ELASTOSIL® CAT UV
Organometallic catalyst for addition-curing two-part silicone rubber grades (RTV-2).
ELASTOSIL® CAT UV is a suitable catalyst component for addition-curing silicone elastomers SEMICOSIL® UV enabling fast UV curing at room temperature in combination with long pot-life.
The correct mixing ratio of addition curing silicone component SEMICOSIL® UV and ELASTOSIL® CAT UV (typically 10:1) is given in the datasheet of the addition-curing silicone elastomer.
ELASTOSIL® CAT UV is intended to be used only for processing in dispensing equipment configurations with direct mixing of SEMICOSIL® UV and ELASTOSIL® CAT UV in the mixing tube (.i.e. after the dispensing head). It is not intended to be applied in premixes that are stored in separate reservoirs or distribution systems.
All surfaces must be clean and free of contaminants that will inhibit the cure of the 10:1 mixture of SEMICOSIL® UV / ELASTOSIL® CAT UV.
Examples of inhibiting contaminants are sulfur containing materials, plasticizers, urethanes, amine containing materials and organometallic compounds – especially organotin compounds. If a substrate’s ability to inhibit cure is unknown, a small scale test should be run to determine compatibility.
ELASTOSIL® CAT UV is supplied in specific packagings allowing the material transfer to reservoirs of state-of-the art dispensing equipment without exposure to ambient light. For this purpose a reusable opening fixture is mounted on the can closure Informations can be provided by the regional sales managers.
To ensure homogenity of the corresponding A component, usually the addition curing silicone SEMICOSIL® UV must be stirred thoroughly before processing. Typically also ELASTOSIL® CAT UV is stirred in the reservoir of the dispensing machine. Disscolved air is removed by standard degassing of reservoir contents.
After exposure to ambient light or daylight ELASTOSIL® CAT UV should be immediately processed and not stored any longer.
ELASTOSIL® CAT UV contains the organometallic UV active catalyst, the corresponding components A the crosslinker. Even traces of the catalyst may cause gelling of the component containing the crosslinker. Therefore tools (spatula, stirrers, etc.) used for handling the catalyst-containing component or the catalyzed compound must not come into contact with this component.
SEMICOSIL® UV grades should be thoroughly mixed with ELASTOSIL® CAT UV at a 10 : 1 ratio by weight or volume. Typically static mixing with tube configurations 24/6 or higher (increased no. helical turnings or lower diameter) are sufficient.
To eliminate any air introduced during dispensing or trapped under components or devices a subsequent vacuum encapsulation may be recommended.
UV Irradition on ELASTOSIL® CAT UV activates the UV-active catalyst. In combination with SEMICOSIL® UV grades a very fast cure can be achieved. Cure speed can be tuned in typical ranges between minutes and < 10 sec depending on UV Intensity and dose.
Reaction proceeds after end of UV irradition. Cure is achieved for those areas irradiated with UV light. In case shadow cure is required a suitable alternative catalyst can be used.
For the curing an UV lamp (Fe-lamp, D-bulb) with an emission between 250 and 350 nm can be used. It is recommended not to use lamp systems that emit light with wavelengths below 250 nm. An high power UV-LED may also be used (365 nm) for applications allowing minimum distance to the light source. As light penetration depth is reduced 365 nm in UV-LED in comparison with discharge lamp pretests are recommendable to check feasibility for specific application.
Curing time of SEMICOSIL® UV / ELASTOSIL® CAT UV (10:1) is highly dependent on UV-activation. Significant differences in curing time are obtained for curing different layer thicknesses and for using different substrate materials.