Wacker Elastosil® RT 629 A/B – Antistatic Addition-Cure Silicone for Pad Printing & Printing Pads

Premium Antistatic Addition-Cure Silicone for Professional Pad Printing and Industrial Printing Applications

ELASTOSIL® RT 629 A/B is a pourable, addition-cure (platinum-cure) two-component silicone rubber that vulcanises at room temperature (RTV-2). The cured rubber is turquoise, has a medium hardness of Shore A 31 and a low mixed viscosity of 8,000 mPa·s, so the material flows extremely well and releases trapped air easily. Its distinctive feature is its antistatic formulation, which rapidly dissipates static charge from the surface of the printing pad. With a working time of approx. 40 minutes, a tack-free cure time of 3 hours at room temperature and a mix ratio of 10:1 by weight, this is a fast, shrinkage-free system for the professional production of antistatic pads.

Key Benefits

• Hardness Shore A 31 – medium hardness that strikes the right balance between dimensional stability and ink transfer for printing pads.
• Tear strength 25 N/mm – high mechanical strength and long-term hardness stability for a long pad service life.
• Tensile strength 6 N/mm² and elongation at break 500% – excellent elasticity that copes with repeated compression without fatigue.
• Mixed viscosity 8,000 mPa·s – very good flow and self-degassing for bubble-free, highly detailed casts.
• Working time 40 minutes – generous pot life with a fast, shrinkage-free cure in 3 hours that can be accelerated further with heat.
• Antistatic formulation – rapid dissipation of static charge, essential when printing sensitive electronic components.

Typical Applications

• Production of antistatic printing pads for industrial pad printing.
• Printing on keyboards, switches and control panels.
• Printing on sensitive electronic components where electrostatic discharge must be avoided.
• Printing on toys, sporting goods and automotive parts.
• High-volume printing applications with high print speeds and high print accuracy.
• Adjusting the hardness with Wacker Silicone Fluid AK 35 for softer pads.

Processing Instructions

1. Stir component A and component B thoroughly, each separately in its container, to redistribute any settled fillers evenly.
2. Weigh out in a 10:1 ratio by weight (A:B). Important: only use A and B components with the same batch number. The platinum catalyst is contained in component B.
3. Mix A and B slowly and thoroughly (in a figure-of-eight motion or mechanically), scraping the sides and bottom, until the mixture is homogeneous and free of streaks.
4. Optional: degas the mixture under reduced pressure (10–20 mbar) in a vacuum chamber.
5. Pour in a thin stream from a low height within the pot life of approx. 40 minutes.
6. Leave to cure for approx. 3 hours at room temperature. Curing can be accelerated considerably by heating.

Inhibition of Addition-Cure Silicones

ELASTOSIL® RT 629 A/B is an addition-cure (platinum) silicone and is therefore susceptible to inhibition. Substances such as sulphur and sulphur-containing compounds, amines, tin compounds, condensation-cure silicones and certain modelling clays can retard or prevent curing. If in doubt, always carry out a preliminary test and keep incompatible materials away from the fresh mix.

Processing and Dilution

The hardness can be reduced by adding Wacker Silicone Fluid AK 35. The dilution table shows the Shore A and Shore 00 hardness at different oil percentages.

About the Manufacturer

Wacker Chemie AG is a global market leader in the development and production of silicones for industrial and technical applications.

Professional Support

Do you need advice on the right hardness, dilution or processing for your pad printing application? Feel free to contact us – our specialists will be happy to help you select and process the right material.