A new generation of highly transparent liquid silicone rubbers for lighting technologies will be presented by Wacker Chemie AG at the 20th International Trade Fair for Plastics and Rubber K 2016.Producing crystal-clear optical lenses and coupling elements for high heat and light exposure is now made possible by the LumisilLR 7601.
The product is predominantly characterised by a significantly lower volatile content, which especially benefits processors. The vulcanisates only need to be thermally postcured for sensitive applications. Due to the low volatile content the postcuring time can be reduced for these applications, and the molded part suffers significantly less shrinkage. LumisilLR 7601is suitable for lenses, sensors and optical coupling elements in lighting technologies and can be processed cost effectively in large-scale injection molding processes. K 2016 will take place in Düsseldorf, Germany, from October 19 to 26.
Three years ago, the company also hit the headlines at the K show with its highly transparent liquid silicone rubber for optical applications. Thanks to a special formulation concept, the company succeeded in formulating silicones in such a way that they can transmit visible light virtually unobstructed and withstand thermal stressing of up to 200°C even for long periods.
These benefits are also offered by the new liquid silicone rubber LumisilLR 7601 that Wacker will showcase at K 2016. Like its predecessor, the product offers outstanding transparency and heat resistance, making Lumisil LR 7601 superior to many other materials. Whereas polycarbonate and polymethyl methacrylate gradually yellow when exposed to heat, artificial or natural light, or ultraviolet radiation, the new silicone elastomer remains crystal clear, even under continuous exposure. The refractive index for all Shore hardness values is 1.41.
Another advantage of the LumisilLR 7601 is it has significantly lower volatile components than the previous product. These are largely removed during production, which in many cases virtually eliminates the need for thermal postcuring. If postcuring is still necessary, it can be substantially shortened. Moreover, linear shrinkage after postcuring is just half that of the previous product. Consequently, there are considerably fewer geometrical changes.
LumisilLR 7601has a comparably low viscosity, which remains largely unchanged by shear forces. For this reason the grades – in contrast to conventional liquid silicones – can be injection molded very easily at low shear rates. They fulfill all material requirements that play a key role in the manufacture of optical elements.
Preferred applications for LumisilLR 7601are in lighting technology, for example, optical lenses. The resultant lens bodies can direct and shape a lamp’s light as is increasingly the case in modern vehicle headlamps. In adaptive front lighting systems, optical elements made of LumisilLR 7601can help to ensure that the road is optimally illuminated under any traffic conditions.
LumisilLR 7601is extremely heat and radiation resistant. It is therefore ideal for applications with high-performance LEDs, which become very hot in continuous operation and emit very high-energy light. In combination with light emitting diodes, entirely new designs and housing structures are possible. Incidentally, this not only applies to car headlamps, but also to the development of energy-efficient and cost-effective lighting solutions, for example, in the general lighting field.
LumisilLR 7601covers four types with hardness values between 50 and 80 Shore A. The liquid silicone rubber can be readily processed by injection molding. This makes it possible to cost-effectively produce even delicately structured molded parts on a large scale. Lenses made from LumisilLR 7601are resistant to aging and weathering, they are electrically insulating, water-repellent and low-temperature flexible.