Wacker Elastosil® RT 623 A/B – Red-Brown Addition Silicone for Pad Printing & Printing Pads

Premium Red-Brown Addition Silicone for Professional Pad Printing and Printing Pad Applications

Wacker Elastosil® RT 623 A/B is a pourable, addition-curing, two-component platinum-based silicone that vulcanizes at room temperature without chemical shrinkage. Component A is a white paste with a viscosity of 15,000 mPa·s, component B is a liquid red-brown fluid of 800 mPa·s, mixed together in a weight ratio of 9:1 (A:B). The cured rubber has a Shore A hardness of approximately 31, a density of 1.12 g/cm³, and a remarkably high tear strength of over 30 N/mm. With a pot life of 30 minutes at 23°C and a tack-free curing time of 5 hours at room temperature — significantly accelerated by heat — the material has been specifically developed as a base material for the production of printing pads for the pad printing industry.

Key Benefits

• Shore A 31 – medium hardness that is ideal for pad-printing applications where form elasticity and durability must be balanced.
• Tear Strength > 30 N/mm – exceptionally high mechanical strength (ASTM D 624 B) ensures a long service life of printing pads at high production speeds.
• Tensile Strength 7.5 N/mm² with 700% Elongation at Break – combination of strength and flexibility to withstand thousands of printing cycles.
• Linear Shrinkage < 0.1% – dimensionally stable, essential for reproducible printing results and exact detail reproduction.
• Pot Life 30 minutes – Curing Time 5 hours at 23°C – ample processing time with rapid demolding, can be accelerated by heating.
• Mixing Ratio 9:1 (A:B) by weight – easy to weigh and suitable for mechanical dosing equipment.

Typical Applications

• Production of printing pads for pad-printing on keyboards, toys, and sports equipment
• Printing on irregular surfaces and multi-level substrates in the automotive industry
• Industrial printing on electronic components and housings
• Pads for high print runs (more than 100,000 prints per pad) at print speeds above 1,000 prints per hour
• Printing pads where print precision of less than 0.01 mm is required
• Replacement of worn pads in existing pad printing machines

Processing Instructions

1. Thoroughly stir component A and component B separately before use to evenly distribute sedimented fillers and pigments. Component A is a paste and requires more vigorous stirring than component B.
2. Mix components in a weight ratio of 9:1 (A:B). Important: use only A and B components with the same lot number (batch number) — cross-mixing of different batches leads to abnormal curing and mechanical properties.
3. Mix slowly and thoroughly until a homogeneous red-brown color is achieved without streaks or spots. Regularly scrape the walls and bottom of the mixing vessel. Avoid air entrapment by stirring slowly.
4. Optionally vacuum the mixture at 10–20 mbar for several minutes to remove entrapped air. For pad production, this is highly recommended to prevent air inclusions in the printing surface.
5. Pour within the 30-minute pot life (at 23°C) in a thin stream and from a low height at one point to minimize air entrapment.
6. Allow to cure for 5 hours at 23°C until tack-free. Full curing and optimal mechanical properties are achieved within 24 hours. The curing time can be significantly reduced by post-curing at elevated temperatures (e.g., 70°C).

Inhibition Warning

Wacker Elastosil® RT 623 A/B is an addition- (platinum) curing silicone and is sensitive to curing inhibition. Avoid contact with sulfur and sulfur-containing compounds (natural rubber, EPDM, polysulfides), amine-containing substances (amine-cured epoxy resins, polyurethanes), organotin compounds (including condensation silicone catalysts) and uncured latex. If in doubt, test a small amount on the model surface before processing the full amount.

About the Manufacturer

Wacker Chemie AG is a world market leader in the development and production of silicones for industrial and technical applications. From Burghausen (Germany), Wacker has been supplying high-quality silicone rubbers to the pad printing, mold making, prototyping, and composites industries since 1947.

Professional Support

Do you have specific questions about the choice of a printing pad silicone, the correct hardness for your substrate, or the influence of oil dilution (Wacker Silicone Fluid AK 35) on the Shore hardness? Our technical specialists are happy to assist. Contact us via chat, phone, or email — we will be happy to help you select the right material for your production process.