SEMICOSIL 949 UV A/B - Wacker Chemie - Silicones

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.
Handling
- 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.
Mixing
- 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.
Curing
- 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 UVactivation.
- 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
UV-activation
(140 mW/cm²)
Curing time
at 25°C(2 mm)

5 s 2 min

10 s 1 min

20 s
cured after 40 s UV

Properties

Catalyst Properties


	Value	Units	Test Method / Conditions
Dynamic Viscosity (at 25°C)	200	mPa·s	DIN EN ISO 3219
Mix Ratio	10:1	parts by weight	-
Pot Life (at 23°C)	min. 1	day	-

Cured Properties


	Value	Units	Test Method / Conditions
Density (at 23.0°C)	0.97	g/cm³	DIN EN ISO 1183-1 A
Shore Hardness 00 (at 23°C)	40	-	ASTM D 2240

Uncured Properties


	Value	Units	Test Method / Conditions
Density (at 23°C, Componenet A)	0.97	g/cm³	DIN EN ISO 2811-2
Density (at 23°C, Componenet B)	0.97	g/cm³	DIN EN ISO 2811-2
Dynamic Viscosity (Component A, at 25°C)	150	mPa·s	DIN EN ISO 3219
Dynamic Viscosity (Component B, at 25°C)	1000	mPa·s	DIN EN ISO 3219
Platinum Catalyst in Component (UV active organometallic catalyst)	Component A	-	-
Platinum Catalyst in Component (UV active organometallic catalyst)	Component B	-	-

Properties