Textile Information

Suitings - Never out of fashion

noreply@blogger.com (Navnath) — Thu, 18 Jan 2024 11:40:00 +0000

A woolen suit is a type of formal or semi-formal attire typically made from wool fabric. Wool is a natural fiber obtained from the fleece of sheep and is known for its warmth, breathability, and versatility. Woolen suits are popular choices for business, formal events, and cold weather due to the natural insulating properties of wool.

Here are key aspects and features of woolen suits:

Material: Woolen suits are crafted from wool fabric, which can vary in thickness, texture, and quality. Common types of wool used for suits include merino wool, worsted wool, and tweed.
Versatility: Woolen suits come in various styles, making them versatile for different occasions. From classic business suits to more casual options, woolen suits can be tailored to suit a range of dress codes.
Warmth and Insulation: Wool is an excellent insulator, providing warmth in colder temperatures. Woolen suits are ideal for fall and winter, helping to keep the wearer comfortable in chilly weather.
Breathability: Despite its warmth, wool is a breathable fabric, allowing moisture vapor to escape. This makes woolen suits comfortable to wear for extended periods without feeling overly hot.
Durability: Wool is known for its durability and resilience. A well-constructed woolen suit can withstand regular wear and maintain its shape over time.
Wrinkle Resistance: Wool has natural wrinkle-resistant properties, meaning that woolen suits often resist creasing and wrinkles, helping the wearer maintain a polished appearance.
Style Options: Woolen suits come in various styles, including single-breasted and double-breasted jackets, with options for different lapel styles, pocket designs, and trouser cuts. The fabric can also be woven in different patterns, such as herringbone or plaid.
Color Choices: Woolen suits are available in a wide range of colors, allowing individuals to choose traditional and neutral tones for business or more vibrant options for special occasions.
Customization: Tailoring plays a crucial role in the fit and appearance of a woolen suit. Many individuals prefer custom or made-to-measure suits to ensure a precise fit and a personalized style.

Polyester-wool blended suiting combines the advantages of both polyester and wool fibers, creating a fabric that offers a range of benefits. Here are some advantages of polyester-wool blended suiting:

Durability:

Polyester is known for its durability and resistance to wear and tear. Blending polyester with wool enhances the overall strength and longevity of the fabric, making it more durable and less prone to damage.

Wrinkle Resistance:

Polyester has natural wrinkle-resistant properties, and blending it with wool can reduce the likelihood of wrinkles and creases. This makes polyester-wool blends a good choice for those who want a suit that maintains a polished appearance throughout the day.

Affordability:

Polyester is generally more affordable than pure wool. Blending polyester with wool allows for the creation of cost-effective suiting options that still benefit from the positive characteristics of both fibers.

Ease of Care:

Polyester-wool blends are often easier to care for than pure wool. Polyester's resistance to shrinking and stretching can contribute to the fabric's overall ease of maintenance.

Color Retention:

Polyester has excellent color retention properties, and blending it with wool can help maintain the vibrancy of colors in the fabric. This is particularly advantageous for those who want a suit with lasting color appeal.

Moisture Wicking:

Wool is known for its moisture-wicking properties, helping to regulate body temperature and keep the wearer comfortable. Blending polyester with wool can enhance these moisture-wicking capabilities.

Versatility:

The combination of polyester and wool creates a versatile fabric suitable for a range of climates. It provides warmth in cooler weather, and the moisture-wicking properties make it comfortable in various temperature conditions.

Crease Recovery:

Polyester-wool blends often exhibit good crease recovery, meaning that the fabric tends to bounce back to its original shape after being stretched or compressed. This contributes to a neat and well-maintained appearance.

Reduced Allergenicity:

Some individuals may be sensitive or allergic to certain fibers. Blending wool with polyester can reduce potential allergenicity while retaining some of the desirable properties of wool.

Availability of Blends:

The market offers a variety of polyester-wool blends with different ratios of the two fibers. This allows consumers to choose blends that align with specific preferences for comfort, performance, and cost.

Back in Fashion - Woolen Shawls

noreply@blogger.com (Navnath) — Wed, 17 Jan 2024 09:15:00 +0000

Woolen shawls are versatile and popular accessories known for their warmth, comfort, and aesthetic appeal. They come in various styles, patterns, and origins, catering to diverse cultural and fashion preferences. Here's some technical information on woolen shawls:

Origins of Woolen Shawls:
- Pashmina Shawls: Originating from the Kashmir region in India, Pashmina shawls are made from the fine wool of the Pashmina goat. They are known for their softness, warmth, and luxurious feel.
- Cashmere Shawls: Similar to Pashmina, Cashmere shawls come from the wool of Cashmere goats. These goats are found in various regions, including Kashmir, Mongolia, and parts of China.
- Merino Wool Shawls: Merino wool, sourced from Merino sheep, is commonly used to create shawls. Merino wool is known for its fine fibers, softness, and excellent insulating properties.
Styles of Woolen Shawls:
- Jamawar Shawls: Originating from Kashmir, Jamawar shawls are intricately woven with elaborate designs and patterns. They often feature paisley motifs and are considered highly luxurious.
- Kani Shawls: Another type of Kashmiri shawl, Kani shawls are handwoven using a traditional wooden loom. They often showcase vibrant colors and detailed patterns.
- Jacquard Shawls: These shawls are woven using a Jacquard loom, allowing for intricate patterns and designs. Jacquard shawls can incorporate various motifs and textures.
- Embroidered Woolen Shawls: Some shawls feature embroidery, adding decorative elements. Embroidery can be done by hand or machine, and it enhances the visual appeal of the shawl.
Uses of Woolen Shawls:
- Winter Accessories: Woolen shawls are excellent winter accessories, providing warmth and insulation against cold weather. They are often preferred over other materials due to the natural insulating properties of wool.
- Fashion Statements: Shawls, especially those with intricate designs or luxurious materials like Pashmina, are popular as fashion accessories. They add a touch of elegance to various outfits.
- Cultural Significance: In many cultures, woolen shawls hold cultural significance and are worn during ceremonies, weddings, or religious events. They can symbolize tradition and heritage.
- Travel Accessories: Lightweight woolen shawls are convenient for travel. They can be easily folded and carried in a bag, offering comfort during flights or in changing weather conditions.

Sweaters - saviour in winter

noreply@blogger.com (Navnath) — Wed, 17 Jan 2024 06:09:00 +0000

Why Wool:

Natural Insulation: Wool fibers have natural insulating properties, providing warmth in cold weather. The crimp in wool fibers creates small air pockets, trapping heat and maintaining a comfortable temperature.
Moisture Wicking: Wool can absorb moisture vapor and wick it away, keeping the wearer dry and comfortable. It can absorb up to 30% of its weight in moisture without feeling damp.
Breathability: Wool allows the skin to breathe, making it suitable for various weather conditions. It regulates body temperature by releasing excess heat during activity.
Odor Resistance: Wool fibers have natural antibacterial properties, reducing the development of odor.
Biodegradability: Wool is a renewable and biodegradable fiber, making it an environmentally friendly choice.

Benefits of Wool Sweaters Over Other Fibers:

Warmth: Wool provides excellent warmth compared to many synthetic fibers.
Odor Resistance: Wool naturally resists odors, making it a good choice for active wear.
Moisture Management: Wool can absorb and release moisture, keeping the wearer dry.
Durability: Wool fibers are resilient and can withstand repeated use.
Sustainability: Wool is a renewable resource, and many wool production practices are environmentally sustainable.

Color or Dyes Used for sweater:

Natural Colors: Wool is available in a range of natural colors, including white, brown, black, and various shades of gray.
Dyeability: Wool easily takes up dyes, allowing for a wide range of colors and patterns in sweaters.
Eco-Friendly Dyes: With growing environmental awareness, many manufacturers use eco-friendly or low-impact dyes for wool garments.

End Applications:

Winter Wear: Wool sweaters are popular for winter wear due to their excellent insulation properties.
Casual and Formal Wear: Wool sweaters come in various styles, making them suitable for both casual and formal occasions.
Outdoor Activities: Wool is used in activewear due to its moisture-wicking and temperature-regulating properties.
Layering: Wool is often used as a layering material in outdoor activities to provide warmth without adding bulk.
Fashion Garments: Wool is a versatile material, and designers often use it in high-end fashion garments.

Overall, woolen sweaters are favored for their natural properties, comfort, and sustainability, making them a popular choice in the clothing industry.

Acid dyes are commonly used for dyeing wool because wool is a protein-based fiber, and acid dyes bond well with protein fibers. Here are some key points about acid dyes used for dyeing wool:

1. Compatibility with Wool:

Acid dyes are specifically designed to work well with protein fibers like wool. The chemical structure of wool allows it to form strong bonds with acid dye molecules, resulting in vibrant and long-lasting colors.

2. Application Process:

Acid dyes are typically applied in an acidic environment. This is achieved by using an acid such as acetic acid or citric acid during the dyeing process. The acid helps open up the wool fibers, allowing the dye molecules to penetrate and bond.

3. Color Fastness:

Acid dyes are known for their excellent color fastness. They resist fading due to exposure to light, washing, and other environmental factors, making them suitable for durable and long-lasting wool garments.

4. Wide Color Range:

Acid dyes offer a broad spectrum of colors, allowing for a wide range of color options when dyeing wool. This versatility is essential for creating diverse and attractive wool garments.

5. Level Dyeing:

Acid dyes provide good leveling properties, meaning they dye the wool evenly, minimizing the risk of uneven color distribution. This is crucial for achieving consistent and aesthetically pleasing results.

6. Bright and Vibrant Colors:

Acid dyes are known for producing bright and vibrant colors on wool. The dye molecules bond effectively with the wool fibers, resulting in intense and saturated hues.

7. Heat Setting:

After dyeing, wool dyed with acid dyes often requires heat setting to enhance color fastness. This involves subjecting the dyed wool to a controlled heat treatment to ensure the dye molecules are properly set and won't bleed or fade easily.

8. Environmental Considerations:

While acid dyes themselves may contain synthetic components, advancements have been made to develop more environmentally friendly versions. Some acid dyes now come in formulations that reduce environmental impact, but it's essential to check specific products for eco-friendly characteristics.

Woolen Scarf

noreply@blogger.com (Navnath) — Mon, 15 Jan 2024 11:48:00 +0000

Woolen scarves come in various types, and their characteristics depend on the type of wool used, the weaving or knitting technique, and additional treatments or processes applied. Here are some key technical aspects to consider:

Wool Type:
- Merino Wool: Known for its softness and fine fibers, merino wool is a popular choice for scarves. It is moisture-wicking, breathable, and has natural insulating properties.
- Lambswool: Derived from the first shearing of lambs, lambswool is soft and lightweight, making it suitable for scarves.
Weaving or Knitting Technique:
- Plain Weave: The simplest weaving technique, creating a balanced and durable fabric.
- Twill Weave: Diagonal patterns that add texture and flexibility to the scarf.
- Herringbone: Zigzag pattern that resembles the skeleton of a fish, providing an interesting visual appeal.
- Ribbed Knit: Vertical lines of raised stitches, creating a stretchy and textured surface.
Blend and Combinations:
- Wool Blends: Scarves may include a combination of wool with other fibers like silk, acrylic, or nylon. Blends can enhance durability, softness, or specific performance characteristics.
- Cashmere Blend: Combining wool with cashmere adds a luxurious touch, increasing softness and warmth.
Finishing and Treatments:
- Brushed Finish: Creates a softer surface by brushing the fibers, resulting in a fluffier texture.
- Fringes: The ends of a scarf may have fringes, adding a decorative element.
- Dyeing Techniques: Scarves can be dyed using various techniques, such as solid colors, ombre, or patterns.
Gauge (Knit Scarves):
- Gauge refer
  s to the number of stitches and rows per inch. A lower gauge typically results in a thicker and warmer scarf, while a higher gauge creates a lighter and more breathable fabric.
Weight:
- Lightweight Scarves: Suitable for milder climates or as fashion accessories.
- Heavyweight Scarves: Provide extra warmth and insulation, ideal for colder weather.
Texture and Pattern:
- Cable Knit: Features intertwining stitches, creating a pattern resembling cables.
- Fair Isle or Jacquard: Intricate patterns and designs created by alternating colors in the knitting process.

Wool Fiber

noreply@blogger.com (Navnath) — Wed, 20 Dec 2023 10:15:00 +0000

Wool Fiber:

1. Source and Types of Wool Fiber:

Source: Wool is primarily obtained from the fleece of sheep, but it can also come from other animals such as goats (cashmere and mohair), rabbits (angora), and certain camelids.
Types: Common types of wool include Merino, Shetland, Lambswool, and Mohair.

2. Chemical Structure of Wool Fiber:

Wool is composed of protein fibers, primarily keratin. The basic chemical structure is a complex protein polymer with amino acid chains.

3. Physical and Chemical Properties of Wool Fiber:

Physical Properties: Soft, resilient, elastic, breathable, and excellent insulator.
Chemical Properties: Reactive to acids, sensitive to alkalis, susceptible to moth damage.

4. Process from Wool Fiber to Wool Fabric:

Shearing: Wool is sheared from animals.
Sorting and Grading: Sorting by quality.
Scouring: Cleaning to remove impurities.
Carding: Aligning fibers for spinning.
Spinning: Creating yarn.
Weaving or Knitting: Formation of fabric.

This post contains affiliate links. If you make a purchase through these links, I may earn a small commission at no additional cost to you.

5. Process for Wool Bleaching:

Scouring: Removes impurities.
Bleaching: Uses chemicals to lighten color.
Rinsing: Removes residual bleach.

6. Wool Dyeing:

Skein Dyeing, Piece Dyeing, or Top Dyeing: Methods to apply color.
Natural and Synthetic Dyes: Used to achieve desired shades.

7. Advantages of Wool Over Other Natural Fibers:

Insulation: Excellent thermal properties.
Absorbency: Can absorb moisture without feeling damp.
Durability: Resilient and resistant to wrinkles.
Renewability: Sustainable and biodegradable.

8. Final End Products Using Wool Fiber:

Apparel: Sweaters, suits, scarves, socks.
Home Textiles: Blankets, carpets, upholstery.
Accessories: Hats, gloves, and more.

Wool's versatility makes it suitable for a wide range of products, blending comfort, warmth, and style.

Trevira Moisture Control: The Fibre For A New Generation Of Fabrics

noreply@blogger.com (Navnath) — Fri, 03 Aug 2012 15:43:00 +0000

Climate catastrophes have caused shortfalls in the supply of natural fibres, there have been increasing difficulties in the wool market, and there is a growing global focus on sustainability. These factors have brought man-made fibres more into the foreground again – and mainly polyester. The fibre manufacturer Trevira is meeting this trend with a new fibre for high quality clothing, one that shows great potential in terms of innovation, coupled with supreme comfort for the wearer, and it is recyclable.

The new fibre is called Trevira Moisture Control and supplies these requirements. Fabrics made from it have the proven characteristics of Trevira apparel textiles, including very good pilling properties, excellent fastness to colour, resilience and easy care qualities. In addition, they offer an improved semi-dull appearance, firstclass soft handle, and optimal moisture management, above all in 100% Trevira qualities.

Research at the Hohenstein Institutes has demonstrated in terms of appearance and comfort that in every respect a suit in 100% Trevira Moisture Control matches a classic business suit in 100 % wool. Made from the new fibres, the Trevira suit impresses with its elegant, high quality looks, its very good wear properties and its standard of comfort, assessed by Hohenstein as “very good”. Traditional synthetics offer no comparison with these materials, which herald a new generation of fabrics.

Wear trials conducted at airlines have shown that a uniform in 100% Trevira Moisture Control guarantees the wearer an optimal feel good effect, accompanied by high standards of resilience. The fibre profile has a special dual channel system that accelerates transport of condensation molecules given off from the skin, from inner to outer layer. Moisture conducted onto the textile surface is quickly dispersed there and evaporates rapidly. In this way the inner side of the textile touching the skin stays drier, preventing an unpleasant chill effect.

Textiles containing the new fibres are ideal for use in corporate wear, business clothing or sportswear. Trevira Moisture Control may be used 100 % or in blends with wool.

Trevira Moisture Control – properties at a glance

Very good moisture management
Rapid dispersion and evaporation of moisture
Quick drying
Good pilling characteristics
Easy care
Washable with good fastness standards
Pleasant handle
Good electro-static properties
Resistant to UV light and chlorine

SOURCE: Trevira

ENERGY CONSERVATION IN WET PROCESSING

noreply@blogger.com (Navnath) — Sun, 12 Feb 2012 21:22:00 +0000

(a) ENERGY CONSERVATION IN SIZING

Foam sizing : in this method foam is used for sizing. Hence considerably less water is required as compared to the conventional sizing. This results is saving in energy and time for evaporation of size.

High pressure squeezing during sizing : this saves the energy as well as the water. after sizing material is squeezed at high pressure to remove maximum water from it. Because of this energy required for drying the material is saved.

Simultaneous dyeing and sizing: for denim warp yarns by using rapiodogen dyes and stabilizer with sizing formulation sizing and dyeing can be carried out simultaneously. This saves energy and water.

B) ENERGY CONSERVATION IN BLEACHING

Fast bleaching with VAPORLOC machine

Mather and platt developed this machine. In this machine, bleaching can be carried out in 90 to 120 seconds at a temperature of 135 degree C. and pressure 30-psi. for this process hydrogen peroxide, stabilizers and suitable alkali is used. 50% energy can be saved with this process.

Novel method : this is a combined desizing scouring and bleaching of polyster/cotton blend. This is carried out is which using material to liquors ratio1:25. the liquor consists of hydrogen peroxide(35%w/v) magnesium sulphate heptahydrate (1.6gpl) sodium hydroxide(4gpl) wetting agent (0.5gpl) EDTA(2gpl) and gluconic acide (2gpl) at 95 degree C for one hour. The washing is giving at 95 degree C.

Potassium permanganate method : cotton goods can be bleached with potassium permanganate. This saves energy and water. It also gives eco-friendly effluent.

Cold pad-batch method : in this method peroxide bisulfate used as a bleaching agent. The bath also contains some compounds which accelerate the bleaching reaction like urea glucose sodium citrate methyl carbonate tetra acetyl ethylene diamine etc.

DSB process: in this process desizing scouring and bleaching takes place in a single stage. The bath contains hydrogen peroxide peroxygen booster sodium silicate peroxide sulphates etc. to this some compounds like urea glucose which accelerate the peroxide reaction are added. This process saves energy water and labor.

C) ENERGY CONSERVATION IN MERCERISATION

It is the process in which the material is treated with concentrated sodium hydroxide solution indeally at at 15 to 20 degree C. this gives luster to the material and the absorptivity of the material is increased considerably.

In mercerization process saving in energy can be done if the process is carried out on wet-on-wet basis I e the in between drying process is eliminated which saves the energy.

Hot mercerization can be done so that scouring is eliminated at 70*c so without doing separate scouring process yarn or fabric is directly subjected to hot mercerization.

Caustic recovery : for the caustic recovery maximum washing is given to the fabric. Temperature of the washing water is maintained at 90*c and suction is provided. All this results in 80 to 85% of the caustic recovery.

D) ENERGY CONSERVATION IN DYEING

Cost savings and quality improvement in dye house can be dine by some process modifications and suitable replacement of processing machines.

Some of these processes are given bellow.

Energy saving by padding mangle

Cost savings and quality improvement in dye house can be done by some process modifications and suitable replacement of processing machines.

Some of these processes are given bellow.

Energy saving by padding mangle

Padding mangle mainly used for two purposes 1) to impregnate any processing solution in fabric 2) to remove excess amount of processing liquor from the fabric by squeezing. Kusters mangle is a modified from which has uniform expression percentage with low wet pick-up. Expression percentage can be changed by changing speed and pressure. On this machine uniform and accurate results are obtained with the saving in energy.

Pad-jig method

This method can be used for dyeing with vat reactive azoic dyes with this method. Dyeing quality is improved with respect to levelness and solidity of shades. Dye penetration is also good. In this power & steam required is less.

Colour

noreply@blogger.com (Navnath) — Fri, 03 Jun 2011 15:30:00 +0000

Colour attributes

Each colour has its own distinct appearance, based on three elements: hue, chroma and value (lightness). By describing a colour using these three attributes, you can accurately identify a particular colour and distinguish it from any other.

Hue : Hue indicates a particular colour sensation which is dependent simply on the relevant wavelength; the inherent colour of a thing; the purest or brightest form of a colour having no white or black mixed with it. Quite simply, hue is how we perceive an object’s colour — red, orange, green, blue, etc. Each hue has an intrinsic tonal value on the chromatic scale.

Chroma: Chroma is the extent of a colour’s brightness or saturation; the purity of a colour, in other words, how close the colour is to either gray or the pure hue. For example, think of the appearance of a tomato and a radish. The red of the tomato is vivid, while the radish appears duller.

Lightness: Lightness is the luminous intensity of a colour. It is that attribute of a colour which indicates the extent of the light which it reflects. Colours can be classified as light or dark when comparing their value.

Spandex

noreply@blogger.com (Navnath) — Sun, 11 Jul 2010 07:36:00 +0000

Spandex, Lycra or elastane is a synthetic fibre known for its exceptional elasticity. It is made up of a long chain polymer called polyurethane, which is produced by reacting a polyester with a diisocyanate. Spandex gained interest quickly due to it’s superiority to the strength in durability of rubber. Spandex also has a better resistance to dry heat & oil, in comparison to rubber. The level of comfort and wicking ability found in Spandex are unparalleled, and do not exist in such high amount with any other fabric. Spandex is being used in a continually widening array of clothing articles, including woven and knits, and synthetics and natural fibers.

PHYSICAL PROPERTIES:-

1. Cross section- spandex filaments are extruded usually from circular orifices, but the evaporation of solvent or the effects of drying may produce non-circular cross-sectional shapes. This may take various forms. In the multi-filament yarns, individual filaments are often fused together in places. The number of filaments in a yarn may be as few as 12 or as many as 50;the linear density of filaments ranges from 0.1 to 3 tex (g/km).

2. Density: The density of spandex filaments ranges from 1.15 to 1.32 g/cc, the fibres lower density being based on polyesters.

3. Moisture regain: The moisture of fibres from which the surface finish has been removed lies between 0.8 & 1.2%

4.Length:It can be of any length. May be used as filament or staple fibre

5.Colour: It has white or nearly white colour.

6. Luster :-It has usually dull luster.

7.Strength: Low strength compared to most other synthetic fiber.

8.Elasticity: Elastic properties are excellent. This is the outstanding characteristic of the fibre.

9.Heat: The heat resistance varies considerably amongst the different degrades over 300 F.

10:Flammability:It Burn slowly.

11:Electrical conductivity: It has Low electrical conductivity.

12. Breaking tenacity: 0.6 to 0.9grams/denier.

CHEMICAL PROPERTIES.

1. Acid: Good resistance to most of acids unless exposure is over 24 hours.

2.Alkalies: Good resistance to most of the alkalies, but some types of alkalies may damage the fibre.

3.Organic solvents: offer resistance to dry cleaning solvents.

4.Bleaches: can be degreaded by sodium hypochloride. chlorine bleach should not be used.

5.Dyeing: A full range of coloures is available. Some types are more difficult to dye than others.

Optical Brightening Agents

noreply@blogger.com (Navnath) — Sat, 08 May 2010 10:05:00 +0000

Certain organic compounds can absorb shorter wave-length ultra-violet light and re-emit it at longer wave-lengths in visible spectrum. Therefore a surface containing a fluorescent compound can emit more than the total amount of daylight that falls on it, giving an intensely brilliant white. Compounds that possess these properties are called Optical Brightening Agents or OBA's. The effect is only operative when the incident light has a significant proportion of ultraviolet rays such as sunlight. When OBA treated fabric is exposed to UV, it glows in the dark.

OBA is not a substitute for bleaching. It is used to obtain brilliant market whites. These "white" whites can be obtained without over bleaching and damaging the fibre. On cellulose, it has poor wash fastness but most commercial laundry detergents contain OBA's so they are constantly replenished.

Polyester History

noreply@blogger.com (Navnath) — Mon, 19 Apr 2010 23:29:00 +0000

Polyesters have been known from time immemorial. Even in antiquity man knew & used natural polyesters, known up to the present time more often as resins, such as dammar gum, shellac, yacca gum, copal, amber etc. These products find use even at the present day .

A long known form of polyesters is represented by widely used coatings, which various vegetable oils (linseed, tung etc.) form on drying in the air. However, the real blossoming of the chemistry & technology of polyesters is closely bound up with the development of methods for the production and synthesis of an enormous number of synthetic polymers, which represent a group of high molecular weight compounds. The first member of which was synthesized as long as 1833.

The first introductions for the synthesis of polyesters from hydroacids are due to Gay-Lussac & Palouze , who obtained a solid polymer on heating lactic acid. In 1861, Heintz obtained a polymer from glycolic acid by heating it to 240°C, subsequently, the preparation of polyglycollide was studied by Menshutkin , Dessaignes , Kelcule , Anschutz , Bischoff and Walden and others. Sokolov obtained three-dimensional polyester by polycondensation of glyceric acid.

Polyesters of polybasic acids & polyhydric alcohols was first synthesized by Berzelius , who reported in 1847 that on heating glycerol and tartaric acid a non-crystalline pliable mass was formed which on the heated state could be drawn into long filaments. Similar reaction was carried out by Berthelot between glycerol and sebacic and camphoric acids, and by van Bemmelen between glycerol and succinic & citric acid, Smith investigated reaction between glycerol and phthalic anhydride in 1901.

The first report on the preparation of polyesters by the polymerization of cyclic esters is due to Bischoff and Walden8 who converted cyclic ester glycollide into the polymer polycollide under influence of heat as well as in presence of traces of zinc chloride.

Menshutkin in 1881 was the first to apply kinetic methods to the investigation of the polyesterification reaction. He studied the esterification of ethylene glycol by succinic acid. In 1882, he determined the limiting degree of esterification of glycolic, lactic and dimethgycollic acids.

A particularly pronounced development in the investigation of synthetic polyesters occurred after 1925, when the work of Tilicheyev , Maksorov , Carothers , Kienel and others led to the synthesis of a series of new compounds of this type, they also demonstrated the possibility of the wide practical application of the polyesters in the industry.

Carothers and his coworkers pioneered the work on synthetic fibres. They first produced spinnable polyester of high molecular weight by condensing ,-diols with alkanedioic acid. Carothers and Hill jointly succeeded in carrying out the polycondensatoin as part of molecular distillation or simply by passing nitrogen through the condensation melt until a fibre forming polyester resulted.

In the early 1940’s the Calico Printer Association Ltd. began to study the effect of molecular symmetry on the condensation polymers. Schlack , in Germany and Whinfield and Dickson , in Great Briton used dicarboxylic acids for the production of polyester fibres almost at the same time. While Schlack used terephthalic acid and 1,4-butandiol, Whinfield and Dickson used combination of terephthalic acid and ethylene glycol.

Fibre forming aliphatic polyesters was produced in the early 1930s, but these products had low melting points and were unsuitable for commercial use17. Laboratory scale quantities of polyethylene terephthalate were prepared by 1941 in Britain. E. I. du Pont de Nemours Co. Inc . acquired US patent rights for PET in 1948, and Imperial Chemical Industries (ICI) of the UK obtained patent rights for the rest of the world. The World War II considerably retarded any further developments so that large-scale production of polyester fibres in different countries was not started until the 1950’s. In Britain the manufacture of polyethylene terephthalate fibres began on a pilot scale in 1948. The fibre being marketed as Terylene. Since then the production of Terylene was extended rapidly.

Polyester fibres became available commercially in the United States in 1953, and production expanded enormously in 1960s and 1970s. At Wilton, in Yorkshire, ICI started a large plant with annual capacity of 11 million lbs. divided equally between filament yarn and staple. In 956, a second unit of similar capacity began production and a new Terylene plant in Northern Ireland followed this .

Non linear optics Dyes

noreply@blogger.com (Navnath) — Wed, 07 Apr 2010 21:28:00 +0000

Non linear optics is concerned with the interaction of electromagnetic radiation with various media to produce new radiations which is altered in phase, frequency, amplitude, etc, from the incident radiation. The rapid growth of laser technology coupled with telecommunications, industry’s need for sophisticated optical switching devices required for data transmission in this computer age has prompted an enormous interest in non linear optical materials. Organic colorants are best understood as pi electron organic molecules with conjugated donor and functional groups. Non linear optical processes in pi electron organic and polymeric systems have attracted considerable interest because their understanding has led not only to compelling technological promise but also to new phenomenon, new theoretical insights and new materials and devices. The pi electron systems are invariably excited by electromagnetic reactions and this is so with organic colorants which invariably interact with the visible portions of the electromagnetic radiations. Such pi electron excitations occurring on the individual molecules, or polymer chain units are the basic origin of the observed non resonant nonlinear optical coefficients which are often usually large. The coefficients are often broad band and ultra fast. The frequency dependence of these coefficients is determined by many body electron correlations effects. New challenges in non liner optics (NLO) materials are being presented, resulting in new methods of ultra structure synthesis and the discovery of entirely new materials and high performance compositions exhibiting high thermal, mechanical and chemical stability. NLO materials are of widespread interest for optoelectronic applications such as electro-optic wave guiding, frequency modulation or optical information processing. We synthesize and study organic dyes, oligomers and polymers with NLO properties.

NLO properties are characterized by molecular hyperpolarizabilities, the second order terms of which can be measured by EFISH (electric field induced second harmonic generation) experiments. We use a recently developed setup which allows EFISH experiments on solutions of non absorbing as well as of absorbing compounds. The molecular origin of optical nonlinearity is due to the electrical polarization of a molecule as it interacts with electromagnetic radiation. These interactions may change the frequency, phase, polarization or path of incident light. Dyes are predisposed for NLO applications because the mobile electrons that are responsible for the absorption of visible light also bring along the polarizability of the molecules, which is necessary for SHG. When it comes to practical applications of compounds with nonlinear optical properties, a major synthetic challenge is to construct non centrosymmetric molecular systems with suitable processability. Amorphous polymers with covalently attached chromophores can meet this goal.

Background

The origin of second order non linear optical effects in organic molecules is traced to the presence of strong donor acceptor interactions. In 1970, davydov and his co-workers reported a strong second harmonic generation (SHG) in organic molecules having electron donor and acceptor groups connected with benzene ring. This discovery led to an entirely new and useful concept of molecular engineering to synthesize new organic materials for the SHG studies. From 1980 onwards tremendous growth occurred in design and development of organic materials for second order non liner optics.

Non liner optics

It is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the dielectric polarization “P” responds nonlinearly to the electric field ‘E’ of the light. This nonlinearity is typically only observed at very high light intensities such as those provided by pulsed lasers. Nonlinear optics gives rise to a host of optical phenomena.

Dyes used of NLO

Organic dyes appropriate for the polymers include those having

1. At least one hydrosilation reactive carbon -carbon double bond.

2. Absorption maxima between 300-2000nm or more particularly between 300-700nm and extinction coefficients at the absorption maxima greater that about 2X103 L/mol cm

Two or more organic dyes can be used in combination. Preferred moieties for providing hydrosilation reactive carbon -carbon double bonds are pendant alkenyl chains particularly those where the carbon -carbon unsaturated bond is in the terminal position and strained endocyclic bicycloalkenyl groups, because these carbon -carbon double bonds are highly reactive for hydrosilation. Suitable such alkenyl chains are the vinyl, allyl, and 3-butenyl groups appropriate strained endocyclic bicycloalkenyl moieties. Particularly suitable dyes are those including

• And electron donor group

• An electron acceptor group

• A delocalized pi electron system linking these two groups especially where the combination of these groups exhibits and NLO response.

The absorption band of an organic colorant can be tailored by

• Either increasing the pi conjugation length

• Or by substituting donor acceptor groups to a conjugated system

As a result the absorption characteristics of the uv visible spectrum can be shifted and will have either bathochromic (red shift) or hypsochromic shift (blue shift).

Finishing with UV absorbers

noreply@blogger.com (Navnath) — Sat, 02 Jan 2010 19:37:00 +0000

UV absorbers include all organic and inorganic compounds which preferentially absorb UV radiation. These compounds have negligible absorption in the visible region and consequently a high light fastness. UV absorbers have to be distributed mono-molecularly in the substrate for maximum effect. Besides, they should meet other criteria such as :

absorb effectively throughout the UV region (280-400nm)

be UV stable itself

dissipate the absorbed energy in such a way so as to cause no degradation or colour change in the medium it protects.

UV absorbers act on the substrate by several ways - by converting electronic excitation energy into thermal energy via a fast, reversible intramolecular proton transfer reaction; functioning as radical scavengers; and, functioning as singlet oxygen quenchers

Chemistry of UV absorbers

All organic UV absorbers applied industrially to textile materials in wet processing are derivatives of one of the three different structures given below :

a) o-hydroxybenzophenone

b) o-hydroxyphenylbenzotriazole

c) o-hydroxyphenyltriazine

Of the inorganic substances with UV absorbing characteristics, titanium dioxide deserves special mention

For all common fibres except acrylics, UV absorbers are now available that are like colourless dyes and are applicable with dyes by most of the usual methods. Separate application procedure is not needed. Care is needed only when they are applied with fluorescent whitening agents (FWAs)

Non reactive UV absorbers based on oxalic anilides, triazine or triazol compounds, salicylic acid esters, substituted acrylonitrile or nitrilo-hydrazones, emulsifying agents, water and polysiloxanes have also been reported

Nomenclature of dyes:

noreply@blogger.com (Navnath) — Fri, 01 Jan 2010 05:10:00 +0000

Certain letters appear after the words indicative of the color of the dye. These represent the tone of the dye and also the intensity of the tone. This G indicates GELB= yellowish tone, R indicates ROT= reddish tone, and B indicates BLEU=bluish tone. Alkali fast Green 3B is a green acid dye with considerable bluish tone. (This is indicated by the suffix 3B.)

In case of Vat dyes the names would appear as Indanthrene Yellow RK, here R indicates ROT= reddish tone and K indicates that the dye is of IK class. If the letter N appears instead of K then it indicates that the dye is of IN class.

In case of reactive dyes the letter C indicates that the dye is cold brand dye. H indicates the dyes are hot brand dye.

Suffix or addition	Meaning	Example	Class of the dye (if specific)
G, R, B	Gelb=yellowish, Rot=reddish, Bleu=bluish tone indication	Cloth red G, red dye with yellowish tint	------
2G, 3G etc	Indicates the increasing tone	Indanthrene yellow 4GK, and IY 5GK	------
L	Indicates that the dye is fast to light	Basacryl yellow 7GL	------
C, H	Cold brand dye, Hot brand dye	Premative C, Procion H	Reactive dyes
HE ME etc	High exhaustion, medium exhaustion etc		Reactive
HE ME etc	High energy etc		Disperse

Natural dyes classified on the basis chemical nature of colouring matter

noreply@blogger.com (Navnath) — Thu, 31 Dec 2009 07:32:00 +0000

Natural dyes can be classified on the basis chemical nature of colouring matter:-

Flavones:-
The yellow colours are derivatives of hydroxy and methoxy substituted flavones or isoflavones. Eg: - jackfruit bark

Indigoid:
The dyestuff is extracted from Indigofera tinctoria, a bush of the pea family. The dye is extracted from the leaves of the plant.

Dihydropyrane :-
These are principal colouring matters of logwood and they give dark shades on cotton, silk, and wool.

Anthraquinone:
Some of the most important red dyes are based on the anthroquinone structure. These are obtained from both plants and insects. These dyes have good fastness to light. They form complexes with metal salts and the resultant metal–complex dyes have good fastness.eg. Manjitha

Anthocyanidins: -
This class includes carajurin, obtained from the leaves of Bignonia chica and Awabanin. It dyes silk in blue shades eg. Beet Root

Carotenoid :-
This class includes the orange pigment carotene found in carrots. The dyes based on carotenoid structure are annatto and saffron.

Alpha-hydroxy naphthoquinones:-
The Lawsone or Henna is the most prominent member of this class. It is obtained from the leaves of Lawsonia inermis. Another similar dye is Juglone obtained from the shell of unripe walnuts.

Author : Supriya Sagar Kanzarkar (SGGS I.E & T, Nanded)

carrier dyeing of polyester fabrics

noreply@blogger.com (Navnath) — Fri, 18 Dec 2009 13:37:00 +0000

The dyeing of polyester fabric using disperse dyes can be carried out by four methods
Carrier dyeing method

* High temperature dyeing method
* Thermosol dyeing method
* Solvent dyeing
Carrier dying
Certain hydrocarbons, amino acids, amides, alcohols, phenols, and esters accelerate the rate of dyeing of polyester fibres with the disperse dyes from aqueous medium at temperature of up to 100C. the dyeing assistants alter the dispersing properties of the dyes and the physical properties of the fibre so that more of the dye transfers from the dye bath liquor to the fibre substrate. These additives are called as carriers, which swells the fibre and ultimately cause relaxation. They reducing intermolecular forces operating in the fibre and act as molecular lubricants thereby allows the dye molecule to force itself inside the fibre. The carrier that are used are also called swelling agents for the polyester fibre.

Typical dyeing procedure with carriers is as follows
The dye bath is set at 60C temperature and with pH 4-5. Fabric material is run for 10 min and aqueous dispersion of dye along with carrier (3-5 gpl) is added in two stages with a gap of 15 min. Carrier is dispersed in water at least for 30 min before use to avoid insoluble particle of carrier, which may cause a carrier mark in the fabric. dyeing is continued for about 60-90 mins. Other auxiliaries such as dispersing agent 0.5to 1 mg per lit. is also added to ensure good dispersion throughout the dyeing.

Disadvantages of carrier dyeing
1. Centre selvage variation may occur
2. Carrier mark problem
3. Tailing effect
4. This method is suitable only for light and medium depths
5. Complete removal of residual carrier is difficult
6. Most of carriers are toxic, gives unpleasant smell to fabric
7. Dyeing process takes more time as compare to other methods
8. It may turn out to be costly process due to high prices of carrier themselves.

Industrial application of textile fibres

noreply@blogger.com (Navnath) — Wed, 02 Dec 2009 12:33:00 +0000

Technological developments have broadened the scope of applications of the textile fibres. High performance Textiles are gaining importance day by day due to their versatile applications in endless areas. The advent of areas like Geo – Textiles, Industry, and Building – construction, Medical field, Automotives, Agriculture, Sports, Clothing, and Packaging have widened the reign of textile fibres-The Emperors of Industry.
The world production of textile fibers has risen to 57.7 million tons in the year 2000. This corresponds to per capita consumption of 9.5 kg/year. A production volume of 77 million tons has been predicted for the year 20101. Technical textiles are generally recognized to be one of the most dynamic and promising areas for the future of textile industry. They are mostly defined as the textile materials and products manufactured primarily for their technical performance and final properties rather than their aesthetic or decorative characteristics.
The application of high performance textiles is increasing drastically because of their versatile properties. The necessary properties engineered into these fibers include those of antibacterial, deodorant, temperature control, elasticity, absorbency, and sensitivity to light and heat. This paper focuses on some of the important high performance and unconventional textiles, which finds specialized uses in the present scenario 2, 12 The tensile strength of the textile fibres is the most important for their industrial applications. The strength characteristics of the textile fibres can be improved by various developments in the manufacturing processes and the processing stages, e. g. The breaking length of the Aramid fibre was 190 Km in 1990, but it was improved to 223 Km in 1996. This is possible because of continuous research and developments in the field of manufactured fibres. The lightweight construction potential of fibres for the reinforcement of plastics is shown in Fig: 1 Fig. 1. The lightweight construction potential of fibres for the reinforcement of plastics
Some of the most widely used high performance textile fibres have been discussed below in brief:

Aramid:

The most important property of these industrial purpose fibers is their resistance to the actions of various chemical agents. They are distinguished by their good resistance to dilute acids and bases, while better chemical resistance is seen in Kevlar fibers. The common drawback of the aramid fibers is their low resistance, which is caused by absorption of ultraviolet radiation. Amongst aramid poly (p -phenylene terephthalamide) is the most successful high performance fiber. They are particularly used in reinforcement of radial tires both in the belt where the modulus contributes to tire performance and is the characteristics where the strength contributes to the durability. The tire system should have impact and fatigue resistance, durability and high-speed performance.
The necessary reinforcing fiber properties are high strength and modulus strength retention after fatigue and adhesion to rubber 3. They are used in filter bags for hot state gases, press cloths for industrial presses (e.g.: application of permanent press finishes to cotton and cotton/polyester garments) and insulation papers for electrical motors and transformers.
P-aramid fiber excels in these applications as compared to steel because in order to impart same strength as that of aramids, steel has to be 3-4 times heavier than the corresponding fiber. The combined attributes of low density, high strength, and stiffness of Kevlar fiber has led to numerous current aerospace composite uses, including exterior structure of aircraft and helicopters, interior aircraft structure, missile and space application.

Pre-Treatment of Cellulosic Textiles

noreply@blogger.com (Navnath) — Sun, 28 Jun 2009 07:40:00 +0000

Textile fabrics, either in yarn form or fabric form or hank form, are subjected to different processing procedures depending on its textile end use. The grey cloth is chemically and mechanically processed to give a marketable finish. The sequence of the preparatory process depends on the machinery available, the ease of the availability of water, the type of fabric and the composition of the blend.

A good preparatory process has several objectives, which are given as follows:
a) Removal of loose hairy protruding fibres from the surface of the fabric to give a smooth, even and clean looking face.
b) Removal of natural impurities like oils, fats, waxes, greases, natural matter, lignin and sizing material like starches.
c) To obtain an absorbent fabric, which is ready for dyeing or printing process.
d) To obtain softer and proper white fabric, depending on its application.5

Desizing:
A sized warp is a weaver’s necessity, but a great drawback for the processing department. Warp sized removability depends on the film forming size. Size mainly consists of starch, wax and tallow. All these remain on the warp yarns after weaving the cloth. The process of removal of starch sized from the cloth is known as desizing.

Factors affecting desizing:

1. Concentration of desizing agent.
2. Resolution of size.
3. Alkaline and acidic condition
4. Mechanical properties

Mechanism of desizing:
Chemically, starch is a poly-ά- glucopyranose containing straight chain (amylase) and branch chain (amylopectin) water insoluble polymers. The breaking of these long chain compounds to a shorter one is due to hydrolysis or due to oxidative degradation.

Desizing methods:
1. Hydrolytic method of desizing
2. Oxidative method of desizing

Hydrolytic desizing, which is most prefered over the Oxidative desizing, again classified into three methods. These are
1. Rot steep
2. Acid steep
3. Enzymatic desizing

Rot steep: This is the least expensive and oldest method of desizing in which no special chemicals are added. Here starch-sized fabric is passed through a padding mangle and saturated with water at 400 C to give 100% pick up. Then the fabric is allowed to remain for 24 hours, during which starch becomes solubilised in water because of fermentation.

Limitations:
1. This method does not yield uniform results.
2. It requires large floor space area and longer duration of time.

Acid steep: Dilute sulphuric or hydrochloric acid may also be used to hydrolyse the starch from the sized fabric. A 0.25 % (w/v) solution of the acid at room temperature (300 C) is sufficient for the purpose. By using acid solution, the duration of the desizing process may be reduced to 8-12 hours.

Limitations:
1. Local evaporation of water during the storage period may cause hydrolysis of cellulose itself leading to weakening of cotton at the places where evaporation has taken place.
2. This method does not yield uniform results.

Enzymatic Desizing
Enzymatic desizing is a more advanced method for removing the starch. Enzymes are complex, protienaceous substances, which are secreted by the cells of the living organisms and they have a very good water solubility. Three principal types of starch splitting enzymes used for desizing are ά-amylase,ß-amylases and amido glucosidase The origin of these enzymes also plays an important role in the activity of enzymes. These enzymes are highly specific and work at different specific temperature and pH.

Natural dyes

noreply@blogger.com (Navnath) — Sat, 20 Jun 2009 14:32:00 +0000

Natural dyes comprise those colourants that are obtained form animal or vegitable matter without chemical processing. Natural dyes are generally non-substantive and hence must be used in conjunction with mordants.

CLASSIFICATION OF NATURAL DYES: -

Based on chemical structure:
Indigoids: -
The dyestuff is extracted from Indigofera tinctoria, a bush of the pea family. The dye is extracted from the leaves of the plant.
Anthraquinones: -
Red dyes are based on anthraquinone structure. These dyes are characterized by good fastness to light.
Alpha napthaquinones: -
Lawsone or Henna is the most prominent member of this class. It is obtained from the leaves of Lawsonia inermis. Another similar dye is Juglone obtained from the shell of unripe walnuts.
Flavones: -
The yellow colours are derivatives of hydroxy and methoxy substituted flavones or isoflavones. Eg: - jackfruit bark
Dihydropyrans: -
These are principal colouring matters of logwood and they give dark shades on cotton, silk, and wool.
Anthocyanidins: -
This class includes carajurin, obtained from the leaves of Bignonia chica and Awabanin. It dyes silk in blue shades.
Carotenoids: -
This class includes the orange pigment carotene found in carrots. The dyes based on carotenoid structure are annatto and saffron.

Based on Color
Blue Dyes: Natural indigo, sulphonated natural indigo and the flowers of the Japanese “Tsuykusa”
Red Dyes: The colour index lists 32 red natural dyes. The prominent among them are madder (Rubia tinctorum L), Manjeet (Rubia cordifolia), Brazil wood/Sappan wood (Caesalpina sappan L), Al or Morinda (Morinda citrifolia L).
Yellow Dyes: Colour index lists 28 yellow dyes. Some of the important yellow dyes are, black oak (quercus velutina), tumeric (curcuma longa), and weld
(reseda luteola) and Himalayan rhubarb (rheum emodi).

Natural dyes

CI Natural No. of Dyes
Yellow 28
Orange 6
Red 32
Blue 3
Green 5
Brown 12
Black 6
__________
92

Structures of only 67 are known
Many dyes have more than one colouring compound
Some dyes have identical structures
Some dyes have structures similar to synthetic dyes.

Extraction: -
In general the extraction of the dye is carried out by boiling the contents in water for optimum time (found out by optimization of parameters) which is 45 to 60 minutes in most cases. The solution is filtered and cooled. The filtrate is used as a dye.
Apart form this there are two other methods of extraction of dyes. These are 1) solvent extraction e.g., Alkamin Natural Red 24,
and 2) supercritical fluid extraction.

MORDANTS
Natural dyes are either substantive, needing no mordant, or adjective requiring one. The majority of natural dyes need a chemical in the form of a metal salt to create an affinity between the fibre and the dye these chemicals are called as mordants, thus mordant is a chemical, which can fix itself on the fibre and also combines with the dyestuff. A link is therefore formed between the dyestuff and the fibre, which allows certain dyes with no affinity to be fixed on to the fibre. Tannins, metallic salts and oils are used as mordants.

Tannins
In the dyeing of textiles with natural dyes, tannins are used as natural mordants. These are high molecular weight compounds (between 500 to 3000) containing phenolic hydroxyl groups to enable them to form effective cross-links between proteins and other macromolecules.
The stability of the tannin treated fibre depends upon the pH, ionic strength and metal chelators. Tannins may be further classified into two on the basis of their chemical structure as:
- Hydrolysable tannins obtained from myrobalan fruit, oak bark, gallnuts,
pomegranate rind, sumac leaves.
- Condensed tannins like catechin obtained from acacia catechu.

Metallic mordants
There are several different metal salts that can be used for mordanting. The most effective ones are: -
Alum – potassium aluminum sulphate
Copper – copper sulphate
Chrome – potassium dichromate
Iron – ferrous sulphate
Tin – stannous chloride, stannic chloride.

Oils
Oil –mordants are mainly used in the dyeing of Turkey Red Colour from madder. The main function of the oil-mordant is to form a complex with alum used as the main mordant. Since alum is soluble in water and does not have affinity for cotton it is easily washed out from the treated fabric. The naturally occurring oils contain fatty acids such as palmitic, stearic, oleic, ricinolic etc. and their glycerides. The –COOH groups of fatty acids react with metal salts and get converted into –COOM, where M denotes the metal, for instance in the case of alum it would be Al. subsequently, it was found that the treatment of oils with concentrated sulphuric acid produces sulphonated oils which possess better metal binding capacity than the natural oils due to the introduction of sulphonic acid group, -SO3H. The sulphonic acid can react with metal salts to produce –SO3M. The bound metal can then form a complex with the mordant dye such as madder to give Turkey Red colour of superior fastness and hue.

Methods of mordanting
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.
Cotton:
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.
Wool:
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.
Silk:
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.

Effects of mordanting
 Some of the natural dyes can form metal-complexes and thereby yield different colours with different metal salts.
 Mordanting improves the wash fastness of the dyes as the dyes are fixed on to the textile substrate.
 Treatment with tannins makes the dyeings dull. Alternatively, if a water-soluble salt such as alum is applied on to a cotton substrate and is then insolubilised by treatment with alkali then the insoluble salt of aluminum is deposited in the material. This provides metal chelating areas for the natural mordant dye. This kind of treatment can form the basis to get bright shades of natural metal complexing dyes.

Environmental problems posed by mordants: -
There is a tendency to use all types of metal salts for the purpose of mordanting disregarding the restrictions laid on the permissible quantities of different metals by the German ban. Accordingly the indicative maximum permissible quantities of different metals in the ultimate product are as follows: -

METALS LIMIT (ppm)
Arsenic 1.0
Lead 1.0
Cadmium 2.0
Chromium 2.0
Cobalt 4.0
Copper 50.0
Nickel 4.0
Zinc 20.0
Mercury 0.02

The upper limits of the presence of metals vary from product to product and are different for different eco-marks. However there is no upper limit on aluminum, iron and tin. Hence one can use these salts for complexing and mordanting.
According to eco-standards copper and chrome are red- listed and hence are not to be used. Another problem posed by a mordant is that a substantial proportion of it is left unexhausted in the residual dyebath and may cause serious effluent problems Researchers claim that the use of heavy metals is not necessary because the resulting shades can be obtained from other natural dyes and also advocate the use of environmental friendly mordants by craft workers. Aluminum and iron are relatively innocuous; they are abundantly available and produce excellent dyeings.

MERITS AND DEMERITS OF NATURAL DYES:-

ADVANTAGES OF NATURAL DYES: -
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.

LIMITATIONS OF NATURAL DYES

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

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

Textiles in Shoe

noreply@blogger.com (Navnath) — Sun, 31 May 2009 09:43:00 +0000

In the revolution of branded footwear industry role of textiles has been very important. It played a vital role in manufacturing and functioning of shoes such as wedding shoe, running shoe, rain boots, etc, but more specifically sports shoes. A shoe can contain wide range of textile material such as nylon, rubber, membrane, latex and neoprene for its coatings and finishes
If we can look at these within the shoe can be explain with various parts of shoe such as upper (everything above the sole i.e., it is the part of the shoe that keeps the sole attached to the foot), Linings
(inner surfaces of the upper to protect the foot and enhance comfort, non-wovens and more recently combinations of hydrophilic and hydrophobic fabric layers are used),Body of the upper (abrasion-resistant fabrics and impregnated fabrics are often used in), Shoelaces and other closures (most often either braided or woven from cotton, nylon or polyester). Footbed (as top covers, most commonly laminated nylon, polypropylene, or polyester fabrics).

Polyester

noreply@blogger.com (Navnath) — Wed, 27 May 2009 14:47:00 +0000

Polyester/ Polyethylene terephthalate (PET) is a category of polymers which contains ester functional groups in their main chain. Polyester includes naturally occurring chemicals, such as in the cutin of plant cuticles as well as synthetic such as in the polycarbonate and polybutyrate. Polyester may be produced in numerous forms such as fibres, sheets and three dimensional shapes. (200)
Polyester fibres are man-made fibres in which the forming substance is a long chain polymer composed of at least 85% by weight of an ester of dihydric alcohol and terephthalic acid. (201)

Polyesters are the polymers in the forms of fibres having hydrocarbon backbone which contain ester linkages. Hydrolysis of polyester by acid catalysed using dilute hydrochloric acid or sulphuric acid is a reversible process. But using alkali is the usual way of hydrolysing esters. By using alkali the reactions are irreversible and products are easier to separate.

Properties of polyester fibres.
Physical Properties:
The moisture regain of polyester is 0.2 to 0.8 and specific gravity is 1.38 or 1.22 depending on the type of polyester fibres is moderate. The melting point of polyester is 250-300°C. A wide of polyester fibres properties is possible depending on the method of manufacture. Generally as the degree of stretch is increased, which yields higher crystallinity and greater molecular orientation, so are the properties e.g. tensile strength and initial Young’s modulus. Shrinkage of the fibres also varies with the mode of treatment. If relaxation of stress and stain in the oriented fibre occurs, shrinkage decreases but the initial modulus may be also reduced.

Miscellaneous Properties:
Polyester fibres exhibit good resistant to sunlight and it also resists abrasion very well. Soaps, synthetic detergents and other laundry aids do not damage it. One of the most serious faults with polyester is its oleophilic quality. It absorbs oily material easily and holds the oil tenacity.
Chemical Properties:
Effect of alkalies: Polyester fibres have good resistance to weak alkalies high temperatures. It exhibits only moderate resistance to strong alkalies at room temperature and is degraded at elevated temperatures.
Effect of acids: Weak acids, even at the boiling point, have no effect on polyester fibres unless the fibres are exposed for several days. Polyester fibres have good resistance to strong acids at room temperature. Prolonged exposure to boiling hydrochloric acid destroys the fibres, and 96% sulfuric acid and causes disintegration of the fibres.
Effect of solvents: Polyester fibres are generally resistant to organic solvents. Chemicals used in cleaning and stain removal do not damage it, but hot m-cresol destroys the fibres, and certain mixtures of phenol with trichloromethane dissolve polyester fibres. Oxidizing agents and bleachers do not damage polyester fibres.
Polyester fibres have taken the major position in textiles all over the world although they have many drawbacks e.g., (a) low moisture regain (0.4%), (b) the fibres has a tendency to accumulate static electricity, (c) the cloth made up of polyester fibres picks up more soil during wear and it also difficult to clean during washing (d) the polyester garments from pills and thus, the appearance of a garment is spoiled, (e) the polyester fibres is flammable. Thus, it has been suggested that surface modifications can have an effect on hand, thermal properties, permeability, and hydrophilicity.
Polyester fabrics have been widely accepted by consumers for their easy care properties, versatility and long life, Inspite of such acceptance, complaints concerning their hand, thermal properties and moisture absorbency have been cited
Improved moisture absorbency of polyester fibres can be achieved by introducing hydrophilic block copolymers. However, this modification can lead to problems of longer drying time, excessive wrinkling and wet cling In addition, penetration of water into the interior of the fibres has not been clearly shown to improve perceived comfort
Polyester fibres are susceptible to the action of bases depending on their ionic character. Ionizable bases like caustic soda, caustic potash and lime water only effect the outer surface of polyester filaments. Primary and secondary bases and ammonia, on the other hand, can diffuse into polyester fibre and attack in depth resulting in breaking of polyester chain molecules by amide formation
One of the surface modifications is the controlled hydrolysis of polyester. The action of strong base leads to cleavage of ester linkages on the fibre surfaces the result is the formation of terminal hydroxyl and carboxylase groups on the fibre surface. Hydrolysis is believed to increase the number of polar functional groups at the fibre surface.

Cotton Fibre Morphology

noreply@blogger.com (Navnath) — Sat, 16 May 2009 16:27:00 +0000

Cotton Fibre Consists of four regions

Cuticle : Very thin outer layer containing wax amd pectic material

Pectin:

1. A peculiar group of carbohydrates of very complex composition.They are usually present as C and Mg salts.In immature fibres there is relatively high amount pectins (6%).
2. In mature fibres it is relatively high amount pectins (0.9-1%).
3. Decrease in pectin content with parallel increase in cellulose content proves that pectin is the parent substance from which cellulosic is formed
4. Function is to protect the fibre from atmospheric oxidation

Primary wall:

1. Composed of cellulose, Pectic and fatty matter
2. Formed in the first phase of growth
3. Cellulose fibrils are disposed transversely or circularly to produce high peripheral strength and also makes it weaker in length wise direction of the fibre and account for the low strength of immature fibre
4. In all native-cellulose fibres, the molecules are highly oriented parallel to one another, but they spiral round the fibre, thus reducing the degree of orientation parallel to the fibre axis.
5. In flax, ramie, hemp, and other bast fibres, the spiral angle is small – less than 6° - so that these fibres are highly oriented and give high strength and low extensibility.
6. In cotton, however, the spiral angle lies between 20° and 30°, and the fibres can extend more easily by stretching the spiral.

Secondary wall:

1. Formed during second phase of growth and makes up about 90% of the total weight.
2. This wall is composed of successive layers of cellulose deposited on the inner side of the primary wall without increase in diameter
3. Strength of the fibre is determined by secondary wall

Lumen:

* Central hollow canal whose dimensions varies over a wide range
* Contains protein, mineral salts and pigments

Course Hero

noreply@blogger.com (Navnath) — Sat, 02 May 2009 19:21:00 +0000

Just few days back I came across a good educational site 'course Hero'. What is Course Hero? This is how they describe themselves:"Course Hero was built by students to help students! Its an open social learning network for students, educators and self-learners to publish, share and view academic resources online. Course Hero provides critical and timely learning assistance through our user-contributed materials and most importantly online study groups comprised of students, educators and self-learners." Course Hero facilitated our studying process.
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Fibre Classification, Cotton fibre 1

noreply@blogger.com (Navnath) — Thu, 30 Apr 2009 18:15:00 +0000

What is Fibre

Fibre is a unit matter, which possesses the properties of fineness, flexibility and a high ratio of length to thickness to be used in textile. It is a smallest unit used in a textile structure. It may be combined with others to make yarn or fabric.

Classification of Textile Fibres Based on Origin
Classification of Textile Fibres based on its chemical constitution

Cotton Fibre

- It is Natural, Vegetable, Cellulosic fibre

- It is the Oldest fibre reportedly found in found in Indus valley

- Account for more than 50% of total world fibre production

- Botanically belongs to Gossypium Family

- Productive regions accdg. to importance

1. US 2. India 3. Russia 4. Brasil 5. Egypt 6. China

Friction Spinning

noreply@blogger.com (Navnath) — Fri, 10 Apr 2009 15:10:00 +0000

The need to rotate the package at the twist insertion rate coupled with rapid increase in spinning tension with spinning speed sets a limit to the spindle speeds achievable in ring spinning. Open end spinning methods where open-end of the yarn alone needs to be rotated for imparting twist was therefore, developed to achieve high delivery rates. Rotor spinning which is one of first methods developed on this principle has well established itself as an alternate to ring spinning in course count range for certain end uses. Friction spinning represents an alternate open-end spinning method to rotor spinning which holds promise of still higher delivery rates.

Frictions spinning technologies works on the principle of open-end or wrap (Fasciated)/core spinning. The general principle of working of friction spinning in its simplest form can be described as below.

As in the above diagram, separating them from slivers generates a stream of fibres, which is transported through a duct. The fibres are then directed towards the nip of two rotating drums called friction drums .The fibres are collected close to the nip of these drums. The friction drums have perforations on it and suction from inside holds the fibres on the surface. There is a long slot inside the friction drums located close to the nip point along the length of friction drums and the rest of the area inside the perforated drum has a shield. So, the yarn at the nip of the friction drum is subjected to a radial force generated as a result of airflow over yarn.

This is shown in figure 2 , This radial force serves as a normal load and frictional force is generated between the yarn and the surface of friction drum. It can be observed from the same figure that at the closest proximity of the friction drums they rotate in opposite direction and the frictional force thus developed, produces a torque on the yarn tail. Continuous rotation of the drum produces twist in the yarn leading to gradual integration of fibres in the yarn tail. The yarn is withdrawn in the direction of the axis of the friction drums and is wound on a bobbin.

Fig.2 : Forces acting on the yarn tail and the vector diagram.