Relationships between fiber and yarn tensile properties E. Hequet1,2, N. Abidi1, J. Gannaway2 1Texas Tech University – PSS-ITC 2Texas A&M - TAES Funded by International Cotton Research Center and the Texas Department of Agriculture - FFR January 10, 2008

Background Cotton breeding programs must strive to deliver fibers that perform better in textile manufacturing. This is critical for effective competition with various man-made fibers and with international growths of cotton.

Background Several fiber properties not measured in the cotton breeding programs have a large impact on processing performance. Among these are the elongation characteristics associated with fiber strength.

Background In general, most of the breeders simply ignore fiber elongation because: The weak negative correlation between HVI elongation and HVI strength. The lack of calibration procedures for HVI elongation makes it impossible to rely on such data.

Elongation vs. HVI tenacity 547 wild-type cotton samples R2 = 0.131 ***

Elongation vs. HVI tenacity 567 commercial varieties

Background There is a weak negative correlation between fiber elongation and tenacity. However, this level of correlation does not preclude simultaneous improvement of fiber tenacity and fiber elongation.

Work of rupture calculations We cannot record the curves load-elongation for the HVI. Nevertheless, the HVI work of rupture should be related to the product tenacity * elongation.

Protocol: Experiment 2 To confirm this we tested 32 samples on a tensile tester (50 reps per bale – speed of the pulling clamp 50 mm/min). Recorded the force-elongation curves. Calculated the work of rupture.

Tensile Strength Tester

Load vs. Elongation l0

Work of rupture from testometric vs. HVI Tenacity * Elongation

Estimated HVI work of rupture WSS vs Estimated HVI work of rupture WSS vs. HVI Tenacity for selected elongations 9% Base: 24 cN/tex – 6% El. 8% 7% 6% 5% 4%

Background This demonstrates the importance of fiber elongation in the work of rupture of fiber bundles. Breeding for improved work of rupture should result in lower fiber breakage when the cotton fibers are submitted to different mechanical stresses (ginning, carding, spinning, and weaving).

Experiment 1 Repeatability of HVI tensile properties

Repeatability of HVI tensile properties 3 bales homogenized according to ICCS protocol Card web samples tested 6 times per day during a three days period 10 replications

Repeatability of HVI tensile properties

Repeatability of HVI tensile properties

Repeatability of HVI tensile properties

Repeatability of HVI tensile properties

Repeatability of HVI tensile properties The current HVI systems do not provide elongation measurements as repeatable as we would like. Nevertheless, the repeatability is good enough to distinguish between high, medium, and low elongation. It should suffice for breeding programs.

Experiment 2 Fiber properties vs. yarn tensile properties

Fiber properties vs. yarn tensile properties 21 cultivars were selected. Planted with two field replicates at TAES. Stripper harvested and saw ginned (seed cotton cleaners + lint cleaning). Lint tested on HVI (4-4-10) and AFIS (5 reps of 3,000 fibers). 30Ne carded ring spun yarn (Suessen Fiomax 1000). Yarn tested on UT3 and Tensorapid.

HVI Strength among cultivars and field replications R2 (Rep 1 vs. Rep 2) = 0.780

HVI elongation among cultivars and field replications R2 (Rep 1 vs. Rep 2) = 0.914

Fiber properties vs. yarn tensile properties The charts of the HVI tensile properties among cultivars and field replications show that there is little variations between replications (environment) and large variations between cultivars (genetic).

Yarn tenacity among cultivars and field replications R2 (Rep 1 vs. Rep 2) = 0.914

Yarn tenacity among cultivars and field replications R2 (Rep 1 vs. Rep 2) = 0.700

Fiber properties vs. yarn tensile properties The charts of the yarn tensile properties among cultivars and field replications show that there is little variations between replications (environment) and large variations between cultivars (genetic). This confirms that these two fiber and yarn parameters are quite heritable.

Yarn work of rupture (RS 30Ne) vs. Tenacity * Elongation

Fiber properties vs. yarn tensile properties There is a direct effect of both yarn elongation and yarn tenacity on the yarn work of rupture Therefore, to improve yarn performance the breeders should work on both yarn elongation and yarn tenacity.

Fiber properties vs. yarn tensile properties Due to the cost of spinning tests and the amount of raw material needed to perform such tests, yarn tensile properties need to be predicted from fiber properties.

Yarn elongation: Predicted vs. Observed (RS 30Ne)

Yarn strength: Predicted vs. Observed (RS 30Ne) Predicted = 11.67 + 12.269 L(w) – 0.1147 Hs + 15.409 MR R2 = 0.938

Fiber properties vs. yarn tensile properties Breeding for fiber strength and elongation only will not always lead to better yarns. The cotton fibers need also to be more mature and finer, as well as longer and more uniform. It is of interest to note that yarn strength can be better predicted with AFIS than with HVI.

Experiment 3 Validation: Fiber properties vs. yarn tensile properties

Validation fiber properties vs. yarn tensile properties 32 commercial bales were selected. Lint tested on HVI (4-4-10) and AFIS (5 reps of 3,000 fibers). 30Ne carded ring spun yarn (Suessen Fiomax 1000). Yarn tested on UT3 and Tensorapid.

Validation fiber properties vs. yarn tensile properties On this independent set of cottons the same relationships were found. The best single predictor of yarn elongation is fiber elongation with a coefficient of correlation of 0.801 while the best single predictor of yarn strength is standard fineness with a coefficient of correlation of -0.918.

Experiment 4 Validation over a large range of yarn counts

Validation fiber properties vs. yarn tensile properties 4 commercial bales were selected. Lint tested on HVI (4-4-10) and AFIS (5 reps of 3,000 fibers). Combed ring spun yarn from 32Ne to 78Ne (Suessen Fiomax 1000). Yarn tested on UT3 and Tensorapid.

Evolution of yarn tenacity over a range of yarn counts

Evolution of yarn elongation over a range of yarn counts

Validation over a large range of yarn counts There are no interactions between the yarn tenacity or the yarn elongation readings and the yarn counts. The intercepts are different but not the slopes. Therefore, we can expect similar rankings of the cultivars for any yarn count (within the spinable range for that cultivar)..

Conclusion The work of rupture (of a bundle of fibers or a yarn) is critically important and is determined by both tenacity and elongation. We demonstrated that a combination of fiber properties could provide good estimates of yarn elongation and yarn strength.

Conclusion Even though the HVI elongation measurement needs to be perfected, its use in breeding programs could lead to improved yarn quality and processing performance.