Compounding with Engineering Polymers

PTFE compounds may contain other additives in the form of fiber or bead, which are less expensive than engineering pol5uners. Some useful fillers include glass, and metals oxidesl which also induce abrasion resistance. Abrasion resistance testing in a push-pull cable indicated that inclusion of 10 parts per hundred (phr) of pol q)henylene sulfide (relative to PTFE) and 25 phr of glass beads increased the life 

Glass Fiber, wt. % Average Particle Size, SSG Apparent Density, g/1 Shrinkage, /o Tensile Strength, MPa Break Elongation, /o 

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Polyurethanes are usually classified as engineering polymers characterized by the presence of the carbamate group (-0-CO-NH-). The major route for the preparation of polyurethanes is the reaction between a diisocyanate and a hydroxyl-rich compound with at least two hydroxyl groups, according to Scheme 2.2,... 

Nylon, the first commercial thermoplastic engineering polymer, is the prototype for the whole family of polyamides. Nylon 6,6 began at Du Pont with the polymer experiments of Wallace Carothers in 1928, and made its commercial debut as a fiber in 1938 and as a molding compound in 19A1. By 1953, 10 million lbs of nylon 6,6 molding compound represented the entire annual engineering plastic sales. 

Recycled resins (all commodity and some engineering ones) are commercially available. A comparative list of prices of the virgin and recycled resins is shown in Table 16.5. The prices of recycled plastics are quite competitive. Evidently, while the quoted prices of commodity resins are reasonably close to these of virgin materials, the situation vis-a-vis condensation polymer is atrocious. The only way to make profit on the latter materials is to upgrade them by the recyclers ABC and supply compounds with well-defined and reproducible set of properties to a specific market niche. As it will be discussed later, the addition-type polymers can be reused after restabilization and compounding, whereas the condensation-type ones may require molecular repair to bring up... 

For engineering purposes, the most useful classification of polymers is based on their thermal (thermomechanical) response. Under this scheme, polymers are classified as thermoplastics or thermosets. As the name suggests, thermoplastic polymers soften and flow under the action of heat and pressure. Upon cooling, the polymer hardens and assumes the shape of the mold (container). Thermoplastics, when compounded with appropriate ingredients, can usually withstand several of these heating and cooling cycles without suffering any structural breakdown. This behavior is similar to that of candle wax. Examples of thermoplastic polymers are polyethylene, polystyrene, and nylon. 

A relatively inert substance added to plastics to improve their physical, mechanical, thermal, electrical, or other properties or to lower cost or density. A compound or substance added to a polymer during the initial synthesis process or in subsequent processing to decrease the volume of resin needed to produce a given product. Fillers are generally much lower in cost than the resins they are used in, thus reducing resin cost per part. Fillers or extenders are generally not used with engineering resins. 

Description of the mechanical properties of polymer composites are also made by considering the properties of particulate-long fiber and laminate composites through the different models generated in the literature. It is shown that, many advantages can be derived by use of liquid crystalline compounds as reinforcing fillers to produce blends with engineering thermoplastics. 

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