Impurities of Different Fibers with Their Percentages

In this blog we will discuss about impurities of different fibers with their percentages. The main ingredient of cotton is cellulose (94%). It also contains many other component which is known as cotton impurities.

Impurities on cotton fiber
Impurities on cotton fiber
ImpuritiesPercentage (%)Removal process
Mineral matter1.3Scouring
Oil, fat & waxes0.6Scouring


Jute is cellulosic best fiber. The main ingredient of jute is cellulose (94%). It also contains many other component which is known as jute impurities.

ImpuritiesPercentage (%)Removal process
Hemi-cellulose22.2Mild scouring
Lignin10.8Mild scouring
Water slabs1.50Mild scouring
Fat, waxes & color pigment0.5Fat→ scouring, Color pigment→bleaching.


Wool is an animal fiber. The main ingredient of wool is keratin (61%). It also contains many other component which is known as wool impurity.

ImpuritiesPercentage (%)Removal process
Oil & fats11Scouring
Burrs & others1.2Carbonizing


Silk is an animal fiber. The main ingredient of silk is fibroin (76%). It also contains many other components which is known as silk impurity.

ImpurityPercentage (%)Removal process

Types of Impurities of Different Fibers

  1. Introduction to Fiber Impurities
  2. Natural Fibers and Their Impurities
    • Cotton
    • Wool
    • Silk
  3. Synthetic Fibers and Their Impurities
    • Polyester
    • Nylon
    • Acrylic
  4. Impurities in Regenerated Fibers
    • Viscose
    • Lyocell

Introduction to Fiber Impurities

Impurities in fibers can arise from various sources, including environmental contamination, processing methods, and inherent material properties. These impurities can impact the fiber’s strength, durability, dye ability, and overall performance. Identifying and managing these impurities is essential for ensuring the quality and consistency of the final product.

Natural Fibers and Their Impurities


Cotton is a widely used natural fiber, prized for its softness and breathability. However, it contains several impurities:

  • Cellulosic Waxes and Pectins (0.5-1%): These are natural substances present in the cotton fiber that need to be removed during processing.
  • Proteins and Amino Acids (1-1.5%): Residues from the cotton plant.
  • Mineral Salts (0.5-1%): Includes calcium, magnesium, and other salts absorbed from the soil.
  • Dirt and Dust (1-2%): External impurities collected during harvesting.


Wool, known for its warmth and resilience, also contains impurities:

  • Grease (10-25%): Lanolin, a natural grease, must be removed.
  • Suint (2-10%): Water-soluble salts excreted by sheep.
  • Vegetable Matter (1-3%): Plant debris like seeds and grass.
  • Dirt and Dust (1-5%): Similar to cotton, wool attracts soil particles.


Silk is valued for its luxurious feel and luster, but it is not free from impurities:

  • Sericin (20-30%): A protein that acts as a gum, binding the silk fibers.
  • Wax and Fats (0.5-1%): Small amounts of natural lipids.
  • Mineral Matter (0.5-1%): Traces of minerals from the silkworm’s diet.

Synthetic Fibers and Their Impurities


Polyester is a popular synthetic fiber with the following impurities:

  • Oligomers (0.5-1%): Small polymer chains that need to be filtered out.
  • Catalyst Residues (0.1-0.5%): Remnants from the polymerization process.
  • Spin Finish Oils (0.5-1%): Applied to aid processing and must be cleaned off.


Nylon is known for its strength and elasticity, but it includes:

  • Monomers (0.1-0.5%): Unreacted monomer residues.
  • Additives (0.5-1%): Stabilizers and plasticizers that might need to be removed.
  • Spin Finish Lubricants (0.5-1%): Applied for manufacturing ease.


Acrylic fibers, used for their wool-like qualities, contain:

  • Residual Solvents (0.5-1%): Left from the polymerization process.
  • Monomers (0.2-0.5%): Unreacted chemicals.
  • Processing Oils (0.5-1%): Used to facilitate fiber extrusion.

Impurities in Regenerated Fibers


Viscose, made from cellulose, has the following impurities:

  • Sulfur Compounds (0.5-1%): Byproducts of the xanthation process.
  • Residual Sodium Hydroxide (0.2-0.5%): Used in cellulose dissolution.
  • Additives (0.5-1%): Softening agents and dyes.


Lyocell, a more eco-friendly regenerated fiber, includes:

  • Residual Solvents (0.5-1%): Primarily N-Methylmorpholine N-oxide (NMMO).
  • Spin Finish Agents (0.5-1%): Applied to assist fiber formation.


Understanding the impurities found in different fibers and their percentages is critical for many businesses to provide the highest quality final products. Natural fabrics like cotton and wool, as well as synthetic choices like polyester and nylon, require particular treatments to efficiently eliminate impurities. By removing these contaminants, producers can improve the performance, durability, and aesthetic aspects of their fibers, resulting in better goods for consumers.

By going into the mechanics of fiber impurities, this guide seeks to provide a full grasp of what to expect and how to deal with these issues, allowing both producers and consumers to make informed textile market decisions.

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