SEMICOSIL® 949 UV A/B
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)
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