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WACKER Primer G 791 A/B – Addition-curing primer for silicone rubber & substrate adhesion

All primers for silicones All products by Wacker

⚠️ For commercial and professional users only. WACKER® PRIMER G 791 A/B is a solvent-based industrial product that, according to the manufacturer's safety data sheets, is not intended for sale to private consumers. Both components are highly flammable and component B is classified as a reproductive toxicant. Work only in a well-ventilated area with the prescribed personal protective equipment.

Premium addition-curing primer for professional silicone-on-silicone and substrate adhesion

WACKER® PRIMER G 791 A/B is a two-component, addition-curing priming system diluted in an organic solvent. The primer is applied to the substrate and forms a firmly adhering primer film after curing. When an addition-curing silicone rubber is then applied to the primed substrate and vulcanized, a strong, lasting bond forms between the silicone rubber and the substrate. The two components are mixed in a 1:1 ratio by weight, have an active substance content of approximately 20 percent by weight, and a pot life of 2 to 3 days at room temperature. Component A is opaque to whitish, component B clear yellowish. The product is mainly used for bonding addition-curing silicone rubbers onto already vulcanized addition-curing rubbers.

Key benefits

✓ 1:1 mixing ratio by weight → simple, predictable dosing of component A and B without complex weighing steps.
✓ Pot life of 2 to 3 days at room temperature → generous working time, extendable to about 1 week when cooled to 6 °C.
✓ Active substance content approximately 20 percent by weight → thin, even film build-up by brush, dipping or spraying.
✓ Curing 20 to 60 minutes at 100 to 120 °C → fast vulcanization of the primer film in an industrial process.
✓ Maximum adhesive strength after about 4 days → post-curing at 70 to 150 °C further improves adhesion.
✓ Specifically matched to POWERSIL® XLR® 630/640 → especially suitable for bonding onto vulcanized silicone rubber of the same grade.

Typical applications

→ Surge arresters and high-voltage components
→ Cable accessories and cable fittings
→ Insulators
→ Bonding addition-curing WACKER® ELASTOSIL® RTV-2, LSR and R plus
→ Bonding WACKER® POWERSIL® RTV-2 and LSR
→ Adhesion improvement between addition silicones and already vulcanized silicone substrates

Processing instructions

Ensure the surface to be primed is dry and free from grease, oil, wax, dust, rust or other contaminants. Also remove any release-agent residue from a previous vulcanization cycle.
Clean the surface with a non-polar solvent (for example mineral spirits, boiling range 80 to 140 °C), followed by a polar solvent such as acetone. Roughen very smooth surfaces by grinding until the shine disappears and remove loose particles.
Homogenize component A and B separately before use.
Mix A and B in a 1:1 ratio by weight. The pot life of the mixed product is 2 to 3 days at room temperature, extendable to about 1 week at 6 °C.
Apply the primer in a thin layer by brush, dipping or spraying.
Vulcanize the primer film for 20 to 60 minutes at 100 to 120 °C.
Apply the silicone rubber preferably soon after heating, and no later than about 2 days after priming. Keep the primed surface free from contamination.
Maximum adhesive strength is in some cases only reached after about 4 days. Post-curing the cured rubber at 70 to 150 °C further improves adhesion.

⚠️ Fire and health warning. Due to its high organic solvent content this is a highly flammable liquid (flash point component A −4 °C, component B 3 °C). Keep away from heat, sparks and open flames, do not smoke, and take measures against static electricity. Component B may damage fertility or the unborn child. Component A can form hydrogen on contact with bases, alcohols or acids. Use only in a well-ventilated area.

Storage and shelf life

Keep opened containers well sealed and store them cool and dry. The best-before date is shown per batch on the label. Storage beyond this date does not automatically mean the product is unusable, but the properties must then be checked for the intended use.

About the manufacturer

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

Professional support

Unsure about the right surface preparation, curing temperature or the combination with a specific silicone rubber? Our specialists are happy to help you achieve a reliable bond. Contact us for tailored advice.

Product Properties

Mix ratio1:1Mixing ratio A : B
Cure time
60minutes
Time until full cure

Component Properties

Color AOpaque to whitishColor of component A
Color BClear yellowishColor of component B
Viscosity A
4000mPa·s
Viscosity of component A
Viscosity B
85mPa·s
Viscosity of component B
Density A
0.77g/cm³
Density of component A
Density B
0.73g/cm³
Density of component B

Application

Use caseAdhesion improvement between addition-curing silicones and substratesIntended use
Cure speedFastHow quickly the material can be demoulded
Cure conditionHeatCondition under which the material cures

Safety Information

GHS classification: highly flammable liquid and vapour (H225). May be fatal if swallowed and enters the airways (H304). Causes skin irritation (H315) and may cause drowsiness or dizziness (H336). May damage fertility or the unborn child (H360FD, component B). Toxic to aquatic life with long-lasting effects (H411). Component B contains a substance of very high concern (1,2-dimethoxyethane). Recommended personal protective equipment: chemical-resistant gloves (fluororubber or PE/EVOH laminate), tight-fitting safety goggles, protective clothing and, where ventilation is insufficient, respiratory protection with an ABEK filter. Use only in a well-ventilated area, away from ignition sources, and do not eat, drink or smoke while working. Wash hands thoroughly after use. This is a summary. Always consult the full Safety Data Sheet (SDS) for component A and component B for complete hazard information before working with this product.

Safety Pictograms	Safety Data Sheets (SDS)
GHS hazard pictograms Required protection (ISO 7010)	📥 EN SDS WACKER PRIMER G 791 A 📥 EN SDS WACKER PRIMER G 791 B

Signal Word	H‑code	Hazard Statement	P‑codes	P‑statements
Danger	H225	Highly flammable liquid and vapour	P210 P233 P240 P241 P280 P303+P361+P353 P370+P378	Keep away from heat, hot surfaces, sparks, open flames and other ignition sources Keep container tightly closed Ground and bond container and receiving equipment Use explosion-proof equipment Wear protective gloves/clothing/eye protection/face protection IF ON SKIN (or hair); take off immediately all contaminated clothing. Rinse skin with water/shower In case of fire; use appropriate extinguishing media
Danger	H304	May be fatal if swallowed and enters airways	P301+P310 P331 P405 P501	IF SWALLOWED; immediately call a POISON CENTER/doctor Do NOT induce vomiting Store locked up Dispose of contents/container in accordance with local regulations
Warning	H315	Causes skin irritation	P264 P280 P302+P352 P333+P313	Wash thoroughly after handling Wear protective gloves/clothing/eye protection/face protection IF ON SKIN; wash with plenty of water and soap If skin irritation or rash occurs; get medical advice/attention
Warning	H336	May cause drowsiness or dizziness	P261 P271 P312	Avoid breathing vapours/spray Use only outdoors or in a well-ventilated area Call a POISON CENTER/doctor if you feel unwell
Danger	H360	May damage fertility or the unborn child	P201 P202 P280 P308+P313 P405 P501	Obtain special instructions before use Do not handle until all safety precautions have been read and understood Wear protective gloves/clothing/eye protection/face protection IF exposed or concerned; get medical advice/attention Store locked up Dispose of contents/container in accordance with local regulations
Warning	H411	Toxic to aquatic life with long lasting effects	P273 P391 P501	Avoid release to the environment Collect spillage Dispose of contents/container in accordance with local regulations

More information about H and P statements: UK HSE &ECHA

Technical data sheets

Frequently asked questions

What is the delivery time for my order?

Orders placed and paid on working days are in most cases shipped the same day. Weekend orders are processed on the next working day.

Indicative delivery times: Netherlands usually within 1 working day, Belgium and Germany typically 1–2 working days, other countries depending on destination and carrier. These are guidelines, not guarantees: peak periods, public holidays or carrier delays can have an effect.

What is the return policy?

You have 30 days to return after receipt. Email info@siliconesandmore.com within 30 days of delivery with your name and order number. The full conditions are in our return policy.

How can I track my order?

As soon as your order has shipped, you'll receive a track & trace code by email. It can take up to 24 hours before the code is active.

I have a problem with my order – how do I reach you?

Contact us via our contact page or email info@siliconesandmore.com. We're happy to help you quickly.

Can I order as a business?

Yes. Apply for a business account; we review your application within 3 working days. After that you order while logged in and pay on invoice, with payment terms of 14 days after delivery.

EU businesses outside the Netherlands with a valid VAT number order with VAT reverse-charged (0%, intra-community supply). The VAT number is stored in your business account; it cannot be added to an order after it has been placed.

WACKER Primer G 791 A/B – Addition-curing primer for silicone rubber & substrate adhesion