the fibres with oil or tannic acid and then impregnating treated fabric with solution of mordant, whereby the metallic mordants are held on to cotton via oil or tannic acid.

Unlike cotton, wool is highly receptive towards mordants. Due to its amphoteric nature wool can absorb acids and bases equally effectively. When wool is treated with a metallic salt it hydrolyses the salt into an acidic and basic component. The basic component is absorbed at –COOH group and the acidic component is removed during washing.
Wool also has a tendency to absorb fine precipitates from solutions. These precipitates are superficially sorbs onto surface of fibres and the dye attached to these gives poor rubbing fastness.

Like wool, silk is also amphoteric and can absorb both acids as well as bases. However, wool has thiol groups (-SH) from the cystine amino acid, which act as reducing agent and can reduce hexavalent chromium of potassium dichromate to trivalent form. The trivalent chromium forms the complex with the fibre and dye. Therefore potassium dichromate cannot be used as mordant effectively.



1) Health and safety aspects of natural dyes: Though all natural dyes are not 100% safe they are less toxic than their synthetic counterparts. Many of the natural dyes like turmeric, annatto and saffron are permitted as food additives. Many natural dyes have pharmacological effects and possible health benefits.
2) They are obtained from renewable sources.
3) Natural dyes cause no disposal problems, as they are biodegradable.
4) Practically no or mild reactions are involved in their preparation.
5) They are unsophisticated and harmonized with nature.
6) Many natural dyes have the advantage that even though they have poor wash fastness ratings, they do not stain the adjacent fabrics in the washing process because of the non-substantive nature of the dye towards the fabric. An exception to this is turmeric, which shows substantivity for cotton.
7) Natural dyes are cost effective
8) It is possible to obtain a full range of colours using various mordants.


The limitations of natural dyes that are responsible for their decline are: -

Ø Availability
Ø Colour yield
Ø Complexity of textile dyeing process
Ø Reproducibility of shade
Besides these there are other technical drawbacks of natural dyes: -
These are: -
Ø Limited number of suitable dyes
Ø Great difficulty in blending dyes
Ø Non-standardized
Ø Inadequate degree of fixation
Ø Inadequate fastness properties except few exceptions
Ø Water pollution by heavy metals and large amounts of organic substances.

Sunday, December 16, 2007


The processes by which we remove sizes are known as desizing. Sizing is the need for the weaving but is an obstacle for the dyeing. It can be done by many ways such as acid steep, rot steep, enzymatic etc. in all these enzymatic desizing is dominating because of its eco-friendliness and also because of its characteristics that is it acts at specific sites only at definite pH, temperature and concentration. Mainly starch is used as the ingredient in sizing.

Chemically starch is poly-α-glucopyranose in which straight chain (amylase) and branched chain (amylopectin) polymers are present. Both constituents of starch are insoluble in water, but they can be solubilised by hydrolysis of these long chain compounds to shorter ones. Thus under suitable conditions starch can be progressively hydrolyzed to the following stages. In desizing the hydrolysis reaction is carried out up to the stage of soluble dextrin only and not further to a-glucose.

Like starch polyvinyl alcohol is also common. Since it is a powerful film forming sizing agent and because of the ease with which it can be removed (it is soluble in water) it is an ideal sizing agent. The molecular weight and the degree of hydrolysis are the two primary factors, which influence its solubility in water, the solubility decreasing with increasing molecular weight. The desizing of polyvinyl-treated fabrics involves three steps- swelling, dissolving and dispersing. In contrast to starch, enzymes, normally used for desizing starches, do not hydrolyze it. The principle steps in the desizing procedure are

Wetting out with suitable wetting agent.

Steeping for affecting the swelling and softening of the polyvinyl alcohol film.

Rising thoroughly in overflowing water.

Desizing efficiency is found in two ways conventional and

TEGEWA method.

Conventional Method:

In this method we first take the weight of the sized fabric, let it be W1. Then desize the fabric, dry & take the weight, let it be W2. After that the fabric is treated with 3gpl (35%) HCl at 700 C for 30 min. dry & take the weight of the fabric. Let it be W3.

Total size = W1-W3.

Residual size = W2-W3.

Desizing Efficiency = (Total size – Residual size)/Total size X 100.


Reagent: potassium iodide (10 gm. Of KI (100%) in 100 ml water, add 0.6358 gm of iodine (100%) stir and shake; iodine is completely dissolved. Fill up to 800 ml with water then complete to 1000 ml with ethanol. (Shelf life approx 6 months only).


Spot drop wise solution onto fabric.

2. Rub in gently.

3. Assess change of colour.

Note: the test must be carried on fabric cooled down to room temperature; residual alkalinity has to be neutralities prior to the test.


Grey fabric:

No change of colour = no starch size present.

Pale blue to bluish = presence of starch size or blend

Violet =of starch size with synthetic size

Desized fabric:

Pale blue to bluish violet = refer to violet scale TEGEWA This indicates residual Starch content.

Sunday, December 9, 2007

Colour Fastness


Fastness is the fundamental requirement that coloured textiles should
withstand the conditions encountered during processing following colouration
and during following their subsequent useful life.
Light Fastness:
How confident are you that your fabric will perform well exposed to light or will colors fed or the fiber loosed their strength is always a question in front of most of manufactures. For some manufactures the light stability is an oblivious concern.
Degradation to textiles from exposure to light typically includes color change, fading yellowing and loss of tensile strength. If light fastness and weathering do not seem like significant consideration for particular product, this kind of damage causes millions of dollars in product losses every year.
This degradation occurs when light breaks chemical bonds in dyes and fibers. Sunlight is made up of ultra violate light, visible light and infrared radiation. While short wave UV causes most of the physical property damage to fibers, it is generally the longer wave UV and visible light that causes textile fed. This means that both outdoor product, like balloons, tents, and awnings and indoor product like apparel and curtains are vulnerable+. Even products exposed to harsh indoor lightning or sunlight through window glass in bright retail or commercial environment are susceptible.
For manufacturers of the fabric used outdoors, light exposure is one of the several concerns. High temperature and moisture in the form of rain, dew, and humidity can also be damaging. Light, heat and moisture in combination may synergistically contribute to even greater product degradation than anyone of these elements alone.

This method is intended for determining the resistance of the colour of textiles of all kinds and in all forms, and of leather, to the action of daylight.
If there is a possibility o a sample being photochromic, the test of photochromism shall be applied additionally.
A specimen of textile or leather is exposed to daylight under prescribed conditions, including protection from rain, along with eight dyed wool standards. The fastness is assessed by comparing the change in colour of the specimen with that of the standards.
1. Fabric size: 1 x 6 cm
2. Fastness rating: 1 to 8
Blue wool cloth ranging from 1 to 8
i. C.I. Acid Blue 104
ii. C.I. Acid Blue 109
iii. C.I. Acid Blue 83
iv. C.I. Acid Blue 121
v. C.I. Acid Blue 47
vi. C.I. Acid Blue 23
vii. C.I. Solubilised Vat Blue 5
viii. C.I. Solubilised Vat Blue 8

Pattern dyed with 3 dyes should be deceived after dyeing. The patterns of light fastness from 1-8 may be obtained from ISI.
The BS 1006:1978 test of day light exposure specifies that sample should be tested together with standard dyed wool patterns of light fastness. 1-8 respectively cover with opaque sheet of card board or aluminum leaving the other half exposed.
When daylight is used fading is slow and quicker answer is often necessary under commercial purpose. Hence, xenon arc lamp is used. The SED of this lamp bears a close resemblance to a natural light.
Test reports:
Report the numerical rating for light fastness. It is represented by the figure alone (in the case of using the standards denominated 1-8).If this rating is equal to or higher than 4 and the preliminary assessment is equal to or lower than 3, report the later figure in brackets. If the specimen is photochromic, the light fastness shall be followed by bracketed P along with the grey scale rating.

Monday, December 3, 2007

Fastness of Dyed Textiles

Dyeing is defined as an operation or a series of operation by means of which uniform color of permanent character is produced on a substrate. This implies that it should not be possible to wash the color out easily in laundering, nor should it fade rapidly when exposed to light. There is probably no dye, which can be guaranteed not to alter shade under all condition. Wide variation in the fastness properties of dyes are observed on number of factors, e.g. chemical constitution of the dye, nature of substrate, method of application, auxiliary chemicals added during dyeing etc.
A number of tests are necessary to cover all the important properties of any one dye because good fastness to one influence is not necessarily accompanied by equal fastness to exposure to other condition.Tests may be divided into those of customer significance, such as light, wash; perspiration, rubbing, sublimation and hose concern only the unshrinkable treatment, carbonization etc.

Monday, November 26, 2007

Application of Chitosan in textile Wet Processing

Chitin and chitosan have higher affinity for dyes and metals and certain surfactants, which
contribute to water pollution. Using the shellfish waste thus has two-fold
advantage: -

a) First to find a viable method to purify dye wastewaters.

b)To use natural resources, which could otherwise had been wasted.

After use for color removal the spent sorbent further finds use as a fibrous raw material for papermaking.

The use of chitosan as a combined thickener and binder in pigment printing has been studied in comparison with the commercial printing system. Printing pastes made from chitosan, acetic acid and pigments at appropriate viscosity give stable pastes and satisfactory results on polyester and polyester –cotton blends.

Chitosan can also be used in the dyebath, because due to the unimolecular structure it has an extremely high affinity for many classes of dyes, including disperse, direct, reactive, acid, vat, sulphur etc. Rate of diffusion of dyes in cellulose is similar to that in cellulose. Sorption of chitosan is exothermic: hence an increase in temperature leads to an increase in dye sorption. At lower pH chitosan free amines are protonated causing to attract anionic dyes.

Chitosan is used as a shrink-proofing agent and also is used to increase the dye uptake of wool. In its protonated form, it exhibits the behavior of a cationic polyelectrolyte, forming viscous solutions and interacting with the oppositely charged molecules. Thus it is suitable for processing of wool near its isoelectric point, offering minimum fiber damage and providing good quality. However the main limitation is the uneven distribution on the fabric surface.A new ecological method for shrink proofing of the wollen fabric is based on the enzymatic pretreatment and chitosan deposition on the wollen fabric. This
method shows the enzymatic pretreatment has an essential influence on the shrink proofing qualities and chitosan stabilizes the shrink proofing property. It also increases the kinetics of dyeing and causes a decrease in hydrophobicity.

Antimicrobial finishing is very important because cotton fabrics have poor resistance to microorganisms and thus the possibility of harming the human body. Due to the Antimicrobial action of the amino group at the C-2 position of the
glucosamine residue, chitosan is also known to be an antimicrobial polysaccharide. The ability of chitosan to immobilize microorganisms derives from its polycationic character. Its protonised amino groups block the protein sequences of microorganisms, thus inhibiting further proliferation. Chitosan binds to the negatively charged bacterial surface disrupting the cell membrane and altering its permeability. This allows materials to leak out of the bacterial cells resulting in cell death. Chitosan can also bind to DNA inside the cell inhibiting mRNA and hence protein synthesis. Recent studies have revealed that chitosan is more effective in inhibiting the growth of bacteria than chitosan oligomers. Also the antibacterial effect of chitosan oligomers are reported to be dependent on its molecular weight.
1,2,3,4-Butanetetracarboxylic acid (BTCA) and citric acid are representative of polycarboxylic acids that crosslink with cotton through an esterification reaction. BTCA is the most effective of these plycarboxylic acids, but its cost is very high; citric acid is a less effective crosslinking agent but is not as costly. However, cotton fabrics treated with citric acid alone exhibit appreciable yellowing, although there have been some investigations undertaken to reduce this yellowing.
Generally, cellulose is treated with chitoan by dissolving the chitosan in dilute acetic acid solution, but this method does not create any firm chemical bonds between chitosan and cellulose and thus is not durable to repeated laundering. The esterification reaction not only occurs between citric acid and cellulose but also between citric acid and the hydroxy groups of
chitosan, and free carboxylate groups can also react with the amino groups of chitosan resulting in a salt linkage. It is widely known that the Antimicrobial properties of cotton treated with chitosan is attributed to amino groups of chitosan, which convert to ammonium salts in dilute acid solution; the salt then binds to the negatively charged surface of the microorganism..

As a durable press and an Antimicrobial finishing agent for cotton fabric, citric acid and chitosan show satisfactory results. The WRA and DP rating of treated cotton fabrics increase, and there are slight improvements in tensile and tear strength using chitosan as abn extender of the crosslinking chain. A high Antimicrobial property level is obtained by treatment with CA as
well as chitosan, and despite repeated launderings, the Antimicrobial property remains at over 80%.
Chitosan is expected to be one of the safest and most effective Antimicrobial agents for hospital applications where many antibiotic substances are used. Chitosan is especially important in depressing the growth of methicilin resistant taphylococcus aureus, which is resistant to most antibiotic substances. Hygienic yarns can also be made through the addition of chitosan fibres. Chitosan fibers are blended with cotton fibers and a yarn is spun out of this blend; 10% chitosan component is sufficient to achieve a hygienic effect. This effect should endure 20 washes.(1)currently, there is also a hightened interest in protecting health care workers from diseases that might be carried by patients. Especially for surgical gowns, there is an increasing need to protect medical staff from infection by bloodborne pathogens such as HIV and HBV> gowns should be able to prevent “ strike through” or “wetting out” of the fabric, and so surgical gown materials should have not only
Antimicrobial properties but also blood barrier properties. Chitosan and fluoropolymers seem to be the most suitable finishing agents for providing surgical gown materials with barriers against microorganisms and blood. Because many medical products including surgical gowns are used in close proximity to human skin, the hand and air permeability of these materials are also very important. Recently, single-use gowns made from non-woven have gained in popularity because non-woven fabrics block fluids so well and single-use gowns are so reliable.

One of the most important characteristics of chitosan is its Antimicrobial activity at specific molecular weights. Protonated amine groups in chitosan inhibit the growth of microorganisms by holding negatively charged microorganism ions. Many studies have examined chitosan as an Antimicrobial finish for textile materials, either for production of low molecular weight
chitosan followed by its application on textile fibers or for co-spinning or co-casting of low molecular weight chitosan with cellulose molecules to make Antimicrobial fibers and films. However, these methods had to produce chitosan with specific molecular weights, which could considerably increase production costs. In addition, insolubility of chitosan in neutral or alkaline conditions further limited its application.

A quarternery ammonium derivative of chitosan, N-2-hydroxy propyl-3-trimethylammonium chitosan chloride (HTCC), is synthesized as an Antimicrobial finish for cotton using a reaction of glycidyltrimethylammonium chloride (GTMAC) and chitosan. The use of crosslinking agents or binders increase laundering durability of cotton treated with HTCC. A 5% nonionic binder applied along with 0.1% or higher concentration of HTCC on cotton is quite effective in increasing the laundering durability of the HTCC-treated cotton.

There are some reports about the utility of chitosan polymer to impart Antimicrobial activity in textile finishing. For example, chitosan salt produced by an organic acid was bound to the surface of textiles by a tremendous amount of resin, which formed cross-links. When fully deacetylated chitosan is depolymerised into chito-oligosaccharide with sodium nitrite, its DP can be
controlled by adjusting the amount of sodium nitrite added to the acetic acid solution containing the fully deacetylated chitosan.Chitosan when applied along with DMDHEU results in a substantial improvement in soil removal when oily soil is applied to cotton fabrics. The highest levels of soil removal are exhibited by fabric samples treated with DMDHEU with chitosan of average molecular weight below 21,000. the improvement in soil removal attributes to the prevention of deep soiling due to blocking of pore structure abd the increase in hydrophilicity by chitosan treatment.Chitosan treated samples of cotton with resin treatment show higher moisture regain values, this is because amine and hydroxyl groups provide reactive sites for
water.Various methods such as physical, chemical, and biological treatments are used for deodorizing. In the field of cosmetics, antibacterial agents, antiperspirants, and fragrances are used to effectively reduce or mask malodors. The antibacterial agents
control the bacteria that decompose human fats found in sweat to produce low molecular weight fatty acids. Using the same technology, the textile industry applies antibacterial agents for odor control. However, because antibacterial agents can attack human skin as well, there are only a limited number of such chemicals allowed for use in textile treatment.Over the past
few years, a considerable number of studies have been done on the performance of chemical deodorizers that swiftly couple with targeted odor substances. Their neutralizing ability makes such of low molecular weight substances less volatile. For example, these chemical deodorizers can target sweat, which generally shifts from human skin to fabric and then is concentrated to generate unfavorable odors after bacterial decomposition.

However, existing chemical deodorizes are highly surface active and can cause unpleasant results such as discoloration, aggregation, and skin irritation. Notably, most of the highly active substances are hydrophilic, and their activities become
weak under hydrophobic conditions. Chitosan was selected because while its primary amino group possibly deodorizes, its high molecular weight offers safety. The polymerization reactions of methacrylic acid with chitosan were done in water, and the emulsions were free of monomeric acid. The polymer particles showed high deodorizing performance, even in hydrophobic and hydrophilic circumstances, and fabric treated with the emulsion was also found useful for deodorizing.

In the manufacturing and coloration of cotton fabrics, the textile industry experiences dyeing problems with some lots of cotton. The cotton does not absorb dye uniformly and creates tiny white or light-colored spots. This results from small
clusters of immature cotton called neps. Immature cotton results from a variety of reasons e.g. plant disease, insect attack, premature harvesting after using harvest-aid chemicals, or adverse weather conditions.

Previous research has shown that pretreatment of cotton fabrics with chitosan significantly improves the dye coverage of neps. After dyeing with reactive dye using standard procedure dyed fabrics are treated with chitosan by exhaust or pad-batch method. The chitosan treatment alone did not cover the neps in the dyed fabrics. However, after redyeing with 0.1-0.2 dye, the neps were more or less completely covered. The coverage ratings increased from 1-2 to 4-5. The chitosan aftertreatment and redyeing with a small amount of dye caused very little change in total color difference value. There is a significant increase
in k/s value of dyed fabric. Nep coverage improved the quality of the dyed fabrics.

Among synthetic fibers, polyester (PET) exhibits excellent properties such as elastic recovery, dimensional stability. However, it does not absorbwater or moisture well. As a result, friction can cause static electricity to occur. Electric resistivity of natural fibers is 109 to 1010 Ω.cm; polyester fiber is less than 1015 Ω.cm; water is 103 Ω.cm. This static electricity causes electric shock, fiber contamination during textile finishing.Many endeavors to endow an antistatic property to polyester include research to change the characteristics of fiber surface. Chitosan shows high moisture regain even in low relative humidity and does not swell much in water; thus it can resist the decrease the durability that water causes. A permanent antistatic finish can be achieved by crosslinking hydrophilic materials that form an insoluble conductive sheath on the surface of the fiber. So chitosan seemingly has the potential to improve the water-absorbency and antistatic properties of polyester fiber.

Polyester fibers can be grafted with AA or NVF by preirradiation with γ rays. By acid hydrolysis, amide groups on the fiber surface can be converted into amino groups. Chitosan can then be grafted to modified polyester surfaces by either esterification or imine formation. The highest surface density of amino groups can be achieved by imine formation between chitosan and glutaraldehyde- treated PET-g-NH2.

Chitosan grafted polyesters show antibacterial activity for MRSA, S. aureus-2, and E. coli. The antibacterial activity increases with the surface density of amino groups. Furthermore, the antibacterial activity for E. coli is higher than that for the other bacteria, whereas the antibacterial activity for MRSA is the lowest.

Monday, November 19, 2007


Chitin was described for the first time in 1811 by Braconnot, who was professor of Science of Nancy, France. Chitosan was discovered by Rouget in 1859. He was found that chitin, which has been boiled in a very concentrated potassium hydroxide solution, becomes soluble in diluted solutions of iodine and acid, where as chitin was stained brown.

The production of chitin and chitosan is currently based on crab and shrimp shells discarded by the canning industries in Oregon, Washington, Virginia, and Japan and by various finishing fleets in the Antarctic. Several countries possess large unexploited crustacean resources e.g. Norway, Mexico, and Chile. The production of Chitosan from crustacean shells obtained, as a food industry waste is economically feasible, especially if it includes the recovery of carotenoids. The shells contain considerable quantities of astaxanthin, a carotenoid that has so far not been synthesized, and which is marketed as fish additive in aquaculture, especially for Salmon.

Chitin and Chitosan:

Chitin, poly- (1,4)-2 acetomido-2-deoxy-ß-D-glucose, is the second most abundant natural polymer. Its chemical structure is similar to that of cellulose, differing only in the second carbon position where the hydroxy groups are replaced by an amino acetyl group. Chitosan is the deacetylated form of chitin, i.e. poly- (1,4)-2amido-2-deoxy- ß-D-glucose. Chitin and chitosan are widely distributed in animals and fungi and are the basic polysaccharides that are the major component of the shells of crustacean such as crab, shrimp and crayfish.
Chitin and chitosan have the potential to reduce and to solve some problems for creating “Greener environment

The following is a chronological order of the processes needed to produce Chitosan from crustacean shells

Size reduction—Protein Separation (NaOH)—Washing—Demineralization (HCl) – Washing and Dewatering – Chitin -- Deacetylation (NaOH) – Washing and Dewatering – Chitosan.

Chitin and Chitosan are natural resources refined from the waste products of the crabbing and shrimp industry. Chitin is produced from the processing waste of shellfish, frill, clams, oysters, squid, and fungi. They have a high percentage of Nitrogen (6.89%) compared to the synthetically substituted cellulose, which has 1.25% nitrogen. Chitosan has amino groups and hence it exhibits many properties, such as biodegradability, which are different from the cellulose. Chitin does not melt; it is insoluble in water, dilute acids, cold alkalies, and organic solvents. However, the solvents like formic acid, concentrated mineral acids, and tetrechloroacetic acid can dissolve Chitin, but they are not convenient and lead to polymer degradation. On the other hand, Chitosan is readily soluble in most aqueous solutions, like that of 5% formic acid and acetic acid because of the basicity of the primary amine groups. Chitosan dissolves readily when electric repulsions (corresponding to cationic charges)
are more important than the attracting interactions (such as hydrogen bonding and Vander Walls interactions). The solubility of chitosan is also favoured by the process of hydration of various, mainly charged sites. As a result, the ratio between NH3+ and NH2 groups, a parameter directly related to the charge density of the polymer, is a very important factor in ascertaining the properties of chitosan. The basic difference between
Chitin and Chitosan is the degree of deacetylation (DAC), which is the same as the relative amount of free amount amine. Chitosan is obtained from chitin by treating the latter with strong caustic soda and heat, which removes the N-acetyl groups.

As a natural renewable resource with a number of unique properties, chitosan is now attracting more and more scientific and industrial interest from diversified fields such as chemistry, biochemistry, medicine, pharmacology, biotechnology, and food and textile sciences. Properties such as biodegradability, biocompatibility, non-toxicity, wound healing and antimicrobial activity have generated much research work. Many unique products have been developed for various applications such as surgical sutures, artificial skin, cosmetics and dietary foods.

Almost all properties of chitin and chitosan depend on two fundamental parameters; the degree of acetylation and the molecular mass distribution (or average molecular weight), although they do have some contrasting properties. The molecular weight of chitin and chitosan can be determined by methods such as chromatography, light scattering and viscometry. Viscometry is by far the most simple and rapid method for the determination of average molecular weight by measuring an intrinsic viscosity for several concentrations of chitosan or chitin solutions.

Properties of Chitosan:

  • Solution properties of Chitosan in free Amine (-NH2) form soluble in acidic solutions.
  • Insoluble at pH’s> 6.5
  • Insoluble in H2SO4
  • Limited solubility in H3PO4
  • Insoluble in most organic solvents
  • Soluble at pH’s < 6.5
  • Forms viscous solutions
  • Solutions shear thinning, forms gels with polyanions
  • Will remain soluble in some alcohol-water mixtures

Chemical properties of Chitosan

Chitosan is a linear polyamine (poly-O-glucosamine) with reactive hydroxyl and amine group

Chitin and chitosan are natural biopolymers. They have no antigenic properties, and thus are perfectly compatible with living tissue. Their antithrombogenic and hemostatic properties make them very suitable for use in all fields of biology.


Chitosan forms films that are permeable to air. It facilitates cellular regeneration while protecting tissue from microbe attack. In addition, chitosan has been found to have a biostimulant effect on the regeneration of tissue.
Lysozome that kills various germs increases 1.5 to 2 times as fiber made from chitosan comes in contact with the skin it also activates nitrogen, which regenerates the skin. This property has allowed it to be used in making an
artificial skin for skin grafts on high degree burns and in surgical applications such as chitin suture thread. It binds to mammalian gum tissue. It accelerates the formation of osteoblasts responsible for the formation of bone.

Anticholesterolemic agent
Chitosan can trap lipids at their insolubilization pH in the digestive tract. Administered to rats, chitosan considerably reduces the level of cholesterol in the blood.

Chelation agent
Chitin and its derivatives are remarkable chelation agents. Chitosan is used for a wide rangeof applications: as a chromatography medium, or for trapping heavy metals, or for water treatment. It chelates many transitional metal ions

Chitin and chitosan are biodegradable biopolymers. Enzymes-chitinase and chitosanase-break them down into oligopolymers that are then dealt with by the metabolism. It is biodegradable to normal body constituents.

Strengthening the immunity

Fibers made from chitosan strengthen the immunity of the human body to expel foreign matters when disease germs or viruses enter the body.

Antimicrobial activity
It is also a fungi static and has spermicidal and antitumor properties. Generally chitosan (D.A.=9.9%, concentration 0.15%) is proved to be free from mildew activity during four cultivating days. The activity increases with increase in concentration of chitosan.

Electric properties of Chitosan
Fibers made from chitosan can effectively generate static electricity due to its high molecular weight. It has a unique resistance value similar to other natural high molecular matters such as cellulose or rayon.

Deodrant properties of Chitosan

Chitosan eliminates stink of sweat and other odors. It has humid retention properties due to the amine radical & is also a central nervous system.

This post is contributed by Imran Mallick, M. Tech, UICT (formerly UDCT)

Friday, November 9, 2007

Soluble dyes for wool
comprise acid, mordant, and metal-complex dyes. Acid dyes are classified broadly into the following three groups, according to their dyeing and wet fastness properties, though many dyes have intermediate properties:

Leveling or equalizing acid dyes, which require a strong acid (usually H2SO4 is used) to give good exhaustion of the bath. They have poor fastness to washing, milling, and other wet processes, but good leveling properties, i.e. the dye distributes itself evenly throughout the fibres on continued boiling.

Milling acid dyes,
which are dyed neutral or from a weakly acid bath (acetic acid is usually used). They have good fastness to washing, etc, but they usually have poor leveling properties.

Super Milling acid dyes,
which are dyed from a weakly alkaline bath (ammonium sulphate is usually used). They have very good fastness to washing, etc, but they have very poor leveling properties.

All acid dyes are applied at the boil. Glauber salt is used to retard dyeing and thus to assist in obtaining level dyeing.


M: L 1:30
Dye bath additives for leveling type
10% Glauber salt + 3% H2SO4
+ dye solution

Dye bath additives for Milling type

10% Glauber salt + 1% CH3COOH
+ dye solution

Dye bath additives for Super Milling type
3% leveling agent + 3% CH3
COONH4 Solution

Adjust dye bath for 1% shade and 1:50 MLR. Start dyeing at room temperature. Raise temperature to boil. Keep at boil for one hour. Finally squeeze the hanks, rinse with cold water, squeeze and dry.

Thursday, November 8, 2007

Garment Processing

'Garment processing' is nothing but preparation, dyeing, printing and finishing operations performed on apparel that has been fully made and is ready for sale. Newer fashion trends through continuous product and process development is a key to be successful, as consumers are more fashion conscious irrespective of kid’s wear, men’s garments or lady’s garments. Garment wet processing has become the key element of product development. The five “F’s” are very important for consumer satisfaction 1) Fabric 2) Finishing 3) Fit 4) Factory 5) fashion. All these five elements interact with each other to create new and exciting looks for the future. The important factor in garments from customer satisfaction is look, colour and feel of the garments, which must be appealing. The effect of garment wet processing should create attractive fashions and should differ from garments manufactured from processed fabrics.

Apart from the fashion and trends, garment wet processing also have advantages in economics and other aspects they are listed as

Advantages Of 'Garment Processing'

Handling of smaller lots economically

Enables various special effects to achieved

Distressed look can be effectively imparted

Unsold light shades can be converted into medium and deep shades

By the time the garment has been in a boiling dyebath and then tumble-dried, it will have adopted its lowest energy state and will not suffer further shrinkage under consumer washing conditions

Latest fashion trends can be effectively incorporated through garment wet processing by immediate feedback from the customer

But Advantages Are Also Associated With Disadvantages,

Disadvantages of 'garment processing'

High cost of processing

A little complicated dyeing

Garment accessories like zips, buttons, etc impose restrictions. The garments produced from woven fabrics create many problems and it has been found that the existing textile treatment styles as developed for piece dyed fabric cannot be just assembled for garment wet processing operation such as garment dyeing, unless they have been engineered from the original design stage for garment dyeing.

The factors governing processing of ready-made garments are

• Sewing Thread

• Metal Components. Shrink behavior

• Accessories

• Foreign substances

• Interlining

• Care labeling.

Friday, October 26, 2007



As the regulated quota system comes to an end in 2004 and the free globalise market takes over, the priorities of textile manufacturers as well as consumer all over the globe are undergoing dramatic change. In this global competition ‘quality’ and ‘eco - friendliness of process and product‘ plays key role. In this paper a brief introduction of research in various fields of biotechnology to achieve the quality product through eco friendly processes is given. Advances in the field of fibre production and modification, use of different enzymes in the textile processing, and waste management using the biotechnology is also discussed.

Textile industries are facing a challenging condition in the field of quality and productivity, due to the globalization of the world market. The highly competitive atmosphere and as the ecological parameters becoming more stringent, it becomes the prime concern of the textile processor to be conscious about quality and ecology. Again the guidelines for the textile processing industries by the pollution control boards create concern over the environment-friendliness of the processes. This in turn makes it essential for innovations and changes in the processes. As a result, the research and development strategies of the textile processors will be highly focused and the challenges will force many changes in the textile industry. Biotechnology is one such field that is changing the conventional processing to eco friendly processing of the textiles.
Biotechnology is the application of living organisms and their components to industrial products and processes. In 1981, the European federation of Biotechnology defined biotechnology as “integrated use of Biochemistry, Microbiology, and chemical engineering in order to achieve the technological application of the capacities of microbes and cultured tissue cells. Defining the scope of biotechnology is not easy because it overlaps with so many industries such as the chemical industry or food industry being the majors, but biotechnology has found many applications in textile industry also, especially textile processing and effluent management. Consciousness and expectations for better quality fabric and awareness about environmental issues are two important drivers for textile industry to adopt biotechnology in its various areas.

The major areas of application of biotechnology in textile industry are given below:
Improvement of plant varieties used in the production of textile fibres and in fibre properties
· Improvement of fibres derived from animals and health care of the animals
· Novel fibres from biopolymers and genetically modified microorganisms
· Replacement of harsh and energy demanding chemical treatments by enzymes in textile processing
· Environment friendly routes to textile auxiliaries such as dyestuffs
· Novel uses for enzymes in textile finishing
· Development of low energy enzyme based detergents
· New diagnostic tools for detection of adulteration and Quality Control of textiles
· Waste management­­1, 2

3. Improvements in Natural fibres:

Biotechnology can play a crucial role in production of natural fibres with highly improved and modified properties besides providing opportunities for development of absolutely new polymeric material. The natural fibres under study are cotton, wool and silk.
3.1 Cotton
Cotton continues to dominate the market of natural fibres. It has the greatest technical and economic potential for transformation by technological means. Genetic engineering research on the cotton plant is currently directed by a two-pronged approach
Solving the major problems associated with the cultivation of cotton crop, namely the improved resistance to insects, diseases and herbicides, leading to improved quality and higher yield.
The long – term approach of developing cotton fibre with modified properties, such as improved strength, length, appearances, maturity and colour.
3.1.1 Transgenic cotton
Each year, thousands of research hours and hundreds of thousands of dollars are spent to prevent cotton from caterpillars that love to eat cotton. Cotton growers fight to produce a saleable product using pheromones (insects mating hormones) and monitoring. Use of excessive pesticides is posing serious threats to the green image of cotton.
After years of research, a completely new kind of tool is available for cotton growers to ward off the pink bollworm, one of the major cotton pests. About ten years ago, Monsanto scientists obtained a toxin gene from the soil bacterium called Bt (which is the nickname for Bacillus thuringiensis) and inserted it into cotton plants to create a caterpillar-resistant variety. The gene is DNA that carries the instructions for producing a toxic protein. The toxin kills caterpillars by paralyzing their guts when they eat it. Plants with the Bt toxin gene produce their own toxin and thus can kill caterpillars throughout the season without being sprayed with insecticide. Because the toxin is lethal to caterpillars but harmless to other organisms, it is safe for the public and the environment.
Monsanto registered their Bt gene technology for transgenic cotton under the trademark Bollgard and authorized selected seed companies to develop cotton variety carrying the patented gene.
More stable, long lasting and more active Bts are now being developed for the suppression of loopers and other worms in cotton. Insect resistance is also being developed using a ‘wound- inducible promoter‘ gene capable of delivering a large but highly localized dose of toxin within 30-40s of an insect biting.
3.1.2 Coloured cotton
Developments of fibres containing desirable shades in deep and fast colours would change the face of the entire processing industry. Coloured cottons are also being produced not only by conventional genetic selection but also by direct DNA engineering.
Although several naturally coloured cotton varieties have been obtained by traditional breeding methods, no blue variety exists. As blue is in great demand in the textile industry, particularly for jeans production, synthetic fabric dyes are used. However, the ingredients of these synthetic dyes are often hazardous and their wastes are polluting.
Additionally, they take time and energy to work into the cloth. Natural blue cotton does not have these disadvantages and, therefore has great market potential. The genetic engineers plan to insert into production of blue dye, until a cheaper synthetic method is discovered. By 2005, Monsanto hopes to have this blue-coloured cotton commercially available.
3.1.3 Hybrid cotton
Another major breakthrough has been the ability to produce cotton containing natural polyester, such as polyhydroxybutyrate (PHB), inside their hollow core, thereby creating a natural polyester/cotton fibre. About 1% polyester content has been achieved and it has led to 8-9% increase in the heat retention of fabrics woven from these fibres. Other biopolymers, including proteins, may also be introduced into cotton core in a similar manner.
These customized fibres will be tailored to the need of the textile industry. New properties may include greater fibre strength, enhanced dyeability, improved dimensional stability, reduced tendency for shrinking and wrinkling and altered absorbency. Greater strength will allow higher spinning speeds and improved strength after wrinkle-free treatments. Improved reactivity will allow more efficient use of dyes. Thus reducing the amount of colour in effluents. To reduce the waste generated during scouring and bleaching processes, it would be interesting to have fibres with less of pectins, waxy materials and containing enzymes that can biodegrade environmental contaminants. These fibres would be placed in filters through which contaminated water is passed.

The use of biotechnology has the potential of control and specificity in polymer synthesis which is difficult, if not impossible, to achieve in chemical systems. New materials produced using advanced biologically – based approaches represent the textiles of the future.
4.1 Protein Polymers:
Biological systems are able to synthesize protein chains in which molecular weight, stereochemistry, amino acid composition and sequence are genetically determined at the DNA level. A current area of investigation is to understand those features of protein polymers that confer high tensile strength, high modulus and other advantageous properties. Once those features are understood, the tools of biotechnology will make possible entirely new paradigms for the synthesis and production of engineered protein polymers. If they can be made economically viable, these new approaches will help to reduce the dependence on petroleum and furthermore will enable the production of materials that are biodegradable. Use of transgenic plants for large-scale production of these and other synthetic proteins is being explored.
Efforts in biosynthesis have been directed towards the preparation of precisely defined polymers of three kinds (1) natural proteins such as silks, elastins, collagens and marine bioadhesives, (2) modified versions of these biopolymers, such as simplified repetitive sequence of the native protein, and (3) synthetic proteins designed de novo that have no close natural analogues. Although such syntheses pose significant technical problems, these difficulties have all been successfully overcome in recent years. Using this technology, a whole new class of synthetic proteins with advanced properties, known as bioengineered materials, is being created.
4.1.1 Spider silk:
Spider dragline silk is a versatile engineering material that performs several demanding functions. The mechanical properties of dragline silk exceed those of many synthetic fibres. Dragline silk is at least five times as strong as steel, twice as elastic as nylon, waterproof and stretchable. Moreover, it exhibits the unusual behavior that the strain required to cause failure actually increases with increasing deformation.

4.2 Other New Fibres Sources:
There are many more biopolymers, of particular interest in sanitary and wound healing applications, which include bacterial cellulose and the polysaccharides such as chitin, alginate, dextran and hyaluronic acid. Some of these are discussed below:
4.2.1 Chitins and Chitosans:
Chitins and chitosans both can form strong fibres. Chitin is found in the shells of crustaceans, such as crab, lobster, shrimps etc. Resembling cellulose, the chitin consists of long linear polymeric molecules of beta- (1-4) linked glycans. The carbon atom at position 2, however, is aminated and acetylated. Fabrics woven from them are antimicrobial and serve as wound dressing products and as anti-fungal stockings. Chitosan also has promising applications in the field of fabric finishing, including dyeing and shrink proofing of wool. It is also useful in filtering and recovering heavy and precious metals and dyestuffs from the waste streams.
Wound dressing based on calcium alginate fibres are marketed by Courtaulds under the trade name ‘Sorbsan’. Present supplies of this polysaccharide rely on its extraction from certain species of bacteria. Dextran, which is manufactured by the fermentation of sucrose by Leuconostoc mesenteroides or related species of bacteria, is also being developed as a fibrous nonwoven for specialty end uses such as wound dressings. Additional biopolymers, not previously available on a large scale, are now coming into the market, thanks to biotechnology.
4.2.2 Bacterial cellulose:
Cellulose produced for industrial purposes is usually obtained from plants sources or it can be produced by bacterial action. Acetobacter xylinium is one of the most important bacteria for cellulose production as sufficient amounts can be produced which makes it industrially viable. Cellulose produced by Acetobacter, which has the ability to synthesize cellulose from a wide variety of substrates, is chemically pure and free of lignin and hemicellulose. Cellulose is produced as an extra cellular polysaccharide in the form of ribbon like polymerization, high tensile strength and tear resistance and high hydrophilicity that distinguishes it from other forms of cellulose. This bacterial cellulose is being used by Sony Corporation of Japan in acoustic diaphragms for audio speakers. They are also being used in the production of activated carbon fibre sheets for absorption of toxic gas and as thickeners for niche cosmetic applications. In medical field, because of the hydrophilic and mechanical properties of bacterial cellulose, it is used temporarily as skin substitute and in wound healing bandages.
4.2.3 Corn fibre:
An entirely new type of synthetic fibre derived from a plant is Lactron. This environment – friendly corn fibre was jointly developed by Kanebo Spinning and Kanebo Gohsen of Japan. Lactron, the polylactic acid fibre is produced from the lactic acid obtained through the fermentation of corn starch. Strength stretchability and other properties of Lactron are comparable to those of petrochemical fibres such as nylon and polyester. As the material is compatible with human body, it is being used for sanitary and household applications. In addition to clothing the company is also promoting its non-clothing applications, e.g. construction, agricultural, papermaking, auto seat covers and household use.
The energy required for production of corn fibre is low and the fibre is biodegradable. Moreover, no hazardous gases are created when it is incinerated and the required calories for combustion are only one-third or half of those required by polyethylene or polypropylene. It safely decomposes into carbon dioxide, hydrogen and oxygen when disposed of in soil. Lactron is being marketed in various forms such as woven cloth, thread and non-woven cloth.
4.2.4 Polyester fibres:
It has been known since 1926 that certain polyesters are synthesized and intra-cellulose deposited in granules by many micro-organism. Some of these materials have been formed into fibres. Polyhydroxybutyrate (PHB) is an energy storage material produced by a variety of bacteria in response to environmental stress. It is being commercially produced from Alcaligenes eutrophus by Zeneca Bioproducts and sold under the trade name Biopol.
As PHB is biodegradable, there is considerable interest in using it for packaging purposes to reduce the environmental impact of human garbage. Thus it is already finding commercial application in specialty packaging uses. Because of its immunological compatibility with human tissue, PHB also has utility in antibiotics, drugs delivery, medical suture and bone replacement applications.

The development of biocidal fabrics was based on the idea of activating textiles with reactive chemicals to impart desirable properties. The latest research however is aimed at producing fabrics containing genetically engineered bacteria and cell strains to manufacture the chemicals within the textiles thereby making the chemical stores within the fabrics the self-replenishing materials.
A collaborative project is on between the textile science research team at University of Massachusetts, Dartmouth and the bio-engineers at Harvard medical to carry out research leading to the production of a class of fabrics with special properties called biofabrics. Biofabrics will contain micro-fabricated bio-environments and biologically activated fibres. These fabrics will have genetically engineered bacteria and cells incorporated into them that will enable them to generate and replenish chemical coatings and chemically active components.
Niche applications for bio-active fabrics exist in the medical and defense industries, e.g. drug producing bandages or protective clothing with highly sensitive cellular sensors, but biofabrics may form the basis of a whole new line of commercial products as well e.g. fabrics that literally eat odours with genetically engineered bacteria, self – cleaning fabrics, and fabrics that continually regenerate water and dust repellents.
For such an approach to be successful, technologies will have to be developed to micro-fabricate devices able to sustain cellular or bacterial life for extended periods, exhibit tolerance to extremes of temperature, humidity and exposure to washing agents, as well as tolerance to physical stress on the fabrics such as tension, crumpling and pressure2.

Textile finishing sector requires different chemicals, which are harmful to the environment. Sometimes they may affect the textile material if not used properly. So instead of using such chemicals we can use the enzymes. The finishing of denim garments has been revolutionized by application of enzymes. Enzymes are very specific in action when they are used under the required conditions. The processes in which enzymes can be used are desizing, scouring, bleaching, biowashing, degumming etc.

Enzymes in Textile processing

Fig : Enzymes in Textile processing

Amylase, pectinase, and glucose oxidase are enzymes used for desizing, scouring, and bleaching respectively in enzymatic preparation processes. Desized samples show completely size removal using amylase enzyme. Samples scoured with pectinase are immediately and uniformly wet. Amount of pectin and other substances left on scoured samples from both conventional and enzymatic processes were measured along with sample strength and whiteness index. Samples bleached with glucose oxidase obtain whiteness index 15-20 degree improvement with low strength loss. Conventional preparation of cotton requires high amounts of alkaline chemicals and consequently, huge quantities of rinse water are generated. An alternative to this process is to use a combination of suitable enzyme systems. Amyloglucosidases, Pectinases, and glucose oxidases have been selected that are compatible concerning their active pH and temperature range. A process has been developed that allows the combination of two or all three preparation steps with minimal amounts of treatment baths and rinse water. Whiteness, absorbency, dyeability and tensile properties of the treated fabrics have been evaluated.
The use of biocatalyst in the textile industry is already state of the art in the cotton sector. Research and development in this sector is primarily concentrating on:
- Optimizing and making routine the use of technical enzymes in processes that are already established in the textile industry today.
- Replacing established conventional processes with the aid of new types of enzymes, particularly from extremophile micro-organisms, under stringent conditions (temperature of surfactant or organic components etc)
- Preparing enzyme-compatible dyestuff formulations, textile auxiliary agents and chemical mixtures.
- Producing new or improved textile product properties by enzymatic treatment.
- Providing biotechnological dyes and textile auxiliary agents, which are suitable for industrial use, and can possibly be synthesized in-situ (i.e. on-line for the application process).
6.1 Extremophile Micro-Organisms:
Numerous micro-organisms have learnt to live in very different and difficult environmental conditions, e.g. in high temperatures, in acid and alkaline conditions and in the presence of salt concentrations. These extremophile micro-organisms live in the most inhospitable and unspoilt environments on earth. Where other micro-organisms do not exist, they are to be found in the deepest oceans under pressures of more than 100 bar, in hot volcanic sources at over 100 C in cold regions at temperatures around freezing point, in salt lakes (up to 30% salt concentration) and also in surroundings with extreme pH values (pH <2,> 9). The cell components (enzymes, membranes) of extremophile are optimally adapted to extreme environmental conditions, and have characteristics (stability, specificity and activity), which make them interesting for biotechnological application.
At the Hamburg-Harburg (D) University of Technology, a comprehensive screening programmed for isolating exremophile micro-organisms (like starch, proteins, and hemicellulose for example) has been implemented which is able to produce enzymes for breaking down biopolymers, alkanes, polyaromatic carbohydrates (PAK) plus fats and oils. Within the framework of these studies, a range of biotechnologically relevant enzymes like amylases, xylanases, proteases, lipases and DNA polymerases for example have been enriched and characterized.
6.2. Conversion Of Natural Polymers By Extremozymes:
Starch is one of the most important biopolymers on this earth. The macromolecule built up from glucose units, plays an outstanding role in the food industry under the collective concept “modified starch” this is found in many foods. Amylases and branching enzymes for example are used for modifying starch. With the aid of thermostable starch-modifying enzymes, starch finishing can be carried out more purposefully and efficiently, since for example the space-time yield at high temperatures is significantly better due to improved starch solubility. Thermo-alkali-stable enzymes (active at pH >8 and 600C) are used in washing and harness rinsing agents in order to remove tenacious starch accumulations with simultaneous reduction in detergent quantity.
6.3. Cyclising Enzymes:
So-called cylodextrins can be produced from starch with the aid of cyclising enzymes (cyclodextringlycosyltransferase, CGTase) from the recently isolated thermoalkaliphile bacterium Anaerobranca gottschalkii. Hydrophobic active substances or volatile aromas can be encapsulated in these cyclodextrins. Cyclodextrins were isolated by Villiers as early as 1891. In those days, cyclodextrins were regarded as curiosities of no technical value.
The properties of cyclodextrins have been altered by chemical change (derivatives). The target of much research work is to fix a reactive cyclodextrin derivative on cellulosic or protein fibres by forming a new chemical bond on the fibre. The molecules have a hollow space, which is suitable for absorbing diverse substances like perfume for example. Many application possibilities and effects arise out of this complexing like for example:
-Increased water solubility
-Change of rheological characteristics
-Stabilization against UV radiation, thermal disintegration, oxidation and hydrolysis
-Reduction of unpleasant smells
-Absorption of microbe-eliminating products
6.4. Cellulose From Extremophile Micro-Organisms:
Cellulose is also a biopolymer built up of glucose units. It forms the framework of higher plants and is an important resource in the textile industry. The use of cellulases in detergents leads to colour revival (colour detergent) and the improved removal of vegetable soiling. Cellulases are also successfully used in ‘biostoning’. In contrast to conventional cellulases, which are obtained from mesophilic fungi as a rule, cellulose-hydrolyzing enzymes from extremophile micro-organisms have the advantage of being capable of use even at high temperatures and pH values.
6.5 Xylanolytic enzymes:
Xylanolytic enzymes form another group. Xylan is heterogeneous molecule (basic component: xylose sugar), which makes up the largest proportion of the polymeric vegetable cell wall component hemicellulose. Xylanophile micro-organisms have enormous biotechnological potential. Thermobile xylanases are already being produced on an industrial scale today, and are used as fodder and food additives. In past years, interest in xylanases was concentrated particularly on enzymatic paper bleaching. Current studies have shown that the enzymatic treatment of paper is an ecologically and economically sound alternative to the hitherto employed chlorine-based bleaching process.
Enzymes which can for example destroy the coloured attendant substances of cotton are of interest to the textiles industry. The quantity of caustic soda and salt required in peroxide bleaching could be reduced by this type of enzymatic bleaching.
Reuse of the bleaching liquor after hydrogen peroxide bleaching is already possible today by using the enzyme ‘catalase’ after bleaching. This enzyme destroys excess hydrogen peroxide, making use of the bleaching liquor for other finishing stages possible.
Windel Textil GmbH & Co. (D) already uses the so-called ‘Bleach-Cleanup’ process, in which bleaching agent residues are removed from textiles, resulting in a reduction of energy, time and water-intensive washing operations at high temperatures.
Research projects at the German Wool Research Institute (DWI) in Aachen (D) are devoted to the use of enzymes in wool processing, including the removal of vegetable residues from the wool, increasing the degree of whiteness, improving handle, improving dyeability by increasing intensity of colour and for felt-free finishing.
Already interesting in practice is the felt-free finishing of wool. An enzyme not previously employed in the textile industry modifies the scale-like surface of wool fibres preventing felting. The enzyme ‘Lanazym’ has hitherto been used only in discontinuous batch processing.3

The synthetic dyes are designed in such a way that they become resistant to microbial degradation under the aerobic conditions. Also the water solubility and the high molecular weight inhibit the permeation through biological cell membranes. Anaerobic processes convert the organic contaminants principally into methane and carbon dioxide, usually occupy less space, treat wastes containing up to 30 000 mg/l of COD, have lower running costs and produce less sludge4. Azo dyes are susceptible to anaerobic biodegradation but reduction of azo compounds can result in odour problems. Biological systems, such as biofilters and bioscrubbers, are now available for the removal of odour and other volatile compounds. The dyes can be removed by biosorption on apple pomace and wheat straw5. The experimental results showed that 1 gm of apple pomace and 1 gm of wheat straw, with a particle size of 600µm, were suitable adsorbents for the removal of dyes from effluents. Apple pomace had a greater capacity to adsorb the reactive dyes taken for the study compared to wheat straw.

7.1 Decolourization Of The Dye House Effluent Using Enzymes:
The use of lignin degrading white-rot fungi has attracted increasing scientific attention as these organisms are able to degrade a wide range of recalcitrant organic compounds such as polycyclic aromatic hydrocarbons, chlorophenol, and various azo, heterocyclic and polymeric dyes. The major enzymes associated with the lignin degradation are laccase, lignin peroxidase, and manganese peroxidase. The laccases are the multicopper enzymes, which catalyze the oxidation of phenolic and non-phenolic compounds.
However, the substrate of the laccases can be extended by using mediators such as 2, 2’-azoinobis-(3-ethylthiazoline-6-sulfonate), 1-hydroxybenzotriazole. The following fungi have been used for laccase production and for the decolourization of synthetic dyes, Trametes Modesta, Trametes Versicolour, Trametes Hirsuta, and Sclerotium Rolfsii 6 From the results obtained it was clear that Trametes Modesta laccase showed the highest potential to transform the textile dyes into colourless products. The rate of the laccase catalyzed decolourization of the dyes increases with the increase in temperature up to certain degree above which the dye decolourization decreases or does not take place at all. The optimum pH for laccase catalyzed decolourization depends on the type of the dye used. Dyes with different structures were decolourized at different rates. From these results it can be concluded that the structure of the dye as well as the enzymes play major role in the decolourization of dyes and it is evident that the laccase of Trametes Modesta, may be used for decolourization of textile dyestuffs, effluent treatments, and bioremediation or as a bleaching agent.
Another study carried out by E. Abadulla et al, has shown that the enzymes Pleurotus ostreatus, Schizophyllum Commune, Sclerodium Rolfsii, Trametes Villosa, and Myceliophtora Thermiphilia efficiently decolourized a variety of structurally different dyes. This study also shows that the rate of reaction depends on the structure of the dye and the enzyme7.
Activated sludge systems can also be used to treat the dyehouse effluents. But the main difficulty with activated sludge systems is the lack of true contact time between the bacteria of the system and the suspended and dissolved waste present. Immobilized microbe bioreactors (IMBRs) address the need of increased microbial/waste contact, without concomitant production of excessive biosolids, through the use of a solid but porous matrix to which a tailored microbial consortium of organisms has been attached. This allowed greater number of organisms to be available for waste degradation without the need of a suspended population and greater increased contact between the organisms and the waste in question8.

The advent of biotechnological applications in textile processing widens the already existing wide horizons to produce aesthetically colourful magnanimous and ecologically friendly textiles, ringing in a new era of synergetic application of life sciences. As of today the huge textile industry is open to welcome the immense possibility of the various biotechnological applications limited by the limitations of being eco friendly and not harming either the food web or the life cycle of any other living creature. Such awareness is gradually metamorphosing a tool that could be intelligently used to meet the demand of our fashion trends.
Enzymes, bacteria and insects could be biologically modified into a fashion promoter if engineered with great caution. A major breakthrough in the textile industry is eagerly awaited through these biotechnological applications.

Biotechnology, Edited by H. J. Rehm and G. Reed
Biotechnology application in textiles industry, Deepti Gupta, Indian Journal of Fibres & Textile Research Vol.26, March-June 2001.
Biotechnology: process and products, Andrea Bohringer, Jurg Rupp, International Textile Bulletin, June 2002.
The Biotechnology Approach to Colour Removal from Textile Effluent, by Nicola Willmott et al. J of Soc. Of Dyers and Col., 1998, 114, 38-41.
Removal of dyes from a synthetic textile dye effluent by Biosorption, by T. Robinson, et al, Water Research, 36, 2002, 2824-2830.
Decolourization of textile dyes by laccases, by G. S. Nyanhongo, et al, Water Research, 36, 2002, 1449-1456.
Enzymatic decolourization of Textile Dyeing Effluents, by E. Abadulla et al, Textile Res. J. 70 (5), 2000, 409-414
Improving Bio-treatment For Textile Waste Decolourization, by Caroline A. Metosh et al, American Dyestuff Reporter, July/August19

Wednesday, October 24, 2007

Biotechnology in Textiles

The rapid developments in the field of genetic engineering have given a new impetus to the biotechnology. This introduces the possibility of 'tailoring' organisms in order to optimize the production of established or novel metabolites of commercial importance and of transferring genetic material (genes) from one organism to another. Biotechnology also offers the potential for new industrial processes that require less energy and are based on renewable raw materials. It is important to note that biotechnology is not just concerned with biology, but it is a truly interdisciplinary subject involving the integration of natural and engineering sciences. Defining the scope of biotechnology is not easy because it overlaps with so many industries such as the chemical industry or food industry being the majors, but biotechnology has found many applications in textile industry also, especially textile processing and effluent management. Environmental protection is becoming a serious concern for textile wet processors. Dyes discharged from textile dyeing and finishing processes are a priority pollutant because of their visibility at low concentrations. Most dyes have low toxicity but their components and breakdown products can be more toxic. Physical and chemical treatment techniques are effective for colour removal but use more energy and chemicals than the biological processes. They also concentrate the pollution into solid or liquid streams requiring additional treatment or disposal. Biotechnological methods can completely mineralize pollutants and are usually cheaper.

Biotechnology in Textiles:
Biotechnology has its roots in the dawn of the history. It is not new to textile industry, it has been used in textile processing for the enzymatic removal of starch sizes from woven fabrics for most of this century and the fermentation vat is probably the oldest known dyeing process. The scope of enzymes in textile industry is very wide. This can be understood by looking at the wide spectrum of applications in textiles. The major areas of application of biotechnology in textile industry are Improvement of plant varieties used in the production of textile fibres and in fibre properties, Improvement of fibres derived from animals and health care of the animals, Novel fibres from biopolymers and genetically modified micro-organisms, Replacement of harsh and energy demanding chemical treatments by enzymes in textile processing, Environment friendly routes to textile auxiliaries such as dyestuffs, Waste management.
Textile processing industry is characterized by high consumption of energy and resources and time consuming processes. Lot of pollutants are generated by textile industry, especially textile processing sector produces most of the pollutants, mostly water pollutants. Waste water from textile industry, especially process houses, is characterized by high COD and BOD, suspended solids and intense color due to the extensive use of dyes. This type of water must be treated before discharging it into the environment. The water must be decolorized; harmful chemicals must be converted into harmless chemicals. . Biological treatments have been used to reduce the COD of textile effluents. Instead of using the chemical treatments various biological methods can be used to treat the waste water from the textile industry. These methods include, Biosorption, use of Enzymes, Aerobic and anaerobic treatments etc. Only biotechnological solutions can offer complete destruction of the dyestuff, with a co-reduction in biological oxygen demand (BOD) and chemical oxygen demand (COD). In addition, the biotechnological approach makes efficient use of the limited development space available in many traditional dyehouse sites
Many azo dyes and harmful chemicals, like p-chlorophenol have been banned from use. The area in which biotechnology is required exactingly is the treatments on waste water generated during textile processing. The presence of chemicals, like formaldehyde, salts, phenols, dyes, alkalis and acids, heavy metals, polyvinyl alcohol in waste water is very harmful to the environment. So these chemicals must be either removed or converted into harmless chemicals by treating them chemically or biologically.

Though the industrial Biotechnology is in the early stages of development but its innovative applications are increasing and spreading rapidly into all areas of manufacturing. It is already providing useful tools that allow for cleaner, more sustainable production methods and will continue to do so in the future. Adoption of biotechnology ensures the cleaner environment; also it cuts the cost of the processes. Textile industry, which is responsible for generation of lot of pollutants in all forms, must adopt the biotechnology, especially in the processing sector, to reduce the consumption of energy as well as other resources.

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Wednesday, October 17, 2007


Navanath Pingle, Laxmikant Jawale, Prashant Vispute.
Department of Fibres and Textile Processing Technology
University Institute of Chemical Technology
University Of Mumbai, India


Whilst, the India has abolished the textile quota regime of textiles, one has to face tremendous amount of competition from producers of all over the world. One has to be very productive, economical, quality conscious, environment friendly with assured reproducibility. Modern technologies are going to play very major role in this. Ink jet printing is one such promising technique, which will be a critical tool in the hands of production units. In this article attempt is made to familiarize ink jet printing.

Drastic changes are taking place in the textile printing; quick response, globalization and ecology impose substantial demands on the different components of the printing process. They force the textile printers to focus on: shortening and flexibility of the pre-print process; printing right first and the next time, reducing down time of the printing machine, short run production, and stock risks. Consumers are demanding a greater variety of colour and design. They want fabrics that express their individuality in their environments and in the clothes that they wear. Today's ecological stringent demands ask for eco processes minimizing waste of raw materials and pollution of the environment. In short these demands have common denominations: flexibility and versatility. Conventional printing lacks the above demands. The answer lies in digital printing. The jet-printing technology has yet to make the leap into mainstream. Although digital printing is already claimed as the most significant technological advancement to the textile printing industry in over 30 years, the adaptation of these new systems has been much slower than many had anticipated or expected, due to specific technological limitations (hardware, print head or nozzle, ink classes). These hurdles must be overcome for Commercial exploitation of these new technologies.


Ink-jet printing involves squinting droplets of ink, which make contact with substrate image. Ink-Jet can be divided into two major technology types: Continuous and Drop-on-Demand. Each of these subdivided further as shown in figure:


l.Continuous Ink-Jet Printing (CIJ):
As the name implies, in Continuous Ink-Jet systems a continuous stream of ink droplets is ejected from nozzle on to the substrate. Two designs are possible in the designing of this method. In the first design, charged ink droplets are deflected on to the paper to form the image and the uncharged droplets are collected in gutter. This is called as raster scan continuous Ink-Jet method. In the second design, the uncharged ink droplets form the image and the charged ink droplets are deflected into the gutter. This is the Binary Continuous Ink-Jet system. While in Hertz technology, fine mist of the uncharged droplets form the images. Hertz Technology is more suited to color printing than the previous two methods.1
Continuous Ink Jet printing is further divided into two main types viz; Piezoelectric and Thermal Excitation.

Fig 2. Principle of continuous stream ink-jet printing (raster scan method/the Sweet system)

A) Piezo-eleetric Technology
Piezo-electricity is a phenomenon of producing electricity by application of pressure on a crystal, which is capable of conducting electricity through it.4 This method has been suitably exploited for ink jet printing technology. Piezo ink jet printing relies on different principles for the expulsion of ink from the cartridge nozzles. In this technology, an electrical charge is applied to the cartridge nozzles which excites a small piezo crystal that is inside. As the piezoelectric crystals are stimulated, the crystals change shape and squeeze the ink chamber. This action is similar to the action of squeezing an oilcan, and forcefully expels the ink from the nozzle.

(a) Continuous ink jet-binary deflection. (left)
(b) Continuous ink jet- multiple deflection. (middle)
(c) Continuous ink jet - Hertz method (right)

After leaving the nozzle, the drops are electically charged by an amount that depends on the image to be printed. The drops then pass through an electric field to cause then to deflect. There are two ways of deflecting the drops in piezoelectric- driven Continuous Ink Jet. In the binary deflection method droplets are directed to a single pixel location in the medium or to the recirculation gutter. In the multiple deflection method the deflection is variable so the drops can address several pixels. These two concepts are illustrated in the Fig.3 (a) and (b).

In the Hertz method, the amount of ink deposited per pixel is variable. This is achieved by generating very small drops at the speed of 40m/s with excitation frequencies of over 1 MHz (see Fig 3 (c)). The drops not intended to reach the medium are charged ad deflected to the gutter. The printing drops are given the smaller charge to prevent them in merging in flight.

Since the piezoelectric process does not utilize heat, the cartridge life of these printers is greatly expanded, cartridges should last a minimum of one year under heavy usage. Piezoelectric print heads can use a wider range of inks than thermal inkjet printers because the heat is removed from the process. This means that solvent-based ink systems and pigmented-ink formulations will be more readily available, which increases the development capabilities for better inks in the future. Although piezo is currently the lesser-utilized technology, many experts predict that the long-term development of ink jet print devices will use the piezo technology because of the greater through-put speeds offered and the wider latitude with the types of inks that can be developed 6.

Drop-on-Demand, or impulse, inkjet systems differ in two major respects from continuous Ink-Jet systems. First, all the ink droplets are used to form the image none are wasted. Ink droplets are ejected only where a dot is required on the substrate, i.e. they are produced "on demand ". Secondly, the droplets are not charged. Hence there is no deflection involved. Drop on Demand Ink Jet systems may be subdivided into two broad types, namely piezo and thermal (or bubble jet). In DOD printing a significant proportion of the solid ink resides on the surface of the paper giving the print an embossed feel.(2,3,4)

Principle of Drop On Demand printing (5)

principle of bubblejet printing

Bubble-Jet or thermal technology is a well-known technology. The technology relies on a thermal pulse to generate the ink drop. This technology was the first of the drop on demand. The technique boils the water content of the ink and the resulting steam pressure forces a droplet of ink out of the nozzle. In these engines, the computer signal heats a resistor to a high temperature(>360 C) which creates a vapor bubble in a volatile component in the ink, the vapor bubble expands and exits the nozzle followed by a contraction of the bubble causing a drop of ink to be ejected on the textile substrate. The vapqur bubble must then cool and collapse allowing the ink chamber to refill from a reservoir. Cycle time is limited to approximately 10,000 drops per second and the volume per drop of ink is typically 150 to 200 Pico liters.

The main advantage of the thermal ink jet technology is the low cost of nozzle fabrication. It is made using the mass production technique based on the integrated circuits. The system restricts the use of binder containing pigment inks. The major problem with the thermal ink jet is the high nozzle and resistor failure rate resulting from rapid thermal cycling. As the heater to boil the water has to work in a semi-explosive way, the temperature can rise up to 360 C, which can cause the nozzle to burn out. The high temperatures cause often decomposition of ink components, which leads to poor heat transfer and / or nozzle clogging. Therefore only thermal stable inks can be used. These defects are unpredictable.

Principle of Bubble jet printing.