1. Exam 2 Study Guide2. Chapter 6 – Manufactured Fibera. Steps in fiber manufacturei. (Spinning)1. wet spinninga. rayon, lyocell and some acrylicsb. natural materials dissolved in chemical, extruded into a chemical bath, chemical reacts with solution to coagulate the fiberc. irregular cross section and striations2. dry spinninga. regeneratedb. natural matericals dissolved in chemicalc. Extruded into warm aird. Chemical evaporates from fiber leading to coagulatione. Irregular cross section & striations3. melt spinninga. Synthetic and inorganic fibersb. Chemicals combined to create base substance usually as a flake or beanc. Synthesized flakes or beans are meltedd. Extruded into cold aire. Fiber solidifiesf. Shape of spinneret holes determine shape of fiberi. Lobularii. Dog bone iii. Hollowii. Develop the solution (dope)iii. Extrude through a spinneretiv. Coagulate or solidify the fiberv. Draw the fibervi. Fiber modifications in spinning1. Additives to solutiona. Color, delusterantsb. Function- flame resistance, antimicrobial2. Co-extrusiona. Microfibersb. Bicomponent fibersvii. Drawing/Orientation1. Godet wheels draw out fiber to increase polymer orientation2. More drawing=more crystallinityb. Manufactured regenerated cellulosic fibers i. Manufactured rather than naturalii. Begins with natural sources of cellulose; then regenerated celluloseiii. Produced from natural substances containing cellulose in an unusable form, then treated with chemicals to produce a solution that can be regenerated or reformed as a fiberiv. Rayon1. Rayon was the first regenerated fiber produced in 18822. It was originally sold as “artificial silk”; consumer concerns lead to new name in 1924 based on process3. 100% cellulose, no lignin. Originally used wood pulp4. produced as filament5. FTC defines rayon as “a manufactured fiber composed of regenerated cellulose, as well as manufactured fibers composed of regenerated cellulose in which substituent have replaced not more than 15 percent of the hydrogen of the hydroxyl groups”6. Forms of rayona. High-wet-modulus rayon (structure is more like cotton)i. Greater resistance when wetii. Water is used rather than caustic soda in the dissolving stageiii. Other names are polynosic rayon and modaliv. Has greater strength; stretches lessv. Used for cords in tires and some apparelvi. Have less a crenulated cross sectionvii. Cuprammonium rayon (properties similar to viscose rayon)viii. Fiber is wet spun from cellulose dissolved directly in cuprammonium, silkier than viscoseix. discontinued due to copper contaminated water waste, Bemburg rayon (used in lining jackets)7. Viscose Rayon- Most common type of rayona. The first commercially successful manufactured fiberb. Dissolving process- harvested trees are stripped of their bark, sun-dried, then cut into strips, and finally reduced to chips. Chips are treated to remove lignin; the resulting dissolving pulp is more than 95 percent cellulose. (spun from a solution of cellulose xanthate in sodium hydroxide)c. Steps: These steps use large amounts of chemicals and wastei. Steeping or slurring- placed in a soaking press of sodium hydroxide to separate the polymer chains, then the sodium is pressed out of the pulp leaving a slurry consisting substance called alkali celluloseii. Aging- the alkali cellulose is shredded into fluffy particles called white crumbs and set for days while the cellulose chains are broken into shorter polymers that can be dissolved more easilyiii. Xanthation-carbon disulfide is added to the crumbs which produces xanthate and the color changes to bright orange and is now solubleiv. Dissolving and Ripening-the crumbs are placed in dilute sodium hydroxide and aged, producing a thick and viscous fiber named viscose; which looks like honeyv. Filtration- the viscose is filtered and any delustering or pigments for coloring may be addedvi. Extrusion-forcing the viscose through the spinneret (wet spun into a dilute sulfuric acid) regenerated into long filaments. d. Molecular structurei. Is composed of cellulose, like cottone. Physical Propertiesi. Color: white and lustrousii. Structure: amorphousiii. Shape: serrated cross section, making striations along lengthiv. Viscose Rayon, Cotton, and Linen of similar weave and construction will be of comparable weightf. Mechanical Propertiesi. Low strength - shorter polymers than natural fibers (when compared with cotton and flax)ii. Weaker when wet than dry (handle carefully when laundering)iii. Low abrasion resistanceiv. Good draping qualities and aesthetics (interior designers like this)v. Stretches, does not recover1. Some have been reformulated to resist stretchingvi. Wrinkles easily , the amount of shrinkage is usually highvii. A higher-strength version is produced by modifying the manufacoring processg. Chemical Propertiesi. Very absorbent (because of amorphous molecular structure)1. Dyes easilyii. Good conductivity (no static cling)iii. Burns easily- continues burning when removed from flame h. Uses of Viscose Rayoni. Apparel, Interior fabrics 1. Often blended with other fibers to improve performanceii. Non-woven applications1. “cotton” balls, disposable dust cloths, disposable diapersiii. Some rayon can be washed but watch it, Most should be dry cleaned, be sure to read the labelv. Lyocell1. Manufactured by Acordis (used to be called Coutaulds), European manufacturers2. The Lenzing group acquired trade name is Tencel3. Newer type of rayon; good drape4. A fiber that is composed of cellulose precipitated from an organic solution in which no substitution of the hydroxyl groups takes place and no chemical intermediates are formed (dissolved directly in N-methylymorpholine)5. Wood pulp, possibly bamboo (dissolving pulp, like viscose rayon)6. Manufacturing process more environmentally friendly (the green fiber)7. Non-Toxic solvent, recycle chemicals8. Stronger than viscose rayon; can be laundered (easy care properties)9. More crystalline structure than viscose rayon; fibers do fibrillate after several launderings (splinter off giving fuzzy appearance)10. Other properties are similar to rayon (high moisture regain, comfortable, and dyes readily)vi. Acetate1. Chemical modification of cellulose that has acetate groups2. Modified on a molecular level (Hydroxyls replaced by acetyl groups)a. Which turns the cellulose into thermoplastic (low melting point)3. Harder to dye4. Dissolving pulp is soaked in acetic acid.a. Other chemicals addedb. Water