Processing of weft-stretch spandex woven
By: Dr. Syed Muhammad
Imtiazuddin and Sohail Tiki (Director AVM Chemicals)
Fabrics containing Spandex elastane yarn require careful
control of processing conditions to preserve the intrinsic
elastic properties of the fibre while obtaining the required
fabric characteristics. These dyeing and finishing conditions
should be chosen with care because the performance of Spandex
elastane can be changed by prolonged hot/wet treatments, certain
chemicals excessive tension and high temperature. It is,
therefore, necessary to be fully aware of the physical changes
required to develop the desired weight, width, stability and
As compared with ordinary 100% cotton fabric, the width of
weft-stretch SPANDEX fabric should be shrunk in the weft
direction during the processing and therefore it is recommended
to carry out the processing of fabric properly after grasping
the relationship among the three, namely, grey fabric width,
finishing width and weft stretchability (generally, about
20%-30% shrinkage in the weft direction). [3,4]
Tension, temperature, the concentration of process chemicals
and the duration of treatments must be kept to a minimum because
they affect the elastic properties and the appearance of the
finished goods. In particular, the tension must be kept to a
minimum during those steps which are carried out at an elevated
temperature, i.e. relaxation, hot wet processing, drying and
curing. Although the use of high temperatures and tensions does
not degrade Spandex, fabrics containing it lose some
power/stretch when they are hot-stretched and this loses cannot
be recovered. 
Fabrics containing Spandex are sensitive to unsaturated oils,
greases, fatty acids and their derivatives, which tend to
discolour and degrade elastane yarns. Such compounds sometimes
serve ad lubricants for hard fibres and they vary from one yarn
producer to another. Pine oil, used in printing, cutting or
boarding, can also affect stretch fabrics. It is essential to
make sure that these lubricate, if present, will not discolour
or degrade Spandex during the usual course of processing.
In general, the duration of treatments and the concentration
of chemicals applied in the wet process should not exceed the
minimum necessary to attain the best performance of the treated
goods. The duration and concentration of bleaching baths, the
duration and pH of dye baths, the duration of solvent scouring,
the treatments which involve caustic soda or acids, the
selection of carries for Spandex/polyester dyeing, as well as
resin curing catalysts and conditions, need particular
The selection of a particular processing route depends on the
desired appearance, the required performance of the fabric in
use and fabric composition. Stretch fabrics include a large
variety of fabrics, each with their particular features, and it
is impossible to advise one general process route for all of
A standard discontinuous process suitable for most stretch
The first two steps involve Spandex elastane directly and
govern the future performance of the stretch fabric or garment,
while the remaining steps must take into account the specific
features of Spandex to retain the best benefits. The above
standard sequence may not apply to certain woven fabrics.
Different procedures also apply to continuous processes.
A grey fabric containing Spandex must be exposed in a relaxed
condition to steam, hot water or warm organic solvent before
dyeing and finishing. Relaxation of the grey fabric relieves
residual stresses caused by the tension of the Spandex yarns
These stresses can distort the structure, deform the design,
and cause puckering of the fabric. Such effects show up
especially in clear faced or regularly patterned woven and
The potential shrinkage in the grey fabric should also be
removed to obtain an evenly dyed and uniformly finished product.
A stretch fabric is therefore relaxes at an early stage of
its finishing by one of the following methods:
- Passing over a stem table.
- Steam framing.
- Solvent scouring.
- Hot water treatment.
Steam table relaxation is preferred because complete
relaxation can be achieved. The time of relaxation will depend
upon fabric construction and rate of steam generation.
Steam farming consists of overfeeding a fabric over a steam
box fixed at the stenter inlet. The stenter should then only dry
the steam relaxed fabric. Combined steam relaxation and heat
setting give less uniform results than relaxation and
heat-setting in separate steps.
The continuous solvent scouring services to relax and dry
clean fabrics at the same time. It provides a good width wise
relaxation and a controlled length-wise relaxation of treated
Relaxation by hot water occurs when a non-heat-set grey
fabric is washed or dyed without stress. This is an efficient
way to relax the fabric, but it may leave permanent creases or
interfere with the subsequent heat-setting of the relaxed
textile. The fully relaxed fabrics are stable for washing.
Care is needed to maintain and control fabric:
- Dimensional stability.
Spandex under tension will be set when
- Given time (cold set).
- Steamed above 120oC.
- Processed in water above 100oC.
- Exposed to dry heat above 180oC.
- Contributes to fabric stability.
- Better crease resistance.
- Can achieve wider width/lower weight.
- Lower recovery power.
- Potential and elongation loss and change of handle.
- Vibrating steam table.
- Steam framing.
- Solvent scouring.
- Tensionless hot washing.
Heat setting and drying
- Temperature, overfeed and width control.
- Continuous range.
Shrinking treatment in width
The width shrinking treatment of grey fabric is carried out
by using an open soaper. This treatment is necessary to give the
fabric a stabilized width by hot water treatment (80 – 90oC) and
a proper elasticity, thereby making the succeeding process go
smoothly. This treatment, by using an activator, can serve also
as washing and desizing.
Scouring and Bleaching
A continuous desizing, scouring, bleaching range can be used
in this context. It is safe to carry out scouring and bleaching
by stages, using a tensionless jigger. However, as mentioned
before, a treatment by strong alkali or at high temperature and
high pressure must be avoided.
Continuous dyeing by using a pad steamer, for example, is
possible. Dyeing of cotton or polyester can safely be applied.
Conditions and facilities used for dyeing ordinary
polyester/cotton mix woven (disperse/reactive, disperse/vat) can
safely be adopted. However, when using a high
temperature/high-pressure dyeing machine, attention should be
paid to possible damage on SPANDEX. If any damage is found, the
use of a carrier is recommended. Using high temperature is not
The Spandex fabrics sometimes need stain removal or
stripping, if they are dyed unevenly, too dark or are stained
during finishing. The elastane component of the fabric imposes
restraints on the selection of suitable stripping agents.
Reducing agents do not degrade “SPANDEX” elastane fiber and are
therefore recommended. Alkaline reducing baths are preferred,
whenever compatible with the type of “SPANDEX” and the hard
fibre in the fabric.
Dye stripping by compounds that release chlorine, such as
hypochlorite or chlorite, will weaken and degrade the elastane
fibre and therefore unsuitable for the processing.
Some recommended procedures are
1. Color correction or light stain removal.
- 1 g/l non-ionic surfactant.
- 1-2 g/l trisodium phosphate.
- 15-20 minutes at 85oC.
2. Partial stripping or removal of medium stains.
- 1-3 g/l sodium dithionite (hydrosulfite).
- 1-2 g/l tri sodium phosphate.
- 15-20 minutes at 85oC.
3. Alkaline stripping.
- 5% sodium sulphoxylate formaldehyde.
- 1% amphoteric dispersing agent.
- Sodium hydroxide to pH 10-11.
15 minutes at 90-95oC , then soap and rinse the fabric to
4. Acid stripping
- 1% zinc sulphoxylate formaldehyde
- 1% amphoteric dispersing agent
- Adjust bath to pH 5 if needed
- Treat 15 minutes at 85 oC, then soap and rinse till fabric
pH is neutral.
- A complete color strip, usually followed by redyeing
represents extra processing of the stretch fabric which may
weaken it and impair its subsequent performance in use.
Depending upon the use, resin finish, softening finish and so
on are carried out. The finishing also concerns handle, look and
dimensions, and can impart special properties to fabrics
It comprises both mechanical and chemical treatments which
all require careful control of applied tension, temperature,
time and chemicals.
The mechanical finishing includes the steps either before or
after dyeing and printing which change the physical features of
a fabric. The methods chosen to finish a fabric containing
SPANDEX should, in general, involve little or no tension,
particularly when the treated fabric is hot.
The joint action of high tension and heat may reset or
overset the fabric and cause loss of its final relativity. Low
tension allows the best relaxation, improves dimensional
stability, and gives a supple handle to the goods.
Fabrics that have been overstretched in processing tend to
relax afterwards causing difficulties in cutting, and high or
irregular shrinkage of garments.
SPANDEX will withstand without undue damage most of the
mechanical finishes applied to rigid
- Mangle or spin dry.
- Steam relax or shrink.
- Semidecate or decate.
- Press or Palmer-press.
- Raise, send or suede.
- Calendar or emboss.
Key rules to follow are “do not stretch hot fabric” and “no
tension for long periods”.
Hot air drying, usually on pin stenters with overfeed,
removes non-extracted water and establishes the final width and
weight of the fabric.
Temperatures should not exceed 110oC when drying stretch
fabrics. The time of drying and the resultant speed of fabric
passage, will depend on the weight and structure of the fabric,
but should not be longer than the minimum needed to dry it.
Heating should be uniform over the entire fabric and over
drying must be avoided as it may slightly yellow the fabric. The
risk of yellowing is increased when the drying air is heated
directly with oil or gas burners.
The same advice also applies to drying required to fix or
develop any chemical finishes of fabrics of Spandex.
Fabrics containing SPANDEX withstand many chemical treatments
or finishes which serve to change or improve their look,
surface, handle, performance or properties. SPANDEX is
compatible with many.
- Water repellents
- Resin finishes for easy care, when used with organic
- Resin finishes to impart body, when used with organic
- Rot-proofing agent.
- Coating finishing in emulsion.
- Bayazit M.A: Dimensional and physical properties of
cotton/spandex. Single jersey Fabrics, Textile Res. J. 73 (1),
- Hicks EM, Ultee. A J and Drougas J: Spandex Elastic
Fibers, Science, New Series 147, 373-379, 1965.
- 1995, ‘’ Bayer Takes Aim at North America with Spandex
Plant’’, Textile World. No.8. pp86-88.
- Luke, J.E.2001, “Spandex world Trends”, Textile world.
- Fibers 2000, “Dupont high global elastane yarn investment.
New capacities for generic elastane yarn”, Man-made fiber
yarn. Book No.8.
- Fibers in 2003, Textile Monthly. No.4, 2004.
- Wet processing of fabrics containing Lycra elastane, Basic
information, Dupont Technical Bulletin No. 517, Wilmington,