广东纺织职业技术学院：《纺织材料学》课程教学资源（PPT课件，英文版）3 Wool Fibers

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Chapter 10 Wool Fibers

Chapter 10 Wool Fibers

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Morphology FIGURE 10.2 Photomicro- graph of wool fiber showing the surface scales overlapping toward the tip of the fiber and an oval cross-section 50 um(left) H 10 um(right)

Morphology

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structures of wool fibers 口 Submicrostructure ■ Cotex core of the wool fiber. 90% of the fiber volume consists of countless long spindle-shaped cells held together by intercellular cement

Structures of wool fibers ❑ Submicrostructure ◼ Cotex ➢ core of the wool fiber: ➢ 90% of the fiber volume, ➢ consists of countless long, spindle-shaped cells held together by intercellular cement

广京费飘职业轼水学院 Wool fibers under polarized s of ot tholey optical microscope

Wool fibers under polarized optical microscope

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structures of wool fibers 口 Submicrostructure ■ Cotex can be divided into 2 sections Orthocotex containing less cystine and thus less s-s bonds Paracortex containing more cystine absorbing less water two sections spiral around each other along the er len the two sections respond to heat and moisture differently forming 3-D crimp

Structures of wool fibers ❑ Submicrostructure ◼ Cotex ➢ can be divided into 2 sections: ◼ Orthocotex containing less cystine, and thus less S-S bonds ◼ Paracortex containing more cystine, absorbing less water. ◼ two sections spiral around each other along the fiber length. ◼ the two sections respond to heat and moisture differently forming 3-D crimp

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structures of wool fibers a Submicrostructure Cotex: each cortex cell composed of ◆ macrofibril ■ microfibrils · protofibrils keratin polymer molecules (polypeptide)

Structures of wool fibers ❑ Submicrostructure ◼ Cotex: each cortex cell composed of macrofibrils ◼ microfibrils ▪ protofibrils - keratin polymer molecules (polypeptide)

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structures of wool fibers a Keratin polymer: helix of amino acids Structural characteristics 18 different amino acids each with -N-c-c- backbone > a helix: 3 amino acids per turn(right-handed helix) Diversity of amino acids: good for dyeing Polar groups in amino acids hydrophilicity s Cystine amino acid: contains sulfu degradation by moths and beetles Big side groups and spiral molecular configuration hard to be packed well leading to low crystallinity(only 25-30%)

Structures of wool fibers ❑ Keratin polymer: helix of amino acids ◼ Structural characteristics ➢ 18 different amino acids: each with -N-C-C￾backbone ➢ a helix: 3 amino acids per turn (right-handed helix) ➢ Diversity of amino acids: good for dyeing ➢ Polar groups in amino acids: hydrophilicity ➢ Cystine amino acid: contains sulfur: degradation by moths and beetles ➢ Big side groups and spiral molecular configuration: hard to be packed well leading to low crystallinity (only 25-30%)

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structures of wool fibers Intermolecular bonding cross-linking: 2 cystine amino acids one on each of the two adjacent chains form a cystine link, a covalent bond(s-s bond, increasing strength and elasticity. Ionic bond: salt linkage formed when two amino acids are in close proximity responsible for reacting with acid dyes Hydrogen bonds: between amide groups but have relatively low density due to more amorphous phase and packing difficulties

Structures of wool fibers Intermolecular bonding ◼ Cross-linking: 2 cystine amino acids one on each of the two adjacent chains form a cystine link, a covalent bond (S-S bond), increasing strength and elasticity. ◼ Ionic bond: salt linkage formed when two amino acids are in close proximity: responsible for reacting with acid dyes. ◼ Hydrogen bonds: between amide groups but have relatively low density due to more amorphous phase and packing difficulties

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Properties of wool fibers 口 Mechanical properties relatively low strength or tenacity high elastic recovery high flexi bility ■ high resilience ■| ow initia|modu|us ow abrasion resistance ■ ow stiffness ■| ow toughness properties change as water absorption changes

Properties of wool fibers ❑ Mechanical properties: ◼ relatively low strength or tenacity ◼ high elastic recovery ◼ high flexibility ◼ high resilience ◼ low initial modulus ◼ low abrasion resistance ◼ low stiffness ◼ low toughness ◼ properties change as water absorption changes

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Properties of wool fibers ● Comfort properties: high heat of wetting due to more amorphous phase than many other fibers) slow the rate of evaporation of body water water repellent due to epicuticle 3-D crimp traps more air reducing thermal conductivity air space N 2/ 3 of total volume low luster due to crimp and scales ■ odor absorbent i high pilling but easy to remove

Properties of wool fibers Comfort properties: ◼ high heat of wetting due to more amorphous phase than many other fibers) ◼ slow the rate of evaporation of body water ◼ water repellent due to epicuticle ◼ 3-D crimp traps more air reducing thermal conductivity air space ~ 2/3 of total volume ◼ low luster due to crimp and scales ◼ odor absorbent ◼ high pilling but easy to remove