WACKER® Primer G 791 A/B

Adhesion promoting primer

• Cable Accessories
• Arresters
• Insulators

Bonding agent preferably used for bonding addition-curing silicone rubbers onto vulcanized, addition-curing rubbers (e.g. WACKER® ELASTOSIL® RTV-2, LSR and R plus or WACKER® POWERSIL® RTV-2 and LSR). WACKER® PRIMER G 791 A/B is especially suited for bonding addition-curing POWERSIL® XLR® 630/640 onto vulcanized silicone rubber of the same grade.

Processing

• Surfaces to be primed have to be dry and free from grease, oil, wax, dust, rust or other contaminants. Also mold-release agent from the previous vulcanization cycle on the silicone rubber substrate has to be removed.
• The surface should be cleaned, e.g. with a non-polar solvent such as mineral spirits (boiling range between 80 °C and 140 °C), followed by a polar solvent, such as acetone. Very smooth surfaces may be roughened by grinding until the shine of the surface disappears. Loose particles must be removed.
• Components A and B must be homogenized before use. A and B are mixed in a ratio of 1:1 by weight. The pot life of the catalyzed primer mixture is 2 – 3 days at room temperature and can be prolonged by cooling to approx. 1 week at 6 °C. Storage must be in properly sealed containers.
• Wacker Primer G 791 A/B [1.0] is applied in a thin film layer with a brush, by dipping or spraying. The primer film has to be vulcanized for 20 – 60 minutes at 100 – 120 °C.
• The silicone rubber should be applied to the primed surface soon after the heating process, if possible. It is recommended that this is done not later than approximately 2 days after priming the substrate. Otherwise a drop in adhesive strength may occur. Prior to the application of the silicone rubber, the primed surface has to be kept free of contaminations.
• Note: Initial adhesion directly after vulcanization of the rubber will in many cases be high already. In some cases, however, initial adhesion will be sufficient for handling the composite while maximum adhesive strength will only be achieved after about 4 days. Additional post curing of the cured rubber at 70 °C – 150 °C will further improve adhesion. Once opened, containers of WACKER® PRIMER G 791 A/B should be kept well sealed and stored in a cool and dry place.