TEXTILE FIBRES AND YARNS -SIMPLE NOTES

 

 

TEXTILE

FIBERS

AND

YARNS

 

 

 

Mr. P.MURUGAN

 

UNIT I

1. Introduction of Textile Fibers:

Textile fibres are raw materials used in the production of fabrics, yarns, and textiles. They can be categorized into natural fibres (from plants, animals, or minerals) and synthetic fibres (man-made).

• Classification:
• Natural Fibres:
• Plant Fibres: Derived from plant sources (e.g., cotton, flax, jute, hemp).
• Animal Fibres: Obtained from animals (e.g., wool, silk, mohair).
• Synthetic Fibres:
• Regenerated Fibres: Made from natural polymers (e.g., rayon, lyocell, acetate).
• Synthetic Fibres: Manufactured from petrochemicals (e.g., polyester, nylon, acrylic).
• Physical Properties:
• Length: Staple (short) or filament (long) fibres.
• Strength: Ability to resist breakage under tension.
• Flexibility: How easily a fibre bends without breaking.
• Elasticity: Ability to return to original shape after being stretched.
• Fineness: Thickness of the individual fibre.
• Chemical Properties:
• Moisture Absorption: Fibres vary in how much water they absorb.
• Reactivity to Chemicals: Resistance to acid, alkali, and other chemical agents.
• Dye Affinity: How easily fibres take up and retain dyes.

---

2. Cotton:

• Botanical Classification:
• Cotton is a fibre obtained from the seed pod of the Gossypium species, belonging to the Malvaceae family.
• Commercial Classification:
• Upland Cotton (Gossypium hirsutum): Most commonly used, with a short to medium fibre length.
• Sea Island Cotton (Gossypium barbadense): Known for longer, finer fibres; often used for high-quality fabrics.
• Properties:
• Softness: Cotton is soft and comfortable to wear.
• Breathability: Allows air circulation, making it ideal for warm weather.
• Absorbency: Excellent moisture-wicking properties, which help to keep the body dry.
• Shrinkage and Wrinkling: Cotton fabrics tend to shrink and wrinkle easily.
• Durability: Strong when dry, but loses strength when wet.
• End Uses:
• Clothing: Shirts, pants, dresses, undergarments.
• Home Textiles: Bed linens, towels, curtains.
• Medical Textiles: Bandages, surgical dressings.
• Organic Cotton:
• Cultivated without the use of synthetic chemicals or pesticides. Organic farming practices aim to improve soil health, reduce environmental impact, and protect workers from harmful chemicals.
• Benefits: More sustainable, better for the environment, and often softer than conventionally grown cotton.

---

3. Flax (Linen):

• Properties:
• Strength: Flax is one of the strongest natural fibres, stronger than cotton.
• Luster: Has a natural sheen, which gives linen fabric a distinguished look.
• Absorbency: It has excellent moisture-absorbing properties, better than cotton.
• Drapability: Linen fabrics have a crisp, structured feel, which can soften with use but remains less elastic than cotton.
• Wrinkling: Linen is prone to wrinkling, but many people appreciate this as part of its "natural" aesthetic.
• End Uses:
• Apparel: Suits, dresses, blouses, and summer clothing.
• Home Textiles: Tablecloths, napkins, bed linens, and curtains.
• Industrial Use: Ropes, sailcloth, and paper.
• Organic Flax:
• Just like organic cotton, flax grown organically avoids the use of chemical fertilizers, pesticides, or herbicides, making it a more eco-friendly choice.

---

4. Wool:

• Producing Countries:
• Major producers include Australia (the world’s largest producer), New Zealand, China, and South Africa.
• Grading:
• Wool is graded based on the diameter of the fibres (microns). Merino wool is the finest grade and is known for its softness and warmth.
• Wool is categorized into fine wool, medium wool, and coarse wool based on its fibre thickness.
• Properties:
• Warmth: Wool provides excellent insulation due to its natural crimp, which traps air.
• Elasticity: Wool is elastic, allowing fabrics to return to their shape after being stretched.
• Moisture-Wicking: Absorbs moisture away from the skin without feeling wet, making it breathable.
• Flame Resistance: Wool is naturally flame retardant, which is an advantage in certain applications.
• Durability: Strong, resistant to abrasion, and resilient to wear.
• End Uses:
• Apparel: Suits, coats, sweaters, and scarves.
• Home Textiles: Blankets, carpets, and upholstery.
• Specialty Fabrics: Sportswear, thermal wear, and insulation materials.
• Felting:
• Wool can be felted by applying heat, moisture, and pressure, which causes the scales on the wool fibres to lock together. Felt is used in a variety of crafts, hats, and thick woolen fabrics.
• Woollen vs. Worsted Yarns:
• Woollen Yarns: These are made from carded wool, resulting in a thicker, fuzzier, and bulkier yarn. They are used for heavier garments like sweaters and blankets.
• Worsted Yarns: Made from combed wool, resulting in a finer, smoother, and stronger yarn. Worsted yarns are used in formal wear, suiting, and fine knitwear.

---

5. Silk:

• Producing Countries:
• China is the leading producer of silk, contributing about 70% of global production, followed by India, Brazil, and Thailand.
• Degumming:
• The process of removing the sericin (a gummy substance) from raw silk using an alkaline solution. This makes the silk more lustrous and soft.
• Weighting:
• Weighting involves treating silk with metallic salts to enhance its weight, drape, and shine. This process can make the silk feel heavier and more luxurious but can reduce its durability.
• Properties:
• Luxurious: Known for its smooth texture and natural sheen.
• Lightweight and Strong: Silk is very lightweight but strong, offering a high strength-to-weight ratio.
• Moisture-Wicking: Silk absorbs moisture well and dries quickly.
• Breathable and Comfortable: Ideal for both summer and winter, as it maintains body temperature.
• End Uses:
• High-End Apparel: Dresses, ties, scarves, evening wear.
• Home Textiles: Luxury bedding, cushions, and drapes.
• Industrial Applications: Medical sutures (because of its strength and biocompatibility).
• Wild Silk Varieties:
• Tussah Silk: Produced by wild silkworms such as Antheraea mylitta and Antheraea paphia. It’s less lustrous and coarser than cultivated silk, often used for more rustic textiles.
• Eri Silk: Also known as "peace silk", it’s produced by the Samia ricini silkworm. It is more sustainable as the silkworm is not killed in the harvesting process, making it eco-friendly. Eri silk is soft and thermal, used for casual garments, blankets, and shawls.

 

 

 

UNIT II

 

1. Methods of Filament Spinning:

Filament spinning involves converting a polymer solution or melt into continuous filament yarns that can be used to make fabrics or textiles. The two main methods are dry spinning, wet spinning, and melt spinning.

• Dry Spinning:
• Used for synthetic fibres like acetate, nylon, and modacrylic.
• The polymer is dissolved in a solvent to form a solution, which is then extruded through a spinneret into hot air. The solvent evaporates, leaving behind solid filaments.
• Wet Spinning:
• Typically used for viscose rayon and nylon.
• The polymer is dissolved in a solvent to create a solution, which is extruded into a chemical bath. The polymer precipitates out, solidifying into filaments.
• Melt Spinning:
• Used for polyester, nylon, and polypropylene.
• The polymer is melted and forced through a spinneret into cool air or water, where it solidifies to form filaments.

After spinning, the filaments can be drawn (stretched) to increase strength and improve their properties.

---

2. Semi-Synthetic Fibres:

Semi-synthetic fibres are fibres made from natural polymers that have been chemically modified to make them more suitable for textile production. These fibres often originate from cellulose (plant matter) but undergo chemical processes to modify their structure.

a. Regenerated and Modified Cellulose:

• Regenerated Cellulose:
• Made by chemically treating natural cellulose (from wood pulp or cotton linters) to create a solution that can be extruded into fibres. Common examples are viscose rayon, lyocell, and acetate.
• Modified Cellulose:
• Cellulose is chemically modified to change the properties of the fibre. For example, high-performance fibres like high wet modulus (HWM) rayon are made by altering the cellulose structure to increase its durability, strength, and moisture absorption.

---

3. Viscose Rayon Process Flow:

Viscose rayon is one of the oldest and most widely used semi-synthetic fibres. The manufacturing process involves converting cellulose into a soluble form (viscose) and then spinning it into fibre.

Process Flow:

1. Preparation of Cellulose:
• Wood pulp or cotton linters are treated with sodium hydroxide (NaOH) to make "alkali cellulose."
2. Xanthation:
• The alkali cellulose is treated with carbon disulfide (CS₂) to form cellulose xanthate (viscose).
3. Dissolution:
• The cellulose xanthate is dissolved in a dilute sodium hydroxide solution to form the viscose solution.
4. Filament Spinning:
• The viscose solution is extruded through a spinneret into a sulfuric acid or other bath to regenerate the cellulose into solid fibres.
5. Drawing:
• The fibres are drawn to orient the molecular chains, improving strength and performance.
6. Washing and Finishing:
• The fibres are washed, neutralized, and dried to create the final product.

---

4. HWM (High Wet Modulus) Fibres:

High Wet Modulus (HWM) fibres are a type of rayon that is modified to have improved strength and durability when wet, making them more durable and suitable for more demanding end uses.

·         Properties:

• HWM fibres have better wet strength, meaning they maintain their strength and dimensional stability even when wet.
• They have enhanced durability, higher resistance to abrasion, and better dye uptake than regular viscose rayon.

·         End Uses:

• HWM rayon is used in high-performance applications such as medical textiles, workwear, activewear, and automotive fabrics.

---

5. Brief Study of Semi-Synthetic Fibres:

a. Bamboo Fibre:

• Properties:
• Bamboo fibre is derived from the pulp of the bamboo plant. It is soft, biodegradable, and has natural antibacterial and anti-fungal properties.
• It is highly absorbent, breathable, and moisture-wicking, making it suitable for activewear and undergarments.
• End Uses:
• Clothing: T-shirts, socks, and undergarments.
• Home Textiles: Towels, bed sheets, and blankets.
• Medical Textiles: Due to its antimicrobial properties, bamboo is used in bandages and hygiene products.
• Production:
• Bamboo fibres are often produced by chemical processes like lyocell or viscose processes.

b. Lyocell:

·         Properties:

• Lyocell is made from wood pulp and is one of the most environmentally friendly regenerated cellulose fibres. The process uses a closed-loop system, where most of the chemicals used are recovered and reused.
• Lyocell is soft, smooth, breathable, and moisture-wicking, with a luxurious feel similar to silk.

·         End Uses:

• Clothing: Dresses, blouses, trousers, and casual wear.
• Home Textiles: Bed linens, towels, and blankets.
• Medical Textiles: Wound dressings and hygiene products.

·         Production:

• The production of lyocell involves dissolving wood pulp (from hardwood trees, typically eucalyptus, beech, or spruce) in a solvent called N-methylmorpholine-N-oxide (NMMO). The solution is then extruded through a spinneret to form fibres.

c. Soya Bean Fibres:

·         Properties:

• Soya bean fibres, also known as soy silk, are made from the waste products of soybeans (soybean hulls). These fibres are biodegradable, soft, and have a smooth, silky texture.
• They are hypoallergenic and have moisture-wicking properties, similar to wool and silk.

·         End Uses:

• Clothing: Sweaters, cardigans, and casual wear.
• Home Textiles: Bedding, towels, and drapery.
• Eco-friendly Fabrics: Because of its natural and sustainable production, it’s also used for eco-conscious fashion and products.

·         Production:

• Soya bean fibres are produced by chemically processing the soy protein (usually a by-product of tofu production) into a gel-like substance, which is then spun into fibres.

UNIT III

 

1. Polymer – Terminologies – Types of Polymers & Polymerization

A polymer is a large molecule composed of repeating structural units called monomers, which are linked together by covalent bonds. Polymers are essential in the production of synthetic fibres, plastics, rubbers, and more.

Key Terminologies:

• Monomer: The basic building block or repeating unit of a polymer.
• Polymerization: The chemical process by which monomers are chemically bonded to form a polymer.
• Molecular Weight: The total mass of a polymer molecule. Higher molecular weight typically means greater strength and durability.
• Degree of Polymerization: The number of monomer units in a polymer chain.
• Copolymer: A polymer made from two or more different types of monomers.

Types of Polymers:

1. Thermoplastics: These polymers can be melted and reformed multiple times without undergoing chemical changes. Examples: Polyethylene (PE), Polypropylene (PP), Polystyrene (PS).
2. Thermosetting Polymers: These polymers harden permanently when heated and cannot be re-melted. Examples: Epoxy, Bakelite, Phenolic resins.
3. Elastomers: Polymers that are highly elastic and can stretch and return to their original shape. Example: Rubber.

Polymerization:

• Addition Polymerization (Chain Growth Polymerization): Monomers with unsaturated bonds (like ethylene) add onto a growing chain, forming long chains without by-products. Example: Polyethylene (PE), Polystyrene (PS).
• Condensation Polymerization (Step Growth Polymerization): Monomers react to form polymer chains, releasing small molecules like water or alcohol as by-products. Example: Nylon (polyamide), Polyester.

---

2. Synthetic Fibres: Brief Study on Polyamide, Polyester, Poly Acrylic, and Spandex

a. Polyamide (Nylon):

·         Trade Names: Nylon 6, Nylon 66 (e.g., DuPont, Orlon).

·         Properties:

• High tensile strength, wear-resistant, and durable.
• Good elasticity and abrasion resistance.
• Poor UV resistance (can degrade in sunlight) and can absorb moisture.

·         End Uses:

• Clothing: Hosiery, activewear, and swimwear.
• Home Textiles: Carpets, upholstery.
• Industrial: Ropes, conveyor belts, and tire cords.

b. Polyester:

·         Trade Names: Dacron, Terylene, Coolmax.

·         Properties:

• Strong, durable, and resistant to shrinking and stretching.
• Low moisture absorption and high resistance to mildew.
• Resistant to wrinkles, retaining its shape and color.

·         End Uses:

• Clothing: Shirts, jackets, suits, and sportswear.
• Home Textiles: Curtains, bed linens, upholstery.
• Industrial: Geotextiles, automotive fabrics, and insulation.

c. Poly Acrylic (Acrylic):

·         Trade Names: Orlon, Dralon, Acrilan.

·         Properties:

• Soft, lightweight, and wool-like feel.
• Excellent color retention, resistant to fading.
• Can be sensitive to abrasion, but resilient to chemicals.

·         End Uses:

• Clothing: Sweaters, scarves, hats, and socks (often as a substitute for wool).
• Home Textiles: Blankets, carpets, and upholstery.
• Industrial: Outdoor fabrics, awnings, and artificial fur.

d. Spandex (Lycra/Elastane):

·         Trade Names: Lycra, Spandex, Polyurethane.

·         Properties:

• Extremely stretchy (can stretch up to 5 times its original length).
• Excellent recovery after stretching, soft, and lightweight.
• Resistant to sweat, chlorine, and UV light.

·         End Uses:

• Clothing: Activewear, performance wear (e.g., gymnastics, swimwear, dancewear).
• Sports Equipment: Athletic uniforms, cycling shorts.
• Medical Textiles: Compression garments.

---

3. Drawing and Effects

·         Drawing is the process of stretching the polymer fibres after spinning, which aligns the polymer molecules in a parallel arrangement, thus improving the strength, durability, and crystallinity of the fibre.

·         Effects of Drawing:

• Increased Strength: Molecules align and form stronger bonds.
• Improved Durability: The fibre becomes more resistant to abrasion and wear.
• Reduced Stretchability: Drawing decreases the fibre’s elasticity but enhances dimensional stability.
• Enhanced Lustre: Drawing can improve the surface smoothness of the fibre, leading to a shinier appearance.

---

4. Texturisation: Definition, Types, and Properties of Textured Yarns

Texturization is a process applied to filament yarns (usually synthetic) to impart bulk, elasticity, and texture. It involves altering the yarn's structure by introducing crimps, twists, loops, or bends.

Types of Texturization:

1.      False Twist:

• The yarn is twisted, heat-set, and then untwisted, which creates a crimped texture.
• Used for making yarns with elasticity and stretch, commonly used in polyester and nylon.

2.      Air Jet Texturizing:

• The yarn is passed through high-speed jets of air, creating loops and crimp.
• This method is faster and cost-effective, used to produce textured polyester or nylon yarns.

3.      Knitting (Curling) Texturization:

• The yarn is knitted into a mesh fabric, then heat-set to produce crimp.
• This method is used for high-bulk yarns.

4.      Stuffer Box Texturizing:

• The yarn is passed through a box that forces it to become crimped as it is drawn into the box.

Properties of Textured Yarns:

• Increased Bulk: The yarn appears thicker, adding volume without increasing weight.
• Elasticity: Textured yarns provide greater stretch and recovery.
• Softness and Warmth: Textured fibres are often softer and warmer than non-textured counterparts.
• Improved Aesthetics: Textured yarns have a more pleasing look and feel, often used in decorative fabrics.

Uses of Textured Yarns:

• Apparel: Sportswear, activewear, and clothing requiring stretch and comfort.
• Home Textiles: Upholstery fabrics, drapery, and carpets.
• Industrial: Elastic fabrics used in the automotive and medical industries.

---

5. Microfibres:

Microfibres are fibres that are finer than conventional fibres, typically less than 1 denier in thickness. These fibres are produced by splitting or drawing fine filaments of synthetic polymers such as polyester, nylon, or acrylic.

Properties:

• Softness: Microfibres are extremely soft to the touch.
• High Strength: Despite their small size, microfibres can be very strong and durable.
• Lightweight: Their small diameter makes them very light.
• Breathability and Moisture Absorption: Microfibres are often used in fabrics that need to wick moisture away from the body or allow air circulation.
• Water Repellency: Some microfibres are treated to be hydrophobic (water-resistant).

End Uses:

• Clothing: Activewear, lingerie, and outerwear.
• Cleaning Products: Due to their fine structure, microfibres are used in cleaning cloths, mops, and towels because they trap dust and dirt effectively.
• Home Textiles: Bedding, upholstery, and soft furnishings.
• Sports Equipment: Microfibre is used in sports gloves, shoes, and accessories due to its durability and comfort.

 

UNIT IV

 

1. Classification of Yarn Types

Yarn is classified based on the spinning method used to produce it, the fiber source, and the length of the fibre.

Classification by Fiber Length:

• Staple Yarn: Made from short fibres (typically 1-2 inches long). Most natural fibres (cotton, wool) are staple fibres, and they need to be spun into yarn using a spinning method that handles short fibres.
• Filament Yarn: Made from long, continuous fibres (e.g., polyester, nylon, silk). Filament yarns are produced by drawing out the continuous filaments from a spinneret.

Classification by Spinning Method:

• Ring Spun Yarn: Made by continuously drawing and twisting the fibre to create a smooth and strong yarn. Common for both cotton and synthetic fibres.
• Rotor Spun Yarn: Made by a rotor spinning machine, which is a faster method for spinning short fibres into yarn.
• Open-End Spun Yarn: Similar to rotor spinning, but here the yarn is twisted in an open-end device, which is faster and cheaper.
• Air-Jet Spun Yarn: Spun using air jets, typically for synthetic fibres, which bind the fibres together without the need for traditional twist.

Classification by Twist:

• S-Twist: The yarn is twisted in a clockwise direction.
• Z-Twist: The yarn is twisted in a counter-clockwise direction.

---

2. Staple Spinning System – Types

Staple spinning involves converting short fibres into continuous yarn. There are several types of staple spinning systems, each suited to different types of fibres and required yarn properties.

Types of Staple Spinning Systems:

1.      Ring Spinning:

• The most common method for producing high-quality yarn, particularly cotton. In this process, fibres are drawn out, twisted, and wound onto spools.

2.      Open-End Spinning:

• In open-end spinning, fibres are gathered and spun using a rotor, eliminating the need for a spindle. This method is faster and cheaper than ring spinning but produces lower-quality yarn.

3.      Rotor Spinning:

• Involves the use of a rotor to twist the fibres together. Rotor spinning is faster than traditional ring spinning and produces a coarser yarn. This method is particularly used for spinning cotton and other short fibres.

4.      Air-Jet Spinning:

• A method where compressed air is used to twist the fibres, making it ideal for synthetic fibres like polyester. Air-jet spinning is fast but results in a weaker yarn compared to ring-spun yarn.

---

3. Yarn Manufacturing Process

Yarn manufacturing involves several steps, starting with raw materials (e.g., cotton or wool) and ending with the formation of yarn. The process includes cleaning, carding, drawing, twisting, and spinning.

a. Ginning:

• Objectives:
• Separation of cotton fibre from seeds.
• Cleaning of the cotton, removing impurities such as leaves, dirt, and stalks.
• Preparation of cotton for further spinning processes.
• Process Sequence:
• Harvesting: Cotton is harvested from cotton plants, and cotton bolls are opened to release the fibre.
• Ginning: Cotton fibres are separated from cotton seeds using a mechanical gin (roller gin or saw gin). This process removes most impurities and prepares cotton for spinning.

b. Blow Room:

·         Objectives:

• Opening: Raw cotton is broken into smaller pieces to loosen the fibres.
• Cleaning: Further removal of any remaining impurities.
• Blending: Different batches of cotton are mixed to ensure uniformity of the fibre.

·         Process Sequence:

• Cotton is fed into a series of machines that fluff up the cotton and separate any remaining dust, dirt, or leaves.
• The cotton is then formed into a lap (a thick sheet of cotton fibres) for the next step in the process.

c. Carding:

• Objectives:
• Separation and alignment of cotton fibres into a continuous sliver (a long, untwisted rope of fibre).
• Blending: Carding helps further blend the fibres, making them uniform.
• Process Sequence:
• The lap from the blow room is fed into the carding machine, which combs the fibres and aligns them in a more parallel arrangement.
• The result is a carded sliver, which is then prepared for drawing.

d. Drawing:

• Objectives:
• Elongation and alignment: The sliver is stretched to further align the fibres, improving the uniformity and strength of the yarn.
• Process Sequence:
• The carded slivers are fed into a drawing frame where they are elongated and blended into a finer, uniform sliver.
• Drawing increases the fibre parallelism and provides a better quality yarn in subsequent stages.

e. Combing:

• Objectives:
• Removing short fibres: Combing removes shorter fibres that can reduce yarn strength and smoothness.
• Improvement of uniformity: Combed fibres are more aligned and have fewer tangles.
• Process Sequence:
• The drawn sliver is passed through the combing machine, which removes shorter fibres (called noils), leaving only long, uniform fibres.
• Combing produces a more even and stronger yarn, improving quality but increasing cost.

f. Simplex (or Roving Frame):

• Objectives:
• Further elongation and preparation of the sliver for the final spinning process.
• Twisting: The sliver is given a slight twist to form a roving that is then ready for spinning.
• Process Sequence:
• The sliver is drawn out and twisted slightly to create a roving (a finer, elongated strand). This step adds a small amount of twist to the fibres, preparing them for the ring spinning or other spinning methods.

g. Ring Frame (Spinning):

• Objectives:
• Twisting: The roving is further twisted and drawn to form the final yarn.
• Winding: The yarn is wound onto spools for later use in fabric manufacturing.
• Process Sequence:
• The roving is drawn, twisted, and wound into yarn on a ring spinning machine. The twisting imparts strength to the yarn and ensures the fibres are held together in a continuous strand.

Comparison of Carded and Combed Yarn:

• Carded Yarn:
• Produced from carded slivers (no combing step).
• Coarser, bulkier yarn with more unevenness in thickness.
• Suitable for lower-quality fabrics.
• Combed Yarn:
• Produced from combed slivers (removal of short fibres).
• Finer, smoother, and stronger yarn with fewer imperfections.
• Suitable for high-quality fabrics, soft to the touch, and durable.

---

4. Principles and Process Sequence of Advanced Spinning Methods

a. Rotor Spinning:

• Principle:
• Rotor spinning involves a high-speed rotor that twists the fibres into a yarn. In this system, fibres are separated, inserted into the rotor, and twisted by centrifugal forces.
• Process Sequence:
• Feeding: The sliver or fibre is fed into the rotor.
• Twisting: A rotating mechanism twists the fibres together to form yarn.
• Winding: The yarn is wound into bobbins.
• Advantages:
• Faster and more cost-effective than ring spinning.
• Can spin shorter fibres effectively.
• Suitable for coarser yarns.
• Disadvantages:
• The yarn is usually weaker and more irregular than ring-spun yarn.

b. Compact Spinning:

• Principle:
• Compact spinning improves the quality of yarn by reducing the amount of air between the fibres during spinning. The process compacts the fibre bundle to produce smoother, stronger, and finer yarn.
• Process Sequence:
• Pre-twisting: The fibres are drawn, and then the fibre bundle is compacted to reduce air gaps.
• Spinning and Winding: The yarn is spun and wound onto bobbins.
• Advantages:
• Finer and smoother yarn with fewer imperfections.
• Reduced yarn hairiness, which leads to a better fabric appearance.
• Better yarn strength and uniformity compared to traditional ring spinning.

 

UNIT V

 

Post-Spinning Process

Once the yarn is spun, it undergoes various post-spinning processes to prepare it for use in fabric manufacturing. These processes help to enhance the quality, strength, and appearance of the yarn.

1. Cone Winding

• Objective: Cone winding is the process of transferring yarn from smaller spools (or bobbins) onto larger cones for further processing or packaging.
• Process: The yarn is unwound from bobbins and wound onto conical packages, which are easier to handle during weaving or knitting.
• Purpose:
• To facilitate efficient yarn transportation.
• To create uniform packages for easy unwinding during fabric production.

2. Doubling

• Objective: Doubling involves combining two or more single yarns to produce a yarn with improved strength, texture, and durability.
• Process: Two or more single yarns are twisted together in the opposite direction of the original yarn twist. This results in a yarn with increased tensile strength and an altered appearance.
• Advantages:
• Increases the yarn's strength and durability.
• Improves consistency in yarn diameter and texture.
• Helps in achieving desired properties for specific applications (e.g., smoothness, elasticity).

3. Reeling

• Objective: Reeling is the process of winding yarn from a skein onto a reel, often used for silk and other natural fibres.
• Process: Yarn is transferred from a hank or skein onto a reel or spool for packaging or further processing.
• Purpose:
• To prepare yarn for dyeing, finishing, or weaving.
• To ensure smooth unwinding during the production process.

---

Ply Yarn and Single Yarn Characteristics

• Single Yarn:
• Definition: A yarn made from one strand of fibre twisted together.
• Characteristics:
• Simple structure: Single yarns have a basic twist and are used in a variety of applications.
• Limited strength: Typically weaker than ply yarns due to the lack of additional yarns.
• Smooth finish: Single yarns tend to have a smoother texture.
• Ply Yarn:
• Definition: A yarn made by twisting two or more single yarns together.
• Characteristics:
• Stronger and more durable: The combined structure of multiple yarns increases strength and abrasion resistance.
• More texture: The twist can give the yarn more texture and a rougher surface.
• Applications: Used where higher strength or special characteristics are needed, such as in denim and cords.

---

Properties Required for Export Quality Hosiery Yarns

For hosiery yarns to meet international standards, they must possess certain properties that ensure performance, durability, and comfort:

Key Properties:

1. Smoothness: Hosiery yarns should have minimal defects or irregularities, ensuring a smooth, soft feel against the skin.
2. Strength: The yarn should be strong enough to withstand wear and stretch, especially for elastic hosiery products like socks and tights.
3. Elasticity: High elasticity ensures that the hosiery retains its shape after stretching and conforms well to the body.
4. Evenness: Uniformity in thickness and twist ensures that the fabric is consistent, reducing the risk of defects during knitting or weaving.
5. Colour Fastness: The yarn should retain its colour after washing and exposure to light.
6. Softness: Hosiery yarn should feel comfortable on the skin, making soft and high-quality fibres, like cotton or nylon, desirable.
7. Durability: Long-lasting wearability, with resistance to abrasion, is crucial for hosiery items like stockings, socks, and tights.

---

Yarn Twist and Its Importance

Yarn Twist:

• Definition: Twist refers to the number of turns per unit length that are inserted into a yarn during spinning.

Types of Twist:

1. S-Twist: The yarn is twisted in the direction resembling the letter "S". This is the most common twist direction for yarns.
2. Z-Twist: The yarn is twisted in the opposite direction, resembling the letter "Z".

Importance of Twist:

• Strength: The twist imparts tensile strength to the yarn. More twist results in stronger yarn, but excessive twist can make the yarn stiff.
• Elasticity: Twist contributes to the elasticity of the yarn. For fabrics requiring stretch (e.g., hosiery), moderate twist is preferred.
• Appearance: The amount of twist influences the appearance of the fabric. A tightly twisted yarn produces a smoother, more compact yarn, whereas a looser twist creates a softer, bulkier yarn.
• Texture: Twist also influences the texture and feel of the fabric. Higher twist levels can make a yarn more compact and smooth, while lower twist can create a more open, softer texture.

---

Yarn & Package Defects

Common Yarn Defects:

1. Slubs: Thick, irregular areas along the yarn caused by uneven fibre feeding or inconsistent twisting.
2. Snarls: Tangling or knotting of yarn, often due to issues in the spinning or winding process.
3. Thick and Thin Places: Areas where the yarn's diameter is either too thick or too thin, causing uneven fabric.
4. Broken Filaments: Weak or broken filaments can cause the yarn to have irregular tension and breakage.
5. Holes: Holes in the yarn or package due to improper handling or defects in the fibres.

Common Package Defects:

1. Package Collapse: When the yarn package becomes unstable or collapses during handling or transport.
2. Uneven Winding: Winding defects that lead to uneven package formation, causing difficulties during weaving or knitting.
3. Dirty or Contaminated Packages: Dirt or foreign matter in the yarn package can cause defects in the finished fabric.

---

Yarn Numbering Systems

Yarn numbering systems are used to describe the thickness or fineness of yarn. Different systems are used for different types of yarns, such as cotton, wool, or synthetic.

Common Systems:

1.      Denier (d): A unit of measure for filament yarns, indicating the mass in grams of 9,000 meters of yarn. A higher denier number means a thicker yarn.

• Example: 30 denier yarn is finer than 100 denier yarn.

2.      Tex: A metric system used for both filament and staple yarns, representing the mass in grams of 1,000 meters of yarn. The higher the tex number, the thicker the yarn.

• Example: 20 tex is finer than 50 tex.

3.      Cotton Count (Ne): A system used for cotton yarns, where the number indicates how many hanks (840 yards each) make up one pound of yarn. A higher count means a finer yarn.

• Example: 40s cotton yarn is finer than 20s cotton yarn.

---

Blended Textiles: Types of Blending, Benefits, Double Yarn

Types of Blending:

1. Mechanical Blending: Fibre blending in the bale before spinning, commonly used for cotton and polyester blends.
2. Chemical Blending: Combining synthetic fibres during their chemical production, such as in polyester-cotton blends.

Benefits of Blending:

• Cost Efficiency: Blending cheaper fibres (like polyester) with more expensive fibres (like cotton) can reduce overall fabric cost while maintaining desirable properties.
• Improved Properties: Blended textiles can combine the best properties of both fibres, such as the comfort of cotton and the durability of polyester.
• Enhanced Performance: For example, wool-polyester blends can enhance the softness and thermal properties of wool with the durability of polyester.

Double Yarn:

• Definition: A yarn made by twisting two or more yarns together to improve strength and texture.
• Properties: Stronger and more durable than single yarns. They can also provide added texture or design, such as in heathered yarns.
• Uses: Often used in sweaters, jackets, and knitted garments.

---

Classification of Sewing Threads & Applications

Sewing threads are classified based on their material, structure, and purpose:

Types of Sewing Threads:

1. Cotton Threads: Soft and natural, ideal for hand sewing, quilting, and lightweight fabrics.
2. Polyester Threads: Stronger and more durable than cotton, commonly used for machine sewing and commercial applications.
3. Nylon Threads: Known for their strength and flexibility, used in heavy-duty applications like upholstery and outdoor gear.
4. Silk Threads: Luxurious and fine, used for high-end clothing, embroidery, and delicate fabrics.

Core Spun Sewing Thread:

• Definition: A type of sewing thread that consists of a central core (often polyester) wrapped in a layer of another fibre, typically cotton or nylon.
• Advantages:
• Strength: The core provides high tensile strength.
• Softness: The outer fibre layer gives a soft, smooth finish.
• Durability: Excellent resistance to wear and abrasion.
• Versatility: Suitable for various applications, including garment manufacturing, automotive textiles, and sportswear.