Unit 2 - Lecture 8 Topic 2 Flashcards
What types of bonds are present in wool structure?
Weak van der waals bonds, hydrogen bonds (stronger bonds formed between polar side-groups), ionic bonds – or salt linkages (between the acidic and basic side-groups), and disulphide bonds – or cystine linkages (strong covalent bonds).
What is the fine structure of wool like?
Wool is shaped in an alpha-helix keratin polymer. This is a helical arrangement that helps wool’s resilience and elasticity. Extensive extension can permanently distort wool. Humid conditions facilitate extension, but also recovery.
Is wool more amorphous or crystalline?
Wool is about 25-30% crystalline and about 70-75% amorphous.
What is the physical structure of wool like?
Wool is a biological composite material making it very unique. It contains a cuticle, cortex, and cell membrane complex which acts as an intracellular cement.
What is the cuticle structure of wool like?
The cuticle is made of the epicuticle (surface layer), exocuticle, and endocuticle. It’s cuticle cells are 2-3 layers of flattened, overlapping cells with scales that have a directional frictional effect. Scales cause wool to felt, which creates dimensional instability during laundering. The cuticle protects the fibre from chemical and physical damage. The epicuticle is hydrophobic, due to lipids covalently bonded to the surface.
What is the cortex of wool fibres like?
The cortex is the central mass of the fibre. Cortical cells are split into two further types; Ortho & Para cells. These cells have a bilateral arrangement responsible for fibre crimp. Most physical and chemical behaviour of wool is a result of the cortex.
What are cortical cells in wool useful for?
The fibrillar, spiralling structure within cortical cells allows for the flexibility, elongation, elastic recovery & tenacity of wool.
How is the cell membrane complex important to wool?
The cell membrane complex surrounds each cortical cell. It is the only continuous phase in wool fibres. These fibres have different proportion of amino acids: Low levels of cystine and high levels of polar molecules (eg, tyrosine) and non-reactive phenylalanine. This gets easily swollen and is accessible to chemicals and water.
