MS sealant — modified silane, sometimes written SMP — is the answer to one specific problem: silicone cannot be painted. If a joint has to move and then disappear under a coat of paint, silicone is ruled out no matter how good its other figures are. MS polymer is what fills that gap.
What MS sealant actually is
The backbone is a polyether chain terminated with silane groups. It cures with atmospheric moisture, like silicone and like polyurethane, but the chemistry contains no isocyanates and no solvents. That is the practical difference behind most of the claims made for it: low odour on site, no solvent shrinkage as it cures, and a safety profile that keeps it usable in occupied interiors.
What it does well
- Paintable once cured. The property nothing in the silicone family can offer.
- Bonds without primer to most construction substrates — timber, metal, stone, concrete, most plastics. Silicone families each have substrates they must avoid; MS is unusually forgiving.
- Non-staining on porous stone. No plasticiser migration, so no shadow along the joint on marble or granite.
- Bonds to damp substrates, which matters more on a real site than in a laboratory.
- Low odour, no solvents — usable indoors while other trades are working.
What it does not do
MS is a compromise chemistry and it is worth being honest about the cost of the compromise. It does not match a structural silicone for long-term UV and heat resistance, so it is not the material for a glass curtain wall — that is what HP-9900 at ≥1.8 MPa and −50 °C to +150 °C exists for. It is also more expensive per cartridge than either silicone or acrylic, so specifying it where a silicone would do is money spent for nothing.
Where it belongs
- Joints that will be painted or over-coated
- Door and window perimeters in finished interiors
- Mixed-substrate bonding where one adhesive has to hold timber, metal and stone
- Interiors where solvent odour is a problem
- Natural stone joints where staining is unacceptable
Our MS range
We have not published figures for this range yet. That is deliberate: every number on this site traces to a product datasheet or the printing on the cartridge, and until we can stand behind the MS figures they do not go on a page. Tell us the application and we will send the current datasheet directly.
If the joint does not need painting, you are almost certainly better served by a silicone — see the full chemistry comparison, or go straight to neutral silicone for facades and stone and acid silicone for glass.
