THE STRUCTURE AND BASIC PROPERTIES OF PLASTICS

There are some fairly broad basic guidelines that can be followed when designing a product to be made from plastics. This chapter analyzes the major groupings of plastic materials in terms of their characteristics [201-253] Chapters 3-5 then present a review of basic structural design considerations. Information about and data on plastic materials are given in Chapter 6. 

Elastomers are flexible. Plastics can provide flexible to rigid foams. Reinforced plastics or composites are plastics (polymers or resins) with reinforcing additives, such as fibers and whiskers, added, basically, to increase the product s mechanical properties. Throughout this book these terms are used precisely according to their respective areas of interest. 

The term plastics is not a definitive one. Metals, for instance, are also permanently deformable and are therefore plastic. How else could roll aluminum be made into foil for kitchen use, or tungsten wire be drawn into a filament for an incandescent light bulb, or a 90 t (100 ton) ingot of steel be forged into a rotor for a generator Likewise the different glasses, which contain compounds of metals and nonmetals, can be permanently shaped at high temperatures. These cousins to polymers and plastics are not considered plastics within the context of this book. 

The term plastics became attached to polymeric materials because these materials are basically capable of being molded or formed, as are clay or plaster. Potters use wet clay to create their art, although these objects are not called plastics. Despite this seeming 

Allyl diglycol carbonate (CR-39) Polymethylmethacrylate (acrylic) (PMMA) 

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