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PROCESSING THERMOPLASTIC COMPOSITES 24 James L. Throne 24.1 INTRODUCTION Thermoplastic polymers are seldom converted into products without the time-dependent application of temperature, pressure, shear or other types of mechanical manipulation. The mechanical manipulation of plastics is called 'polymer processing'. Many polymer processes and combinations of polymer processes are used in modern commercial manufacturing. The selection of a process to produce a thermoplastic polymer product from pellets, powder, or other granular forms begins with general characteristics of the prod- uct itself. The two primary concerns to be met in the manufacture of any polymer product are: 0 Will the finished part meet all required, specified and desired design criteria? 0 Can the product be produced at the mini- mum cost for the projected market size? The first concern focuses primarily on the ability of the polymer to meet mechanical and environmental challenges throughout its func- tional lifetime. This is shown as the left branch of the Fig. 24.1 schematic'. The second concern deals with the economic ability to process the acceptable polymers into the useful product, and this is shown as the right branch of Fig. 24.1. Commercial polymers are rarely pure. Even 'neat' polymers or polymers that contain no Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7 Machinery Shape or Part Production Requirement Product Requirements Electrical Environmental Rigidity Tempera tu re Possible Polymer Families Processes Fiber Type Fiber Length I Other Adducts t i Concerns I Compound Grades I Economics 1 Final Polymer Fig. 24.1 A schematic for choosing the proper poly- mer and an attendant process'. fillers, reinforcements or foam cells, usually have one or more adducts or additives that alter the basic characteristics of the polymer. Table 24.1 gives a short list of some of the adducts used with thermoplastics*. Some of these, such as coupling agents, are vital in achieving the desired final solid mechanical performance of other adducts, such as fillers and reinforcements. Typical fillers used in
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526 Processing thermoplastic composites Table 24.1 Adducts in thermoplastic polymers’ Antioxidants Antistatic agents Colorants and pigments Coupling agents Flame retardants Fillers Foaming agents Heat stabilizers Mold release agents Odor suppressors Plasticizers Processing aids Emulsifiers Lubricants Reinforcing fibers Ultraviolet stabilizers Viscosity depressants thermoplastic polymers are given in Table 24.23. Typical fibrous reinforcements used in thermoplastic polymers are given in Table 24.34. Filled, reinforced and foamed thermo- plastics offer great breadth of solid mechanical properties. In many cases, they offer substan- tial processing challenges, as well. Nearly all thermoplastic processes shape the polymer in its fluid state (The most notable exception to this is thermoforming, where forming occurs when the polymer is in a rubbery state.
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This note was uploaded on 03/16/2010 for the course MECHANICAL ME765401 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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