THE CHEMISTRY OF POLIMERS AND PLASTIC

THE CHEMISTRY OF POLIMERS AND PLASTIC - THE CHEMISTRY OF...

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Unformatted text preview: THE CHEMISTRY OF POLYMERS AND PLASTICS BAADJIES M.F 15470318 ORGANIC CHEMISTRY 214 Table of Contents 1. What is a polymer? Polymers are chemical substances composed of polymer molecules, which in turn, consist out of many atoms (Greek: poly = many). Polymer molecules usually have a thousand or more atoms, therefore they have molar masses [Weinheim, 1985].Such an example is the ethylene units in polyethylene R(CH CH ) n R. Another term that could be used to describe a polymer molecule is a macromolecule [Weinheim, 1985]. [Weinheim, 1985] Macromolecules constitute the simplest individual chemical constituents of a polymer. Examples of macromolecules that exist in nature are acids, proteins, polysaccharides, polprenes and lignins. Semi synthetic polymers such as cellulose acetates formed from cellulose, is an act of chemical transformation of natural polymers. Most polymers are, however, synthesized chemically from molecules with low molar masses, the so- called monomers. Examples are the preparations of polyethylene from ethylene and poly (vinyl chloride) from vinyl chloride [Weinheim, 1985]. 1.1 Nomenclature These are some of the few nomenclature systems used for the naming of polymers: Long-known Natural polymers often have trivial names. Examples are cellulose, the polymeric sugar(-ose) of the plant cell; casein, the most important protein of milk and cheese ( Lactin: caseus= cheese); nucleic acids, the acids found in the cell nucleus; catalase, a catalyzing enzyme. Synthetic Polymers are often named after their monomers. Polymers of ethylene thus lead to polyethylene, those of styrene to polystyrene, those of vinyl chloride to poly(vinyl chloride), and those of a lactam to a polylactam. [Weinheim, 1985]. In polymers there are repeating characteristic groups that form chains and they are named according to the chain. Polyamides are thus polymers with amide groups NHCO- in their repeating units; example ~ [NHCO(CH ) 5 ] n~ = polyamide 6= nylon 6 = poly( - caprolactam). Other examples are polyesters with esters groups -COO- or polyurethanes with urethane groups -NH-CO-O- in the chains. IUPAC recommends the use of constitutive names, similar to those used in inorganic chemistry. The nomenclature of low and high molar mass inorganic molecules follows the additivity principle. 1.2 Polymer Composites The term composite has various meanings. In general, it denotes a complex material in which two or more distinct substances combine to produce some properties not present in any individual component. Polymer composites are defined as composites in which at least one component is of a polymeric nature. In accordance with the general definition of a composite and in contrast to the engineering use of the word, the term polymer composite is often used to cover not only heterogeneous mixtures of a polymer and another material....
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This note was uploaded on 05/02/2010 for the course CHEMISTRY 214 taught by Professor Arrnot during the Summer '09 term at Stellenbosch University-South Africa.

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THE CHEMISTRY OF POLIMERS AND PLASTIC - THE CHEMISTRY OF...

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