Polycarbonate application

Ab initio calculations with full geometry optimization on diphenyl carbonate and diphenylpropane are carried out to determine the bond geometries and the conformational energies and then to compute the unperturbed chsin dimensions of the bisphenol A polycarbonate. Application of these results to the RIS model of the PC chain leads to the prediction of the unperturbed chain dimension. 

Electronics giant NEC of Japan has entered the fray with a polycarbonate containing a silicone FR. The company has licensed Sumitomo Dow to be the manufacturers of this special polycarbonate. Sold as NuCycle, the new material is used to make NEC s liquid crystal display monitors and battery packs for portable computers. It is also applied for other polycarbonate applications, covering projectors and plasma flat screens. 

While PC/ABS continues to perform well for instmment panels, there is still a threat being posed by long glass fibre-reinforced pol q)ropylene. High temperature PMMA also poses a threat to some small polycarbonate applications inside the car and may be a threat for inner headlamp lenses in a few years time. 

Broad-band benzoxazinone UV absorber characterized by low volatility, and recommended for thermoplastic polyester and polycarbonate applications. 

A recently introduced polycarbonate-based blend offers a low coefficient of thermal expansion. This new thermoplastic is designed for large sheet applications such as doors or siding. Its high dimensional stability will eliminate warping from exposure to varying temperatures. 

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). 

Although the nylons are not generally considered as outstanding electrical insulators, their toughness and, to some extent, their temperature resistance, have led to applications in coil formers and terminal blocks. Indeed, the new nylon 46 materials would appear to be of particular interest here. Acetal resins, polysulphones, modified PPO and polycarbonates, however, present a challenge to applications in this sphere. 

The transparent polyamides have increased significantly in importance in recent years. For transparent applications they are competitive with poly(methyl methacrylate), polycarbonates, polysulphones and MBS. In terms of toughness they are like polycarbonates, polysulphones and MBS and much better than the... 

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). 

Although somewhat more expensive than the general purpose thermoplastics, polycarbonates have established themselves in a number of applications. The desirable features of the polymer may be listed as follows ... 

Although the general electrical properties of the polycarbonates are less impressive than those observed with polyethylene they are more than adequate for many purposes. These properties, coupled with the heat and flame resistance, transparency and toughness, have led to the extensive use of these resins in electrical applications. 

Other polymers are as rigid, others are as transparent, others are even both more rigid and as transparent, but the bis-phenol A polycarbonate is the only material that can provide such a combination of properties, at least at such a reasonable cost. The application of polycarbonates therefore largely arise where at least two and usually three or more of the advantageous properties are required and where there is no cheaper alternative. 

The toughness and transparency of polycarbonates has also led to a number of other industrial applications. In Great Britain one of the first established uses was for compressed air lubricator bowls. In the first five years of commercial... 

Because of the above properties, together with other features such as the ability to mould to close dimensional tolerances, low warpage, low shrinkage, low moisture absorption and good surface finish, polycarbonate-ABS alloys have become widely used in the automotive industry, for electrical applications and for housings of domestic and business equipment. 

Polycarbonates based on tetramethylbisphenol A are thermally stable and have a high Vicat softening point of 196°C. On the other hand they have lower impact and notched impact resistance than the normal polymer. Blends with styrene-based polymers were introduced in 1980, and compared with PC/ABS blends, are claimed to have improved hydrolytic resistance, lower density and higher heat deflection temperatures. Suggested applications are as dishes for microwave ovens and car headlamp reflectors. 

The polysulphones tend to be used in applications when requirements cannot quite be met by the much cheaper polycarbonates and possibly aromatic polyethers. In many of the fields of use they have replaced or are replacing ceramics, metals and thermosetting plastics rather than other thermoplastics. 

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