Spandex
is segmented polyurethane-some blocks or segments of the molecular chains
(polyurethane) are "hard" while other segments (polyester) are
"soft" or elastic. When the fiber is relaxed, the soft chains are
tangled together; they straighten out under tension, but always pull back to
the shortened tangle. Spandex can stretch up to seven times its original length
and recover instantly when tension is released.
Spandex
is the most complex and expensive of all synthetic fibers to make, originally
developed by DuPont; production under their trademark name LYCRA® still
dominates the market worldwide and is one of the most-recognized consumer
brands. The early use of spandex seldom went beyond applications in which
rubber had been used, such as elastic waistbands and what is termed
"intimate apparel." Even in these basic applications, technology is
being developed to give better performance. LYCRA® SOFT (by DuPont) is aimed to
deliver comfort (a softer fit) along with good control in waistbands or body
shaping apparel.
Spandex
is now being used in an ever-widening array of articles, for wovens as well as
knits, in amounts from about 3 percent to upwards of 50 percent in combination
with other fibers. A Technical Bulletin of February 1995 from Bayer
Corporation22 indicated use of their DORLASTAN® spandex in a range of 2-10
percent in outerwear; 2-25 percent in underwear (and a similar range in
swimwear); 2-40 percent in pantyhose; 10-45 percent in foundation garments; and
35-50 percent in medical hosiery.
Beyond
these, there has been a considerable increase in the use of spandex in all
kinds of active wear. This parallels consumer preference trends to clothing
especially designed for vigorous sports (athletic compression garments) as well
as for "second skin" clothing fashions. There are demographic changes
as well, with older consumers representing more of the market and wanting
comfort stretch in, for instance, jeans. A strong turn to cotton knits brought
introduction of blends with spandex, since recovery in cotton knits, especially
at cuffs, is better with a small amount of spandex in the yarns. There has also
been a positive response by consumers to wearing traditional tailored clothing
made of fabric that provides more ease of movement and holds its shape better;
this has been seen with clothing of wool and of linen.
None
of this would promote this relatively costly synthetic, however, if it did not
have great advantages over rubber. It is much stronger and can be used
uncovered; this means that power stretch can be obtained with a much finer yarn
than with rubber, allowing much lighter "contour fashions":
foundation garments, swimwear, and all kinds of action wear, to say nothing of
medical support stockings. It is also used in a number of other yarn
"configurations" as a core wrapped with staple or filament of other
fibers.
Spandex
also has good resistance to dry heat and oil and can be dyed as rubber cannot,
so it does not "grin through" in a stretched-out fabric, as a rubber
core would. The fine, uncovered yarns have had a tendency to break and protrude
through swimwear after wear, and one of the few basic drawbacks of spandex has
been yellowing in chlorine bleach. Use of more colored articles and changes in
care procedures make yellowing less troublesome, and changes have been made in
the fiber as well. A special type of LYCRA is offered by DuPont for swimwear,
with chlorine resistance and more durability.
Use
of a small amount of spandex with regular filament nylon in pantyhose results in
a smooth feel with good fit, an improvement over the use of textured stretch
nylon yarn, which is duller and more easily snagged. Here, again, DuPont offers
a special form for knitters of hosiery, in blends with any fiber to ensure a
consistent body-hugging fit; it may be given the trademark LYCRA® 3D when
DuPont's construction standards have been met.
The
muscle vibration encountered by many sports participants can be reduced by
wearing compression garments. However, it took intensive research to develop
fabrics and garments that would do this and still allow unrestricted movement.
Results of a five-year study done at Penn State Center for Sports Medicine were
released in 1998 by DuPont. Garments incorporating the then-newly developed
LYCRA® POWER and made to specification were reported to give a 10-20 percent
average improvement in force and power production in subjects who were
"fatiguing" after standard repetitive jumping tests. So, all that
sleek athletic wear can offer definite physiological advantages-making you feel
right as well as look right.
The
few trademark names for spandex other than LYCRA® and DORLASTAN® are GLOSPAN®
and CLEERSPAN® (by Globe), LINEL® and LINEL® COMFORT (by Fillattice), and
OPELONTM (by DuPont/ Toray).\
MANUFACTURING PROCESS
