Polyurethane vs silicone sealant: which one for the job
Cranco carries both. The chemistry decides how fast it skins, what it sticks to, and whether you can paint it.
The two polyurethanes Cranco carries are paintable. None of the silicones is.
Which to take
Take polyurethane where the joint has to be painted, and on concrete and masonry. Dymonic 100 and Vulkem 116 are both paintable, both list concrete and masonry, and Dymonic 100 is rated +100/-50% in the field.
Take silicone on glass and metal, and where you need it to skin fast. DOWSIL 790 skins in 9 minutes, DOWSIL 795 in 15 and Tremsil 200 in 20, against Dymonic 100's 2 to 3 hours and Vulkem 116's 6.
Dow says the paint film will not stretch with a silicone bead and will crack, peel and most likely not adhere. That is the line to remember when a painter follows you onto the job.
The polyurethanes Cranco carries
| Product | Chemistry | Movement capability | Skin time | Paintable |
|---|---|---|---|---|
| Dymonic 100 | Polyurethane | +100/-50% (field, ASTM C719 Modified); ±50% (ASTM C719 standard) | 2 to 3 hours | Yes |
| Vulkem 116 | Polyurethane | 25 % | 6 hours | Yes |
| TremGlaze U1500 | Polyurethane | 25 % | 6 hours | Yes |
The silicones Cranco carries
| Product | Chemistry | Movement capability | Skin time | Paintable |
|---|---|---|---|---|
| DOWSIL 790 Silicone Building Sealant | Silicone | ASTM C719 extension/compression +100/-50%; ISO 9047 ±25% (highest category) | 9 minutes (23°C, 50% R.H.) | No |
| DOWSIL 795 Silicone Building Sealant | Silicone | ±50 percent | 15 minutes | No |
Is polyurethane or silicone the better sealant?
Neither is better. Polyurethane is the paintable one and it belongs on concrete and masonry that moves. Silicone skins in minutes and holds on glass and metal, and the ones Cranco carries are not paintable.
Product pages and related comparisons
- Caulking, sealant and PU foam The full range
- Caulking against sealant
- Dymonic 100 against Vulkem 116 Two polyurethanes head to head
- DOWSIL 791 against DOWSIL 795 Two silicones head to head