Want to buy cotton yarn in Ludhiana? Quality is an important factor. Each cotton bale comes with unique fibre properties. You can identify these properties with a combination of instrument evaluations using High Volume Instrument. It is important to gather this information as it is required while marketing the bale for sale and in textile mills during processing.

Fibre Evaluation 

HVI classification uses the following quality factors: 

  1. Length uniformity index
  2. Staple length
  3. Micronaire
  4. Strength
  5. Colour
  6. Colour grade
  7. HVI trash

Length Uniformity Index

Cotton yarn evenness and strength depend on length uniformity. It also affects the spinning process efficiency. A low length uniformity index makes it difficult to process and leads to lower-quality yarn. Length uniformity index =mean length/upper-half-mean length

 The HVI system has a length sensor that measures the mean length and upper-half-mean length. Cotton fiber has a natural length distribution. Cotton fibre has a higher length uniformity index with lower variation in the length distribution.

HVI Length Uniformity Index (%) Degree of Uniformity 
Below 77  Very low 
77-79 Low 
80-82 Intermediate 
83-85 High 
Above 85  Very High 

 Staple Length 

Staple length is the average length of the spinnable fiber. Hand stapling is the traditional process of manually estimating the staple length. A cotton classer performs hand stapling. Today, HVI is used for calculating staple length. The following factors lead to short staple length: 

  • Water stress 
  • Extreme temperatures
  • Nutrient deficiencies 
  • Insect pressure 
  • Excessive cleaning 
  • Excessive drying

Staple length affects the following in the spinning process: 

  • Yarn strength 
  • Yarn evenness 
  • Yarn efficiency 

Micronaire 

Fibre fineness and maturity is measured in Micronaire. It measures compressed cotton fibre’s air permeability. The fineness and maturity of fibre play an important role in fibre processing. Micronaire affects the following: 

  • Neps (knots of tangled fibre)
  • Processing waste
  • Spinning performance
  • Dyed fabric appearance
  • Yarn and fabric quality

You must match the fibre micronaire to the applications. 

Strength 

Genetics determine fibre strength. This is the reason why cotton variety is an important factor for fibre quality. Fibre strength also depends on the environment and crop management. HVI is used to measure fibre strength. Fibre strength is the force in grams that breaks a bundle of fibre in a tex unit in mass.  

Strength (grams per tex) Description of degree of strength 
23 and below  Weak 
24-25 Intermediate 
26-28 Average 
29-30 Strong 
31 and above  Very strong 

Colour and Color Grade

Cotton fibre colour depends on several factors. The following are the environmental factors that affect the colour of the cotton fibre: 

  • Freezes 
  • Rainfall 
  • Microorganisms 
  • Insects 

The following are other factors that can affect colour:  

  • Grass 
  • Soil
  • Leafy portion of the plant 

When it comes to storage, the following factors affect colour: 

  • Temperature 
  • High levels of moisture 

A cotton calorimeter is used for measuring cotton colour. The degrees of reflectance is used to express the colour. It ranges between 50 and 85 units. It indicates how grey or white the sample is. It also indicates yellowness. White cotton has higher degrees of reflectance.          

HVI Trash 

Cotton plant bark, leaf and other parts lead to trash particles in cotton fibre. In HIV instruments, a video camera is used to scan the surface of a sample. An image processing software is used to measure the percentage of surface that trash particles occupy.  

So, these are the key quality factors for cotton yarn. Cotton yarn quality is important for the products you manufacture.