K 2010: New Polycarbonates Target LED Lamps

Plasticstechnologies are evolving to promote more widespread use of LEDs for streetlighting and automotive headlamps.

One of theinteresting LED displays at K 2010 this week in Dusseldorf, Germany, featurescustom polycarbonates made with a new multi-material injection moldingprocess.

BayerMaterialScience is showing LED lenses for headlights and fiber optics fordaytime running lights in the front headlamps of the new Audi A8.

Thecomponents were developed in collaboration with Audi AG and Hella KGaA Hueck& Co. The ten plastic lenses used in the headlamp are made from MakrolonLED 2245, which offers high transmission for long light paths, high thermalresistance and excellent yellowing stability to LED light.

"Ourmaterial meets the high optical requirements for exposed headlamp parts and iswithin the narrow color tolerance range. It also enables enhanced designfreedom and a considerable weight reduction," says Martin Dobler, an expert inoptical polycarbonate applications at Bayer MaterialScience. LED lenses arearound 50 percent lighter than their glass counterparts.

Thepolycarbonate headlamps are expected to be particularly attractive tomanufacturers of electric vehicles, who are leading the fight against vehicleweight.

Therectangular, slightly curved LED headlamp lenses for the Audi A8 are 4 cm long,2 cm wide and 1 cm thick. They cannot be produced via standard injectionmolding because of the complex shape and thick walls of the optical components.

A newmulti-layer injection molding process offers sophisticated mold temperaturecontrol to provide dimensional stability and fast cycle times forhigh-precision LED lenses with walls of greatly varying thickness.

Road Lighting

LED streetlamps made with polycarbonate in place of glass are also a Sabic focus.

The conceptwas drawn up in conjunction with Cologne-based agency DESIGNquadrat GbR because of efforts inmany European countries to reduce the costs of powering street lights. Thereare 27 million street lights in operation throughout Europe.

Almost allmajor international light manufacturers are working on concepts for LED streetlamps for a very good reason. A street light based on a 901 milliwatt-outputLED can produce the equivalent luminance as a traditional light with only halfof the power consumption.

The streetlamp on display at K 2010 is designed with a two-leaf floral shape. One leafincorporates six LEDs with one lens each. A photovoltaic cell is integrated in aleaf pointing towards the sun to further reduce the amount of energy drawn fromthe electricity grid.

"The design of the LED lenses shows that,compared with glass, polycarbonates offer much greater design freedom forprecision optical parts," says Klaus Reinartz, head of the global LED projectfor general lighting at Bayer MaterialScience.

Otheradvantages of polycarbonate include its high heat resistance and high break andshatter resistance, which protects the LED lamps against vandalism.

Expanded useof polycarbonate in lighting fits into plans by resin producers to find newmarkets to replace packaging applications that have been cut back because of concernsabout bisphenol A in the transparent, high-impact plastic.