Page 291 - Handbook of Properties of Textile and Technical Fibres

Tensile properties of cotton fibers: importance, research, and limitations 265

an index of appearance, strength, uniformity, and level of imperfections. However, the
spinner is much more concerned about how the yarn user views yarn quality. The
knitter may have more detailed criteria of yarn quality including the following:

1. A yarn that can unwind smoothly and conform readily to bending and looping while running
through the needles and sinkers of the knitting machine; this translates to flexibility and
pliability.
2. A yarn that sheds low fly in and around the knitting machine; this translates to low hairiness
and low fiber fragmentation.
3. A yarn that leads to a fabric of soft hand and comfortable feeling. This translates to low twist,
low bending stiffness, and yarn fluffiness or bulkiness.
4. A yarn that has better pilling resistance. This translates to good surface integrity.
5. A yarn that will not result in the development of common knit defects such as knit holes. This
translates to a strong yarn made from fibers that are strong, tough, and flexible.
The weaver may have a different set of yarn quality criteria:

1. A yarn that can withstand stresses and potential deformation imposed by the weaving
process. This translates to strength, flexibility, and low strength irregularity.
2. A yarn that has a good surface integrity. This translates to low hairiness and high abrasion
resistance.
3. A yarn that can produce defect-free fabric. This translates to high evenness, low imperfection,
and minimum contamination.

In all the above criteria, the tensile parameters of cotton fibers play a vital role.
However, without establishing a fiber-to-yarn engineering system, the contributions
of the key tensile attributes of cotton fibers to yarn and fabric integrity, appearance,
and flexibility will be hardly realized and perhaps wasted in the mist of craft, trial
and error, and scattered experience in the industry.
To understand the nature of fiber-to-yarn strength relationships, it will be important
to briefly discuss two important subjects:

1. Characterization of yarn strength
2. Fiber-to-yarn strength relationships

7.17.1 Characterization of yarn strength
Yarn strength is considered as one of the main criteria characterizing yarn quality.
Indeed, no other yarn characteristic has received more investigative attention than
yarn strength. Most of the studies dealing with yarn strength focused on developing
models characterizing yarn strength as a function of structural parameters and fiber
attributes. Many of these models revealed a great deal of information about the
complex nature of yarn strength. In fact, the interpretation of the strengthetwist
relationship discussed earlier stems from existing models describing the effect of twist
on yarn strength. In recent years, interest in modeling yarn strength with respect to
relevant fiber attributes has increased as a result of the revolutionary development
of fiber testing and information technology, and the introduction of new spinning
technologies (Elmogahzy and Chewning, 2001).