Section - Fibre
Section - Yarn
Section - Fabric
 
     
     
 
 
Manufacturers & Exporters of High Technology & High Quality Textiles Testing Machines
 
 

 Fibre Fineness (Micronaire)  

[Section - Fibre]
   

       

Introduction 

 Principle

 General Description

 

Introduction:
 

Fineness (Weight per unit length and Maturity have been recognized to be two of the important raw cotton characteristics : maturity influences the nepping potential of cotton1, and fineness decides the spinning value of cotton 3 and affects yarn regularity and strength 2.

  

However, until recently separate estimation of fineness and maturity were possible only through laborious procedures using conventional methods. he use of the simple air-flow
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

method was capable of providing only the micronaire value (Mc) which is influenced by both fineness and maturity. Considerable work has, therefore, been going on in various research laboratories to modify the air-flow method to make it capable of providing separate estimates of fineness and maturity. The fineness tester has been modified5,6 to obtain independent estimates of fineness and maturity. A separate estimation of fineness would help in deciding the spinning limit of cotton and in getting an accurate prediction of yarn strength from fibre characteristics. The estimates of maturity would help in the detection and avoidance of immature cottons which are prone to neppiness and dyeing problems.
 Principle Of Operation :
 

When a stream of air is passed through a plug of fibres, the rate of air-flow depends on the dimensions of the plug, the total mass of fibres in the plug, the arrangement of the fibres, and on the average specific surface of the fibres in the plug. Kozeny’s equation connecting air-flow to all the relevant parameters is complicated. However, the relation between air-flow to all the relevant parameters is complicated. However, the relation between air-flow and specific surface can be written in a simple way in the form :
V = K (P/s2)
Where (V) is the volume rate of flow of air through the plur, (s) is the specific surface, (P) is the pressure difference between the incoming and out going air, and (k) is the quantity which includes all the other parameters mentioned above. When these parameters are held constant, the volume rate of air-flow per unit pressure difference is a measure of the specific surface.
For solid man-made fibres, the specific surface is directly related to its denier or fineness, whereas for cotton fibres, which contain a lumen, it is related to both the Fineness and the Maturity of the fibres. However, it has been observed that for cotton fibres, it is possible to get independent estimates of fineness and maturity from the knowledge of the pressure difference (P) measured at two different compression levels7. This procedure, which is discussed below in detail, has been adopted for the work.
Air at a constant pressure (approximately 12.3 cm height of kerosene) is successively passed through an adjustable orifice (needle value) and through a plug of well opened cotton fibres having a fixed mass of 4 gms. This plug of fibres offers a resistance to the air-flow. As a result, some air pressure is built up across the plug. This pressure is measured by means of a manometer.
The manometer readings corresponding to the lower compression level of the fibre plugs have been correlated with the Micronaire valves of the fibres supplied by the United States Department of Agriculture (USDA), whereas readings corresponding to the lower and the higher compression levels of the fibre plugs have been correlated with both the gravimetric fineness (H) and the percent maturity (Pm) (caustic swelling method – ASTM) of the fibres.

General Description Of The Instrument  : 

The instrument provides estimates of :
 

Micronaire value (Mc)
 

Fineness (Wt. Per unit length in mtex-H), and
 

Percent maturity (PM )
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