SEMICOSIL^® 942 UV A/B

All surfaces must be clean and free of contaminants that will inhibit the cure of the 10:1 mixture of SEMICOSIL^® 942 UV A/B . 

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.

SEMICOSIL 942 ^® UV B 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^® 942 UV A must be stirred thoroughly before processing. Typically also SEMICOSIL^® 942 UV B  is stirred in the reservoir of the dispensing machine. Dissolved air is removed by standard degassing of reservoir contents.

After exposure to ambient light or daylight SEMICOSIL^® 942 UV B should be immediately processed and not stored any longer.

SEMICOSIL^® 942 UV B  contains the organometallic UV active catalyst,  the corresponding component 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^®  942 UV A  should be  thoroughly mixed with SEMICOSIL^®  942 UV B 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 SEMICOSIL^® 942 UV B activates the UV-active catalyst. In combination with SEMICOSIL^® 942 UV A a very fast cure can be achieved. Cure speed can be tuned in typical ranges between  minutes and  seconds depending on UV Intensity and dose.

Direct Cure: Reaction proceeds after end of UV irradition. Main cure is rapidly  achieved for those areas irradiated with UV light.

Shadow Cure: areas not directly accessible are cured on longer time scale by second addition curing mechanism (see gel time no irradiated)

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^® 942 UV A/B  (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.