Key Characteristics of Yarn
1. Count (Number)
The yarn count is a measure of yarn thickness.
- Ne (English Count): In the new English system (Ne), the yarn count is expressed as the number of hanks (840 yards each) produced from one pound of yarn.
- Tex: Defined as 1 gram per kilometer or 1 milligram per meter.
- Nm (Metric Count): Indicates the length-to-weight ratio of the yarn. For example, Nm 34 means there are 34 kilometers of this yarn in 1000 grams.
Units of Measurement
| Unit | Abbreviation | Explanation |
|---|---|---|
| Decitex (dtex) | Dtex | 1 dtex = 1 dg/km = 0.1 mg/m |
| Tex (tex) | Tex | 1 tex = 1 g/km = 1 mg/m |
| English Cotton Count | Ne | Ne 1 = 1 hank = 1 × 840 yards per pound |
| Metric Count | Nm | Nm 100 = 100 m per gram |
2. Relative Yarn Count (Count CV)
2.1. Count CV (Coefficient of Variation):
This measures the deviation of the tested yarn count from the nominal count. The lower the value, the better. If the CV exceeds 2%, fabric defects may become visible to the naked eye.
2.2. CV% (Coefficient of Variation in Yarn Thickness):
A statistical measure of variation in yarn thickness during testing. Lower values indicate better and more consistent yarn quality.
3. Twist
- Twist Direction: Refers to the direction of fiber twist relative to the yarn’s passage through the spinning mechanism. It can be either Z-twist or S-twist.
- Z-Twist: Fibers interlock vertically in the direction of the letter Z.
- S-Twist: Fibers interlock vertically in the direction of the letter S.
- Twist Per Meter (TPM): Indicates the number of twists per meter or per inch. Higher values increase yarn strength but may make the yarn stiffer, affect the final product weight, and lead to twisting effects in fabrics. Twist levels vary depending on the application (socks, fabrics, special-purpose textiles, etc.), and each use has an optimal twist range.
4. Imperfections
Imperfections measure the number of thin, thick spots and neps per 1000 meters of yarn.
4.1. Thin Places:
- Areas thinner than -50% of the yarn’s base diameter.
- Fewer thin places indicate more consistent and higher-quality yarn.
4.2. Thick Places:
- Areas thicker than +50% of the yarn’s base diameter, typically 8-12 mm in length.
4.3. Neps:
- Very short areas no longer than 2 mm with a diameter at least three times greater than the base diameter. Fewer neps result in a better appearance for finished products.
Acceptable Imperfection Values for Quality Yarn:
| Imperfection Type | Ring-Spun Yarn | Air-Jet Spun Yarn |
|---|---|---|
| Thin Places (-50%) | Low values | Low values |
| Thick Places (+50%) | Low values | Low values |
| Neps (+200%) | Up to 200% | Up to 280% |
5. Uster%
Uster% measures the unevenness of yarn weight per unit length (grams per square meter) across 1 cm.
- Note: Lower Uster% values indicate higher yarn quality.
6. Degree of Hairiness
Indicates the number of fibers protruding from the yarn body over a 1 cm section.
- Lower values result in better yarn performance during manufacturing due to reduced linting.
- Higher values are desirable for producing fluffy items, such as woolen or acrylic yarns.
Thicker yarns naturally have higher hairiness, while thinner yarns have lower hairiness due to the number of fibers along the length.
7. Breaking Force
Indicates the force required to break a single yarn strand, expressed in centi-Newtons (cN).
- Optimal Value: 18-20 cN/tex. Higher values indicate stronger yarn, but cost considerations and manufacturing speed may influence this parameter.
8. R.K.M.
R.K.M. (Reisskraft Meter): Represents the “length of yarn in kilometers” that would break under its own weight.
- For example, yarn with an R.K.M. value of 15 would break at a length of 15 km under its own weight.
- This metric is equivalent to Breaking Force, expressed in grams/tex.
9. Tensile Strength
Measures the force per unit density required to break the yarn, expressed as grams × force/tex.
- Note: Higher values indicate stronger yarn.
10. Elongation in %
Indicates the percentage of elongation (deformation along the yarn axis) during stretching relative to the yarn’s original length.
- Conclusion: Higher elongation allows for greater tension during manufacturing, leading to better performance.
This page highlights the key characteristics that will help you accurately assess the quality of yarn. While there are certainly more factors to consider, we’ve kept the focus on the essentials without delving too deeply into the topic!