Page 284 - Handbook of Properties of Textile and Technical Fibres

258 Handbook of Properties of Textile and Technical Fibres

6.6 21
20.8
Process B
6.55
Process A strength 20.6
Single-fiber strength (gf) 6.45 Process A Process B 20.2 Single-fiber elongation (%)
strength
20.4
6.5
20
19.8
6.4

19.4
6.35 elongation elongation 19.6
Low gin One Low carding
rate lint cleaner rate
High gin Two High carding
rate lint cleaners rate
Process A: low gin rate One lint cleaner Low carding rate
Process B: high gin rate Two lint cleaner High carding rate
Figure 7.13 Effect of ginning and carding on cotton single-fiber tensile properties.
Derived from the data of S.J. Doh Thesis, 2004.

As one can imagine from the above brief description of potential straining on
the fibers during processing, analysis of the nature of this straining actions and their
impacts can be very difficult, particularly at the high speed of processing utilized in
today’s technology. Therefore, most studies followed an easier way to perform such
analysis, which is by examining the properties of cotton fibers before and after
processing. Some of the findings of these studies are summarized below.
In a PhD study by Song Jun Doh (2004), the effects of carding rates on the tensile
properties of cotton fibers were examined by using different carding rate levels for
cotton fibers that have been followed from the gin to the carding process. A summary
of the effects of these processes on the single-fiber strength of cotton fibers is
illustrated in a graph developed by the authors of this chapter as shown in Fig. 7.13.
As can be seen in this figure, fibers that were subjected to low ginning rate and low
level of lint cleaning (one lint cleaner) continued to gain single-fiber strength and
single-fiber breaking elongation on carding at a low rate. On the other hand, fibers
that were subjected to high ginning rate and high level of lint cleaning (two lint
cleaners) continued to lose single-fiber strength and single-fiber breaking elongation
in the carding process. It should be pointed, however, that within the range of values
obtained in this study, the validity of these results can be highly questioned, particu-
larly with the magnitude of standard deviations associated with single-fiber strength
indicated in the study.
In another study by Elmogahzy and Chewning (2001), the change in HVI bundle
strength during processing was monitored in an actual mill operation and using actual
cotton mixes. As indicated earlier, the HVI bundle strength is only appropriate for
testing cotton fibers extracted from the cotton bale. This is due to the fact that the
calibration process associated with the HVI is based on special cottons drawn from
cotton bales of extreme values of bundle tensile strength. In addition, the HVI cotton
beard is combed and brushed using a standard procedure to minimize fiber crimp and