Global consumption of polycarbonate (PC) has risen by 9% annually on average over the past decade, and producers see this trend as set to continue along the same lines over the next several years. In tonnage terms, demand averages 2m t per year, with North America and Europe each accounting for just under 30% and Asia for somewhat more than 40%. Annual forecasts up to 2006 foresee 8% growth for Europe and North America, 5% for Japan and 15% for the other Asian economies.

The outstanding properties of PC include transparency, heat resistance up to 130 °C, high toughness and excellent dimensional stability. It can be sterilised, welded, or glued and is self-extinguishing. PC is easily blended with other plastics. Some 15% of consumption is for blends – especially popular are blends with styrene polymers such as ABS or SAN.

Polycarbonates are linear polyesters of carbonic acid polymerised from bisphenol-A and phosgene, the dichloride of carbonic acid. Since phosgene is toxic if inhaled and thus requires elaborate safety precautions during production, increasing use is being made of melt re-esterification processes, with diphenyl carbonate replacing phosgene as a feedstock.

More than 60% of the bisphenol-A produced worldwide goes into polycarbonate. In view of this close link, polymer producers frequently operate bisphenol-A production facilities in the direct vicinity of PC plants – notably in Uerdingen / Germany, Antwerp / Belgium, Bergen op Zoom / The Netherlands, Cartagena / Spain, and Mount Vernon, Indiana / USA. Other products based on bisphenol-A and indirect “relatives” of PC include epoxy resins, unsaturated polyesters and polysulphones, antioxidants and flame retardants.

With capacities of 750,000-800,000 t/y, GE Plastics (GEP, Europe: NL-4600 AC Bergen op Zoom; www.geplastics.com) and Bayer (D-51368 Leverkusen; www.bayer.de) are the chief producers of PC. Dow (Europe: CH-8810 Horgen; www.dow.com) and Japan´s Teijin (Tokyo; www.teijin.co.jp) each have capacities of some 300,000 t/y. Smaller Asian suppliers such as Idemitsu, Mitsubishi, SamYang or Thai Polycarbonate produce less than 100,000 t/y. New PC production facilities have been built especially in Asia over the past few years to take advantage of above-average growth. Teijin has invested in Singapore, Dow in Yeochon / Korea and Bayer in Caojing near Shanghai / China.

Electrical engineering is the most important market for PC, taking some 30% of production for housings and covers for products such as distribution boxes, lights and household appliances, among other applications. Here, halogen-free, flame retardant grades have been increasingly used since 2001.

Optical storage media such as CDs and DVDs continue to be fast-growing applications for polycarbonate. While demand here ran at some 100,000 t/y in 1995, the figure is expected to be around eight times that in 2005. Roughly one-quarter of PC production will then be processed into discs. The extremely strict demands imposed on production of these data carriers, now with cycle times of less than three seconds, have prompted the development of particularly easy-flow PC grades since the mid-1990s.

In the construction sector, demand for PC exceeded 300,000 t/y for the first time in 2001. Main applications are solid and hollow-chamber sheet for canopies and greenhouses, as well as conservatory and swimming pool roofing. The two biggest PC producers, GE Plastics and Bayer, also manufacture sheet through subsidiaries.

In the automotive sector, headlamp diffusers in PC have now become internationally established. Their main advantage compared with glass is lower weight and greater freedom in design. In automotive glazing, side and rear windows are made of PC. Their enhanced scratch resistance is achieved through special coatings on the basis of polysiloxanes, polyacrylates or polyurethanes, enabling weight savings of up to 20 kg per vehicle. Thanks to new processing techniques, the maximum attainable surface area for PC glazing has recently been increased to 1m². PC also has an excellent safety rating, since the material has a high impact and break resistance and does not splinter.

PC is the material of choice for sunglasses, sports glasses and protective goggles. It is also being increasingly used for optical correction lenses. In the US, 30% of lenses are already made of PC, while the figure in Europe still hovers below 3%.

As a packaging material, PC plays a key role in the production of refillable five-gallon (19-litre) water containers. Its higher price compared with PVC and PET is offset by the material´s fracture strength and dimensional stability, which make it possible to refill bottles up to 100 times. The use of PC for baby bottles, however, is still controversial. Repeated news reports have suggested that the material gives off bisphenol-A into the bottle contents, particularly when heated in a microwave. Investigations have shown, however, that the concentrations involved are much below EU-recommended levels.

Prices for polycarbonate fell sharply at the start of the 1990s. While in the late 1980s a tonne of material generally cost the equivalent of EUR 4,000 and more, prices began to decline rapidly starting in 1991. In the second half of 1993 and midway through 1999, prices sank to the then lowest- ever level of just over EUR 2,700/t. In 1995 and boom year 2000, PC peaked at around EUR 3,550/t. In June 2003, prices fell below EUR 2,700/t for the first time since 1999, but then hit an all-time low of EUR 2,425/t in December 2003 (see price report for technical thermoplastics in this issue).

PC still remains a high-performance plastic which makes investment in production still appear worthwhile. The price developments outlined above, however, would tend to suggest that it could follow the same route as ABS, which, under pressure from increased Asian investment, is already being seen as somewhat of a commodity.