Fibers, semisynthetic

As discussed, the cultivation of C. sativa with high content of A9-THC (drug-type) is not allowed in many coimtries. Because of this, there is no opportunity to harvest a high amoimt of the medicinally important substance A9-THC directly from plant material. In the synthesis route for semisynthetic A9-THC, natural CBD from fiber hemp plants is employed. It can be extracted with non-polar solvents such as petroleum ether and purified by recrystalUza-fion in n-pentane. This procedure avoids the formation of abnormal CBD and gives the opportunity to produce A9-THC from fiber hemp. Semisyn-fhetic A9-THC is disfinguishable from the synthetic compound because it contains, besides the major product, small amounts of A9-THC-C3 and A9-THC-C4, which are not available in the synthetic product. 

P.R.170 is not always heat stable enough to allow application in polyolefins. In HDPE systems formulated at 1/3 SD, the pigment tolerates exposure to 220 to 240°C for one minute. Its tinctorial strength, on the other hand, is excellent. P.R.170 is also occasionally used in polypropylene and polyacrylonitrile spin dyeing in the latter medium, it satisfies the specifications of the clothing and home textiles industries. Besides, P.R.170 lends color to viscose rayon and viscose cellulose it is used for the mass coloration of semisynthetic fibers made of cellulose last but not least, it colors yarns, fibers, and films made of secondary acetate. 

These fibers are also called semisynthetic since the natural cellulose is modified in some way chemically. 

Rayon. A semisynthetic fiber existing in two coml forms. The first form is comprised of regenerated cellulose as well as mfd fibers consisting of regenerated cellulose in which sub-... 

Bulk-Forming Laxatives. These agents absorb water and swell within the lower GI tract. The increased size of the water-laden laxative stretches the bowel, thus stimulating intestinal movement (peristalsis). Bulk laxatives commonly contain natural and semisynthetic dietary fiber such as bran, psyllium, and methylcellulose. 

Almost every aspect of human life involves carbohydrates in one form or another. Like other animals, we use the energy content of carbohydrates in our food to produce and store energy in our cells. Clothing is made from cotton and linen, two forms of cellulose. Other fabrics are made by manipulating cellulose to convert it to the semisynthetic fibers rayon and cellulose acetate. In the form of wood, we use cellulose to construct our houses and as a fuel to heat them. Even this page is made from cellulose fibers. 

In reference to cloth or fiber, the term acetate usually means cellulose acetate, a semisynthetic polymer made by treating cellulose with acetic anhydride. Cellulose acetate is spun into yarn by dissolving it in acetone or methylene chloride and forcing the solution through spinnerets into warm air, where the solvent evaporates. 

Non-woven fabrics include a wide range of products manufactured from synthetic and semisynthetic fibers. 

Rayon is a semisynthetic fiber because it is prepared from a natural polymeric starting material. The first truly synthetic polymeric fiber was nylon, developed in the 1930s by the American chemist Wallace Carothers at DuPont Company. He knew of the condensation of an amine with a carboxylic acid to form an amide linkage (see Section 7.6) and noted that, if each molecule had two amine or carboxylic acid functional groups, long-chain polymers could form. The specific starting materials upon which Carothers settled, after numerous attempts, were adipic acid and hexamethylenediamine ... 

Semisynthetic and synthetic fibers introduced from the 1920s made new demands on the ingenuity of dye-makers. The commercial value of new polymers relied entirely on the ease of coloration. Normal dyeing is accomplished in aqueous solution, often in the presence of a fixing agent, or mordant. This is ideal for cotton, silk and wool, but not for synthetic fibers such as nylon and polyester, that are plastic in nature. They require... 

Chemical or synthetic fibers are further classified into regenerated and synthetic fibers. Regenerated or semisynthetic fibers are produced from natural products by a chemical procedure or modification. These fibers can, for example, be rayon, acetate silk, and alginate fibers. In contrast, synthetic fibers are completely synthesized from other raw materials, and may, for example, consist of polyesters, polyamides, poly(acrylonitrile), polyolefins, or glass. 

Polymers can be classified in different ways. From the forensic perspective, a reasonable starting point is to divide pol)Tmers into biologically derived polymers (biopol3rmeis) and synthetic organic polymers. Biopolymers are extracted from natural sources such as plants or animals. Even though proteins and DNA are biopolymers of unquestioned importance in forensic science, their analysis resides in the context of forensic biology. The biopolymer we will concentrate on is cellulose, the base material in paper and cotton fibers. Historically and chemically, semisynthetic polymers fall between naturally derived and synthetic polymers. Rayon and cellophane are made from regenerated... 

The first manufactured fibers were regenerated forms of cellulose classified as semisynthetics. Cotton is a versatile fiber, but because the fibers are short, cotton yarns and fabrics consist of these shorter fibers spun together rather than single contiguous fibers as a result, cotton is not a strong fiber. 

A modified polymer, also called a semisynthetic polymer, is a natural polymer compound treated by a chemical reaction. The world s first man-made polymer material—cellulose nitrate—was made from natural cellulose, such as cotton or cotton cloth, that was treated with concentrated nitric acid and concentrated sulfuric acid. A synthetic polymer is a polymer compound synthesized by small molecular weight compounds through chemical methods. Examples of synthetic polymer materials are plastics such as polyethylene, polypropylene, and polyvinyl chloride and fibers such as polyester, nylon, and other synthetic fibers. 

ELEMENTAL DIETS (SEMISYNTHETIC FIBER FREE LIQUID DIETS) ... 

These dietary preparations are free of fiber and other undigestible substances, but contain most of the essential nutrients in forms that require little or no digestion and which may be absorbed completely. Hence, little or no residue from the diet reaches the large intestine. The term elemental means that the nutrients are present in their most elemental or simple chemical forms, although the diets sometimes contain complex forms of certain nutrients. Similarly, the term semisynthetic means that the products contain mainly pure chemical compounds rather than the more complex natural food materials. It is noteworthy that the recent development of elemental diets has made it possible to provide much more nutritious diets for people who... 

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