Primer for Silicone Rubber Most silicones do not bond chemically to a surface. A primer must therefore be used to promote adhesion. Our silicone primers activate the surface via OH bridges and silane/siloxane chemistry, so that silicone rubber (RTV-2/LSR) bonds reliably to glass, metal, aluminium, ceramics, selected plastics and even...
Primers for silicones (5)
Primer for Silicone Rubber
Most silicones do not bond chemically to a surface. A primer must therefore be used to promote adhesion. Our silicone primers activate the surface via OH bridges and silane/siloxane chemistry, so that silicone rubber (RTV-2/LSR) bonds reliably to glass, metal, aluminium, ceramics, selected plastics and even wood. Choose a toluene-free primer where required and match the layer thickness to the substrate for maximum adhesion.
Layer thickness rule: on non-absorbent substrates (glass/metal/aluminium) the primer must be applied ultra-thin—practically monomolecular. On absorbent substrates (wood, porous) more can be applied, or choose a more viscous primer.
When do you use a primer for silicone rubber?
- →Bonding RTV-2/LSR silicones to glass, steel, aluminium, ceramics or coated substrates
- →On wood or other absorbent substrates for better keying and a longer open time
- →As an adhesion promoter before overmoulding/coating or insert moulding of silicone parts
Layer thickness & substrate
Non-absorbent (glass, metal, aluminium)
- Degreased, dry and dust-free
- Apply ultra-thin (cloth/pad/HVLP): the film should be barely visible
- Allow to flash off as per TDS; apply the silicone within the processing window
Absorbent (wood, porous)
- Use a viscous or 2-component silicone primer
- Saturate evenly; wipe off excess material
- Observe the drying/reaction time for best adhesion
Silicone primers – product overview
| Product | Feature | Substrates / Use | Advantages |
|---|---|---|---|
| WACKER PRIMER G790 (toluene-free) | 1-component, fast film formation; toluene-free solvent | Glass, metal, aluminium, ceramics | Toluene-free, clean process, industry standard |
| WACKER PRIMER G795 | 1-component siliconate/silane primer | Glass/steel/aluminium, coated substrates | Proven adhesion for RTV-2 and LSR |
| WACKER PRIMER G791 A/B | 2-component primer for critical adhesion | Metals, engineering plastics (after testing) | Long open time, high shear/peel strength |
| ELASTOSIL® AUX G 3243 | Primer/additive for ELASTOSIL systems | Versatile; thin activation film | Stable, uniform primer layer |
| WACKER PRIMER AV (SLM 74300) | 2-component, higher viscosity | Wood, absorbent substrates, aluminium | Good penetration, long working time |
Application & processing – silicone adhesion promoter
- Clean/degrease: remove dust, grease and release agents (use a suitable mould cleaner/degreaser)
- Apply thinly & evenly: as thin as possible on dense substrates; saturate absorbent substrates without letting it "run"
- Observe flash-off/drying time: follow the TDS (temperature/humidity)
- Process the silicone within the window: if exceeded, prime again
- Adhesion test: small peel/shear trial before series production
Frequently asked questions about silicone primers
Does this work with both addition-cure (platinum) and condensation-cure silicones?
Yes, but check the individual product data sheet. Most of the primers above are designed as adhesion promoters for RTV-2/LSR and perform best with addition-cure systems.
How thin is "thin enough" on glass/metal?
An almost invisible film: practically monomolecular. Layers that are too thick reduce adhesion and can become brittle.
When should I choose a 2-component silicone primer?
For critical substrates or absorbent surfaces (e.g. wood), or when you need a longer open time and higher ultimate adhesion (G791 A/B, AV).
Is G790 really toluene-free?
Yes, G790 is specifically formulated as a toluene-free primer. Always check the current TDS/SDS for the solvent profile.
Advice & ordering
Unsure whether to choose G790 (toluene-free), G795, G791 A/B, ELASTOSIL® AUX G 3243 or Primer AV? We will quickly help you with substrate selection, layer thickness and processing.
Here is an overview of primers and when to use them:
Primers for silicones overview.pdf
Here is a useful general guide on how best to use Wacker primers:
EN - Priming guide for RTV Silicones by Drawin.pdf
If you cannot decide which primer works best, we are happy to help!
For more information, you can also read this brochure: