Unit 2 - Lecture 8 Topic 3 Flashcards
What is the colour, length and diameter of wool like?
Wool is typically creamy white in colour, but other natural colours include black, brown, and grey. Wool is a staple fibre that ranges length from 5-12.5 cm. The diameter ranges as well; fine wools are between 10-25 micrometers, coarse wools between 25-70 micrometers.
Is wool a weak fibre?
The breaking tenacity of wool is quite wool, even lower when wet. This is due to it’s low crystallinity and low degree of orientation.
Is wool resilient?
Wool is extremely résiliant because of it’s 3D crimp and helical polymer structure. Cystine linkages pull polymers back to position, so it can be bent many times without breaking; however this is dependent on moisture content (wool is less flexible when dry).
How durable is wool?
Wool has relatively good abrasion resistance, especially in the coarser fibres, however it is susceptible to insect damage.
Is wool warm?
Wool insulates by trapping air within the fibre, yarns and fabric through it’s 3D crimp shape. As well, it’s high resilience allows crushed fibres to return to original shape after, helping increase warmth.
What are the moisture properties of wool?
Wool has high moisture regain which is higher than cellulosic fibres. This is because of the polar groups and ionic groups in amino acid chains and because of it’s highly amorphous structure. Wool is hygroscopic, allowing it to absorb up to 1/3 of its weight without feeling damp. Further, wool has great heat absorption because it gives off heat during water absorption, an excellent use in cold conditions. Finally, wool has a hydrophobic surface, keeping water off the outside of the wool.
What is the initial modulus of wool like?
Wool has a low initial modulus, related to it’s many amorphous regions and helical configuration which can give out under pressure.
Why do people think wool is prickly?
This is related to fibre diameter. Wool that is <21 microns is typically not perceived to be itchy, but >30 microns is perceived to be itchy.
What is the resiliency of wool like?
Wool has excellent resilience and wrinkle resistance compared to cotton and linen.
What are the lustre properties of wool?
Wool has a low lustre because of the fibre crimp and staple fibre length. Coarser, longer wools with less crimp tend to be more lustrous. Some animal hairs like cashmere also have higher lustre.
Does wool pill?
Wool tends to pill easily but pills break off easily due to the weakness of the fibre.
What is the electrostatic charge of wool?
Wool is susceptible to building up charge in dry climates. In humid environments wool does not build up static electricity.
Is wool flammable?
Wool burns slowly, and self-extinguishes when removed from a flame. It can have flame retardant finishes added for certain applications (eg, upholstery, aviation).
What is the dimensional stability of wool?
Wool felts due to the scales that cause a directional frictional effect. It can have shrink proof treatments to make wool machine washable.
