Short fibers are one of the critical factors affecting the quality of cotton-spun yarn. Under the same processing conditions, the lower the content of short fibers, the higher the yarn's breaking strength and overall quality. But what causes short fibers, and how do they impact yarn quality? Let’s delve into these aspects.
Causes of Short Fibers
Short fibers refer to fibers shorter than a certain length threshold compared to the main fiber length. The percentage of short fibers in total fiber mass is expressed as the short fiber content. There are two primary causes of short fibers:
Natural Growth Deficiency
Short fibers are present in raw cotton due to natural growth variations, especially fibers shorter than 12 mm. Cotton with high short fiber content tends to produce lower-quality yarn.
Processing Damage
Short fibers are also generated during the manufacturing process. In operations like opening, beating, and carding, fibers can be damaged, leading to an increase in short fibers.
Short Fiber Length Standards
Globally, different standards are used to define short fibers:
Uster: Fibers shorter than 10 mm are considered short.
UK/Switzerland: Fibers shorter than the average fiber length.
China: Typically fibers shorter than 12.7 mm or 16 mm are analyzed.
The impact of short fibers on spinning depends on their length:
Fibers of 4-5 mm are generally lost during spinning.
Fibers of 12-15 mm fill the yarn structure but don’t contribute to strength.
Fibers longer than 16 mm positively influence yarn characteristics.
Challenges in Cotton Processing
In opening and carding, short fibers increase the formation of neps and reduce fiber quality.
In combing and drafting, short fibers are harder to control, resulting in floating fibers that affect drafting consistency.
During twisting, short fibers tend to protrude from the yarn surface, forming hairiness that impacts fabric appearance.
Impact on Yarn Quality
Short fibers negatively affect yarn quality due to difficulties in their removal and control during spinning. Key impacts include:
Irregularities in Yarn Structure
Short fibers that remain after cleaning and carding create slubs (thick spots) and thin places in the yarn, leading to unevenness and weaker spots.
Reduced Yarn Strength
Higher short fiber content reduces yarn tensile strength. Short fibers have poor inter-fiber cohesion and break easily under tension, decreasing yarn durability.
Increased Yarn Hairiness
Short fibers increase the number of fiber ends protruding from the yarn body, resulting in fuzziness. This effect is amplified during high-speed processes like winding, where friction intensifies hairiness.
Frequent Yarn Breakages
Short fibers weaken the yarn structure, causing higher breakage rates during weaving or knitting, which impacts fabric quality and production efficiency.
Higher Defect Rates
Studies show that a 2% increase in the short fiber content below 12.7 mm can increase the yarn’s unevenness (CV%) by 1%. Similarly, frequent defects like neps, slubs, and thin places become more evident with higher short fiber content.
The Importance of Controlling Short Fibers
To enhance yarn quality, strict control of short fiber content is essential. Strategies include:
Optimizing the selection of raw cotton with lower natural short fiber content.
Improving machine settings during processes like opening, carding, and combing to minimize fiber damage.
Regular monitoring of short fiber content to ensure consistent quality.
By addressing the challenges posed by short fibers, manufacturers can produce yarn with better strength, uniformity, and aesthetic appeal, leading to improved fabric performance and customer satisfaction.
Conclusion
Short fibers significantly impact yarn quality, influencing everything from tensile strength to fabric appearance. Understanding their causes and effects allows manufacturers to take proactive measures to reduce their content and improve production efficiency. By focusing on short fiber control, you can ensure superior yarn quality and meet the demands of high-performance textile production.