Engineering plastics, additives Fillers

In addition to the broad categories of TPs and TSs, TPs can be further classified in terms of their structure, as either crystalline, amorphous, or liquid crystalline. Other classes (terms) include elastomers, copolymers, compounds, commodity resins, engineering plastics, or neat plastics. Additives, fillers, and reinforcements are other classifications that relate directly to plastics properties and performance. 

In the past engineering TPs have replaced metal in numerous products in many industries by providing improvements in thermal properties.146 The ability to prepare and compound material properties through the choice of plastics with additives, fillers and reinforcements, has allowed the development of the flexibility inherent in TPs to meet the performance requirements required in these different applications. 

The most popular materials are styrenics and olefins, and engineering plastics such as modified polyphenylene ether or polycarbonate (Chapter 2). Fillers for enhanced physical properties, UV stabilizers, and flame retardants are common additives. 

By using different additives, fillers, and so on with the different plastics, more than 17,000 compounds are commercially available worldwide. They are used in the different processes to meet the processes specific melt-flow characteristics or provide cost-to-product performance advantages. They are classified as commodity plastics or engineering plastics. Commodities such as PEs, PVCs, PPs, and PSs (see Appendix A, List of Abbreviations) account for over two-thirds of plastics sales. 

Engineering plastics n. Plastics which are modified by using modifiers, additives, fillers and reinforcements. 

In terms of functions, the emphasis is now on improvement of film processing, anti-static additives, special effect pigments, multi-functional fillers, and stabilizing systems for engineering plastics. Many of the new developments in individual additives are now being offered at the same time in safe, convenient technical masterbatch formulations. 

Modern compounding, especially for technical or engineering plastics, may require the addition of a complex range of materials, each with its own characteristics. The sequence in which these are introduced into the compounder (and the position down the screw) is fundamentally Important. Fillers, with their weight and volume, are usually brought in first, but the latest technology, in which polymerization or cross-linking takes place in the extruder, may alter the sequence. 

Commercial plastics are invariably mixtures of one or more polymers blended with a variety of additives such as colorants, flame-retardants, biocides, etc., all tailored to achieve cost-effective performance for specific applications or processibility requirements. For example, flexible PVC for wire insulation contains one or more plasticizers, and poly (2,6-dimethyl-1,4-phenylene oxide) (PPO), an engineering plastic, is marketed in several grades which may contain varying amounts of lubricants, stabilizers, fillers etc., in addition to the high-impact PS (HIPS) which is added to PPO to modify impact properties and melt viscosity. 

By means of compounding, tailor-made engineering plastics parts are manufactured to satisfy every conceivable application. The warping problem, which existed in the past for the production of large area parts, e.g. for car body parts and bumpers, can be overcome by selected reinforcement/filler systems. Simultaneously the heat distortion temperature could be raised from about 150 °C for pure PBT homopolymer to approximately 210 °C for reinforced polymer. Self-extinguishing behavior was imparted by incorporation of flame retardant synergistic systems. Further, in the last thirty years, many commercial products have been developed by blending PBT with other polymers in the melt. Moreover, a variety of additives, fillers or reinforcements, which have been mentioned previously in this Chapter, may be added to the PBT blends. 

Polymer, endless manufacture of A major contributor to the successful growth of plastic materials is the endless capability of the industry (chemist, engineer, etc.) in producing new polymers, additives, fillers, reinforcements, etc. as well as modifying the materials that presendy exist. There is always a new developing horizon in the world of plastics. 

The use of plastic for manufacture of automotive parts has been growing during the last few decades. Many different types of plastic are used in hundreds of applications. These range from commodity polymers such as PVC and polyethylene to high performance engineering plastics. Furthermore, most of the high performance plastics contain a range of additives, fillers and reinforcements to enhance properties. Polymer blends such as PC/PBT and PC/ABS are also quite common in automotive applications. 

To meet the functional requirements in the end application, additives are often compounded into the engineering plastics. These additives could be glass fibers for increased stiffness and strength, impact modifiers for improved impact toughness, mineral fillers for stable dimensions, stabilizers to prevent UV and heat ageing, and last, but certainly not least, various pigments or colorants to obtain the required color of the final part. All of these will influence the transparency of the compound. 

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