Introduction
Many plastics by themselves have a limited range of useful properties. By incorporating additives and modifiers into the polymers, the properties of the formulated plastic can be tailored to process better and designed to provide a wide range of performance characteristics [1]. For example, rigid polyvinyl chloride (PVC) can be made flexible with the addition of plasticizers; the strength, stiffness, and heat distortion temperature of nylon 6 can be increased with the addition of glass fiber; polyethylene can be made conductive by adding conductive carbon; polypropylene can be made radiation stable by adding free radical scavengers; polycarbonate can be molded in a wide range of colors and effects with pigments; polyesters can be made flame retardant; and brittle polystyrene can be toughened with the addition of impact modifiers. Additives are used to enhance processability; improve toughness, strength, and dimensional stability; improve radiation, light, and thermal stability; provide color and improve aesthetics; improve flame retardance; make plastics conductive, biocompatible, and wear and scratch resistant; and improve long-term aging. This is only a small list of the versatility and benefits of using plastics and additives to design complex parts with tailored properties.