Chemical Characteristics of Wool Fiber:
Whereas cotton, flax and the other plant fibers re basically cellulose, wool is protein. Keratin, the substance of wool is similar in its essential structure to the other proteins from which much of the animal body is built. The chemical structure of wool fiber differs only slightly from that of feathers, hair ad horn.
In their chemical behavior, proteins are quite different from cellulose. They are more easily degraded and attacked by chemicals, particularly of certain types. They do not, in general, have the resistance to environmental conditions that is so characteristic of cellulose.
1. Effect of Acids:
Wool is attacked by hot concentrated sulphuric acid and decomposes completely. It is in general resistant to other mineral acids of all strengths, even at high temperature, though nitric acid tends to cause damage by oxidization. Dilute acids are used for removing cotton from mixtures of the two fibers; sulphuric acid is used to remove vegetable matter in the carbonizing process.
2. Effect of Alkalis:
The chemical nature of wool keratin is such that it is particularly sensitive to alkaline substances. Wool will dissolve in caustic soda solutions that would have little effect on cotton. The scouring and processing of wool is carried out under conditions of low alkalinity. Even weakly alkaline substances such as soap or soda are used with care. Soda will tender wool and turn it yellow if used in too concentrated a solution, particularly if the solution is too hot. Ammonium carbonate, borax and sodium phosphate are mild alkalis that have a minimum effect on wool. Ammonia, carefully used, will not cause damage.
3. Protein Composition:
- Wool is a natural fiber composed primarily of keratin, a protein that is rich in amino acids like cystine. Keratin is a complex, sulfur-containing protein that forms strong, flexible fibers, making wool resilient and elastic.
4. Hydroscopic Nature:
- Wool fibers can absorb moisture up to 30% of their weight without feeling wet. This is due to the hydrophilic groups (like amino and carboxyl groups) in keratin that attract water molecules.
5. Thermal Properties:
- Wool has excellent thermal insulation properties due to the crimped structure of the fibers, which traps air and acts as an insulator. This helps in retaining body heat while keeping the wearer warm.
6. Dye Affinity:
- Wool fibers have a natural affinity for dyes, particularly acid dyes, because of the ionic interactions between the dye molecules and the amino groups in keratin. This allows wool to be dyed easily and with vibrant colors.
7. Resistant to Static and Flame:
- Wool is naturally resistant to static electricity because of its moisture content, which prevents the buildup of static charges. It’s also flame-resistant, meaning it doesn’t ignite easily and tends to self-extinguish when exposed to fire.
8. pH Sensitivity:
- Wool is sensitive to strong acids and bases. It can be damaged or dissolved when exposed to alkaline conditions (high pH), which can break down the keratin structure.
Effect of Organic Solvents:
Wool has a good resistance to dry-cleaning and other common solvents.
Insects:
Wool is attacked by moth-grubs and by other insects.
Micro-organisms:
Wool has a poor resistance to mildews and bacteria and it is not advisable to leave wool for too long in a damp condition.
Uses of Wool Fiber:
One of the first things we meet on entering the world is wool. And, although it is no longer compulsory by law, wool is still very often our closest companion where we leave. Woolies are worn by babies because they are warm and airy. Wool clothes are healthy and hard wearing. The have many other properties- some desirable, some not. All are in one way or another direct consequence of the properties of the fiber itself.
The wool fiber has excellent spinning characteristics. Its crimp enables the fibers to cling tenaciously together when they are spun. Because of this, it is possible to make a relatively strong yarn from wool fibers without twisting them very tightly. Knitting wool, for example, can be spun very loosely and yet is quite coherent.
1. Textiles and Apparel:
- Clothing: Wool is widely used in the production of garments, especially for cold weather. This includes sweaters, jackets, scarves, and suits due to its warmth and insulating properties.
- Socks and Underwear: Wool’s moisture-wicking ability makes it ideal for socks and underwear, keeping the skin dry and comfortable.
- Blankets and Throws: Wool is used in blankets and throws for its warmth and comfort.
2. Home Furnishings:
- Carpets and Rugs: Wool is durable and stain-resistant, making it a popular choice for carpets and rugs.
- Upholstery: Wool’s resilience and aesthetic appeal make it suitable for upholstery in furniture.
3. Industrial Applications:
- Insulation Material: Wool is used as an eco-friendly insulation material in construction, providing both thermal and sound insulation.
- Felt Production: Wool is a key material in the production of felt, which is used in various industrial applications, such as padding, polishing, and soundproofing.
4. Other Applications:
- Fashion Accessories: Wool is used to make fashion accessories such as hats, gloves, and scarves.
- Medical Textiles: Due to its softness and moisture management properties, wool is used in medical textiles, such as bandages and padding.
Wool’s unique chemical properties make it a versatile fiber that is valuable in various industries, from fashion and home furnishings to industrial applications.