LUMISIL® LR 7601/50 A/B
Liquid silicone rubbers of the LUMISIL® LR 7601 series are medium viscosity, two component compounds with short curing times. The vulcanizates are noted for their very high optical transparency and excellent mechanical and electrical properties.
The products can be used at temperatures down to -55 °C and even above +150 °C. The outstanding optical transparency extends over a broad range of the visible spectrum and exceeds the transparency of polycarbonate or polymethylmethacrylate. The refractive index nD₂₅ is in the range of 1.41. LUMISIL® LR 7601/50 A/B is optimized for state-of-the-art requirements of optical parts. In contrast to standard ELASTOSIL® LR grades, the hardness in the product name of LUMISIL® LR 7601/50 A/B reflects the hardness of vulcanized articles in the non-post cured state. Depending on the injection molding parameters, the geometry of the final parts and the post curing conditions, hardness increases after post curing in the range of 5 to 8 points. In addition LUMISIL® LR 7601/50 A/B is listed in various UL (Underwriter Laboratory) standards including f1 rating, i. e. suitable for outdoor use with respect to exposure to Ultraviolet Light, Water Exposure and Immersion in accordance with UL 746C.
Specific features of LUMISIL® LR 7601/50 A/B
- Highly transparent
- Low volatile
- Reduced volatile content
These grades are particularly suitable for the economical production of large series of injection moulded articles with excellent optical transparency. Parts made from LUMISIL® LR 7601/50 A/B can be used for technical applications. These articles are also suitable for use in conjunction with foodstuffs.
Postcured parts can be used for food contact applications and are suitable for use under the Recommendation "XV. Silicones" of the BfR and FDA § 177.2600 under observance of any given limitations on extractable and volatile substances.
The A and B components are delivered ready to use in 20 kg pail and 200 kg drum kits. With adequate metering equipment, they can be pumped directly from the original containers into the injection molding machine and mixed by a static mixer. The mixing ratio is 1 : 1. At room temperature, mixtures of A and B components have a pot life of at least three days.
For maximum transmission and transparency of injection molded parts, any cross contamination with standard silicones have to be avoided. Therefore, we recommend producing LUMISIL® LR 7601 series with a separate line. Additionally, processing parameters like injection speed, holding pressure have to be adapted to the corresponding viscosities of the LUMISIL® LR 7601 series to guarantee exact filling and de-aeration of cavities.
Compared to ELASTOSIL® LR, LUMISIL® LR 7601 series have less mechanical strength. This has to be taken into consideration for the demoulding process, a high shear on parts is not recommended. Demoulding technologies like mushroom ejectors or blowing-off by support of air pressure have been tested successfully.
Polygone® 505 is suitable to remove deposits or residues on sensitive mold surfaces. The use of an ultrasonic bath supports a careful cleaning without attacking the surface. It is recommended to use WACKER® Silicon spray in the initial phase of the injection molding process.
For detailed information refer to our brochure SOLID AND LIQUID SILICONE RUBBER - MATERIAL AND PROCESSING GUIDELINES".
This product is available in 20 kg pail and 200 kg drum kits.
Once opened, containers should always be resealed after use to prevent the platinum catalyst from being poisoned by amines, sulphur or phosphorus compounds. The 'Best use before end' date of each batch is shown on the product label. Storage beyond the date specified on the label does not necessarily mean that the product is no longer usable. In this case however, the properties required for the intended use must be checked for quality assurance reasons.