Cellulose triacetate fiber form

Triacetate fiber n. A manufactured fiber produced from cellulose triacetate in the forms of filament yarn, staple, and tow. Cellulose triacetate fiber differs from acetate fiber in that during its manufacture the cellulose is completely acetylated whereas acetate, which is diacetate, is only partially acetylated. A fiber may be called triacetate when not less than 92% of the hydroxyl groups are acetylated. Fabrics of triacetate have higher heat resistance than acetate fabrics and can be safely ironed at higher temperatures. Triacetate fabrics that have been properly heat-set (usually after dyeing) have improved ease-of-care characteristics because of a change in the crystalline structure of the fiber. Complete textile glossary. Celanese Acetate EEC, New York, 2000. Also see acetate fiber. 

Polymer Plasticizer. Nylon, cellulose, and cellulose esters can be plasticized using sulfolane to improve flexibiUty and to increase elongation of the polymer (130,131). More importantly, sulfolane is a preferred plasticizer for the synthesis of cellulose hoUow fibers, which are used as permeabiUty membranes in reverse osmosis (qv) cells (131—133) (see Hollow-FIBERMEMBRANEs). In the preparation of the hoUow fibers, a molten mixture of sulfolane and cellulose triacetate is extmded through a die to form the hoUow fiber. The sulfolane is subsequently extracted from the fiber with water to give a permeable, plasticizer-free, hoUow fiber. 

It is difficult for dye solutions in water to penetrate synthetic fibers such as polyester, cellulose triacetate, polyamides, and polyacryUcs which are somewhat hydrophobic. The rate of water imbibition differs with each fiber as shown in Table 1 as compared to viscose (see Fibers, regenerated CELLULOSics), which imbibes water at the rate of 100% (1). The low imbibition rate is attributed to the high T obtained when the polymeric fibers are drawn. During this drawing operation the polymer chains become highly oriented and tightly packed, forming a stmcture practically free of voids. 

Amongst the important chemical conversions of macromolecular substances are the various reactions of cellulose. The three hydroxy groups per CRU can be partially or completely esterified or etherified. The number of hydroxy groups acetylated per CRU are indicated by the names, i.e., cellulose triacetate, cellulose 2-acetate, etc. Another commercially important reaction of cellulose is its conversion to dithiocarboxylic acid derivatives (xanthates). Aqueous solutions of the sodium salt are known as viscose they are spun into baths containing mineral acid, thereby regenerating the cellulose in the form of an insoluble fiber known as viscose rayon. 

The basic cellulose unit contains three hydroxyl groups. The triester cellulose triacetate forms when cellulose is reacted with glacial acetic acid. Hydrolysis removes some of the acetate groups to form a secondary ester, which averages about 2.4 acetyl groups per unit rather than three. The secondary ester is then dissolved in acetone and the solution ejected through a spinneret to form fibers. Cellulose acetate processed in this manner is referred to as acetate rayon, but it may be more commonly known by its trade name Celanese. 

Cellulose acetate fibers are defined by the Textile Fiber Products Identification Act as manufactured fibers in which the fiber-forming substance is cellulose acetate in which not less than 92% of the hydroxyl groups are acetylated. Cellulose triacetate is employed to make many tricot fabrics and sportswear. Cellulose triacetate textile is shrink- and wrinkle-resistant and easily washed. 

Cellulose acetate was first prepared in 1865, and was a suitable candidate to replace nitrocellulose. Cellulose triacetate, however, was less soluble in common solvents than nitrocellulose and also was difficult to dye. Lower levels of acetylation gave more tractable, fiber-formable products, which could be more easily dyed, and could be formed into film suitable for photographic use. These were the so-called acetate rayon fibers and plastics, which were also considerably safer to use than nitrocellulose. 

Cellulose triacetate is also prepared by a heterogeneous process in the presence of benzene, a nonsolvent. The triacetate that forms in both processes is hard to mold, but it can be used in films and fibers. The diacetate is more suited for plasticization and molding. 

Hydroxyl groups present on 2, 3, and 6 positiOTis are the sites where derivatization can be carried out. Cellulose esters and ethers are the most important commercial materials. Among the esters, cellulose acetate and cellulose triacetate are film- and fiber-forming materials and have wide range of applications. The inorganic ester nitrocellulose was initially used as an explosive and as a film-forming material. 

Natural polymers can be made into hbers through dissolution of the polymer in an appropriate solvent and then extmsion of the polymer solution into a coagulation bath. As an example, cellulose can be made into viscose rayon fibers, cuprammonium rayon, cellulose acetate and triacetate fibers, lyocell, and modal fibers depending on the processes used to make the fibers. Other natural polymers such as mbber, chitosan, alginic acid, and protein can also be made into fibers in an appropriate fiber-forming process. 

C. Pan, Permeation of water vapor through cellulose triacetate membranes in hollow fiber form, J. Appl. Polym. Sci., 1978, 22, 2307-2323. 

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