TEXTILE FIBERS & THEIR PROPERTIES

Chapter 3 Objectives

  • To recognize and appropriately use terms describing textile fibers and their properties.

  • To describe the relationships between fiber structure and fiber properties.

  • To discuss fiber performance and serviceability to end-use requirements and expectations.

  • To identify commonly used fibers through simple identification procedures.

Fibers: Natural vs. Manufactured

Definition of Fibers

  • "Any substance, natural or manufactured, with a high length-to-width ratio and with suitable characteristics for being processed into a fabric."

  • Fibers are the basic unit of most fabrics.

Natural Fibers

  • Definition: Grown or developed in nature in recognizable fiber form.

  • Sources:

    • Animal (Protein)

    • Plant (Cellulosic)

    • Mineral

  • Characteristics: Typically short, staple length fibers used in spun yarns (with the exception of silk).

  • Examples: Cotton, linen, wool, cashmere, silk.

Manufactured (Man-Made) Fibers

  • Definition: Fibers made from chemical compounds produced in manufacturing facilities.

  • Origin: The material's original form is not recognizable as a fiber.

  • Sources: Can be cellulosic, protein, or mineral sources, or synthetic polymers.

  • Historical Note: The first manufactured fiber was produced in 1885.

  • **Classification (as per Table 3.1, conceptually described in text):

    • Regenerated Man-Made Fibers: Cellulose (e.g., Viscose), Protein, Acetate, Alginate, Lyocell.

    • Synthetic Man-Made Fibers: Polyester, Polyvinyl, Acrylic, Polyolefin.

    • Other Man-Made Fibers: Metallic Fiber, Glass Fiber, Carbon Fiber.

Commonly Used Manufactured Fibers

  • In Apparel & Interiors:

    • Polyester

    • Nylon

    • Olefin

    • Acrylic

    • Rayon

    • Lyocell

    • Acetate

  • In Technical Applications:

    • Spandex

    • Aramids

    • PBI

Fiber Properties

Key Categories of Fiber Properties

  1. Physical Structure: Pertains to visible characteristics like length, diameter, and shape.

  2. Chemical Composition: Relates to the chemical makeup that defines generic fiber groups.

  3. Molecular Arrangement: Describes how molecules are organized within the fiber, affecting properties like strength and elasticity.

Physical Structure

Fiber Length

  • Staple Fiber: Any natural or manufactured fiber produced in or cut to a short length, measured in inches or centimeters.

  • Filament Fiber: Fibers that are extremely long (measured in miles or kilometers) or yarns made of these fibers.

  • Filament Tow: Produced as a loose rope of several thousand fibers, which is then crimped or textured and cut to staple length.

Spun Yarn vs. Smooth Filament Fabrics

Feature

Spun Yarn (e.g., Cotton)

Smooth Filament Fabrics (e.g., Nylon)

Luster

Soft or matte luster

Shiny and lustrous

Feel

Feel fuzzy

Smooth, slick surface, cool to the touch

Surface Condition

Short fiber ends protrude above surface

No fiber ends seen on surface

Fiber Diameter

  • Natural Fibers: Finer fibers generally indicate higher quality.

    • Fineness is measured in micrometers (1/1000 millimeter).

  • Manufactured Fibers: Diameter is precisely controlled during production.

    • Often described using:

      • Denier: Weight in grams for 9,000 meters of fiber or yarn.

      • Tex: Weight in grams of 1,000 meters of fiber or yarn.

      • Denier per Filament (dpf): Calculated by dividing yarn size in denier by the number of filaments. A way to describe individual fiber size within a multi-filament yarn.

Cross-Sectional Shape

  • Natural Fibers: Shape is determined by:

    • The way cellulose is built during plant growth (e.g., cotton).

    • The shape of the hair follicle and protein formation in animals (e.g., wool).

    • The shape of the orifice through which an insect extrudes the fiber (e.g., silk).

  • Manufactured Fibers: Shape is purposefully controlled by the shape of the spinneret opening and the spinning method.

  • **Examples of Cross-Sections (Figure 3.3):

    • Circular, uniform diameter: Nylon, polyester, lyocell

    • Polygonal, lumen: Flax

    • Oval to round, overlapping scales: Wool

    • Flat, oval lumen, convolutions: Cotton

    • Circular, serrated, lengthwise striations: Rayon

    • Dog-bone: Acrylic, spandex

    • Square with voids: Modified nylon or polyester

    • Triangular, rounded edges: Silk

    • Trilobal: Modified nylon or polyester

    • Lobular, lengthwise striations: Acetate

Surface Contour

  • Description: Describes the outer surface of the fiber along its length (e.g., smooth, rough, or striated).

  • Effects: Influences luster, hand, texture, and apparent soiling of the fabric.

Crimp

  • Fiber Crimp: Waves, bends, twists, coils, or curls along the length of the fiber.

    • Benefits: Increases cohesiveness, resiliency, resistance to abrasion, stretch, bulk, and warmth.

    • Mechanism for Warmth: Traps air within the fabric and next to the skin, enhancing insulation.

  • Fabric Crimp: Bends caused by the distortion of yarns due to weaving and knitting a fabric.

Fiber Parts

  • Natural Fibers (except silk): Typically have three distinct parts:

    • An outer covering (cuticle or skin).

    • An inner area.

    • A central core that may be hollow.

  • Manufactured Fibers: Generally simpler in structure, usually consisting of a skin and a core.

Chemical Composition

  • All matter is composed of chemicals.

  • Fibers are classified into groups based on two criteria:

    1. Source: Natural or manufactured.

    2. Chemical Composition: Cellulosic, protein, mineral, or synthetic.

  • Generic Group: Fibers with similar chemical compositions that distinguish them from other groups.

Molecular Arrangement

  • Polymerization: The process of connecting many small molecules (monomers) to produce one very large molecule, called a polymer.

  • Degree of Polymerization: The number of small molecules connected to form a polymer.

  • Amorphous: A random or disorganized arrangement of molecular chains within a fiber.

  • Crystalline: Molecular chains that are parallel to each other in a fiber or in regions within a fiber.

  • Orientation: The alignment of the fiber’s polymers along its longitudinal axis.

  • Stretching/Drawing: A process of pulling a fiber so that the molecular chains rotate and slide until they become oriented and form crystals within the fiber. This process enhances certain fiber properties like strength.

Serviceability

Aesthetics

  • Cover: The ability of a fiber or fabric to occupy space for concealment or protection.

  • Translucence: The ability of a textile to allow light to pass through it.

  • Luster: The way light is reflected from the fiber or fabric surface.

  • Drape: The manner in which a fabric falls or hangs over a three-dimensional form.

  • Texture: The nature of a fabric’s surface as perceived by sight or touch.

  • Hand: The way a fiber or fabric feels to the sense of touch.

Durability

  • Abrasion Resistance: The ability of a fiber to withstand everyday rubbing or abrasion.

  • Flexibility: The ability of a fiber to bend repeatedly without breaking.

  • Pilling: The formation of tiny balls of fiber ends and lint on the fabric surface, caused by abrasion.

  • Strength: The ability of a fiber to resist stress.

  • Tenacity (Tensile Strength): The ability of a textile to resist a pulling force.

  • Cohesiveness: The ability of fibers to cling together, which is important for yarn formation.

  • Elongation: The ability of a fiber to be stretched, extended, or lengthened.

Comfort & Safety

  • Absorbency: The percentage of moisture a bone-dry fiber will absorb from the air under standard conditions of temperature and moisture.

    • Hydrophilic: Fibers with high moisture regain or absorbency; known as "water loving."

    • Hydrophobic: Fibers that have little or no absorbency; known as "water hating."

    • Oleophilic: Fibers that have a high affinity or attraction for oil.

    • Hygroscopic: Fibers with high moisture absorbency that also have the ability to remain dry to the touch.

  • Dyeability: A fiber’s receptivity to coloration by dyes or its dye affinity.

  • Electrical Conductivity: The ability to transfer electrical charges.

  • Wicking: The ability of a fiber to transfer moisture along its surface, often away from the body.

  • Heat (Thermal) Retention: The ability of a fiber to retain heat or to insulate.

  • Heat Conductivity: The ability to conduct heat away from the body.

  • Heat Sensitivity: The ability of a fiber to soften, melt, or shrink when subjected to heat.

  • Flammability: Characteristics of a fabric that pertain to its relative ease of ignition and ability to sustain combustion.

  • Density (Specific Gravity): Weight in grams per cubic centimeter of an object. Affects fabric weight for a given volume.

  • Allergenic Potential: The ability of a fiber to cause a physical reaction (e.g., skin redness).

Appearance Retention

  • Resiliency: The ability of a fiber or fabric to return to its original shape after bending, twisting, and/or compressing.

    • Compression Resiliency: The ability of a fabric or pile to return to its original thickness after compression.

  • Dimensional Stability: The ability of a textile product to retain a given size and shape throughout its use and care.

  • Elasticity: The ability of a strained material to recover its original size and shape immediately after removing stress.

  • Creep: Delayed or gradual recovery from elongation or strain.

  • Aging Resistance: Ability to withstand deterioration over time.

  • Mildew & Moth Resistance: Ability to resist damage from biological agents.

Resistance to Chemicals & Light

  • Chemical Reactivity: Different fibers react differently to various chemicals.

    • Some fibers are very resistant to most chemicals.

    • Others are resistant to certain groups of chemicals but easily harmed by others.

    • This property dictates appropriate cleaning agents and industrial applications.

  • Light Resistance: Exposure to light may damage fibers. Light resistance refers to a finish or fiber modification to minimize the degradative effects of sunlight exposure on the fiber or its dye.

Care

  • Definition: "Treatment required to maintain a textile product’s original appearance."

  • Importance: Improper care can result in unattractive, poor-performing, and uncomfortable products.

  • Considerations: Fiber reactions to water, water temperature, cleaning chemicals, heat in pressing and drying, and storage must be considered.

Environmental Concerns & Sustainability

  • Refers to the way the production, use, care, and disposal of a fiber or textile product impacts the environment.

  • Sustainability is an overarching consideration in textile manufacturing.

Fiber Cost

  • Influencing Factors: Impacted by how a fiber is produced, the number of modifications it undergoes, and marketing strategies.

  • Market Dynamics: Costs for fibers are related to supply and demand.

  • Production Cost: The cost to grow and produce each fiber varies significantly.

  • Consumer Impact: Fiber cost represents only a small percentage of the total cost a consumer pays for a finished textile product.

Fiber Identification

Methods of Fiber Identification

  1. Visual Inspection: Initial assessment based on appearance and hand.

  2. Burn Test: Identifies general chemical composition.

  3. Microscopy: Best for natural fibers, examines lengthwise and crosswise appearance.

  4. Solubility: Uses specific chemical solvents to identify manufactured fibers by generic class and confirm natural fibers.

Visual Inspection

  • Always the first step in fiber identification.

  • Involves visual inspection of a textile for:

    • Length of fiber

    • Luster or lack of luster

    • Body, texture, and hand

Burn Test

  • Purpose: To identify a fiber's general chemical composition (e.g., cellulose, protein, mineral, or synthetic).

  • Limitations: Cannot identify fiber blends.

  • **Steps to Complete (as per Figure 3.7, p. 56):

    1. Ravel out and test several yarns from each direction of the fabric to determine if the same fiber type is present.

    2. Hold the yarn horizontally.

    3. Roll long pieces of yarn into a flat ball or clump for easier handling.

    4. Use tweezers to protect your fingers from the flame.

    5. Move yarns slowly into the edge of the flame and carefully observe what happens (e.g., how it burns, melts, smells).

    6. Repeat this step several times to check results for consistency.

    7. Compare observations to Table 3.7, "Identification by Burning," on p. 55 of the text.

Microscopy

  • Effectiveness: Best suited for the identification of natural fibers.

  • Examination: It's crucial to examine both the lengthwise and crosswise appearance of the fiber.

  • Challenge: Manufactured fibers are generally more difficult to identify accurately using microscopy alone due to their uniform nature/controlled shapes.

  • **Directions for Microscopy:

    1. Clean the microscope lens, glass slide, and cover glass thoroughly.

    2. Place a drop of distilled water on the clean slide.

    3. Untwist a yarn and place several fibers from the yarn onto the slide in the water drop.

    4. Cover the fibers with a cover glass and tap gently to remove any air bubbles.

    5. Place the prepared slide on the stage of the microscope.

    6. Focus with low power first, centering the fiber(s) in the viewing field.

    7. Move to a lens with greater magnification for detailed examination.

    8. Examine both warp and filling yarns if applicable, as fabric may be woven from different fibers in each direction.

Solubility

  • Purpose: Solubility tests are used to identify manufactured fibers by their generic class and to confirm the identification of natural fibers.

  • Method: Involves using a specific chemical solvent for each fiber type.

  • Standardization: Follows AATCC Test Methods.

  • **Examples:

    • Cotton: Dissolves in sulfuric acid.

    • Polyester: Dissolves in m-Cresol.