Fiber segment length distribution on the yarn surface in relation to yarn abrasion resistance

Surface Length Distribution

A new parameter is introduced to quantify the degreeof migration of fibers in the yarn-the distribution of the segment length of afiber on the yarn surface (in short, the "surface lengthdistribution"). A particular fiber comes out of the yarn surface, stays onthe yarn surface for a time, and then re-enters the yarn core, involving tworandom processes, and the length of the fiber segment on the yarn surface isaffected by the surrounding fibers.

Dyed wool tracer fibers have been blended with otherwool fibers in the spinning process, so that they can be observed when theyrise to the yarn surface. The distribution of segment lengths of tracer fiberson the yarn surface reflects their migratory behavior in the yarn. When a fiberundergoes a more idealized migration, it moves from the surface to the core andvice versa (Figure 1). If fibers migrate more frequently, each fiber appearsonly momentarily on each superimposed concentric layer. Thus, we havepostulated that the shorter the fiber's exposure on the surface, the greaterthe extent of migration. Consequently, the fibers are more likely to interlockwith one another to provide a strong cohesion. We expect that the shorter thesurface length, the more frequent the fiber migration. We have found that thesurface length of the yarns follows a gamma distribution. We have plotted theaverage surface length of the yarns versus yarn abrasion resistance (mean rubsto break), obtaining a linear relationship.

Experimental

Semi-worsted yarns of 46 tex and 600 turn per meterwere processed at the Wool Research Organization of New Zealand (WRONZ). Theprocessing parameters were varied to obtain a series of yarns with changingabrasion resistance.

YARN ABRASION RESISTANCE TEST

Brorens et al. [1] evaluated yarn abrasion resistantproperties at WRONZ with their specially designed abrasion tester. Unlikenormal "rubbing" on the yarn surface, this tester recreates themechanism of yarn failure, which is primarily a gradual drafting of the abradedarea.

In the experiment of yarn abrasion described in thispaper, we used the Shirley yarn abrasion tester (Figure 2). The tester consistsof two reciprocating bars: one is made of hardened steel and the other iscovered with the standard abradant used in the Martindale fabric abrasion tester.Eight yarn specimens are tested simultaneously. Yarns are threaded from thefixed holders and clipped onto the flexible holders where sensors are attached.The initial tension exerted on each yarn is 0.5N. When a yarn breaks, theflexible holder falls, a signal is sent to the control unit, and the number ofrubs for that particular yarn is recorded. The abrasion cycles were set to anupper limit of 10,000 rubs, and the elongation of each yarn during the test wasrecorded in every 500 cycles. The elongation curve of each yarn specimen isplotted in Figure 3. Twenty specimens were taken randomly from each yarn typefor the test, and the results are summarized in Figure 4. Type 6 yarns have thehighest proportion of yarn specimens, surviving more abrasion cycles beforebreakage (with more than 12% extension). Using the mean number of rubs to breakas a measure of yarn abrasion resistance, the abrasion results are shown inFigure 5.

SURFACE LENGTH MEASUREMENTS

In Figure 6, a segment of tracer fiber can be seen on the surface of the yarn. With the aid of mirrors, we can locate the starting and ending points of that fiber segment and then measure its surface length. By measuring the lengths of 100 surface segments of each yarn type, we can plot the cumulative distribution of the surface length, as shown in Figure 7. Only yarn type Y1 is presented in Figure 7. For the other yarn types, the results are similar. The gamma distribution functions G(x) fit the cumulative distribution of surface length very well. The Gaussian distribution functions (cumulative normal distribution) are plotted in Figure 7 as well for comparison purposes.

From the experimental data of surface length, the minimum surface length is close to but not less than 1 mm. The estimate of the parameter [gamma] was set to that value. The estimates of the remaining two parameters a and [beta] could be calculated from the mean and variance of the surface length of the yarn.

The means and variances of the surface lengths of the six yarn types and also the corresponding parameter values are shown in Table I. With the values of the parameters given, the pdf for the yarns can be plotted as shown in Figure 8. Yarn type Y6 has the highest proportion of short surface lengths, while yarn type Y1 has the lowest proportion of short surface lengths. For the sake of easy visualization, only yarn types Y1 and Y6 are plotted in Figure 8.

We found that that yarn abrasion resistance is inversely proportional to the average surface length, as shown in Figure 9, and the coefficient of determination R^sup 2^ = 0.9481, i.e., around 94.8% of the variation of yarn abrasion resistance, can be explained by the variable average surface length. As a result, we discovered a simple yarn structural parameter that is closely related to the yarn abrasion resistant properties. The merits of this new parameter include easy measurement and a true reflection of the degree of interlacing of the fibers near the yarn surface. Because the surface fibers are the ones to be measured, we don't need to search for a suitable solvent to optically dissolve the fibers in a yarn in order to highlight the tracer fiber to measure spatial coordinates. This would save a lot of effort during preparation and data processing to generate migration parameters [3].

Conclusions

We have reported our experimental results for the abrasion resistant test. We also introduce a new yarn structural parameter, average surface length, which is highly correlated with the abrasion resistance of yarns. The length of fibers exposed on the yam surface will depend on their interactions with surrounding fibers on the yarn. As a result, the surface length distribution can reflect the degree of yarn interlacing. In addition, the surface fiber length measurement eliminates the error of varying yarn diameter, which influences the location of the yarn axis and thus the accuracy of the migration parameters. More extensive experimental work will be needed to verify the reliability of our new structural parameter for different yarn types, e.g., Solospun.

ACKNOWLEDGMENTS

We are grateful to the Wool Research Organization of New Zealand (Inc.) (now renamed Canesis Network Ltd.) for providing the wool yarns. K. F. Choi wishes to thank J. Lappage, M. Miao, and A. Wilkins for very useful discussions.

Literature Cited

1. Brorens, P. H., Lappage, J., Bedford, J., and Ranford, S. L., Studies on the Abrasion Resistance of Weaving Yarns, J. Textile Inst. 81 (2), 126-134 (1990).

2. Evans, M., Hastings, N., and Peacock, B., "Statistical Distributions," 3rd ed., John Wiley & Sons, NY, 2000.

3. Hearle, J. W. S., Gupta, B. S., and Merchant, V. B., Migration of Fibers in Yarns, Part I: Characterization and Idealization of Migration Behavior, Textile Res. J. 35, 329-334 (1965).

4. Hickie, T. S., and Chaikin, M., Some Aspects of Worstedyarn Structure, Part IV: The Application of Fourier Analysis to the Study of Single-fiber Configurations in a Series of Worsted Yarns, J. Textile Inst. 65, 537-551 (1974).

5. Lappage, J., Weavable Singles Yarn Potential, Wool. Rec. 158, 89 (1999).

6. Morton, W. E., The Arrangement of Fibers in Single Yarns, Textile Res. J. 26, 325-331 (1956).

7. Morton, W. E., and Yen, K. C., The Arrangement of Fibers in Fibro Yarns, J. Textile Inst. 43, T60-T66 (1952).

8. Riding, G., Filament Migration in Single Yarns, J. Textile Inst. 55, T97 -T17 (1964).

Manuscript received July 22, 2003; accepted September 9, 2003.

K. F. CHOI1 AND K. L. KIM

Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

1 Correspondence: The Hong Kong Polytechnic University, Hung Horn, Kowloon, Hong Kong, China, tel: 852-27666535, fax: 852-27731432, email: tcchoikf@inet.polyu.edu.hk

Copyright Textile Research Institute Jul 2004

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Bibliography for "Fiber Segment Length Distribution on the Yarn Surface in Relation to Yarn Abrasion Resistance"

Choi, K F "Fiber Segment Length Distribution on the Yarn Surface in Relation to Yarn Abrasion Resistance".

Textile Research Journal. Jul 2004. FindArticles.com. 30 Nov. 2007.

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