SEMICOSIL® 949 UV A/B is a pourable, addition-curing, 2-part silicone rubber of low viscosity that cures extremely fast after activation by UV light exposure to a soft silicone elastomer.


  • two-part, 10 : 1 mixing ratio
  • low viscosity
  • extremely fast curing at room temperature (after UV-activation)
  • low hardness (Shore 00)
  • offers process control option by UV-light (contains UV-tracer)





Surface preparation

All surfaces must be clean and free of contaminants that will inhibit the cure of SEMICOSIL® 949 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.


The A-component contains an UV-tracer that is dispersed in the silicone. The UV-tracer may be subject to a limited sedimentation. In order to guarantee homogenous product performance (curing time, UV-tracability) it is recommended to homogenize the A-side prior to application by stirring.


Component B of SEMICOSIL® 949 UV A/B contains the platinum catalyst, component A the crosslinker. Even traces of the platinum catalyst may cause gelling of the component containing the crosslinker. Therefore tools (spatula, stirrers, etc.) used for handling the platinum-containing component or the catalyzed compound must not come into contact with this component.

The two components should be thoroughly mixed at a 10 : 1 ratio by weight or volume.


To eliminate any air introduced during dispensing or trapped under components or devices a vacuum encapsulation is recommended.



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 a wavelength below 250 nm.

Curing time of SEMICOSIL® 949 UV A/B is highly dependent on UV-activation.

Significant differences in curing time are obtained for curing different layer thicknesses and for using different substrate materials. Typical values are given below.


UV-activation Time (sec)      Curing time (140 mW/cm²) at 25°C (2mm)

5 sec                                     2 min

10 sec                                   1 min

20 sec                                   40 sec


Use of UV-LEDs

A cure with UV-LEDs is basically possible, however only under certain specific conditions:

  • 365 nm emssion
  • High-Power UV-LED
  • Minimization of distance Silicone surface to LED
  • Layer thickness < 5 mm (depth of light penetration smaller compared to cure with discharge lamps)
  • Matching of  area to be irradiated to UV-LED emission array


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.

Vertrieb & Support

Wacker Chemie AG
Heilbronner Strasse 74
70191 Stuttgart
+49  711  61942-0 (Phone)
+49 711 61942-61  (Fax)

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