RTU Encapsulant

Surface Preparation
- All surfaces must be clean and free of contaminants that will inhibit the cure of RTU Encapsulant. 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
Pot Life (at 23°C)	min. 1	day	-
Mix Ratio	10:1	parts by weight	-
Dynamic Viscosity (at 25°C)	200	mPa·s	DIN EN ISO 3219

Cured Properties


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

Uncured Properties


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

Properties