Fiber strength and cotton yarn

A comparison between the main methods for determining the strength of cotton fibers leads us to the calculation of the correlation between the strength of the same fibers and their related yarns


This research focuses on three cotton blends: one will be called “Blend A”(and its variant A1) composed by 48% cotton Russian SM1”1/16, 38% cotton Central America SM1”3/32 and 14% cotton Arizona SM 1″ 3/32; another will be called “Blend B” composed by 32% cotton Giza 69, 38% of cotton Sudan X4 X5 and X6, 10% Ethiopian cotton 121 and finally 20% cotton Zimbabwe Cerro; another will be called “Blend C” composed by 40% Giza cotton 69, 25% Zimbabwe Cerro cotton and 35% Sudan cotton X3 X4 X5.

For each blend Ne 38 and Ne 50 yarns were produced, combed with medium grade torsion.

Data collection consists of 92 tests involving Pressley and Stelometer fiber strength and Breaking Length in Km of the yarns obtained spinning the above-mentioned fibers.

Table 1 collects average data of fiber strength calculated with Pressley and Stelometer system, as well as the average strength in Km of yarns obtained from each blend and produced title; it also indicates the number of tests carried out on each article.

TAB. 1
Blend Pressley Stelometer Ne Title L.R.Km. n° tests
A 84.9 18.7 38 14.16 14
A1 81.8 18.2 38 13.57 4
B 99.4 24.6 38 17.42 14
C 97.1 24.3 38 17.01 20
A1 82.1 18.3 50 12.74 3
B 99.0 24.5 50 16.97 19
C 97.1 24.4 50 16.79 18

First comparison: between the two different methods of strength calculation on fibers. Comparing 92 Pressley data with 92 Stelometer data of the same blend type and applying the statistical calculation of the correlation, the results are the ones reported in table 2 where it is noted that the correlation coefficient is equal to 0.97 (basically it tells us that both methods can be mutually used) and where the conversion formula and its related example are shown.

In practice, with a minimum margin of error, it can be said that a Pressley of 80 corresponds to a Stelometer of17.18and a Pressley of 105 corresponds to a Stelometer of 27.18.

TAB. 2
Average of Pressley values (X) 94.83
Average of Stelometer values (Y) 23.08
Correlation index 0.97
Theoretic line Y = -14.82+0.4*X
Pressley Stelometer
80 17.18
85 19.18
90 21.18
95 23.18
100 25.18
105 27.18