Short answer
Silicone is the one for glass, windows, weather joints and wet areas. It lasts in sun and rain but won’t take paint. Polyurethane is tough and paintable, and common in concrete and floor joints. Hybrids seal and bond and can usually be painted. We make silicones and acrylics, not PU or hybrid.
All three stay flexible after they cure. They differ in how they handle sun, whether you can paint them, what they stick to and whether they can hold a load.
Seal, bond or both?
Sort this out first. A sealant closes a joint and moves with it. An adhesive holds parts together. Hybrids and polyurethanes are often sold as both; silicone is mainly a sealant. If the bead has to hold something up, you’re choosing an adhesive, and that’s a different decision. See sealant vs caulk vs adhesive.
Silicone
Silicone stays elastic for years in sun and rain, sticks well to glass, glazed tile and metal, and copes with wet areas. It is the standard for window perimeters, glazing top seals, curtain wall joints, bathrooms and kitchens. The downsides: you can’t paint it, and it isn’t made for joints that are walked or driven on.
It comes in two cure types. Acetoxy silicone smells of vinegar, cures fast and grips glass hard, but it can attack natural stone and some metals. Neutral-cure is gentler, and goes on masonry, concrete, stone and most plastics. Our neutral vs acetoxy guide explains the difference.
- Pereseal N: neutral-cure weather silicone, ±30% movement, for windows, cladding and exterior joints
- Pereseal AF: neutral-cure with fungicide, ±30% movement, for bathrooms and kitchens
- Pereseal 802: acetoxy glass and metal silicone, certified to ASTM C920 Class 25, for glazing
- Pereseal MP: general-purpose acetoxy silicone, ±25% movement
Polyurethane
PU sealants are tough, tear-resistant and usually paintable. They’re common in concrete movement joints, precast panel joints and floor joints that take foot or vehicle traffic. They are less UV-stable than silicone, and often need a primer on porous surfaces.
We don’t make a PU sealant. If your joint needs one, we’ll say so rather than sell you a silicone that doesn’t fit.
Hybrid (MS polymer)
Hybrids sit between the two. They seal and bond, can usually be painted, and many are low-odour and go on damp surfaces. Their strong initial grab makes them popular as construction adhesives. Formulations vary a lot, so compare actual products, not the category.
We don’t make a hybrid either.
Which one for which job
Window perimeter or exterior weather joint
Neutral-cure silicone: Pereseal N.
Glazing top seal, glass to metal
Acetoxy silicone: Pereseal 802.
Bathroom or kitchen
Anti-fungal neutral silicone: Pereseal AF.
Indoor gap that will be painted
Acrylic: Pereseal 702.
Painted exterior movement joint, or a floor joint
Polyurethane or hybrid. Silicone won’t take paint or traffic.
Bonding panels or fixtures
A hybrid or construction adhesive.
Tell us about the joint
What’s on either side, how much it moves, and whether it gets painted or walked on. We’ll tell you if one of ours fits.
Contact us
