Chemistry naturally occurring polymers

The earliest applications of polymer chemistry involved chemical modification designed to improve the physical properties of naturally occurring polymers. In 1839, Charles Goodyear transformed natural rubber, which is brittle when cold and tacky when warm, to a substance that maintains its elasticity over a wider temperature range by heating it with sulfur (vulcanization). The first synthetic fibers— called rayons—were made by chemical modification of cellulose near the end of the nineteenth century. 

All synthetic polymers and most naturally occurring polymers are mixtures of individual polymer molecules of variable molecular weights. When defining molecular weights in polymer chemistry, the two most common definitions are the number... 

The earliest applications of polymer chemistry involved chemical modification designed to improve the physical properties of naturally occurring polymers. In 1839, Charles Goodyear... 

A brief, concise review of organic chemistry from the polymer standpoint is available. The most important constituents of living organisms, cellulose and proteins, are naturally occurring polymers, but we will confine our attention largely to synthetic polymers or to important modifications of natural polymers. 

Rubber—an unusual name for an unusual substance—is a naturally occurring aikene polymer produced by more than 400 different plants. The major source is the so-called rubber tree, Hevea brasiliensis, from which the crude material is harvested as it drips from a slice made through the bark. The name rubber was coined by Joseph Priestley, the discoverer of oxygen and early researcher of rubber chemistry, for the simple reason that one of rubber s early uses was to tub out pencil marks on paper. 

Maleic anhydride CAS. 108-3I-6. til, maleic acid [CAS 110-16-7]. (2), and I umarie acid [CAS 110-17-81. i3) are multifunctional chemical intermediates that lind applications in nearly every Held id industrial chemistry. Each molecule contains two acid carbonyl groups and a double bond in the u. position. Maleic anhydride and maleic acid are important raw materials used in the manufacture of phthalic-type alkyd and polyester resins, surface coatings, lubricant additives, plasticizers. copolymers, and agricultural chemicals [see Alkyd Resins Polymers, and Lubricant). Both chemicals derive their common names from naturally occurring malic acid. 

Nevertheless, in the field of physical chemistry of foamed polymers the transition from quantity to quality has not yet occurred practically no generalizations, even of semi-empirical nature, are available which relate the kinetics of moisture and water absorption to the main morphological parameters of polymeric foams (specific gravity, portion of open ceUs, etc.) Very little is known about molecular mechanisms of vapor and moisture transfer taking into account the chemical and physical structure of foams. 

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