The physical properties and performance characteristics of woven fabrics are influenced by several factors:
Factors affecting properties:
(a) Characteristics of warp and weft yarns
(b) Spacing and interlacing of yarns (design and construction)
(c) Modifications produced by finishing
Characteristics of Warp and Weft Yarns
Fibres used to produce yarn significantly influence the yarn characteristics:
Fibre impact on yarn:
Physical properties affects:
Length
Fineness
Weight
Appearance
Softness
Texture
Performance characteristics affects:
Strength
Moisture absorption
Abrasion resistance
Crease recovery
Important yarn characteristics influenced by fibre are:
Yarn Strength:
Influenced by:
Fibre strength
Fibre length
Fibre fineness
Number of fibres per cross-section
Twist level
Yarn Fineness:
Influenced by:
Fibre fineness
Fibre length
Twist level
Yarn Lustre:
Influenced by:
Fibre surface characteristics
Level of twist
Surface Integrity (Hairiness and Abrasion Resistance):
Influenced by:
Length
Fineness
Twist level
Spacing and Interlacing of Yarns
The spacing of ends and picks in a woven cloth is referred to as Sett, expressed as threads per centimetre.
Effects of thread counts on characteristics:
Number of ends and picks per cm affects:
Strength
Tear resistance
Abrasion resistance
Crease resistance
Drape
Weight
Sett Types:
Square Sett: Ends and picks per cm are approximately equal.
Unbalanced Sett: Significant difference in the numbers of ends and picks.
Open Sett Structure: Voids between warp and weft yarns, influencing properties such as:
Air permeability
Consumer comfort
Thermal insulation
Flammability
Design sequence of interlacing warp and weft leads to various weave structures, impacting:
Strength
Tear resistance
Abrasion resistance
Crease recovery
Drape
Weight
Modifications by Finishing
Various finishing techniques modify fabric characteristics:
Mercerisation: Enhances lustre.
Resin finishes: Improve tear resistance and handle.
Calendering and Coating: Impact air permeability and thickness.
Brushing and Raising: Affect insulation properties and softness.
IMPORTANT ASPECTS IN PRODUCING WOVEN FABRIC
Fibres and Filaments: Basis for all fabrics (natural and synthetic).
Fibres: Derived from plants (e.g., cotton, flax) and animals (e.g., wool).
Filaments: Continuous yarns like silk and synthetic fibres.
Types of Yarns
1. Continuous-Filament Yarns
Comprised of long, endless filaments; strength not reliant on twist but may have twist for coherence.
Characteristics:
Flat Continuous Filament Yarns:
Include flat (standard), lustrous or dull varieties.
Types:
Monofilament Yarns: Single extruded synthetic filaments (diameter: 28 microns to 3 mm).
Multifilament Yarns: Produced by twisting filament bunches, high tensile strength.
Textured Continuous Filament Yarns:
Have distortions like crimps, increase bulk.
Bicomponent Continuous Filament Yarns:
Made of two components which may have different characteristics.
Tape or Split Film Yarns:
Made by cutting extruded polymer films into strips or narrow ribbons.
2. Spun Yarns
Created from shorter fibres, depend on inter-fibre cohesion for strength.
Characteristics:
Tend to be hairy, less lustrous, and irregular compared to continuous filaments.
Made by assembling staple fibres which can be natural or synthetic, requiring twisting (cotton/wool systems).
Yarn Density
Yarn structure composed of fibres and air pockets.
Packing Fraction: Indicates air spaces among fibres.
High packing fraction yields stiff, potentially weak yarn.
Low packing fraction risks lacking bulk and integrity.
Yarn density crucial for qualitative attributes in performance:
Comfort
Dimensional stability
Strength
Flexibility
Air permeability
Absorption characteristics.
Yarn Characteristics & Measurements
Yarn Strength
Influenced by:
Fibre strength
Length
Number per cross-section
Twist level.
Yarn Fineness
Described by yarn count
Two key aspects:
Diameter: Contributes to structural characterization such as:
Width
Cover factor
Yarn crimp.
Yarn Twist
Mechanism for binding spun yarns; involves:
Twist direction (S or Z)
Twist level
Twist factor affects yarn strength, flexibility, and overall characteristics.
Surface Integrity
Characterized by:
Abrasion resistance: quantified by cycles endured under tension and abrasive surface.
Hairiness: Measured through methods such as:
Hair count method: Counts protruding fibres.
Hair length method: Measures light scattered by protruding fibres.
THREAD COUNT
Refers to the total number of warp and weft threads in a square inch of fabric. Higher thread counts correlate with better quality, durability, and resistance to wear.
CRIMP
Defined as the difference ratio of a yarn's length before and after interlacing with opposing yarns:
Formula: extCrimp=LfL<em>y−L</em>f
Utilized as:
Crimp % = LfL<em>y−L</em>fimes100
Typical Crimp values range from 0.01 to 0.14 (1% to 14%).
FINISHING
Refinement treatments include:
Bleaching, decatising, printing.
Chemical treatments augment fabric's performance and suitability for use, including:
Anti-static
Anti-bacterial
Water repellent.
Specific Treatments Effects
Crease Resistance
Reduces wrinkles tied to fabric's viscoelastic properties; influenced by:
Fibre type
Yarn twist
Fabric thickness.
Calendering
Enhances fabrics with softer feel, density, and shine through heat and pressure.
Moiré
Processes create unique patterns through specific fabric treatments.
COMPLEX YARNS
Also known as novelty or fancy yarns, are characterized by:
Varied sizes
Irregularities introduced during production for aesthetic value.
Types of complex yarns:
Slub Yarns: Uneven twisting to create bulky segments.
Thick-and-Thin Yarns: Created by variations in extrusion pressure.
Flock Yarns: Tufts of fibres incorporated for visual effect.
Boucle Yarns: Loops project from base yarn at regular intervals.
Chenille Yarns: Resemble hairy caterpillars for texture.
Nub and Knot Yarns: Defined by enlarged sections, often made with different coloured fibres.
USE OF COMPLEX YARNS
Valued primarily for appearance in fabrics, adding texture and design.
Considered softer and stylish but can be less durable; potential for snagging and abrasion damage exists.
COMPOUND YARNS
Consists of at least two components.
Types include:
Covered Yarns: Have a filament or spun yarn core wrapped in another yarn for protection and aesthetics.
Core-Spun Yarns: Feature a fibre sheath surrounding a filament core which enhances strength and appearance.
YARN DOUBLING
Process of twisting two or more yarns together (also known as plying).
Offers improvements in:
Regularity
Strength
Consistency.
TEXTURISING YARN
Alters straight filament yarns into bulkier forms by adding coils, crimps, or loops.
Processes like heat setting yield increased warmth and softness.
YARNS AND THEIR CHARACTERISTICS
Continuous-filament vs spun yarn properties influence fabric performance factors like thickness, weight, texture, handle, and wear resistance.
YARN COUNT
Measurement of yarn fineness based on weight or length metrics, expressed through direct (denier, tex) or indirect (cotton, worsted) systems.
YARN DIAMETER
Expressed through calculations based on direct/indirect systems, reflecting relative thread spacing (d/p ratio).
TWIST IN YARNS
Affects properties such as strength, extensibility, compactness, and appearance.
SUMMARY OF WOVEN FABRIC DESIGN
Weaves are represented graphically indicating yarn arrangements, with plain weave being the most common and foundational weave structure. Meetings of warp and weft form the basis of fabric integrity.