Applications of Bis-phenol A Polycarbonates

Processing temperatures are high and fall between the melting point ( 230°C) and 300°C, at which temperature degradation occurs quite rapidly. 

Polycarbonate melts adhere strongly to metals and if allowed to cool in an injection cylinder or extrusion barrel may, on shrinkage, pull pieces of metal away from the wall. It is therefore necessary to purge all equipment free of the resin, with a polymer such as polyethylene, after processing. 

There is little crystallisation on cooling and after-crystallisation has not been observed. Mould shrinkage is consequently of the order of 0.006-0.008 cm/cm and is the same both along and across the flow. 

In the case of glass-filled polymers, moulding shrinkage is somewhat lower (0.003-0.005 cm/cm). 

Provided due care is taken with respect to predrying and to crazing tendencies, polycarbonates may also be thermoformed, used for fluidised bed coating and machined and cemented. Like metals, but unlike most thermoplastics, polycarbonates may be cold formed by punching and cold rolling. Cold rolling can in fact improve the impact resistance of the resin. 

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Improved flame rating resistance of bis-phenol A polycarbonate Electrical/electronic applications and high-temperature bearings Food trays electroplatable applications Fiberglass-reinforced injection molded parts... 

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. 

Let us first review various thermoplastics used in automotive applications. These include nylon 6,6-based blends (e.g., nylon 6,6-PPO), glass-filled nylon 6,6 with without impact modifiers, homo- and copolymers of PP, polybutylene terephthalate (PBT), polyethylene (PE), bis-phenol A polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), PC-ABS blends, glass-filled PP, and ABS. 

The other important diol which finds wide application in synthesis of flame retardant epoxy thermosets is 4,4 -isopropylidene bis(2,6-dibromo-phenol) (tetrabromobisphenol-A,TBPA).The primary use of TBPA is as a reactive flame retardant in epoxy resin-based circuit boards and in electronic enclosures made of polycarbonate-acrylonitrile, butadiene-styrene, etc. Hexafluorobisphenol-A (bisphenol-AF, hexafluoroisopropylidene diphenol) has also been used for the synthesis of fluorinated epoxy resin aiming at the anticorrosion coatings market for industrial vessels and pipes. The key disadvantages of fluorinated epoxies are their relatively high costs and low Tg, which limit their commercialisation. Thus utilisation of such diols in vegetable oil-based epoxy resins may result in similar performance. 

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