1 Exam 2 Study Guide 2 Chapter 6 Manufactured Fiber a Steps in fiber manufacture i Spinning 1 wet spinning a rayon lyocell and some acrylics b natural materials dissolved in chemical extruded into a chemical bath chemical reacts with solution to coagulate the fiber irregular cross section and striations c 2 dry spinning a regenerated b natural matericals dissolved in chemical c Extruded into warm air d Chemical evaporates from fiber leading to coagulation e Irregular cross section striations 3 melt spinning a Synthetic and inorganic fibers b Chemicals combined to create base substance usually as a flake or bean c Synthesized flakes or beans are melted d Extruded into cold air e Fiber solidifies f Shape of spinneret holes determine shape of fiber i Lobular ii Dog bone iii Hollow ii Develop the solution dope iii Extrude through a spinneret iv Coagulate or solidify the fiber v Draw the fiber vi Fiber modifications in spinning 1 Additives to solution 2 Co extrusion a Microfibers b Bicomponent fibers vii Drawing Orientation a Color delusterants b Function flame resistance antimicrobial 1 Godet wheels draw out fiber to increase polymer orientation 2 More drawing more crystallinity b Manufactured regenerated cellulosic fibers i Manufactured rather than natural ii Begins with natural sources of cellulose then regenerated cellulose iii 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 fiber iv Rayon 1 Rayon was the first regenerated fiber produced in 1882 2 It was originally sold as artificial silk consumer concerns lead to new name in 1924 based on process 3 100 cellulose no lignin Originally used wood pulp 4 produced as filament 5 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 rayon a High wet modulus rayon structure is more like cotton i Greater resistance when wet ii Water is used rather than caustic soda in the dissolving stage iii Other names are polynosic rayon and modal iv Has greater strength stretches less v Used for cords in tires and some apparel vi Have less a crenulated cross section vii Cuprammonium rayon properties similar to viscose rayon viii Fiber is wet spun from cellulose dissolved directly in cuprammonium silkier than viscose ix discontinued due to copper contaminated water waste Bemburg rayon used in lining jackets 7 Viscose Rayon Most common type of rayon a The first commercially successful manufactured fiber b 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 waste i 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 cellulose ii 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 easily iii Xanthation carbon disulfide is added to the crumbs which produces xanthate and the color changes to bright orange and is now soluble iv Dissolving and Ripening the crumbs are placed in dilute sodium hydroxide and aged producing a thick and viscous fiber named viscose which looks like honey v Filtration the viscose is filtered and any delustering or pigments for coloring may be added vi Extrusion forcing the viscose through the spinneret wet spun into a dilute sulfuric acid regenerated into long filaments d Molecular structure i Is composed of cellulose like cotton e Physical Properties i Color white and lustrous ii Structure amorphous iii Shape serrated cross section making striations along length iv Viscose Rayon Cotton and Linen of similar weave and construction will be of comparable weight f Mechanical Properties i Low strength compared with cotton and flax shorter polymers than natural fibers when ii Weaker when wet than dry handle carefully when laundering iii Low abrasion resistance iv Good draping qualities and aesthetics interior designers like this v Stretches does not recover 1 Some have been reformulated to resist stretching vi Wrinkles easily the amount of shrinkage is usually high vii A higher strength version is produced by modifying the manufacoring process g Chemical Properties i Very absorbent because of amorphous molecular structure 1 Dyes easily ii Good conductivity no static cling iii Burns easily continues burning when removed from flame h Uses of Viscose Rayon i Apparel Interior fabrics 1 Often blended with other fibers to improve performance ii Non woven applications 1 cotton balls disposable dust cloths disposable diapers iii Some rayon can be washed but watch it Most should be dry cleaned be sure to read the label v Lyocell manufacturers 1 Manufactured by Acordis used to be called Coutaulds European 2 The Lenzing group acquired trade name is Tencel 3 Newer type of rayon good drape 4 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 chemicals 8 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 Acetate 1 Chemical modification of cellulose that has acetate groups 2 Modified on a molecular level Hydroxyls replaced by acetyl groups a Which turns the cellulose into thermoplastic low melting point 3 Harder to dye 4 Dissolving pulp is soaked in acetic acid a Other chemicals added b Water added cellulose acetate sinks to bottom 5 Flakes dissolved in acetone 6 Dry spinning extruded into warm air that evaporates the acetone 7 Slightly