Wednesday, August 7, 2019

EVALUATION OF COTTON FIBRES MATURIY

Fibre maturity:
Maturity of cotton fibre has big concern to a cotton spinner. The maturiy of cotton fibres plays a decisive role in resulting yarn properties to be spun.
It is the significant characteristic of cotton fibres. Matur,ity of cotton fibre is an indicator which expresses "the degree of development of cotton fibre". The maturiy of fibres tells us how much development has been taken place in the fibres. The cotton fibres do not have regular development within the sample or the fibres obtained from same seed too. This difference among the maturity of various fibres appears becauses of the variations in the degree of the secondary thickening or deposition of cellulose in a fibres.
In  mature fibres, "the secondary wall's thickness is very high". In the some fibres, the lumen gets invisible too.
In the immature fibres, due to some physiological reasons, the secondary deposition of cellulose has not taken sufficiently and in maximum fibres, the secondary thickening is practically gets absent.

The presence of immature fibres appears as a defect in yarn, grey fabric, and processed fabric.  "Excessive neps" appear on the yarn surface if the cotton have immatured fibres in it. The neps appearing in this yarn "influence the appearance of the fabric greatly".

The presence of excessive degree of immature fibres in the yarn results in the form of "weight losses in processing". The balls of immatured fibres appearing on the fabric surface require "extra dose of caustic soda and hydrogen peroxide" to desolve the same during processing. This extra dose of chemicas causes increase in the" processing cost".

 The presence of excessive immatured fibres also "influences the gsm of finished fabric". Due to excessive weight loss occurring during dyeing,  the gsm is of the processed fabric decreased.
The presence of the immatured cotton fibres in the fabric also influences the "dyeing affinity" of the fabric. The immatured fibres have very poor dyeing affinity. The colour of dyed fabric get "uneven" if excessive immatured fibres are present in the fabric.

Maturity ratio:

The 100 fibres are picked up from comb sorter sample. The picked up fibres are selected randomly. These fibres are treated with caustic saoda solution. The concentration of solution is kept 18 %. When the fibres get completely swollen. Each swollen fibres is examined  with the help of a microscope having sufficient magnifying capability. 

Now the observations are recorded accurately. After competition of observation process, the fibres are classified into different maturity groups depending upon the basis of the relative dimensions of wall-thickness and lumen of the fibres. However the procedures followed in different countries for sampling and classification differ in some respects. The swollen fibres are classed into three groups as follows
Normal fibres : Rod( round shape) like fibres with no convolution ( twist) and no continuous lumen are classified as “normal” fibres. 

Dead fibres: Convoluted (twisted) fibres having wall thickness one-fifth or less of the maximum ribbon width are classified as “Dead fibres ".

Thin-walled fibres: The fibres having maturity less than normal and greater than dead fibres are classified as thin walled fibres.

"A combined index known as maturity ratio is used to express the results".
Maturity co-efficient:

Around 100 fibres from comb sorter are spread across the glass slide (maturity slide) and the overlapping fibres are again separated with the help of a teasing needle. The free ends of the fibres are then held in the clamp on the second strip of the maturity slide which is adjustable to keep the fibres stretched to the desired limit. The fibres are then irrigated with 18 % NaOH solution. Now these fibres are  covered with a suitable cap. The prepared slide is examined with the help of microscope. The observations are recorded precisely. Now the data are analysed and then the fibres are categorized into following three groups:

About four to eight slides are prepared from each sample and are examined. The results are expressed as percentage of matured, half-matured and immatured fibres in a sample.  Maturity Coefficient of cotton fibres sample is determined as below:

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