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.
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 namesviscose rayon and art silk in the textile industry. A high luster quality giving a bright sheen.
TYPES OF RAYONRegular Rayon: This rayon has the largest market share. It istypically used in apparel and home furnishing.High Wet Modulus (HWM): This rayon has the same property asregular rayon but with high wet strength. It performs much likecotton in similar end uses.High Tenacity Rayon: This is a modified regular rayon withexceptional strength (two times the strength of HWM rayon). It isprimarily used in tire cord and industrial end uses.Microfibers: This is manufactured from either regular rayon orHWM rayons. Rayon microfibers are very fine. The fabrics frommicrofibers drapes better and are silk-like in hand and appearance.
CHARACTERISTICS OF RAYONIt 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.
PRODUCTION PROCESS Production process used in making rayon is either a continuous or a batch process. Regular rayon (or viscose) is the most widelyproduced form of rayon. This method of rayon production has been utilized since the early1900s and it has the ability to produce either filament or staple fibers.
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
THE PROCESS CONT’D Xanthation The aged "white crumb" is mixed with carbondisulfide in a process known as Xanthation, the aged alkalicellulose crumbs are placed in vats and are allowed to reactwith carbon disulfide under controlled temperature (20 to30 C) to form cellulose xanthine: (C6H9O4ONa)n + nCS2 → (C6H9O4O-SC-SNa)n Yellow Crumb: Xanthation changes the chemical makeup ofthe cellulose mixture and the resulting product is now called"yellow crumb“.Viscose: The "yellow crumb" is dissolved in a caustic solutionto form viscose.Ripening: The viscose is set to stand for a period oftime, allowing it to ripen: (C 6H9O4O-SC-SNa)n + nH2O →(C6H10O5)n + nCS2 + nNaOH.
THE PROCESS CONT’D:-Filtering: After ripening, the viscose is filtered to remove anyundissolved particlesDegassing: Any bubbles of air are pressed from the viscose in adegassing process.Extruding: The viscose solution is extruded through aspinneret, which resembles a shower head with many small holes.Acid Bath: As the viscose exits the spinneret, it lands in a bath ofsulfuric acid, resulting in the formation of rayon filaments: (C 6H9O4O-SC-SNa)n + ½nH2SO4 → (C6H10O5)n + nCS2 + ½nNa2SO4Drawing: The rayon filaments are stretched, known as drawing, tostraighten out the fibers
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 fibersHigh wet modulus rayon (HWM) is a modified version ofviscose that has a greater strength when wet. It also has theability to be mercerized like cotton. HWM rayons are alsoknown as "polynosic" or can be identified by the trade nameModal.
USES OF RAYON Apparel -Blouses, dresses, jackets, lingerie, linings, millinery, slacks, sport shirts, sportswear, suits, ties, work clothes Home Fashions -bedspreads, blankets, curtains, draperies, sheet, slipcovers, tablecloths, upholstery.