Fiber as cellulosics

Some workers refer to cotton lint (the normal fibers) as cellulose to distinguish it from seed cotton (fiber still on the seed) or the entire plant. Herein, the word cellulose has only the strict chemical meaning linear p-(1 4)-D-glucan. In the cell wall, cellulose occurs in small, crystalline microfibrils that are arranged in multilayer structures (see Figure 5.1). An especially important layer is the primary wall (see Figure 5.2) although it is a small fraction of the mature, fully developed fiber. 

Fibers, due to their high aspect ratio, are the most efficient method of improving tear strength (Figure 8.24). Even such weak fibers as cellulose fibers can increase tear strength by a factor of 6. Fibers form large obstacles in the path of crack growth. Fibers with better adhesion to matrix are more efficient. 

Figure 11-12 presents typical experimental curves of solvent content vs distance from the spinning jet [43-45]. These curves are for polymethyl methacrylate spun from a benzene solution. Similar curves [49] have been found for such industrially important fibers as cellulose triacetate. 

TABLE 10.3 Bands Normally Associated with "Fiber" as Cellulosics ... 

The predominant cellulose ester fiber is cellulose acetate, a partially acetylated cellulose, also called acetate or secondary acetate. It is widely used in textiles because of its attractive economics, bright color, styling versatiUty, and other favorable aesthetic properties. However, its largest commercial appHcation is as the fibrous material in cigarette filters, where its smoke removal properties and contribution to taste make it the standard for the cigarette industry. Cellulose triacetate fiber, also known as primary cellulose acetate, is an almost completely acetylated cellulose. Although it has fiber properties that are different, and in many ways better than cellulose acetate, it is of lower commercial significance primarily because of environmental considerations in fiber preparation. 

Fibers for commercial and domestic use are broadly classified as natural or synthetic. The natural fibers are vegetable, animal, or mineral ia origin. Vegetable fibers, as the name implies, are derived from plants. The principal chemical component ia plants is cellulose, and therefore they are also referred to as ceUulosic fibers. The fibers are usually bound by a natural phenoHc polymer, lignin, which also is frequentiy present ia the cell wall of the fiber thus vegetable fibers are also often referred to as lignocellulosic fibers, except for cotton which does not contain lignin. 

Polymers. Hydrocarbons from petroleum and natural gas serve as the raw material for virtually all polymeric materials commonly found in commerce, with the notable exception of rayon which is derived from cellulose extracted from wood pulp. Even with rayon, however, the cellulose is treated with acetic acid (qv), much of which is manufactured from ethylene (see Fibers, regenerated cellulosics). 

A review covers the preparation and properties of both MABS and MBS polymers (75). Literature is available on the grafting of methacrylates onto a wide variety of other substrates (76,77). Typical examples include the grafting of methyl methacrylate onto mbbers by a variety of methods chemical (78,79), photochemical (80), radiation (80,81), and mastication (82). Methyl methacrylate has been grafted onto such substrates as cellulose (83), poly(vinyl alcohol) (84), polyester fibers (85), polyethylene (86), poly(styrene) (87), poly(vinyl chloride) (88), and other alkyl methacrylates (89). 

Typical papers processed using wash deinking are 100% old newspaper and sorted office paper from which toner ink-printed paper has been removed. The effluent from washers is heavily laden with ink, mineral coating and filler particles, and small cellulose fibers. As a result, it can be difficult to clarify. 

Sulfates of sodium are iadustriaUy important materials commonly sold ia three forms (Table 1). In the period from 1970 to 1981, > 1 million metric tons were consumed aimuaHy ia the United States. Siace then, demand has declined. In 1988 consumption dropped to 890,000 t, and ia 1994 to 610,000 t (1,2). Sodium sulfate is used principally (40%) ia the soap (qv) and detergent iadustries. Pulp and paper manufacturers consume 25%, textiles 19%, glass 5%, and miscellaneous iadustries consume 11% (3). About half of all sodium sulfate produced is a synthetic by-product of rayon, dichromate, phenol (qv), or potash (see Chromium compounds Fibers, regenerated cellulosics Potassium compounds). Sodium sulfate made as a by-product is referred to as synthetic. Sodium sulfate made from mirabilite, thenardite, or naturally occurring brine is called natural sodium sulfate. In 1994, about 300,000 t of sodium sulfate were produced as a by-product another 300,000 t were produced from natural sodium sulfate deposits (4). 

These fibrous minerals share several properties which qualify them as asbestiform fibers (/) they are found in large clusters which can be easily separated from the host matrix or cleaved into thinner fibers (1) (2) the fibers exhibit high tensile strengths (1) (J) they show high length diameter ratios, from a minimum of 20 up to >1000 (1) (4) they are sufficiendy dexible to be spun and (5) macroscopicaHy, they resemble organic fibers such as cellulose (2). 

Several cellulose esters (qv) are prepared commercially. Cellulose xanthate [9032-37-5] is made by reaction of cellulose swollen in 8.5—12% sodium hydroxide solution (alkaU cellulose [9081-58-7J) with carbon disulfide and is soluble in the alkaline solution in which it is made. When such a solution, termed viscose, is introduced into an acid bath, the cellulose xanthate decomposes to regenerate cellulose as rayon fibers or cellophane sheets (see Fibers, REGENERATED CELLULOSICS). 

From 1980 to 1988, aimual cellulose acetate flake production in the United States showed a slight decrease in production from 392,000 t to 323,000 t with an aimual decline of —0.4 to —0.1% (Table 6). World demand for cellulose acetate flake has also fallen. A modest recovery has occurred in recent years as a result of the increased demand for cigarette-filter tow world consumption of cigarette-filter tow has risen about 2.5% per year since 1980 (Tables 7 and 8). In contrast, world demand for textile fibers and cellulose ester plastics decline 4.6% and 4.2% per year, respectively (Fig. 9). 

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. 

An older method of cellulose fiber modification is mercerization [22,33-36], which has been widely used on cotton textiles. Mercerization is an alkali treatment of cellulose fibers. It depends on the type and concentration of the alkalic solution, its temperature, time of treatment, tension of the material, and the additives used [33,36]. At present there is a tendency to use mercerization for natural fibers as well. Optimal conditions of mercerization ensure the improvement of the tensile properties [33-35,37] and absorption characteristics [33-35], which are important in the composing process. 

Compression and injection molding are used with amino resins to produce articles such as radio cabinets, buttons, and cover plates. Because melamine resins have lower water absorption and better chemical and heat resistance than urea resins, they are used to produce dinnerware and laminates used to cover furniture. Almost ah molded objects use fillers such as cellulose, asbestos, glass, wood flour, glass fiber and paper. The 1997 U.S. production of amino resins was 2.6 billion pounds. 

Fibers can be added to a gelation solution [1212,1213]. Fibers that will not interfere with the gelation process and will provide adequate reinforcement must be chosen. In addition, they should not adversely affect the ability of the solution to be pumped and injected. In particular, glass fibers and cellulosic fibers meet the requirements as reinforcing fibers for plugging solutions. 

Glass Fibers and Cellulosic Fibers. Glass fibers and cellulosic fibers are specifically disclosed as preferable reinforcing fibers for a gelling solution... 

PH Hermans and D Heikens, Orientation in cellulose fibers as derived from measurements of dichroism of dyed fibers, Reel. Trav. Chim. Pays-Bas, 71 49-55, 1952. 

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