Protein Fibre: Characteristics, Classification and Uses

What is Protein Fibre in Textile?
Protein fibre is a type of fibre that is derived from natural sources that contains proteins. They are produced from various animal and plant sources, such as silk from silkworms, wool from sheep, casein from milk, and others. Protein fibers are formed by animal sources through condensation of α-amino acids to produce repeating polyamide units with various substituents on the α-carbon atom.

Generally speaking, protein fibre is a fibre of moderate strength, resiliency and elasticity. They have excellent moisture absorbency, and static charge is not built up on them. They are fairly resistant to acids, but are readily attacked by bases and oxidizing agents. The fibres have a tendency of yellowing in sunlight. They are comfortable under most environmental conditions, and they possess excellent aesthetic qualities.

Protein fibres have a unique molecular structure that gives them specific physical and chemical properties, such as high tensile strength, excellent insulation properties, and resistance to degradation. These properties make protein fibres suitable for a wide range of applications, including textiles, medical products, and food additives.

In textiles, protein fibres are commonly used for clothing, bedding, and upholstery due to their softness, durability, and insulation properties. In medical products, protein fibres such as casein and silk are used for sutures and wound dressings due to their strength, biocompatibility, and biodegradability. In food additives, casein is used as a protein supplement and emulsifier.

Types of Protein Fibre:
There are several types of protein fibres, including:

1. Silk: Silk is a natural protein fibre obtained from the cocoons of silkworms. It is considered the strongest natural fibre and is characterized by its luster, softness, and strength. Silk is commonly used for clothing, bedding, and upholstery.

silk fiber
Fig: Silk fiber

2. Wool: Wool fibre is obtained from the fleece of sheep and other animals such as goats, alpacas, and rabbits. It is a warm, insulating, and moisture-wicking fibre that is characterized by its crimped structure. Wool is commonly used for clothing, upholstery, and insulation.

wool fibre
Fig: Wool fibre

3. Casein: Casein is a protein obtained from milk and is used as a starting material for making fibres, films, and adhesives. Casein fibres have a soft, silk-like feel and are often used in medical applications, such as sutures and wound dressings.

4. Mohair: Mohair is a lustrous and durable protein fibre obtained from the hair of the angora goat. Mohair is known for its silky texture, warmth, and sheen. It is often used in clothing and textiles.

5. Alpaca: Alpaca fibre is obtained from the alpaca, a domesticated mammal native to South America. Alpaca fibre is known for its softness, warmth, and light weight. It is often used for clothing, blankets, and other textiles.

6. Cashmere: Cashmere is a luxurious, soft, and lightweight protein fibre obtained from the cashmere goat. Cashmere is characterized by its softness, warmth, and light weight. It is often used for high-end clothing and textiles.

7. Angora: Angora is a soft and lightweight protein fibre obtained from the angora rabbit. Angora is known for its fluffiness, softness, and warmth. It is often used for clothing and textiles.

Classification of Protein Fibre:
Two major classes of natural protein fibres are keratin (hair or fur) and secreted (insect) fibres. The most important members of the two groups, respectively, are wool (derived from sheep) and silk (excreted by various moth larvae such as Bombyx mori).

Wool is composed of an extremely complicated protein called keratin, which is highly cross-linked by disulphide bonds from cystine amino acid residues. However, the silk fibre is composed of much simpler secreted protein chains, which are arranged in a linear pleated structure with hydrogen bonds between amide groups on adjacent protein chains.

Regenerated protein fiber is a type of fiber that is produced from natural protein sources, such as casein, which is a protein found in milk. These fibers are created by chemically or mechanically processing the natural protein source to produce fibers with specific properties, such as strength and durability. Examples of regenerated protein fibre, Casein fiber, soy fibre, pea fiber etc.

Properties / Characteristics of Protein Fibre:
The natural protein fibres differ with regard to three major characteristics, which explains their distinct differences:

  • Physical structure of the natural protein fibres: diameter, surface characteristics and fibre structure [e.g. shed-like cuticula, presence of a fibre core (cortex) in wool, combination of different major proteins: fibroin and sericin in silk].
  • Protein conformation, secondary and tertiary structure: the secondary structure of the protein can be in random coil, sheet, twisted and helical conformation.
  • Primary structure of the protein. The major amino acids present in the protein differ with regard to composition and distribution between fibres, but also between different parts of a fibre (e.g. cuticula and cortex of wool, sericin and fibroin of raw silk). Differences are also observed between different types of hair and between breeds of the same fibre group of hair, for example, wool (Merino, Cheviot wool).

Protein fibres have several unique properties, including:

a) Strength: Protein fibres have high tensile strength, making them durable and resistant to breaking. This makes them ideal for use in applications that require strong fibres, such as textiles, medical products, and industrial products.

b) Softness: Many protein fibres, such as silk and wool, are known for their softness and luxurious feel. This makes them ideal for use in clothing, bedding, and fashion accessories.

c) Insulation: These fibres have good insulation properties, making them ideal for use in clothing and bedding. They help to regulate body temperature by keeping heat close to the skin in cold weather and wicking moisture away from the skin in warm weather.

d) Moisture Absorption: Some protein fibres, such as wool, are hydrophilic, meaning they can absorb moisture. This makes them ideal for use in clothing, as they can absorb sweat and help to keep the skin dry.

e) Biodegradability: Silk and casein, are biodegradable, meaning they can break down naturally in the environment. This makes them environmentally friendly and reduces waste.

f) Biocompatibility: Some protein fibres, such as silk and casein, are biocompatible, meaning they are not harmful to living tissues. This makes them suitable for use in medical products, such as sutures and wound dressings.

g) Warmth: Wool and alpaca, are known for their warmth and are commonly used in clothing and blankets.

Uses / Application of Protein Fibre:
A large number of protein-based fibres are used for textile products, technical and medical applications (e.g. wool, cashmere goat hair, angora rabbit hair and silk) as well as regenerated protein fibres (e.g. from soya protein or casein). Textile protein fibre plays an important role in the textile industry due to their unique properties and versatility. They are commonly used in,

1. Clothing: Protein fibres are commonly used in clothing, such as shirts, pants, and dresses, due to their softness, durability, and insulation properties. They help regulate body temperature and wick moisture away from the skin, making them ideal for use in clothing.

2. Bedding: Silk and wool, are used in bedding, such as sheets and blankets, due to their softness, warmth, and insulation properties.

3. Upholstery: Wool and silk, are used in upholstery, such as sofas and chairs, due to their softness and durability.

4. Carpets: Textile protein fibres, such as wool, are used in carpets due to their softness, warmth, and durability.

5. Fashion accessories: Protein fibres, such as silk and cashmere, are used in high-end fashion accessories, such as scarves and shawls, due to their softness and luxurious feel.

6. Industrial products: Spider silk, are being researched for their potential use in industrial products due to their strength and durability.

7. Art and craft: Protein fibres, such as silk and wool, are used in various art and craft applications, such as weaving and embroidery, due to their softness and versatility.


  1. A Novel Green Treatment for Textiles: Plasma Treatment as a Sustainable Technology By Chi-wai Kan
  2. Physical Properties of Textile Fibres (Fourth edition) by W. E. Morton and J. W. S. Hearle
  3. Textile Chemistry By Thomas Bechtold and Tung Pham
  4. Handbook of Textile Fibre Structure | Volume 2: Natural, Regenerated, Inorganic and Specialist Fibres Edited by S.J. Eichhorn, J.W.S. Hearle, M. Jaffe and T. Kikutani

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