Anti Wrinkle Finish
Anti Shrink FinishPraveen D Nagarajan
ANTI-SHRINK FINISHSHRINKAGE:
Shrinkage is the contraction in the dimension of the fabric due
to usage.
Cotton fabric suffers from 2 main disadvantages of creasing and
shrinking during subsequent washing. Creasing is overcome by the
resin finishing whereas the shrinking is prevented by a special
finishing known as Sanforising.
The machine used for that purpose is known as Zero Zero Pre
Shrinking machine.
HOW COTTON SHRINKS?
Cotton has the property of swelling in water and these effects
Shrinking. Also the mechanical stress, strain and tension, during
spinning and weaving etc., when released causes the fabric to
shrink. The cotton fabric, when put in water, swelling takes place
and rearrangement of internal forces takes place. The fibers will
become free from tension and it comes to the original tensionless
state. These are the reasons for shrinkage.
In case of a fabric, the warp yarns are under much strain due to
interlacement than the weft yarns. Hence, when a fabric is allowed
to shrink, the warp yarn shrinkage will be more than weft yarn. To
overcome this, the fabric is extended in widthwise to some extent
in the stenter machine during the finishing process. Then it is
subjected to the preshrink process.
MECHANISM:
The mechanism or principle adopted to produce shrinkage is To
place the fabric on the extended surface of a rubber blanket
represented by the concave surface, When the tension is released on
the blanket, it shrinks; the fabric which is in close contact with
the rubber blanket at the concave surface has no way other than
shrinking along with the blanket. This principle is used to produce
pre shrinking finish with the help of a sanforising or Zero Zero
machine.
METHOD OF PRODUCING SHRINKAGE IN SANFORISING
PARTS1. Feed Rollers, 2. Sprayer, 3. Steaming Unit, 4. Clip
Expander, 5. Cylinder, 6. Felt Blanket,7. Sprayer, 8. Cylinder,9.
Plaiter.
ANTI-SHRINK FINISH
ANTI-SHRINK FINISHThe amount or % of shrinkage depends on:1. The
tension / stretch on the rubber blanket. 2. Thickness of the rubber
blanket. 3. Diameter of the roller.
ANTI-SHRINK FINISHThickness of Blanket to be used If Shrinkage
of fabric before Sanforising is
0.2756 8 cm / m0.48 11 cm / m0.4511 15 cm / m
MACHINE DESCRIPTION:This is a mechanical method of shrinkage
control. The cloth is fed into the machine through the feed rollers
of a mangle. It is used to hold back the cloth and only allow the
felt blanket to contract to the required amount. Otherwise over
shrinking of the cloth occurs. From the feed rollers the cloth
passes between Sprayers to moisten the cloth thereby making the
yarn soft and plastic so that it can be easily compressed by the
blanket. The moistening is assisted by a Steaming unit called
Skyer. Then the cloth passed through a Short Clip Stenter to
control the width of the cloth.
ANTI-SHRINK FINISHThe cloth is passed to the blanket over the
feed roller and is placed in firm contact with stretched surface of
the blanket by electrically heated shoes.
If cold shoes are use, less shrinkage would result. The cloth in
contact with the stretched surface of the blanket. Is passed to the
main steam heated cylinder of the palmer machine so that when the
stretched surface of the blanket is contracted by reversal of
curvature, the cloth also is contracted.
The main cylinder of the machine may be either 60 or 84 in
diameter to the material for which it is intended.After passing a
round of the drum of the palmer machine, the finished material
maybe passed on to an auxiliary finisher. It has an additional
palmer unit
ANTI-SHRINK FINISHIt can be used1) When both sides of the
material are to be finished alike When additional shrinkage is
required. If the additional palmer unit is used, the range is
called as Duplex otherwise it is called as Simplex.
