Plastics chemical composition

Polymer Composition. The piopeities of foamed plastics aie influenced both by the foam stmctuie and, to a gieatei extent, by the piopeities of the parent polymer. The polymer phase description must include the additives present in that phase as well. The condition or state of the polymer phase (orientation, crystallinity, previous thermal history), as well as its chemical composition, determines the properties of that phase. The polymer state and cell geometry are intimately related because they are determined by common forces exerted during the expansion and stabilization of the foam. 

Wax usually refers to a substance that is a plastic solid at ambient temperature and that, on being subjected to moderately elevated temperatures, becomes a low viscosity hquid. Because it is plastic, wax usually deforms under pressure without the appHcation of heat. The chemical composition of waxes is complex all of the products have relatively wide molecular weight profiles, with the functionaUty ranging from products that contain mainly normal alkanes to those that are mixtures of hydrocarbons and reactive functional species. 

Table I shows the chemical composition limits of various aluminum alloys presently used for packaging applications (3). In general, these alloys have good corrosion resistance with most foods. However, almost without exception, processed foods require inside enameled containers to maintain an acceptable shelf life (4, 5). Moreover, when flexible foil packages are used for thermally processed foods, the foil is laminated to plastic materials that protect it from direct contact with the food and also provide heat sealability as well as other physical characteristics (6,7).

Most polymers are very good electrical insulating materials because of their chemical composition, i.e., their electrical conductivity is exceptionally low. Because of this important property, many plastics are used to produce electrically nonconductive parts. However, the high surface resistance leads to an unwanted property the material is prone to electrostatic charge accumulation. To facilitate dissipation of the charge, antistatic agents are incorporated, which combine with atmospheric moisture on the plastic surface to form a conductive film. 

Fisher (1977) found that the bactericidal effects varied from brand to brand and Fisher McCabe (1978) related this to chemical composition. Only cements which give rise to high alkalinity (pH = 11) are effective. These are the cements which are readily decomposed by water, and this relates to the plasticizer used. Hydrophilic plasticizers are required if these cements are to be clinically effective. 

Details of the chemical composition and properties of the wide range of plastics used as engineering material can be found in the books by Butt and Wright (1980) and Evans (1974). 

Materials fundamentals atomic bonding, crystalline structure, imperfection, phase diagrams and kinetics. Materials metals, ceramics, plastics and composites Materials selection for the chemical process industries... 

The rate of burning of plastic igniter cord is primarily governed by the chemical composition of the pyrotechnic and the rate of heat transfer along the support wire. 

Chemicals and materials are vital components of today s technological world, which has slowly evolved from the use of stone axes and bearskins to the development of satellites, antibiotics, alloys, plastics, and composites. This development is impressive but required thousands of years. If the frontiers of chemistry can expand far enough to include material design, the coming progression of technology will be much more rapid. 

Only after the atomic weight units of composition were established, was it possible for chemists to arrange those units successfully in meaningful molecular arrays and conceive the ideas of valence and directional bonding. Molecular structure remains today the central theoretical focus of attention, whether in the realm of molecular biology, biochemistry, chemical pharmaceutics, or polymer plastics. Daltons atomic theory must be seen as the climax of the history of chemical composition and terminates this story. ... 

One of the most desirable aspects of plastics and composites is the ability to make net-shaped parts. The same process that creates the material also creates the structure. The penalty for this advantage is that the process of curing a thermosetting plastic or composite part is irreversible. Any part that is not properly processed represents a loss of part, material and the money and time required to make that part, although larger parts are usually repaired if possible. Proper shape becomes a controlled property in addition to the bulk material properties, such as mechanical (stiffness or strength), physical (density, void content, etc.), chemical (degree of cure or carbonization, chemical resistance), electrical (resistivity, conductivity), or any combination of these. 

There are three types of gemstone materials as defined by the U.S. Federal Trade Commission (1) (/) natural gemstones are found in nature and at most are enhanced (see Gemstones, gemstone treatment) (2) imitation or simulated, fake, faux, etc, material resembles the natural material in appearance only and is frequendy only colored glass or even plastic and (3) synthetic material is the exact duplicate of the natural material, having the same chemical composition, optical properties, etc, as the natural, but made in the laboratory (2,3). Moreover, the word gem cannot be used for synthetic gemstone material. The synthetic equivalent of a natural material may, however, be used as an imitation of another, eg, synthetic cubic zirconia is widely used as a diamond imitation. 

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