Important fiber properties considered for spinning.
Important properties considered for spinning:
- Fibre length & length uniformity.
- Fibre strength & elongation.
- Fibre fineness.
- Fibre maturity.
- Fibre cleanliness.
- Fibre color.
- Fibre stiffness.
- Some chemical deposits.
Share (%) of contribution to yarn quality:
For Ring Yarn
For Rotor Yarn
|3. Fibre strength||20%||24%|
|4. Fibre elongation||05%||08%|
|5. Fibre fineness||15%||14%|
|6. Fibre cleanliness||03%||06%|
Fibre Length: The average length of spun able fibre is called staple length. Fibre with length of 15-50 mm is preferable for yarn manufacturing.
Influences of fiber length in yarn production & Quality:
- Long fiber increase production & quality.
- Higher amount of short influence fiber End breakage ,Increase quantity of waste ,Increase Production & Quality .
- Yarn Strength: Short fiber reduces yarn strength.
- Yarn Evenness: Short fiber causes yarn unevenness.
- Yarn Hairiness: Short fiber causes yarn hairiness.
Beside, fiber length has influence on –
- Spinning limit.
- Handle of the product.
- Luster of the product.
Classification of fibre according to length:
|1. Short stable||1” or less|
|2. Medium stable||1.031” to 1.125”|
|3. Long staple||1.156” to 1.375”|
|4. Extra long staple||1.406” to above|
Classification of fibre according to span length:
2.5% span length(mm)
|Extra long staple||33.0 mm & above|
|Long staple||29.5 mm to 32.5 mm|
|Medium staple||25.0 mm to 29.0 mm|
|Short staple (A-type)||20.5 mm to 24.5 mm|
|Short staple ( B-type)||20.0 mm & above|
Fiber Strength: fibre strength is very often the dominating characteristic. The maximum strength for a fiber is approximately 60 CN/Tex. Normally the breaking strength of cotton is 15-40 CN/Tex.
Very weak cotton fibers are to be avoided because cotton will rupture during processing both in the blow room & carding causes creation of short fibres & deformation in yarn strength & uniformity.
Except for polyester, fibre strength depends on moister content for linen, cotton etc. Fibre strength increases with increasing moisture content, while the reveres happen in case of nylon, viscose etc fibres.
Some significant breaking strength of fibres,
- Polyester = 35-60 CN/Tex.
- Cotton = 15-40 CN/Tex.
- Wool = 12-18 CN/Tex.
Fibre Strength Measuring: Fibre strength is as the Pressley Index (P.I)
Mathematically, the Pressley Index (P.I) = (Breaking load in lb/ Bundle weight in mg)
The following scale is used for classifying fibre strength.
|93 & above||Excellent value|
Fibre Fineness: Fineness is another important characteristic of fibre. The fineness determines how many fibres are present in the cross section of a yarn of a given thickness.
Minimum 30 fibres are needed at the yarn X-section, but there are usually over 100. Now a day this is the minimum value.
Fibre fineness primarily in fluencies
- Spinning limit.
- Yarn evenness.
- Yarn fullness.
Measuring unit: Micronaire value (Mic. value)
Micronaire value= (Weight in μ gm/ Length in inch)
The micronaire value of the fibre should nearly same in single lot.
The fineness scale is as below
|Below 3||Very fine.|
|6.0 & above||Very coarse.|
Fibre Maturity: The cotton fibre consists of cell wall & lumen. Fibre is to be considered as ripe when the cell wall of the moisture swollen fibre represents 50-80% of the round X-section as unripe when it represents 30-45 % & as dead when it represents less than 25%.
Immautre fibre causes,
- Loss of yarn strength.
- A high proportion of short fibre.
- Varying dye ability.
- Processing difficulties mainly during carding.
Fibre Stiffness: Fibre stiffness plays a significant role mainly during rolling, revolving & twisting movements. A stiff fibre cannot properly bound into the yarn, as a result it causes hairiness.
Fibre those are not stiff enough cannot maintain its shape after deformation. In most of the cases this reason leads to formation of neps. The “Slenderness Ratio” can serve as a measure of stiffness.
Slenderness Ratio = (Fiber Length/ Fiber Diameter)
So when slenderness ratio is high, then the stiffness is low.
Fibre elongation: Textile fibre should have at least 1-2% elongation characteristics and preferably slightly more. They must be able to deform in order to width stand high loading but it also have to return to its original shape.
Cotton & wool fibre have 6%-10% & 25%-45% elongation characteristics respectively. For normal textile goods higher elongation property is neither necessary nor desirable. They make the processing in the spinning mill more difficult especially during “Drawing Operation”.
Different types of fibre elongation:
There are 3 types of fibre elongation.
- Permanent Elongation.
- Elastic Elongation.
- Breaking Elongation.
1. Permanent Elongation: That part of the extension through which, the fibre does not return on to its original position.
2. Elastic Elongation: That part of the extension through which, the fibre returns to its previous position.
3. Breaking Elongation: The maximum possible extension of the fibre until it breaks.
i.e the permanent elongation & elastic elongation together.
Importance of fibre elongation: During different stages of fibre & fabric processing forces are applied. If no elongation property is available, the fabric or fibre will break. No recovery will be possible if the fibre does not have elongation property.
|Up to 1.2%||Very clean.|
|7.0% above||Very Dirty.|
Problems due to unclean fibre:
- Metal parts cut the fibres and harmful to spinning machine.
- Vegetable matters make disturbance in drafting.
- Vegetable matters jam the carding pin.
- Mineral matters decay the rolling parts of machine.
Color of fibre: Color gives an indication of the fibres ability to accept dyes in manufacturing process.
Generally the color of cotton fibres is,
- Extra white.
- Yellow stained.
The color of cotton is determined by the degree of reflectance (Rd) & yellowness (+b) in the HVI. Reflectance indicates how bright or dull a sample is, and yellowness indicates the degree of color pigmentation.
A three digit color code is used. The color code is determined by locating the point at which the Rd & +b values intersect on the “Nickerson-Hunter” cotton colorimeter diagram.
Chemical Deposits: The best known sticky substance of cotton fibre is “Honey Dew”
Other chemical deposit’s are-
- Fat & some other synthetic substances.
During spinning of sticky cotton, however the relative humidity of the air in production area should be held as low as possible.