Shaping, of plastics

Shapes of plastic articles include sheets, blocks, hollow rectangles, webs, hollow cylinders and ovoids, complex three-dimensional shapes, rods, tubes, and woven threads. The plastics may be rigid or flexible, in the form of a woven thread, expanded sheet, a structural sandwich , a multiple dispersion of components, or a coating deposited from solution. 

SITC 58, Plastics in Non-Primary Form tubes, pipes, hoses, plates, sheets, film, foil, strips, and other shapes of plastic... 

Piston extruders were, and still are, employed not only for the extrusion of ceramic bodies but also find application in many branches of industry for the shaping of plastic materials, or for bodies which have been plasticized by the tempering process. 

As already stated, the shaping of plastics materials is achieved by the application of heat, pressure or both. There are many ways in which this can be done, depending on the nature of the polymer, the type and size of product and the quantity and dimensional accuracy required. The methods to be described here are moulding by compression, transfer, injection and low-pressure processes. 

The various processes reviewed in this book are used to fabricate all types and shapes of plastic products, ranging from household convenience packages to electronic devices and many others—including the strongest products in the world, used in space vehicles, aircraft, building structures, and so on. Proper process selection depends upon the nature and requirements of the plastic, the properties desired in the final product, the cost of the process, its speed, and product volume. (Note that a plastic also may be called a polymer or a resin.) Some materials can be used with many kinds of processes others require a specific or specialized machine. Numerous fabrication process variables play an important role and can markedly influence a product s aesthetics, performance, and cost. 

Some novel statistical theories of solutions of polymers may also use the parameter. But they also use other interaction parameters discussed below. A number of interaction parameters can be used to account for the Flory-Huggins parameter s dependence on concentratiorr, size and shape of plasticizer molecules, isothermic compressibility and ejqransion of materials, etc." However experimental difficulties in estimating these parameters hmit the application of these theories. The Flory-Huggins parameter is the simplest nttmerical criterion of compatibility. Methods of estimating the Flory-Huggins parameters are similar to the methods of testing for compatibility. The experimental methods are presented in Section 6.3. 

The term usually applied to a process in which the shape of plastic pieces such as sheets, rods, or tubes is changed to a desired form. Usually the term does not include extrusion, molding, or casting, in which forms are made from molten polymers or solutions. 

A wide range of shapes of plastics are allowing an enormous freedom in design and performance of agricultural containers and packaging. This applies to containers for... 

The various characteristic burning temperatures of bitumite coal are shown in the DTA curve. The shoulder peak (from to T ) is the characteristic shape of plastic bitumite coal. 

---