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Knitting has higher requirements for the evenness (even thickness of yarns), softness, particular strength and extensibility, twist (yarns have lower twist). During the process of forming knitted fabrics on knitting machine, yarns are impacted by complicated mechanical actions, such as stretching, bending, twisting and friction. To ensure the normal production and quality of products, knitted yarns should meet following requirements:

 

1. Yarns should have particular strength and extensibility

Strength of yarns is an important indicator for quality of knitted yarns. Yarns suffer from definite tension and reduplicative loading during preparation and knitting. So, the knitted yarns should have particular strength. Besides, yarns are also bended, warped and deformed during the process of being knitted into loop. For this, the knitted yarns should have extensibility, convenient for being bended into loop during knitting and reducing broken ends of yarns.

 

2. Yarns should have good softness 

The softness of knitted yarns is better than woven yarns. Soft yarns are easy for being bended and twisted so that loops of knitted fabrics can have even tissue, clear and beautiful appearance. Meanwhile, it can also reduce broken ends of yarns and damage on looping parts during knitting.

 

3. Yarns should have twist

In general, twist of knitted yarns is lower than twist of woven yarns. If the twist is over high, the softness of yarns is poorer. It cannot be bended or twisted easily during knitting. And it may also easily cause kinks, resulting in knit faults and damaging needles. Besides, yarns having oversize twist have influence the elasticity of knitted fabrics, making loops skew. However, the twist of knitted yarns cannot be too small, otherwise, it has influence on strength, increasing broken ends during knitting. Moreover, the yarns are leavening, making knitted fabrics fluff and pill easily and reducing wearability of knitted fabrics. So, correctly choosing twist is an important way for reasonably choosing yarns. Due to different applications, knitted fabrics have different requirements for twist. 

 

Single jersey should be smooth, tight, having smooth surface and clear lines. The twist of yarns should be higher, which is closed to standards of woven yarns having the same linear density, increasing stiffness and improving fluff and pill. Interlock and elastic fabric should have soft hand feeling and good elasticity. The twist of yarns should be slightly lower. In general, lower deviation of twist of woven yarns having the same linear density. Raising knitted yarns is convenient for napping, making even thickness of pile. Twist should be lower. 

 

What's more, the twist varies with linear density of twist. 

 

4. Yarns should have even linear density and less yarn faults

The homogeneity of linear density refers to homogeneity of yarn evenness. It is an important index of quality for knitted yarns. Yarns having homogeneous evenness are advantageous for knitting and ensuring quality of knitted fabrics, making loops have even tissue and clear cloth cover. If yarns have nubs, knitting cannot be carried out smoothly, causing broken ends of yarns or damage components. What’s more, bars and cloud are easily formed on cloth cover, reducing quality of knitted fabrics. If yarns have snicks, the strength is insufficient which may easily cause broken ends, having influences on quality of knitted fabrics and reducing machine productivity. Because there are multi cam systems on knitting system and feed yarns into loops at the same time, the every yarn should have even thickness and the different thickness of every yarn should be strictly controlled. Otherwise, bars, shadow or other faults can be caused on cloth cover, reducing quality of knitted fabrics.

 

5. Yarns should have good moisture absorption

The ability that yarns absorb moisture in the air is called as moisture absorption. The fibers have different moisture absorption and the absorption varies with the different humitures of air. Yarns used for knitting should have moisture absorption. Under the conditions of the same relative humidity, beside good conductivity, yarns having good moisture absorption are also in favor of stabilization of yarns twist and improving of extensibility, so that yarns can have good knitting performance.

 

6. Yarns should have good smoothness and lower friction coefficient

Knitted yarns should not have impurities and oil stains as far as possible. And they should be smooth. Rough yarns have high abrasion on components, easily damaging components. Besides, it causes many flies in workshop, which not only have influence worker’s health, but also affect productivity of knitting machine and quality of knitted fabrics.