WACKER already hit the headlines at the K show three years ago 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 LUMISIL® LR 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.
However, LUMISIL® LR 7601 offers yet another advantage. The silicone rubber 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.
LUMISIL® LR 7601 has 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 LUMISIL® LR 7601 are 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 LUMISIL® LR 7601 can help to ensure that the road is optimally illuminated under any traffic conditions.
LUMISIL® LR 7601 is 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.
LUMISIL® LR 7601 covers 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 LUMISIL® LR 7601 are resistant to aging and weathering, they are electrically insulating, water-repellent and low-temperature flexible.