In wood and cotton

Figure 5. Rate of heat evolution in wood and cotton. Experiments 70 C included heat of pyrolysis 80 C the material was moist, 130"C it was ovendry between 80" and 130 C, moisture contents are mentioned in %, unless the material was ovendry. 1 — Bowes (28) wood raspings heat values extrapolated from measurements at 190-335 C. 2 — Eriksson and...

Polymers are divided into two classes natural and synthetic. Important biological molecules such as proteins, nucleic acids, and polysaccharides (starches and the cellulose in wood and cotton) are natural polymers. Natural rubber and natural fibers such as silk and wool are also natural polymers. Familiar examples of synthetic polymers include plastics such as polyethylene. Teflon, and Lucite (Plexiglas) and synthetic fibers such as nylon, Orion, and Dacron. In this section we will describe some processes by which polymers are formed from organic compounds. 

While polymers with moderately high performance qualities, such as cellulose in wood and cotton have been known for years, these linear polymers could not be extruded or injection molded. However, they were able to withstand the effects of moderately hostile environments. The classic reinforced thermosets could be compression molded and could also be classified as high performance plastics. In contrast, the general purpose thermoplastics, introduced in the 1930 s, were readily extruded and Injection molded but were not useful at boiling water temperatures. 

Capillary Structure of Cellulose Fibers. The capillary voids in wood and cotton fibers fall into two main categories (1) gross capillaries... 

Brown The determinations of size of the cell-wall capillaries and the cellulases of fungi indicate that the enzymes that have been isolated to date are so large that they probably can penetrate only a few cell-wall capillaries in wood and cotton. This conclusion is supported by Cowling s DP data for the action of the white-rot fungus, Polyporus versicolor, on wood (Figure 13). But it is also contradicted by the same type of data for the effect of both the brown-rot fungus, Poria monticola, on wood (Figure 13) and of Myrothecium verrucaria on mercerized cotton as shown by Selby (60). Thus we believe that the catalysts responsible for the initial depolymerization of cellulose in wood and cotton by these two... 

Natural polymers unlike the S5mthetic ones do possess very complex structure. Natural polymers such as cellulose, wool, and natural rubber are used in many products in large proportions. Cellulose derivatives are one of the most versatile groups of regenerated materials with various fields of application. Cellulose is found in nature in all forms of plant life, particularly in wood and cotton. The purest form of cellulose is obtained from the seed hairs of the cotton plant that contains up to 95% cellulose. The first cellulose derivatives came to the stage around 1845 when the nitration of starch and paper led to discovery of cellulose nitrate. In 1865, for the first time, a moldable thermoplastic made of cellulose nitrate and castor oil. 

In order to fireproof wood and cotton products and to thermally convert biomass into chemicals, researchers must understand cellulose pyrolysis. Extensive research has been conducted in this area and several reviews are available (1-7). 

Among the dopes used may be cited the following combustibles colophony (used by Nobel in his Dynamites of 1869 1873) (Vol 3 of Encycl, p C403R) wood-meal, woodpulp and sawdust in Grisounite and in some Amer Dynamites cork,charcoal (in "Carbodynamite , described in Ref 60, p C52-L) naphthalene (in Rheinischdynamit) and cotton or other forms of cellulose (in "Forcites ). Less frequently have been used peat moss, ivoty nut meal, unbaked com flakes, starch, pulverised peanut hull, pulverized cottonseed hulls and sunflower seed shells... 

Cellulose, a fibrous, tough, water-insoluble substance, is found in the cell walls of plants, particularly in stalks, stems, trunks, and all the woody portions of the plant body. Cellulose constitutes much of the mass of wood, and cotton is almost pure cellulose. Like amylose and the main chains of amylopectin and glycogen, the cellulose molecule is a linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units. But there is a very important difference in cellulose the glucose residues have the /3 configuration (Fig. 7-16),... 

Results with newsprint are roughly intermediate between those for wood and cotton linters. Hydrolysis of the delignified chemical pulp component (about 20% of the total newsprint furnish) and of the accessible carbohydrates of the groundwood component is accomplished with about 4 days of digestion. Further hydrolysis of the groundwood carbohydrate is then stymied by lignin as in the case of red oak and Douglas fir. 

Polymeric materials are today part and parcel of our everyday life. They are used in nearly every branch of industry and are responsible for rapid progress made in many of them. In view of the fact that raw materials and traditional energy resources will be soon depleted, the production of synthetic polymeric materials becomes particularly important as a way to the rational utilization of both. Today, synthetic polymeric materials are used not only as highly effective substituents for expensive and/or not readily available materials such as steel and nonferrous metals, wood and cotton, natural rubber, etc., but also as quite original materials possessing a unique set of valuable properties. 

In this lesson, students begin to examine the unknowns chemical properties. A chemical property of a substance is its ability to transform into new materials. We can observe chemical properties when substances react with one another. For example, when iron is exposed to moist air, a new substance (rust) may form. So, the ability to rust is a chemical property of iron. The ability to burn is a chemical property of wood and cotton. 

Discussion Cellulose is produced in the growth of plants and is the chief constituent of wood and cotton. The purified material is used in making paper and cotton and linen cloth. Silk and wool are animal products, containing nitrogen, which are called proteins wool also contains sulphur. The behavior of cellulose with acids and alkalies is quite different from that of proteins as a consequence it is possible to distinguish by chemical means cotton from silk and wool. The presence of sulphur in wool serves to distinguish it from silk, which does not contain this element. 

Both cotton and wood fibers have a thin primary wall that consists of a loose, random fibrillar network and surrounds the relatively thick secondary wall. The primary wall and adjacent intercellular substance between contiguous cells in wood is referred to as the compound middle lamella. In both wood and cotton the secondary wall usually consists of three layers designated SI, S2, and S3. The SI and S3 layers usually are... 

Penetration of Capillaries in Natural Fibers. The maximum dimensions of cellulolytic enzyme molecules listed in Table V are all smaller than the gross capillaries of both wood and cotton fibers. Thus,... 

Cellulose is found in the cell wall of plant cells and helps to give plants their structure. It is found in large amounts in trees and cotton fibres (which are nearly pure cellulose). Cellulose has many uses, including the making of paper. Cellulose molecules have many O-H bonds and the strength of wood is due, in part, to hydrogen bonding between nearby molecules. 

Emamectin benzoate controls all agronomically important Lepidoptera in vegetables and cotton. Typical application rates for these uses are in the range 8.4-16.8 g-a.i. ha . Some additional uses are the control of some pests in tea and of pine wood nematode in pine trees in Japan. 

Natural polymers often owe their important properties to the fact that they are highly oriented, e.g. cellulose, in the form of wood and cotton, and silk fibre, which is a protein. 

Although this author claims no special expertise in the toxicology of materials, it seems fair to say that the weight of opinion at present is reassuring about fibres in existing use. Glass, aramid and polyethylene fibres are all much safer than asbestos. In common with traditional materials such as wood and cotton, they must always be handled with care, especially if they are finely divided and therefore in respirable forms, i.e. small (<3 pm) diameter short fibres or fine dust. 

The best-known renewable primary sources for natural fibers are wood and cotton. Both of these natural materials consist of basic fibrous units known as fibrils, the diameter of which is probably equivalent to that of the cellulose crystallites. Crystalline and amorphous regions alternate along the length of the fibrils. Several elementary fibrils may also be united in fibrillary structural units [84]. 

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