Introduction of Direct Dyes | Classification of Direct Dye |Application of Direct Dyes | Aftertreatment of Direct Dye

Direct Dye:
Direct Dye is a class of dyestuffs that are applied directly to the substrate in a neutral or alkaline bath. They produce full shades on cotton and linen without mordanting and can also be applied to rayon, silk, and wool. Direct dyes give bright shades but exhibit poor washfastness. Various aftertreatments are used to improve the washfastness of direct dyes, and such dyes are referred to as “aftertreated direct colors.”Direct Dyes are molecules that adhere to the fabric molecules without help from other chemicals. Direct dyes are defined as anionic dyes with substantivity for cellulosic fibres, normally applied from an aqueous dyebath containing an electrolyte, either sodium chloride (NaCl) or sodium sulfate (Na2SO4)..

Direct Dyes 

The dyeing process with direct dyes is very simple, Direct dyeing is normally carried out in a neutral or slight alkaline dyebath, at or near boiling point , but a separate aftertreatment such as cationic dye fixing , to enhance wet fastness has been necessary for most direct dyeing .

Direct dyes are used on cotton, paper,leather, wool, silk and nylon. They are also used as pH indicators and as biological stains.

Chemicals Nature of Direct Dyes:

Chemically they are salts of complex sulfonic acids. 

Structure:-More than 75% of all direct dyes are unmetallised azo structures, great majority of them are disazo or polyazo types.

Ionic Nature:-Their ionic nature is anionic. 

Solubility:-They are soluble in water .

Affinity:-They have an affinity for a wide variety of fibers such as cotton ,viscose, silk jute ,linen etc.. They do not make any permanent chemical bond with the cellulosic fibers but are attached to it via very week hydrogen bonding as well as vander waals forces. Their flat shape and their length enable them to lie along-side cellulose fibers and maximize the Van-der-Waals, dipole and hydrogen bonds. 

Types of Direct Dyes:

The SDC classification of direct dyes is follows

(1) Class A – dyes that are self-levelling, i.e. dyes of good migration or leveling properties.

(2) Class B – dyes that are not self-levelling, but which can be controlled by addition of salt to give level results; they are described as salt-controllable.

(3) Class C – dyes that are not self-levelling and which are highly sensitive to salt, the exhaustion of these dyes cannot adequately be controlled by addition of salt alone and they require additional control by temperature; they are described as temperature-controllable.

Application of Direct Dyes

Direct dyes are usually applied with the addition of electrolyte at or near the boil in the machines capable of running at atmospheric pressure .But in HTHP dyeing machines it is carried out at temperatures above the boil in case of pure as well as blended yarns. 

An addition of alkali, usually sodium carbonate, may be made with acid-sensitive direct dyes and with hard water as well as to enhance the dye solubilisation. When cellulose is immersed in a solution of a direct dye it absorbs dye from the solution until equilibrium is attained, and at this stage most of the dye is taken up by the fibre. The rate of absorption and equilibrium exhaustion vary from dye to dye. The substantivity of the dye for cellulose is the proportion of the dye absorbed by the fibre compared with that remaining in the dyebath.

Dyeing Method

The color is pasted well and dissolved in boiling water to get a lump free solution .An addition of 0.5–2 g l–1 sodium carbonate may be advantageous when applying dyes of only moderate solubility in full depths.

• The dyebath is set at 40°C,
• Raise to the boil at 2 degC min–1
• Hold at the boil for 30–45 min, 
• During hold add 10–15 g l–1 of sodium chloride or calcined Glauber’s salt. Light shades are dyed without or lesser addition of salt.
• Improved yields can be achieved when applying full depths by cooling to 80°C at the end of the period at the boil, adding a further 5 g l–1 salt and rising to the boil again
• Dye bath variables which must be considered for level dyeing,

1.Temperature of Dyeing and rate of heating

2.Electrolyte concentration and addition

3.Time

4.Dye solubility

5.Use of leveling agent 

After Treatment of Direct Dyed Material

The wet fastness properties (particularly washing, water and perspiration) of virtually all dyeing of direct dyes are inadequate for many end uses but notable improvements can be brought about by after treatments.

• Diazotisation and development 
• Metal salt treatments 
• Cationic fixing agents 
• Formaldehyde treatment 
• Cross linking agents and resin treatments 

Stripping:- Most direct dyes can be stripped of the use of stripping salts (Sodium Hydrosulphite) and/or by using a chlorine bleaching agent such as sodium hypochlorite, without harmful effects on the fibres.

Color fastness properties of Direct Dyed material: Generally these dyes are used where high wash fastness is not required.

Wash Fastness: Poor unless treated with suitable dye fixing agent and/or fastness improving finishing agent.

Light Fastness:-Good

Rubbing Fastness: Moderate to Good

Chemical Wash Fastness:- Poor

Introduction of Blowroom Section | Objects of Blow-room | BasicOperations in the Blowroom

Blowroom: 

Blowroom consists a number of machines used on succession to open and clean the cotton fibre. Since the tuft size of cotton becomes smaller and smaller, the required intensities of processing necessitates different machine configuration.

Blowroom

Objects of Blow Room: 

1. Opening:

a) To open the compressed bales of fibres.

b) To make the cotton tuft as small as far as possible.

2. Cleaning:

To remove dirt, dust, broken seeds, broken leaves, and other foreign materials from the fibre.

3. Mixing & Blending:

To make good value of yarn and to decrease production cost mixing and blending is done.

4. Lap or flocks formation:

To transfer opened and cleaned fibre into sheet form of definite width and length which is called lap or in modern system directly feed to the carding machine into flocks form.

Basic Operations in the Blowroom:

• opening 
• cleaning 
• mixing or blending 
• microdust removal 
• uniform feed to the carding machine 
• Recycling the waste 

Blow room installations consists of a sequence of different machines to carry out the above said  operations.Moreover Since the tuft size of cotton becomes smaller and smaller, the required intensities of processing necessitates different machine configuration. 

Technological Points in Blowroom 

Opening in blowroom means opening into small flocks.Technological operation of opening means the volume of the flock is increased while the number of fibres remains constant. i.e. the specific density of the material is reduced 

The larger the dirt particle , the better they can be removed . Since almost every blowroom machine can shatter particles, as far as possible a lot of impurities should be eliminated at the start of the process.Opening should be followed immediately by cleaning, if possible in the same machine. 

The higher the degree of opening, the higher the degree of cleaning. A very high cleaning effect is almost always purchased at the cost of a high fibre loss. Higher roller speeds give a better cleaning effect but also more stress on the fibre. 

Cleaning is made more difficult if the impurities of dirty cotton are distributed through a larger quantity of material by mxing with clean cotton.The cleaning efficiency is strongly dependent on the TRASH %. It is also affected by the size of the particle and stickyness of cotton. Therefore cleaning efficiency can be different for different cottons with the same trash %. There is a new concept called CLEANING RESISTANCE. Different cottons have different cleaning resistance.

If cotton is opened well in the opening process, cleaning becomes easier because opened cotton  has more surface area, therefore cleaning is more efficient . If automatic bale opener is used, the tuft size should be as small as possible and the machine stop time should be reduced to the minimum level possible .

If Manual Bale openers are used, the tuft size fed to the feed lattice should be as small as possible .Due to machine harvesting , cotton contains more and more impurities, which furthermore are shattered by hard ginning. Therefore cleaning is always an important basic operation. 

In cleaning, it is necessary to release the adhesion of the impurities to the fibres and to give hte particles an opportunity to separate from the stock. The former is achieved mostly by picking of flocks, the latter is achieved by leading the flocks over a grid. 

Using Inclined spiked lattice for opening cotton in the intial stages is always a better way of opening the cotton with minimum damages. Ofcourse the production is less with such type of machines. 

But one should bear in mind that if material is recyled more in the lattice, neps may increase. Traditional methods use more number of machines to open and clean natural fibres. Mechanical action on fibres causes some deterioration on yarn quality, particularly in terms of neps . Moreover it is true that the staple length of cotton can be significantly shortened . Intensive opening in the initial machines like Bale breaker and blending machines means that shorter overall cleaning lines are adequate. 

In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities accelerated to a high speed, is substantially greater than that of the opened flocks due to the low air resistance of the impurities. The latter are hurled against the grid and because of their small size, pass between the grid bars into the waste box, while the flocks continue around the periphery of the rotating beater. By using a much shorter machine sequence, fibres with better elastic properties and improved spinnability can be produced. 

Air streams are often used in the latest machine sequence, to separate fibres from trash particles by buoyancy differences rather than beating the material against a series of grid bars. There are three types of feeding apparatus in the blowroom opening machines two feed rollers( clamped) feed roller and a feed table a feed roller and pedals 

Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatest clamping distance between the cylinders and the beating element feed roller and pedal arrangement gives secure clamping throughout the width and a small clamping distance, which is very critical for an opening machine In a feed roller and table arrangement, the clamping distance can be made very small. This gives intensive opening, but clamping over the whole width is poor, because the roller presses only on the highest points of the web. 

Thin places in the web can be dragged out of hte web as a clump by the beaters Honeydew(sugar) or stickiness in cotton affect the process very badly. Beacause of that production and quality is affected. Particles stick to metal surfaces, and it gets aggreavated with heat and pressure. These deposits change the surface characteristics which directly affects the quality and running behavior.

There are chemicals which can be sprayed to split up the sugar drops to achieve better distribution.But this system should use water solutions which is not recommended due to various reasons. It is better to control the climate inside the department when sticky cotton is used. Low temperature ( around 22 degree Celsius) and low humidity (45% RH). This requires an expensive air conditioning set up. 

The easiest way to process sticky cotton is to mix with good cotton and to process through two blending machines with 6 and 8 doublings and to install machines which will seggregate a heavier particles by buoyancy differences.

General factors which affect the degree of opening , cleaning and fibre loss are, 

• thickness of the feed web 
• density of the feed web 
• fibre coherence 
• fibre alignment 
• size of the flocks in the feed (flock size may be same but density is different) 
• the type of opening device 
• speed of the opening device 
• degree of penetration 
• type of feed (loose or clamped) 
• distance between feed and opening device 
• type of opening device 
• type of clothing 
• point density of clothing 
• arrangement of pins, needles, teeth 
• speeds of the opening devices 
• throughput speed of material 
• type of grid bars 
• area of the grid surface 
• grid settings 
• airflow through the grid 
• condition of pre-opening 
• quantity of material processed, 
• position of the machine in the machine sequence 
• feeding quantity variation to the beater 
• ambient R.H.% 
• ambient teperature 

Cotton contains very little dust before ginning. Dust is therefore caused by working of the material on the machine. New dust is being created through shattering of impurities and smashing and rubbing of fibres.  However removal of dust is not simple. Dust particles are very light and therefore float with the cotton in the transport stream.Furthermore the particles adhere quite strongly to the fibres. If they are to be eliminated they are to be rubbed off.The main elimination points for adhering dust therefore, are those points in the process at which high fibre/metal friction or high fibre/fibre friction is produced. 

Removal of finest particles of contaminants and fibre fragments can be accomplished by releasing the dust into the air, like by turning the material over, and then removing the dust-contaminated air. Release of dust into the air occurs whereever the raw material is rolled, beaten or thrown about. Accordingly the air at such positions is sucked away. Perforated drums, stationary perforated drums, stationary combs etc. are some instruments used to remove dust.

Process of Cotton Desizing | Oxidative Desizing | Enzymatic Desizing |Acid Desizing

Desizing

Desizing is the process of removing the size material from the warp yarns in woven fabrics. Sizing agents are selected on the basis of type of fabric, environmental friendliness, ease of removal, cost considerations, effluent treatment, etc.

Desizing, irrespective of what the desizing agent is, involves impregnation of the fabric with the desizing agent, allowing the desizing agent to degrade or solubilise the size material, and finally to wash out the degradation products. 

Desizing Process:

The major desizing processes are:

1. Enzymatic desizing of starches on cotton fabrics
2. Oxidative desizing
3. Acid desizing
4. Removal of water soluble sizes

Enzymatic Desizing
Enzymatic desizing is the classical desizing process of degrading starch size on cotton fabrics using enzymes. Enzymes are complex organic, soluble bio-catalysts, formed by living organisms, that catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a particular substance. A small quantity of enzyme is able to decompose a large quantity of the substance it acts upon. Enzymes are usually named by the kind of substance degraded in the reaction it catalyzes. Amylases is the enzyme that hydrolyses and reduces the molecular weight of amylose and amylopectin molecules in starch, rendering it water that is soluble enough to be washed off by the fabric. Effective enzymatic desizing require strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant.

Advantages of Enzymatic Desizing

• No damage to the fibre
• No usage of aggressive chemicals
• Wide variety of application processes, and
• High biodegradability 

Disadvantages Enzymatic Desizing
Lower additional cleaning effect towards other impurities, no effect on certain starches (e.g. tapioca starch) and possible loss of effectiveness through enzyme poisons.

Oxidative Desizing
In oxidative desizing, the risk of damage to the cellulose fiber is very high, and its use for desizing is increasingly rare. Oxidative desizing uses sodium or potassium persulphates or sodium bromite as an oxidizing agent.

Advantages of Oxidative Desizing

• Supplementary cleaning effect
• Effectiveness for tapioca starches
• No loss in effectiveness due to enzyme poisons. 

Some disadvantages of oxidative desizing include possibility of fibre attack, use of aggressive chemicals and less variety of application methods.

Acid Desizing
Cold solutions of dilute sulfuric or hydrochloric acids are used to hydrolyze the starch, however, this has the disadvantage of also affecting the cellulose fiber in cotton fabrics.

Removal of Water-soluble Sizes
Fabrics containing water soluble sizes can be desized by washing using hot water, perhaps containing wetting agents and a mild alkali. The water replaces the size on the outer surface of the fiber, and absorbs within the fiber to remove any size residue.

Introduction of Medical Textiles | Application of Medical Textiles |Requirements of Textile Material for Medical Applications

Introduction of Medical Textile

Medical textiles also known as Healthcare Textiles. Medical Textiles is one of the most rapidly expanding sectors in the technical textile market.It is one of the major growth areas within technical textiles and the use of textile materials for medical and healthcare products ranges from simple gauze or bandage materials to scaffolds for tissue culturing and a large variety of prostheses for permanent body implants. Textile products are omnipresent in the field of human hygiene and medical practice. Their use is based on a number of typical basic textile properties like softness and lightness, flexibility, absorption, filtering etc.

Advanced medical textiles are significantly developing area because of their major expansion in such fields like wound healing and controlled release, bandaging and pressure garments, implantable devices as well as medical devices, and development of new intelligent textile products. Present day society is undergoing changes like large population size, need of increasing his life span of every individual, various situations and hazards of human activity and civilization including transport accidents, chemical materials, fire, cold, diseases, and sports. Such factors increase the demand of medical textiles. So there are several researching works are going on all over the world in medical textile materials and polymers.

Nano-technique has acquired tremendous impulse in the last decade. Nano-fibre based products as well as nano-coated materials are present innovations in the field of medical. So in our technical poster we have gone through latest medical textiles, nano-based products due to following features and wide range of application.

Nanofibres are very attracted due to their unique properties, high surface area to volume ratio, film thinness, nano scale fibre diameter porosity of structure, lighter weight. Nanofibres are porous and the distribution of pore size could be of wide range, so they can be considered as engineered scaffolds with broad application in the field of tissue engineering. Some other applications like wound dressings, bone regeneration and nanofibres to be the carrier of various drugs to the specific sites, etc.

The consumption of Medical Textiles worldwide was 1.5 million tons in 2000 and is growing at an annual rate of 4.6%. The Indian market size of medical textiles was estimated to be INR 14.8 billion in 2003-04 and is expected to grow to INR 23.3 billion by 2007-08. Market is expected to grow by 8% p.a.

The use of textile materials for medical and healthcare products can be classified into following main areas

• Barrier material (for infection control) 
• Bandaging & pressure garment 
• Wound care material  
• Hygiene material 
• Implantable material (sutures, art. Joints etc) 
• Extra Corporal devices (like art. Kidney etc)

Requirements of textile material for medical applications

• Biocompatible
• Good resistance to alkalis, acids and micro-organisms
• Good dimensional stability
• Elasticity Free from contamination or impurities
• Absorption / Repellency
• Air permeability

Medical Textile Products

Hollow polyester fiber, hollow viscose
Application: Artificial kidney
Function: Remove waste products from patient s blood

Hollow viscose
Application: Artificial liver
Function: Separate and dispose of patients’ plasma and supply fresh plasma 

Hollow polypropylene fiber, hollow silicone membrane
Application: Mechanical lung
Function: Remove carbon dioxide from patients’ blood and supply fresh oxygen 

Uses of Medical Textiles
Medical Textiles are the products and constructions used for medical and biological applications and are used primarily for first aid, clinical and -hygienic purposes. It consists of all those textile materials used in health and hygienic applications in both consumer and medical markets.As such it comprises a group of products with considerable variations in terms of product performance and unite value.Because of the nature of their application many medical products are disposable items.The increased use of textiles in composite applications will provide major growth fiber consumption in terms of volume.The

Traditional applications 

 Include wound care products, diapers, braces, protheses and orthoses, wipes, breathing masks, bedding and covers, ropes and belts etc.

Innovative textile products can both add significantly to effectiveness of medical treatments as well as patient comfort At the same time, new medical textiles, may contribute to cost containment. 

Such innovative products:
Provide new treatment options (textile based implants instead of scarce donor organs; artificial tissues, joints and ligaments), Speed up recovery after medical treatment (innovative wound dressings; light, Breathable orthoses/ protheses) . Enhance quality of life of chronically ill people (functional clothing)

Surgeons wear, wound dressings, bandages, artificial ligaments, sutures, artificial liver/kidney/lungs, nappies, sanitary towels, vascular grafts/heart valves, artificial joints/bones, eye contact lenses and artificial cornea and the like are some of the examples of medical textiles.Medical textiles are textile products and constructions for medical applications. They are used for first aid, clinical or hygienic purposes and rehabilitation

Examples of their application include:

• Protective and healthcare textiles
• Dressings, bandages, pressure garments and prosthetics
• Hygiene products
• Antiseptic wound dressings.

Analysis of Diapers Woven Fabric

EXPERIMENT NAME : Analysis of Diapers woven fabric.

OBJECT :
1. For reproduction.
2. To keep clear conception about fabric structure.
3. To make comments on fabric properties.
4. For fabric specification.
5. To help in criminal case by studying fabric structure.
6. To know the raw material of fabrics.
7. To help in custom inspection.

SAMPLE : 

A piece of diaper fabric.

APPARATUS :
1. Counting glass.
2. Needle.
3. Blade.
4. Scissors.
5. Twist tester.
6. Beesley’s balance.
7. Template.
8. Balance & Wt. Box.
Face & Back Side:
As the cloth is constructed with twill fabric construction, face & back side is not same. Face side is smooth and glassy appearance then back side appearance.

Warp & Weft direction: 

Direction of both warp & weft are indicated by arrow mark has been shown in the sample, selvedge direction is always warp direction & warp direction is more straight and parallel. But weft direction is less straight and parallel. No. of yarn in warp direction is more then weft direction.

Thread Density: 

No. of observation	EPI	Avg. EPI	PPI	Avg. PPI
1	45	45	41	41
2	46		40
3	45		41
4	46		41
5	44		40

Thread count:

No. of observation	Warp count	Avg. Warp count	Weft count	Avg. Weft count
1	21	21	21	21
2	21		21
3	20		20
4	21		22
5	19		21

Twist per inch:

No twist in warp direction or weft direction.
Yarn designation:
For warp : 21 Ne
For weft : 21 Ne

Fabric representation: =    ^{Warp count × Weft count}× Fabric width

                                                             EPI × PPI

                                               =  21 × 21 _{×  fabric width}

                                                     ^{45 × 41}

Design of the fabric :
As the given, sample is diaper design fabric. Its design will be 24 X 24 diamond.
 

GSM (gram per Sq. meter) :
Weight of fabric taken from GSM Cutter = 1.3 gm
1 m2 sample’s weight = 130 gm
GSM = 130

Fabric Raw Material : 

Warp : Cotton
Weft : Cotton

Formula number : diaper 24 X 24

Type of loom : jacquard loom..

END USE:
i) In decorated fabric.
ii) In Shirt fabric.
iii) In Table cloth.
iv) In Screens.
v) On ornamented design.
vi) In design fabric.

PRECAUTION:
i) Ends per inch & picks per inch should be determined carefully.
ii) Beasley’s balance for count & balance for G.S.M should be adjusted before determination.
iii) Warp &weft direction, face &back side, drafting plan, weave plan & lifting plan should be done carefully.

CONCLUSION:
Special thanks to our teacher & her assistance for taught us carefully. This experiment is one of the important experiment for a textile technologist .By this experiment we can learn about the different parameters of the diaper fabric. But with those condition we take all the measure as much as accurate.