Polycarbonate general

VdC/EA/MMA teipolymer (latex) Vinyl chloride/vinyl acetate copolymer Vinylidene chloride Vinylidene chloride/vinyl chloride copolymer Formaldehyde Vinyl chloride Epichlorbhydrin Polyvinyl chloride (latex) Polyvinyl chloride (general) Thermoplastic polyurethane Polycarbonate (flame resistant) Polyurethane flexible foam Polycarbonate (general) Polyurethane rigid foam Acrolein MDI Phosgene TDI... 

Dutta et al. [16] reported the thermal expansion in prepreg film and crossply laminates of prepreg films. The films were prepared from a blend containing 10 wt% of thermotropic LC copolyester (Vectra A950) and 90 wt% polycarbonate (General Electric Corporation bisphenol-A polycarbonate, PC2). The highest order parameter of the PLC phase L57 (s = 0.45) was obtained at a draw ratio of the film 7.6. 

The mechanisms of crack propagation in poly(methyl methacrylate) are particularly amenable to analysis. The situation is not so simple for other polymers. For example, in polystyrene there is usually multiple crazing in the vicinity of the crack tip. In tougher polymers such as polycarbonate general yielding as well as crazing often takes place at the crack tip. In these cases crack propagation does not occur in such a well-controlled manner as in poly (methyl methacrylate) and it is more difficult to analyse. 

Polycarbonate is a polyester in which dihydric (or polyhydric) phenols are joined through carbonate linkages. The general-purpose type of polycarbonate is based on 2,2-bis(4 -hydroxybenzene)propane (bisphenol A) and has the general structure ... 

Fig. 23. Correlation between properties (general characteristics), melt flow index (MFI), and mol wt for standard BPA polycarbonate and CD-modified...

A reexamination of polycarbonate chemistry was carried out about 50 years after the first aromatic polycarbonates of resorcinol and hydroquinone were discovered. In independent investigations at Bayer AG and General Electric, it was discovered that the polycarbonates of BPA could be prepared (eq. 2). Unlike the ahphatic polycarbonates prepared earlier, which were either hquids or low melting sohds, the aromatic polycarbonates were amorphous sohds having elevated glass-transition temperatures. 

In general, polycarbonate resins have fair chemical resistance to aqueous solutions of acids or bases, as well as to fats and oils. Chemical attack by amines or ammonium hydroxide occurs, however, and aUphatic and aromatic hydrocarbons promote crazing of stressed molded samples. Eor these reasons, care must be exercised in the choice of solvents for painting and coating operations. Eor sheet appHcations, polycarbonate is commonly coated with a sihcone—sihcate hardcoat which provides abrasion resistance as well as increased solvent resistance. Coated films are also available. 

Transesterification. There has been renewed interest in the transesterification process for preparation of polycarbonate because of the desire to transition technology to environmentally friendly processes. The transesterification process utilizes no solvent during polymerization, producing neat polymer direcdy and thus chlorinated solvents may be entirely eliminated. General Electric operates a polycarbonate plant in Chiba, Japan which produces BPA polycarbonate via this melt process. 

The most common commercial polycarbonate [24936-68-3] is prepared from 2,2-bis (4-hydroxyphenyl)propane, that is, bisphenol A [80-05-7] and has the general stmcture ... 

Workers at the General Electric Co. have described a new procedure using low viscosity cycHc intermediates to prepare polycarbonate composites (14,15). This work is discussed in the section dealing with novel methods. 

Bisphenol A Polycarbonate grade, no solvent required 150,000 Undisclosed Falling him USA General Electric... 

General Electric Company (U.S.A.), Lexan Polycarbonate—Design... 

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. 

General Electric now also offer polyetherimide-polycarbonate blends. Although these materials are not transparent and have a lower specification than the basic polyetherimide, they are less expensive and find use in microwave oven trays and automotive reflectors. 

Independently at the General Electric Company in America, work was being carried out in search of thermally and hydrolytically stable thermosetting resins. As a by-product from this work the research team at General Electric also produced polycarbonates from bis-phenol A so that by 1958 production of bis-phenol A polycarbonates was being carried out in both Germany and the USA. 

Today about 75% of the market is held by General Electric and Bayer with their products Lexan and Makrolon respectively. Other manufacturers are ANIC (Italy), Taijin Chemical Co., Mitsubishi Edogawa and Idemitsu Kasei in Japan and, since 1985, Dow (USA) and Policarbonatos do Brasil (Brazil). Whilst this market is dominated by bis-phenol A polycarbonates, recent important developments include alloys with other thermoplastics, polyester carbonates and silicone-polycarbonate block copolymers. 

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