What Makes Wool Fabric Unique in Chemistry?
Wool is a textile fibre made from sheep and other species, such as goats' cashmere and mohair, muskoxen's qiviut, rabbit’s angora, and camelid’s various forms of wool.
Wool fibre is a finely ordered structure with the cuticle, cortex, and medulla as its main histological components. Wool fibre is a natural fibre, and its characteristics such as diameter, crimps, and length are important parameters of the wool trait and indicators of the wool's spinning quality.
What is Fleece?
If you are wondering What is Fleece? If there is such a thing as a man-made wonder commodity, fleece it is. While being named after a sheep’s fleece coat, it is made entirely of synthetic materials and is derived from plastic rather than a fluffy sheep's coat.
Properties of Wool
Crimps: Wool fibre is wavy and twisted in some places. Crimp is the name for this waviness. The finer the yarn, the more crimps it will get.
Friction softens the wool fibre, particularly when wet, and is thus beneficial in maintaining a smooth, soft texture in fabrics.
The heat has little impact at low temperatures, but high temperatures weaken the fibre and cause it to lose its colour.
Moisture effect: Wool is the most hygroscopic material on the planet. It can absorb up to 50% of its weight and bear up to 20% of its weight without getting drenched.
When wool fibres are exposed to heat, moisture, and strain, they interlock and contract. Felting is aided by the scale-like exterior of the fibres.
Heat conductivity: Since wool fibre is a weak conductor of heat, fabrics made from it are best suited for winter wear.
Wool is highly durable, and when hung after being wrinkled or formed, it returns to its original form.
It has more strength than silk. Wool loses about 25% of its strength when wet. The yarn's strength will increase as the fibre lengthens.
Wool is a highly elastic material. When it's dry, it's about 10% to 30% stretched, and when it's wet, it's about 40% to 50% stretched. When it's dry, it quickly returns to its original measurements.
Wool has a high resistance to shrinkage. Long-term moisture exposure, on the other hand, can cause shrinkage.
Characteristics of Wool
Antistatic
Anti Wrinkle
Biodegradable
Breathable
Elastic
Fire resistant
Nature’s fibre
Odour resistant
Renewable
Stain-resistant
Soft
Processing Fibres Into Wool
Shearing – Shearing is the method of removing the woollen coat or fleece from an animal. Shearing instruments such as scissors, hand knives, and electric shears are used to do this without damaging the animal.
Scouring – Raw or grease wool is wool that has been taken directly from the sheep. To remove grease, dust, and dirt, raw sheared wool is washed in tanks with detergent and alkali.
Sorting and Grading – Defective or inferior wool is removed after scouring. Sorting is the term for this procedure. Grading is the method of sorting wool based on the weight, colour, and texture of the fibres.
Carding – Wool must be disentangled and washed until it can be used to make clothing. Continuous fibres are formed by separating the intermixed fibres.
Carded wool is twisted into a silver cord to make yarn. Silver is twisted and stretched into a thin thread. A mule spinning system is commonly used to spin woollen yarns.
Washing and Finishing – Woollen yarn is spun or knitted into fabric, which is then used to produce finished goods like clothing, tablecloths, and bags.
Types of Wool Fabric
Here mentioned are the types of wool fibres-
Lambswool is derived from the first shearing of a young sheep (lamb) at about seven months of age. It's also known as virgin wool, but that term also applies to wool that hasn't been processed yet. Shearing the lamb at this point produces wool that is exceptionally smooth, fluffy, and fine, as well as hypoallergenic.
Merino wool is derived from the merino sheep breed, which originated in Spain, though most merino wool is now exported from Australia. Merino wool is known for its fine fibres, which give it a supremely soft hand and make it ideal for garments that come into direct contact with the wearer's skin, such as base layers.
This wool is produced by Shetland sheep from Scotland's Shetland Islands. It's thicker and coarser than other wools, such as merino, due to the region's cold climate.
Mohair is a type of wool that comes from the Angora goat and differs from other types of wool for many reasons. In the shearing process, guard hairs from the goat's topcoat are often mixed in with the undercoat. Angora goats are grown in a mild environment, so their fibres aren't as coarse as other wools; their longer length gives the fibre its smoothness and results in a uniquely fluffy cloth.
When cashmere (Kashmir) goats join the moulting season, they have their undercoats shorn. Since cashmere is shorn from the undercoat, the yield per goat is low, so a single sweater needs two cashmere goats.
Angora wool is the lightest, best, and warmest of the natural fibres, coming from Angora rabbits. Angora fibres are hollow and smooth, similar to alpaca fibres, giving them unrivalled warmth and loft. The fibres are incredibly fine, but they are also extremely fragile. As a result, angora is often blended with other fibres to improve its longevity.
The majority of camel hair comes from Bactrian camels, which are born in cold climates such as Mongolia, China, and Russia, and is collected in the spring when the camel moults. Camel hair has a hollow appearance similar to mohair and is smoother and longer than sheep's fur. As a result, the fabric is lighter and lustrous than sheep's fur, and it's just as soft as cashmere.
The undercoat of the arctic muskox, which is bred in Canada and Alaska, is used to make Qiviut fur. The undercoat of the muskox is shed during the moulting season, and breeders either harvest the wool by combing it or plucking it from the grass. Qiviut is eight times colder than superfine sheep's wool and is finer than superfine sheep's wool. It also does not shrink when submerged in water.
Did You Know?
Alpacas are South American animals that grow hollow fur. Alpaca has a peculiar property that makes them both lightweight and insulating. It's both lighter and warmer than wool from sheep. Alpaca is comparable to cashmere in terms of softness, but it is much heavier. Alpaca hair is hypoallergenic by nature, making it perfect for those who have sensitive skin.
FAQs on Wool Fabric: Meaning, Types, and Key Properties
1. What is wool fabric and from which animals is it primarily obtained?
Wool fabric is a natural textile fibre obtained from the fleece of certain animals. While it is most commonly sourced from sheep, other animals also provide specialty wools. These include the Angora goat (for Mohair), Cashmere goat (for Cashmere), yak, and even camels and rabbits (for Angora wool).
2. What is the basic chemical composition of a wool fibre?
Wool is primarily composed of a natural protein called keratin, the same protein found in human hair and nails. This protein structure, along with lipids, gives wool its characteristic strength, elasticity, and moisture-absorbing properties. The complex chemical makeup makes it a highly functional natural fibre.
3. What are the main types of wool, and what makes them different?
The main types of wool are distinguished by the animal source and the fineness of the fibres. Key examples include:
- Merino Wool: Sourced from Merino sheep, it is known for being exceptionally fine, soft, and suitable for next-to-skin clothing.
- Cashmere Wool: Obtained from the undercoat of Cashmere goats, it is incredibly soft, lightweight, and provides excellent insulation.
- Mohair: From the Angora goat, this wool is known for its lustre, durability, and silky feel.
- Alpaca Wool: Sourced from alpacas, it is soft, durable, luxurious, and naturally hypoallergenic.
4. What are the key properties of wool that make it a useful textile?
Wool possesses several unique properties that make it a highly valued textile, including:
- Insulation: The natural crimp in wool fibres creates tiny air pockets that trap heat, providing excellent warmth.
- Elasticity and Durability: Wool fibres can be bent and stretched thousands of times without breaking, allowing garments to retain their shape and resist wrinkles.
- Moisture-Wicking: It is highly absorbent and can hold moisture vapour without feeling wet, effectively wicking sweat away from the body.
- Odour Resistance: Due to its moisture-absorbing properties, wool naturally resists the buildup of bacteria that cause odours.
- Flame Resistance: Wool is naturally more flame-resistant than many other common fibres.
5. What is the difference between virgin wool and recycled wool?
Virgin wool refers to wool that has been spun into yarn for the first time, directly from a sheep's fleece, without ever having been used or processed before. It is typically stronger and of higher quality. Recycled wool, also known as shoddy, is made by breaking down existing wool fabrics or unused yarn scraps back into fibres, which are then re-spun into new yarn. While more sustainable, recycled wool fibres are shorter and may be less durable than virgin wool.
6. How are raw wool fibres processed into yarn ready for weaving?
The conversion of raw fleece into yarn involves several key steps as per the NCERT syllabus:
- Shearing: The process of removing the fleece from the sheep in one piece.
- Scouring: The sheared wool is washed thoroughly in tanks to remove grease, dust, and dirt.
- Sorting: The fleece is separated based on the quality and texture of the fibres.
- Carding: The clean fibres are passed through rollers with fine wire teeth to straighten and align them into a continuous web called a 'sliver'.
- Spinning: The sliver is then drawn out and twisted to form a strong, continuous thread of yarn.
7. How does the physical structure of a wool fibre contribute to its insulating properties?
The insulating power of wool comes from its natural crimp, which is the fine, wavy structure of the fibre. This crimp creates millions of tiny air pockets within the fabric. Since air is a poor conductor of heat, these trapped pockets form a thermal barrier that prevents body heat from escaping and keeps the cold air out, making wool an excellent insulator.
8. Why does wool fabric feel different from cotton, even though both are natural fibres?
The difference in feel between wool and cotton is due to their fundamentally different compositions and structures. Wool is a protein-based fibre (keratin) with a scaly, crimped surface that makes it feel springy and warm. In contrast, cotton is a cellulose-based fibre that is smooth, soft, and feels cooler to the touch because it conducts heat away from the body more readily.
9. Why is wool known for being odour-resistant compared to synthetic fabrics like polyester?
Wool's superior odour resistance comes from its ability to manage moisture. Wool fibres can absorb significant amounts of sweat vapour and move it away from the skin, keeping the surface dry. Since odour-causing bacteria thrive in moist environments, this property makes the surface of wool fabric less hospitable for them to grow. Synthetic fabrics like polyester cannot absorb moisture vapour, leaving sweat to sit on the fabric's surface, which creates an ideal breeding ground for bacteria.
10. Can wool be worn in warmer weather, or is it only for winter?
While wool is famous for its warmth, certain types of lightweight wool are excellent for warmer weather. The same properties that trap heat in the cold also help to insulate against heat in warmer conditions. Furthermore, wool's exceptional breathability and moisture-wicking ability help to keep the body cool and dry by pulling sweat away from the skin and allowing it to evaporate. Lightweight Merino wool, for example, is a popular choice for summer hiking and athletic wear.
