Tuesday, March 6, 2012

About Polymers


Industrial polymers are synthesized from simple compounds together in long chains. For a class of natural or synthetic substances composed of very large molecules called macromolecules that are multiples of simpler chemical units called monomers. The polymers are many materials in living organisms, including for example proteins, cellulose, and nucleic acids. They also form the basis of minerals such as diamond, quartz and feldspar and such synthetic materials such as concrete, glass, paper, plastic and rubber.

The polymer refers to any number of monomer units. When the number of monomers is very large, the compound is sometimes called a high polymer. Polymers are not limited to the monomers of the same chemical composition or molecular weight and structure. Some natural polymers consist of a single type of monomer. Most natural and synthetic polymers, however, consist of two or more types of monomers. These polymers are known as copolymers.

Organic polymers play a crucial role in living organisms, providing the material and structural basis by participating in processes essential for life. For example, the solid parts of all plants are made of polymers. These include cellulose, lignin and resins different. Cellulose is a polysaccharide, a polymer consisting of sugar molecules. Lignin is a complex of three-dimensional polymer network. Wood resins are polymers of hydrocarbons, simple isoprene. Another isoprene rubber polymer is familiar.

Other important natural polymers are proteins, which are polymers of amino acids and nucleic acids, which are polymers of nucleotides, complex molecules composed of nitrogenous bases, sugar and phosphoric acid. Nucleic acids carry genetic information in the cell. Starch, an important source of food energy plant, natural polymers are composed of glucose.

Many inorganic polymers are also found in nature, including diamond and graphite. Both are composed of carbon. In diamond, carbon atoms are joined in a three dimensional network that gives the hardness of the material. In graphite, used as a lubricant and in pencil "leads", the carbon atoms in the binding of planes that can slide over the other.

Synthetic polymers are produced in a variety of reactions. Many simple hydrocarbons such as ethylene and propylene can be converted into polymers with the addition of a monomer after the growing chain. Polyethylene, which is consist of repeating ethylene monomers, in addition to the polymer. It can be up to 10,000 monomers joined the long, spiral chains. Polyethylene is a crystalline, transparent, and the thermoplastic material, which softens with heat. It 'used for coatings, packaging, molded parts, and the manufacture of bottles and containers. Polypropylene is also crystalline thermoplastics, but is harder than polyethylene. The molecules can be obtained from 50000 200000 monomers. This compound was used in the textile sector and to make the items printed.

In addition to other polymers are polybutadiene, polyisoprene, and polychloroprene, which are all important in the production of synthetic rubber. Some polymers such as polystyrene, are glassy and transparent at room temperature, as well as a thermoplastic material. Polystyrene can be colored any shade, and is used in the manufacture of plastic toys and other objects.

If an atom of hydrogen in ethylene is replaced by the atom of chlorine, vinyl chloride is produced. This polymerizes to polyvinyl chloride (PVC), a colorless, hard, hard, thermoplastic, which can be realized in various forms, such as foams, films and fibers. Produced by the reaction of ethylene vinyl acetate and acetic acid, polymerization is an amorphous, soft resins used in coatings and adhesives, and copolymerizes of vinyl chloride for the production of a large family of thermoplastic materials.

Many important polymers have oxygen atoms or nitrogen, as well as carbon in the main chain. Among these macromolecular materials with oxygen atoms are polyacetals. The easiest way is polyformaldehyde polyacetal. It has a high melting point and is crystalline and resistant to wear and the effect of solvents. Acetal resin is more like any other metal and plastic used in the manufacture of machine parts such as gears and bearings.

A linear polymer is characterized by a repetition of the ester groups in the main chain is called a polyester. Open-chain polyesters are colorless, crystalline materials, thermoplastics. People with high molecular weight (10,000 to 15,000 molecules) are used in the manufacture of films, moldings, and fibers such as Dacron.

Polyamides are of natural origin and milk casein Zein, found in corn (maize), including plastics, fibers, adhesives and coatings are made. Among the synthetic polyamide resins are urea-formaldehyde, which are thermostable. Used to produce moldings and as adhesives and coatings for textiles and paper. Equally important are the known polyamide resins such as nylon. They are resistant to strong, heat and abrasion resistant, fireproof and nontoxic and can be colored. Its best use is known as a textile fiber, but they have many other applications.

Another important family of synthetic organic polymers consists of linear tests urethane group. Polyurethanes are used in the manufacture of elastomeric fibers known as the base layer and spandex production and flexible and rigid foams.

Another class of polymers, organic-inorganic mixed. The most important representatives of this family of polymers are silicones. Its backbone consists of alternating silicon and oxygen atoms with organic groups attached to each of the silicon atoms. Low molecular weight silicones are oils and fats. High molecular weight species are versatile materials that are soft rubber and elastic at low temperatures. They are also relatively stable at high temperatures.

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