文档介绍：Chapter 10 Wool Fibers
Morphology
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
Wool fibers under polarized optical microscope
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.
Structures of wool fibers
Submicrostructure
Cotex: each cortex posed of
macrofibrils
microfibrils
protofibrils
- keratin polymer molecules (polypeptide)
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%)
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.
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
Properties of wool fibers
Comfort proper