Woven Fabrics - Fairchild Books

Types of Threads
Threads may be spun, filament, or core-spun type. Each
has distinctive properties and therefore certain advantages
in specific seams. A comparison of these thread
types is shown in Table 4.3.
All sewing threads, whether spun, filament, or core
spun, are ply yarns. Sewing threads are more highly
twisted and firmer than regular yarns and are often
treated with special finishes or lubricants to improve
sewability.
Thread Finishes
Threads are produced with various finishes, such as mercerized,
soft, glacé, and bonded. In addition, special finishes,
which include flame-resistant and heat-resistant
types (for high-speed sewing), are also produced. Table
4.4 indicates the properties and use characteristics of
thread finishes.
Thread Sizes
Sizes (weight per unit length) of thread are marketed
and expressed with their Tex number designation (see
p. 82). An older system of specifying thread size, the
ticket number system, based on denier and yarn-count
systems, is still in use but is gradually being replaced in
the thread industry. Table 4.5 indicates typical Tex numbers
in thread applications for various sewn products.
Important Factors in Thread Selection
Selecting the correct thread for assembly of finished
goods is of critical importance. The type of thread used
Table 4.3 Comparison oF sewing Thread TYpes
FABRIC SCIENCE
A 84 F
will determine the ease of manufacture, durability of the
product, and satisfaction of the consumer.
Thread size should be as fine as possible, consistent
with the strength requirements of the seam. Finer
threads tend to become buried below the surface of the
fabric and are, therefore, subjected to less abrasion than
seams with heavier thread, which are on top of the fabric.
Finer threads also require smaller needles, producing
less fabric distortion than heavier needles.
The breaking strength of a seam (see p. 321) should
be less than that of the fabric sewn. Many authorities
agree that the seam should be about 60 percent of the
fabric strength. This is to ensure that if excessive stress
is placed on a seam, the seam, rather than the fabric,
breaks. Seams are easily repairable; fabric is not.
If a garment is to be washed in hot water, then its
thread should have excellent resistance to color change
from this medium. Also, the thread should not shrink as
a result of the cleaning method.
Important Thread Factors That Govern
Seam Appearance
When woven-filament yarn fabrics and/or fabrics that
have been finished with resins are sewn, there is sometimes
a tendency for seams to pucker and ripple rather
than to lie flat and smooth. The tendency is greater
in lightweight fabrics than in heavyweight materials.
Some of the causes of puckering are excessive tension
on sewing thread during the sewing process, displacement
or movement of fabric yarn in the sewing operation,
and thread shrinkage that is greater than fabric
shrinkage.
Spun Filament Core Spun
Lower strength than filament. Higher strength than spun; permits use of finer
thread without sacrifice of seam strength.
Versatile and adaptable to
a wide variety of machine
adjustment conditions.
Less likely than filament thread
to cause seam pucker.
Produces neatest seams, but careful machine
adjustments necessary.
Greater possibility of seam pucker than with spun
thread.
Least costly. Less costly than core spun, but more costly than
spun thread; textured filament threads would
be good for knits because they have additional
stretchability.
Combines the best features of
filament and spun threads.
Especially useful in seaming
durable-press garments.*
Same seam puckering tendency
as spun thread.
Most costly.
* Residual resins present in permanent press garments are absorbed by the thread, causing strength loss and abrasion-resistance loss in the
cotton cover of the thread. The polyester core is unaffected by the resin, thus providing continuing seam integrity.