Handbook of Plastics, Elastomers, and Composites
Date: 28 April 2011, 05:35
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Plastics are an important part of everyday life; products made from plastics range from sophisticated articles, such as prosthetic hip and knee joints, to disposable food utensils. One of the reasons for the great popularity of plastics in a wide variety of industrial applications is the tremendous range of properties exhibited by plastics and their ease of processing. Plastic properties can be tailored to meet specific needs by varying the atomic composition of the repeat structure; and by varying molecular weight and molecular weight distribution. The flexibility can also be varied through the presence of side chain branching and according to the lengths and polarities of the side chains. The degree of crystallinity can be controlled through the amount of orientation imparted to the plastic during processing, through copolymerization, by blending with other plastics, and via the incorporation of an enormous range of additives (fillers, fibers, plasticizers, stabilizers). Given all of the avenues available to pursue in tailoring any given polymer, it is not surprising that the variety of choices available to us today exists. Polymeric materials have been used since early times, even though their exact nature was unknown. In the 1400s, Christopher Columbus found natives of Haiti playing with balls made from material obtained from a tree. This was natural rubber, which became an important product after Charles Goodyear discovered that the addition of sulfur dramatically improved the properties; however, the use of polymeric materials was still limited to natural-based materials. The first true synthetic polymers were prepared in the early 1900s using phenol and formaldehyde to form resins—Baekeland’s Bakelite. Even with the development of synthetic polymers, scientists were still unaware of the true nature of the materials they had prepared. For many years, scientists believed they were colloids—a substance that is an aggregate of molecules. It was not until the 1920s that Herman
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