Kapok cellulose

Timel T (1957) Some properties of native hemp, jute, and kapok celluloses. Text Res J 27 (ll) 854-859... 

Fibers (see Fibers, survey) used in textile production can have a wide variety of origins plants, ie, ceUulosic fibers (see Fibers, cellulose esters) animals, ie, protein fibers (see Wool) and, in the twentieth century, synthetic polymers. Depending on the part of the plant, the ceUulosic fibers can be classified as seed fibers, eg, cotton (qv), kapok bast fibers, eg, linen from flax, hemp, jute and leaf fibers, eg, agave. Protein fibers include wool and hair fibers from a large variety of mammals, eg, sheep, goats, camels, rabbits, etc, and the cocoon material of insect larvae (sUk). Real sUk is derived from the cocoon of the silkworm, Bombjx mori and for a long time was only produced in China, from which it was traded widely as a highly valuable material. 

The cellulose molecules are highly oriented in the secondary cell walls. Fibers can be relatively easily obtained from the secondary cell walls of cellulose-rich plants, and mankind has done this from antiquity. Especially cotton, flax, hemp, ramie, jute, esparto grass, and kapok have been used as fiber-yielding plants. 

Kapok is a cocoon silk found in Java and consists of 65% cellulose, 15% lignin, 12% water, pentoses, proteins, and wax. It is used to fill cushions and mattresses and for thermal and acoustic insulation. 

Except cotton and kapok, most of the natural cellulosic fibers are multicellular. They are usually used as groups of individual cells or as bundles of fiber in industrial applications. As a term, a fiber , or a technical fiber [14], refers to a bundle of individual cells bound together by hemicellulose, lignin and other non-cellulosic materials [12]. However, the individual fiber cell is drastically stronger than the fiber bundle [56]. For example, the individual fiber of flax is as stiff as aramid [65]. The individual fiber cell has a lumen inside which imparts a hollow structure to the fiber as seen in Figure 11.7. As an example, okra fibers have a void content of 18-32% [15]. The interface between two cells is called middle lamella [14]. 

Figure 7.28 Melting DSC curve.s for water trapped in various kinds of cellulose [291. Water content (grams of water/gram of sample) = 1.0 g g 1, Kapok 2, linen 3, wood cellulose 4, jute 5, rayon 6, polynosic 7, cotton...

Cellulose content in some natural products % cotton - 94, hemp - 77, flax, kapok, sisal - 75, wood - 40-50, straw - 40-50 ... 

There are only two important classes of natural fibers the carbohydrate fibers and the protein fibers. The carbohydrate fibers are primarily cellulosic fibers from plants, such as cotton, jute, flax, ramie, kapok, sisal, and coconut. The protein fibers are primarily animal furs, generically called wool or hair, and the insect-based secretions called silk, whether from a silkworm or a spider. Raman spectroscopy of these materials has recently been obtained and is described in Sections II.B and II.C. 

Cellulose sel-yo- l6s n [F, fr. Ce//w/e living cell. Fr. NL cellula] (1848) (C6Hio05)n. (1) A polysaccharide (C6Hio05)x of glucose units that constitutes he chief part of the cell walls of plants, occurs naturally in such fibrous products as cotton and kapok, and is the raw... 

In addition to cotton fibers, they are mar r other types of natural cellulose fibers. One major difference between cotton and other natural cellulose fibers is the cellulose content. Cotton fibers are the purest and other natural cellulose fibers have significantly lower content of cellulose. For example, both cotton and kapok are seed fibers, but cotton has the highest cellulose content and kapok has the lowest (13 wt%). The cellulose contents of other natural cellulose fibers are in the range of 40%-90%. Table 4.2 shows the cellulose contents of several natural cellulose fibers. 

Another major difference among different natural cellulose fibers is their morphology. Kapok fibers are obtained from the seed pods of the tropical kapok tree. Like cotton, kapok fibers are unicellular fibers. However, kapok fibers do not collapse and twist after dried (Figure 5.6). Dried kapok fibers have circitlar, hollow (lumen) cross-sectional stmcture with total wall thicknesses of aroimd 2 /rm and fiber diameters ranging from 15 to 35 //m. As a result, kapok fibers have lower densities (0.31-0.38 g/cm ) than most other natural cellulose fibers. 

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