Chapter 2: Background
In the previous chapter, it has already been pointed out that the factors influencing the quality of the final molded product include polymer materials, product design, mold design, process conditions, and process control of the machine. This chapter reviews the basic background of these factors, providing essential fundamentals for computer modeling in the later chapters of this book.
2.1 Molding Materials
There is a general accepted definition for plastics that goes like this: any one of a large and varied group of macromolecular materials consisting wholly or in part of combinations of carbon with oxygen, hydrogen, nitrogen, and other organic and inorganic elements that, while solid in the finished state, at some stage in its manufacture is made liquid, and thus capable of being formed into various shapes, most usually (although not necessarily) through the application, either singly or together, of heat and pressure.1 The great economic significance of plastics is intimately tied to their properties, such as low density, wide range of mechanical properties, easy to process, low thermal/electronic conductivity, high chemical resistance, and reusability.
A fundamental feature of plastics is their variety. There are over 17,000 plastic materials available worldwide. Within the most common plastic families, ...