Applications Using Polycarbonates

polycarbonate offers a broad palette of physical, mechanical, and aesthetic properties, allowing it to serve many different types of apphcations requiring quite different properties. Its performance profile offers 

Second, polycarbonate resins can easily be modified, blended, and tailored to meet market demands in many different arenas. 

because polycarbonate has acquired a unique status as a broadly based specialty polymer, it sells in higher volume and therefore offers a more attractive price position than would normally be expected of a specialty material. 

polycarbonate can be challenging to categorize by market or application since many of its uses are highly technical and focused in a large number of niche segments. Perhaps an easier way to categorize applications in polycarbonate is to differentiate by key properties that help make the polymer commercially successful. A hst of the top 10 most useful properties would include 

While any one or two of these properties can be met by other polymer systems, it would be difficult to find a single family of materials that can provide all these properties simultaneously. Hence, the more of these properties that are required for a given application, the more that polycarbonate becomes the obvious material of choice. 

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Informative and valuable sections of the chapter are Reengineering the Molecule and the previous sections to which this section refers, Commercial Production of Polycarbonate, Polycarbonate Properties General-Purpose and Apphcation-Specific Grades, Applications using Polycarbonates and Processing Polycarbonate. ... 

Electrical, electronic, and technical applications use polycarbonates for a variety of purposes. The worldwide market is about 160,000 t annually. Because of excellent electrical properties (dielectric strength, volume resistivity) and resistance to heat and humidity, polycarbonate is used for electrical connectors, telephone network devices, outlet boxes, etc. Polycarbonate had been popular for use in computer and business machine housings, but the use of neat resin was largely supplanted by blends of polycarbonate with ABS. However, new, highly colored and special effect resins (translucents, flip-flop colors, speckles, etc) have recaptured a significant portion of that market. A total of 25,000-30,0001 of resin is used annually. Polycarbonate also has many technical uses in instrument panels and devices, especially for membrane switches and insulators. Optical quality polycarbonate is the only suitable material for the compact disc market. Since their introduction in 1983, compact discs have shown explosive growth in the consumption of polycarbonate, with utility for audio, video, and computer applications, reaching about 25,0001 of annual production. 

Isopropanol Precipitation of Genomic DNA Ethanol precipitation is commonly used for concentrating, desalting and recovering of nucleic adds. Predpitation is mediated by high concentrations of salt for protein precipitation and the addition of either isopropanol or ethanol for DNA precipitation. Since less ethanol is required for isopropanol precipitation, this is the preferred method for predpitating DNA from large volumes. In addition, isopropanol precipitation can be performed at room temperature, which minimizes the co-precipitation of salt that interferes with downstream DNA applications. Do not use polycarbonate tubes for precipitation, as polycarbonate is not resistant to isopropanol. Use all solutions at room temperature to minimize the co-precipitation of salt. 

Traditional applications of polycarbonate in the medical market, such as filter housings, tubing connectors, and surgical staplers, have relied on the materials unique combination of strength, purity, transparency, and ability to stand all sterili2ation methods (steam, ethylene oxide gas, and gamma radiation). Polycarbonate-based blends blends and copolymers have further extended the materials usefulness to medical applications. 

Recently, impact modifiers have been developed for plastics other than PVC. Polybutylene and other olefinic thermoplastic elastomers, for example, are being used to enhance the processability, toughness, and heat stability of polypropylene film. Hydroxy-terminated polyethers are being used to increase the impact resistance of polystyrene. Other conunon applications are polycarbonate, polyurethane, thermoplastic polyester, epoxy, and polysulfone. 

For applications where polycarbonate homopolymers or copolymers lack sufficient thermal performance, blends with polyetherimide (PEI) are often used. PEI, which also contributes excellent flammability and low smoke generation to the alloy, may be combined with either straight polycarbonate or polycarbonate blends, depending on what other properties are required. The most common uses are found in light reflectors for automotive headlamps, components for aircraft interiors (especially wall and ceiling panels), and food-contact applications for microwave-to-table cookware. 

PolycarbonatG. Polycarbonate, PC, is susceptible to photo-oxidation, and antioxidants are necessary to maintain the low color and high transparency critical to its end-use applications (see Polycarbonates). Phosphites (0.1%) are used to minimized color development dnring processing. It has been shown that the inherent stability of PC is related to the level of phenolic end groups (41). These levels can increase as a result of hmnidity-induced hydrolysis catalyzed by acid. The phosphite chosen must be very stable to avoid the generation of catalytic amoimts of phosphorus acids. 

Blends or Alloys Sometimes two or more plastics are mixed or alloyed to achieve special properties and are known as polyblends. ABS (acrylonitrile, butadiene and styrene) and PBT (polybutylene terephthalate) are often used in engineering applications with polycarbonate, polysulphone, etc. Several combinations and their improved features are given below (see Crawford (1992) for a more complete discussion of alloys). 

The main applications for polycarbonate in the car interior are lenses for instrument panel displays and ceiling lights. Typical applications for PC/ABS in the car interior are instrument panels where fast cycle times are desired and interior components where impact strength, dimensional stability and high heat performance are required. PC/ABS is also used in many other small application areas such as door handles, loudspeaker grilles, B-post finishes, navigation systems housing and interior trim. A small amount of PC/PBT is used inside the ear, mainly for the manufacture of interior trim. 

For many years vinyl chloride-vinyl acetate copolymers had two main uses, in flooring compositions and for long playing gramophone records. Whereas the former application remains strong, the use in gramophone records has dropped sharply, particularly since the widespread acceptance of polycarbonate-based compact discs. 

The use of ABS has in recent years met considerable competition on two fronts, particularly in automotive applications. For lower cost applications, where demands of finish and heat resistance are not too severe, blends of polypropylene and ethylene-propylene rubbers have found application (see Chapters 11 and 31). On the other hand, where enhanced heat resistance and surface hardness are required in conjunction with excellent impact properties, polycarbonate-ABS alloys (see Section 20.8) have found many applications. These materials have also replaced ABS in a number of electrical fittings and housings for business and domestic applications. Where improved heat distortion temperature and good electrical insulation properties (including tracking resistance) are important, then ABS may be replaced by poly(butylene terephthalate). 

The acetal resins show superior creep resistance to the nylons but are inferior in this respect, to the polycarbonates. It is to be noted, however, that limitations in the load-bearing properties of the polycarbonates restrict their use in engineering applications (see Chapter 20). Another property of importance in engineering is abrasion resistance—a property that is extremely difficult to assess. Results obtained from various tests indicate that the acetal polymers are superior to most plastics and die cast aluminium, but inferior to nylon 66 (see also Section 19.3.6 and Chapter 18). 

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