3. ABOUT RAYON
Rayon is the oldest manmade fiber.
The U.S Trade commission defines Rayon as
“man made textile fibers and filament composed
of regenerated cellulose”.
Discovered by C.E.Cross and E.J.Bevan in 1891.
4. RAYON AS A MATERIAL
It is neither a truly
synthetic fiber, nor a
natural fiber.
Is a Semi-synthetic or a
artificial fiber.
Is known by the names
viscose rayon and art silk in
the textile industry.
A high luster quality
giving a bright sheen.
5. TYPES OF RAYON
Regular Rayon: This rayon has the largest market share. It is
typically used in apparel and home furnishing.
High Wet Modulus (HWM): This rayon has the same property as
regular rayon but with high wet strength. It performs much like
cotton in similar end uses.
High Tenacity Rayon: This is a modified regular rayon with
exceptional strength (two times the strength of HWM rayon). It is
primarily used in tire cord and industrial end uses.
Microfibers: This is manufactured from either regular rayon or
HWM rayon's. Rayon microfibers are very fine. The fabrics from
microfibers drapes better and are silk-like in hand and appearance.
6. CHARACTERISTICS OF RAYON
It is strong and durable.
It is extremely absorbent.
It is soft and comfortable.
It is breathable.
It is easily dyed in vivid colors.
It is abrasion resistant.
It resists insect damage.
It looses 30% to 50% of its strength when wet.
It drapes well and does not have a problem with static.
It wrinkles easily.
7. PRODUCTION PROCESS
Production process used in making rayon is either a
continuous or a batch process.
Regular rayon (or viscose) is the most widely
produced form of rayon. This method of rayon
production has been utilized since the early
1900s and it has the ability to produce either
filament or staple fibers.
8. THE PROCESS IS AS FOLLOWS
Cellulose: Production begins with processed cellulose.
Immersion: The cellulose is dissolved in caustic soda:
(C6H10O5)n + nNaOH → (C6H9O4ONa)n + nH2O
Pressing: The solution is then pressed between rollers
to remove excess liquid
White Crumb: The pressed sheets are crumbled or
shredded to produce what is known as "white crumb"
Aging: The "white crumb" aged through exposure to
oxygen
9. THE PROCESS CONT’D
Xanthation The aged "white crumb" is mixed with carbon
disulfide in a process known as Xanthation, the aged alkali
cellulose crumbs are placed in vats and are allowed to react
with carbon disulfide under controlled temperature (20 to
30 C) to form cellulose xanthine:
(C6H9O4ONa)n + nCS2 → (C6H9O4O-SC-SNa)n
Yellow Crumb: Xanthation changes the chemical makeup of
the cellulose mixture and the resulting product is now called
"yellow crumb“.
Viscose: The "yellow crumb" is dissolved in a caustic solution
to form viscose.
Ripening: The viscose is set to stand for a period of
time, allowing it to ripen: (C 6H9O4O-SC-SNa)n + nH2O →
(C6H10O5)n + nCS2 + nNaOH.
10. THE PROCESS CONT’D:-
Filtering: After ripening, the viscose is filtered to remove any
undissolved particles
Degassing: Any bubbles of air are pressed from the viscose in a
degassing process.
Extruding: The viscose solution is extruded through a
spinneret, which resembles a shower head with many small holes.
Acid Bath: As the viscose exits the spinneret, it lands in a bath of
sulfuric acid, resulting in the formation of rayon filaments: (C 6H9O4O-
SC-SNa)n + ½nH2SO4 → (C6H10O5)n + nCS2 + ½nNa2SO4
Drawing: The rayon filaments are stretched, known as drawing, to
straighten out the fibers
11. THE PROCESS CONT’D:-
Washing: The fibers are then washed to remove any residual
chemicals
Cutting: If filament fibers are desired the process ends here.
The filaments are cut down when producing staple fibers
High wet modulus rayon (HWM) is a modified version of
viscose that has a greater strength when wet. It also has the
ability to be mercerized like cotton. HWM rayon's are also
known as "polynosic" or can be identified by the trade name
Modal.
12. USES OF RAYON
Apparel -
Blouses, dresses, jackets, lingerie, linings, millinery, slac
ks, sport shirts, sportswear, suits, ties, work clothes
Home Fashions -
bedspreads, blankets, curtains, draperies, sheet, slip
covers, tablecloths, upholstery.
