Modal is a type of rayon fiber that is stronger and more dimensionally stable when wet than regular viscose rayon. It is produced through a modified viscose process involving treatment with weaker caustic soda and lower concentrations of acids and salts in the coagulating bath. This results in longer polymer chains and a more crystalline structure compared to viscose rayon. Modal fiber is commonly blended with cotton or polyester and used in textiles like towels, bed sheets, and clothing due to its soft, absorbent properties and resemblance to cotton.

1. MODAL

2. INTRODUCTION
*Viscose rayon has a disadvantage that its wet strength is
less than dry strength.
*A Japanese researcher, S.Tachikawa, modified the viscose
process to develop a fibre with a physical structure more
like that of cotton.
*These rayons are known as high-wet-modulus(HWM) rayons.
*It is stronger, more dimensionally stable than viscose rayon,
but it is less absorbent.

3. *The term modulus refers to resistance to stress
and strain.
*HWM means that it resists deformation when
wet.
*HWM rayon, which is sometimes referred to as
high-performance(HP) or Polynosic rayon,
resembles cotton more than it does viscose.
*Modal is an European generic name for HWM
rayon.

4. *The manufacturing process of HWM rayon is a
modified process of viscose rayon.
* The purification process of raw material is
similar to that of viscose rayon.
* The blotter like sheets of purified cellulose is
steeped in weaker caustic soda and squeezed.
* Then the shredder crumbles the sheets.

5. CLASSIFICATION
*Modal comes under the category of man-made fibre .
*Under man-made fibre it comes in the category of
regenerated or semi-synthetic fibre.
*Semi-synthetic fibres are made from raw materials
with naturally long - chain polymer structure and are
only modified and partially degraded by chemical
process in contrast to completely synthetic fibres
such as nylon.

6. SOURCE/ORIGIN
*Modal fibre is mainly
obtained from beech
tree

7. PHYSICAL PROPERTIES
*High breaking strength
*Modal fibre may be fading at one stage but flat to
stretching and pilling.
*Fabric made from modal fibres are shrinkage
resistance .
*Modal are very soft ,shiny ,natural and silky feel
than mercerized cotton.
*Stone deposits from firm water never set down on
the fabric structure.

8. *Modal fabrics should be washed at slighter
temperature only.
*Modal fabrics can be often ironed after washing
like cotton.
*Modal fibre are dimensionally constant and do
not reduce in their size , or get away from their
shape.
*The aging is eliminated and the molecular chains
are not shortened as much .

9. *HWM fibres have longer polymer chains and a more
crystalline structure , but the degree of
polymerization is still less than 1000.
*HWM rayon have high strength from 3.0 to 5.7 gd
(dry) and 1.9 to 4.3 gd(wet).
*The specific grafity of HWM is 1.51,similar to that
of voscouse .
*Moisture regain is 11 to 14%.
*Resilience is better than viscouse.

10. CHEMICAL PROPERTIES
*Treated with 39 to 50 of carbon disulphide to form
cellulose xanthate.
*Mixed with 2.8% sodium hydroxide to form viscose
solution.
*No ripening process and filtered for impurities.
*Pumped to spinneret and extruded into coagulating bath,in
which a low concentration of acid is used with little or no
salts.

11. *This is done for slower regeneration and coagulation to
achieve more stretch and greater molecular
orientation.
*The bath consists of:
(a)Sulphuric acid – 1%
(b)Sodium sulphate – 4 to 6 %
(c)Speed – 20 to 30m/min.
(d)Spinning bath temperature – 25 to 35 °C
(e)Stretch – 150 to 600%

12. *Conductivity to heat and electricity is good.
*Damaged by silverfish.
*Long exposure to sun light causes some loss
of strength.
*Resistance to strong acids is poor.
*Resistance to strong base is excellent.
*Resistance against oxidising agents and
solvents is good.

13. *As it has high modulus ,it is a good choice to blend
with polyester.
*HWM fibres have greater wash ability.
*Their stability and strength are equal to that of
cotton.
*They can be mercerized and finished to minimized
shrinkage.
*They also wrinkle less than viscose rayon in washing
and drying.

14. *The cross-section of HWM rayon is
round.
*Modal fibres are blended with cotton for
knits and towels.
*It is exclusively produced as staple fibre
in order to primarily blended with cotton
or polyester .

15. USES
*Modal is used single or blend with other fibres
like cotton or elasthan in domestic items such as
towels , bed sheets etc.
*Modal fibres were at first produced in the
1930’s for industrial purposes such as exhausters
,conveyor belts and washing pipes.
*Modal fibres are used in wide range of textile
industries like clothing , outwear , changing the
spinning conditions ,chemical solutions and
stretching series of rayon fibre.

16. *Modal can be produced with greater
strength and crystallinity than rayon
fibres.
*Modal fibres are very suitable comfort for
body aware clothing like cherished apparel.
*Modal fibres are extremely absorbent and
rapidly immerse up in water so that it
mostly feels waterless even when holding a
substantial quantity of water.