Premium silicone-resin primer for professional adhesion and embedding applications

Wacker G 795 is a one-component primer (bonding agent) based on reactive siloxanes and silicone resins, dissolved in a mixture of isoalkanes. After the solvent has evaporated, the primer forms a rigid silicone-resin film under the influence of atmospheric humidity that adheres firmly to the substrate. The catalysed silicone rubber applied on top forms a tight bond with this resin film during vulcanisation. The primer is yellowish and clear, has an active substance content of 18% and a density of approximately 0.79 g/cm³. It is preferably used with addition-curing RTV-2 silicones from, among others, the Elastosil M and RT ranges, and also gives silicones with a high oil content (such as pad-printing silicones) excellent adhesion to aluminium or plywood.

Key Benefits

• ✓ Active substance 18% – thin, even resin film that strongly improves adhesion between substrate and silicone rubber.
• ✓ Reaction time from 1 hour – at room temperature and at least 40% humidity, or 10 minutes at 100°C on metallic substrates.
• ✓ Density 0.79 g/cm³ – low-viscosity solution (approx. 2 mPa·s) that is easy to apply by brush, dipping or spraying.
• ✓ Processing window up to 5 hours – apply silicone rubber within 5 hours of drying to avoid loss of adhesive strength.
• ✓ Broad substrate suitability – adheres to metals, wood and various plastics, even under fluctuating temperatures, damp and mechanical stress.
• ✓ Maximum adhesive strength after 4 days – usually sufficient adhesion after 24 hours for trouble-free demoulding.

Typical Applications

• → Improving adhesion of RTV-2 addition silicones on aluminium and other metals
• → Bonding silicone rubber to wood and plywood carrier plates
• → Pre-treatment of plastics such as acrylate, polyamide, polyester and PVC
• → Pad-printing silicones with high oil content on metal or wooden carriers
• → Embedding and bonding metal parts in silicone rubber
• → Applications with fluctuating temperatures, damp or tensile and shear stress

Processing Instructions

1. Make the surface to be primed dry, dust-free and grease-free. First clean with a non-polar solvent (e.g. white spirit, boiling range 80–140°C) followed by a polar solvent, preferably acetone.
2. Remove loose particles; lightly roughen very smooth surfaces by grinding.
3. Apply the primer very thinly and free of air bubbles by brush, dipping or spraying. On smooth, non-absorbent surfaces (such as aluminium) as thinly as possible; on rough or absorbent surfaces (such as plywood) more liberally.
4. Allow to react for at least 1 hour at room temperature and at least 40% relative humidity (monitor with a hygrometer), or 10 minutes at 100°C (metals only).
5. Apply the catalysed silicone rubber immediately after drying, at the latest within 5 hours, otherwise adhesive strength decreases.
6. Maximum adhesive strength is reached after 4 days; usually sufficient adhesion has developed after 24 hours. Heating to 100–150°C can further improve adhesion.

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

Safety and compliance: always consult the safety data sheet (SDS) for complete hazard, handling and processing information before using this product.