Cotton Quality Aspects

UGANDA COTTON – BRIEF ON COTTON QUALITY ASPECTS:

  1. INTRODUCTION:

Uganda cotton can be categorized as medium to medium long staple variety. It is 100% handpicked and almost 100% roller ginned, which makes it a premium fibre. It is common knowledge that roller ginning is ‘gentle’ as compared to saw ginning; it therefore preserves the characteristics and intergrity of the fibre.

  1. COTTON GRADES:

The Uganda cotton grades are grouped into the roller and saw gin sets. The roller gin grades are: UCON, UCOB, UCOP (base grade), UCOA & UCOM. The saw gin grades are UCOSA I & UCOSA II (base grade). However, as mentioned above, over 98% of the crop is roller ginned annually.

The average seasonal proportions of these grades can be illustrated in the pie chart below:

From the above chart it can be noted that over 80% of annual production falls in the first three grades (Base grade UCOP and above).

The organisation biennially prepares and presents to the International Cotton Association (Liverpool) and the Bremen Cotton Exchange a new set of national official standards for appraisal and adoption as the official standards for Uganda cotton. The standards are categorised into the two groups; roller gin set and saw gin set standards. The two associations also establish value differences between the respective grades for trade purposes and arbitration; and these are regularly published in the Liverpool Value Differences circular. Table (i) attached gives the categories of these grades, their respective characteristics, value differences and international equivalents:

  1. FIBRE CHARACTERISTICS:

High Volume Instrument (HVI) testing is regularly conducted on Uganda cotton in our laboratory to confirm its intrinsic fibre characteristics. Table (ii) below gives the average HVI test results.

Table (i) : Average Fibre Characteristics (HVI Mode):

Property

Mean

Spinning Consistency Index (SCI)

62

Micronaire

4.0

Strength (g/tex)

30

Length (mm)

29

Uniformity (%)

85

Short Fibre Index (SFI)

4.5

Elongation

5.0

Colour Grade (CG)

31-1

Rd

75

+b

7.5

Maturity (%)

85

From the above table, it can generally be observed that the fibre characteristics are all in the premium range for any given parameter.

  1. SPINNING POTENTIAL:

Spinning trials to assess the spinning potential of Uganda cotton were conducted at the South India Textile Research Association (SITRA) laboratories at Coimbatore. To ensure broad national sample representativeness, four (4) cotton samples, one each from Northern, West Nile, Eastern and Kazinga channel Zones, were sent for analysis. Given below is a summary of their findings:

      a.  Fibre Quality Properties:

An analysis of the fibre properties was done and the results are as shown in Table (iii).

Table (iii):Fibre Quality Attributes of the Cotton Samples:

Sample

2.5% Span Length (mm)

Micronaire Value

Trash (%)

Spun Yarn counts

Northern

29.24

4.01

2.2

44s & 50s

West Nile

29.24

4.12

2.0

44s & 50s

Eastern

29.76

4.04

1.5

44s & 50s

Kazinga

30.15

3.85

2.0

44s, 50s & 60s

(Source: SITRA, 2007)

       b.  Yarn Quality Attributes:

A quick analysis of the yarn test revealed the following:

  1. In 44s, Kazinga had superior yarn strength and lowest hairiness.

  2. In 50s, Kazinga had superior performance with respect to strength and imperfections.

  3. Yarns made from Kazinga sample performed better in terms of warp and weft breaks during weaving and were able to spin 60s yarn.

  4. Overall, all the yarns exhibited high degree of uniformity.

The definite planting period, uniform weather pattern, hand picking and roller ginning ensure uniform fibre development and processing quality. The uniform fibre characteristics are indeed appropriate for mill lay-downs. This ultimately leads to uniform yarn/fabric and guarantees quality of the finished product.

The above characteristics and analysis point to the fact that Uganda cotton fibre can be marketed in the premium range, fetching higher prices than the fibres frequently used in the computation of the Cotlook A’ Index. With that spinning potential, the overall yarn quality can also be classed as aboveaverage by all spinning standards.