This ultimately results in improved yarn strength. Although fine fibers require careful opening, cleaning and carding to prevent damage that can result in uneven yarn, yarns produced from fine fibers will have more fibers in the yarn cross-section. And while micronaire is not a direct measurement of fiber fineness, it does provide some feedback on fineness. Coarse or mature fibers that resist compression have a high micronaire measurement.Ĭotton fiber gauge/fineness affects processing performance and end-product quality in several ways. Fine or immature fibers that are easily compressed have a lower air permeability and therefore low micronaire. It is determined by measuring the air permeability of a constant mass of cotton fibers compressed to a fixed volume. The micronaire is a measurement of fiber fineness and maturity. The result is reported in “grams per tex.” Strength measurements are conducted on the same beard of cotton used by the HVI to measure staple length and uniformity.Īfter the length measurement is made, the beard is clamped between two sets of jaws that are spaced 1/8 inch apart, then broken. It is key to understand exactly which combination of factors contributes to the highest quality crop and replicate that combination season after season.įiber strength, as measured on the HVI is the force in grams required to break a bundle of fibers in one tex unit in mass-a tex unit being the weight in grams of 1000 meters of fiber length. Growth environment and crop management also play a huge role in determining fiber strength. There is a natural distribution in the length of cotton fibers but the lower the variation in this length distribution, the higher the length uniformity index.įiber strength is largely determined by genetics, so cotton variety plays an important role in fiber quality. The ratio between the “mean length” of fibers and the “upper-half-mean length” of fibers is referred to as the “length uniformity index.” Both the mean length and upper-half-mean length measurements are taken when the fiber beard described above is passed through the length sensor of the HVI system. Cotton with a low length uniformity index has a high variance in fiber length which can make processing difficult and ultimately result in lower-quality yarn.
It also affects the efficiency of the spinning process. Like staple length, length uniformity affects yarn strength and evenness.
Extreme temperatures, water stress, insect pressure, nutrient deficiencies, and excessive cleaning or drying can all shorten the staple length. This is a critical measurement because the staple length of cotton affects yarn strength, evenness, and efficiency of the spinning process.įiber length is determined by an interaction of cotton variety, growth environment, and crop management.
The fibrogram is an arrangement of fibers from the shortest to the longest in terms of span lengths (the distances fibers extend from a random catching point). Today, thanks to technological advances, the staple length is now calculated from the length fibrogram sensed by the HVI. Historically, the staple length was estimated manually, using the “hand stapling” process performed by a cotton classer. What results from the brushing is referred to as a “beard” of fibers which is then passed through a sensing point in the HVI length instrument. Staple length is reported as the average length of the longer half of the fibers (normally called “upper-half-mean” length), measured by clamping a fiber sample, then combing and brushing to make the fibers straight and parallel.