DOWSIL™ 790 Silicone Building Sealant
Features &Benefits
• Low-staining and plasticizer free, suitable for porous substrates
• Excellent performance even in building joints that experience extreme movement
• Extension/compression capability of +100/-50 percent
• Conforms to ISO 11600F-25LM
• Excellent weathering properties and resistance to sunlight, rain, snow, and temperature extremes • Excellent unprimed adhesion to masonry, concrete and natural stone substrates
• Easy application over a wide temperature range
Applications
• Sealing of joints between natural stone
• Sealing of curtainwall joints and mullion joints
• Sealing of expansion and control joints
• Sealing of precast concrete panel joints and many other construction joints
Typical Properties
| Test | Property | Unit | Result |
| As Supplied | |||
| CTM1 98 | Skin-over Time (23°C, 50% R.H.) | min | 9 |
| CTM 95 | Tack-Free Time (23°C, 50% R.H.) | min | 31 |
| CTM 663 | Cure Rate (23°C, 50% R.H.) | ||
| 1 Day | mm | 2.8 | |
| 3 Days | mm | 5.8 | |
| As Cured – After 28 Days at 23°C and 50% RH | |||
| CTM 99 | Durometer Hardness, Shore A | 11 | |
| ISO2 8339 | Modulus 100% | MPa | 0.08 |
| ISO 8339 | Elongation at Break | % | 840 |
| ISO 7389 | Elastic Recovery | % | 78 |
| ASTM3 C719 | Joint Movement Capabilities According to ASTM Standard Extension/Compression | % | +100/-50 |
| ISO 9047 | Joint Movement Capability According to ISO Standard | % | ±25 (highest category) |
| ASTM C 1248 | Staining, Various Substrates | None |
How to Use
Surface Preparation:Ensure that surfaces to be sealed are clean, dry, sound and grease-free. Porous substrates such as concrete, brickwork, mortar, etc. must be mechanically cleaned of loose particles using a steel brush, sanding disc or any similar means. Clean non-porous surface with DOWSIL™ R-40 Universal Cleaner, dry thoroughly with a clean, lint-free cloth and wait for at least half an hour before application of sealant. Note: When using any solvent, always provide adequate ventilation. Avoid heat, sparks and open flames. Use solvent resistant gloves. Observe and follow all precautions listed on solvent container label.
Masking:
Areas adjacent to the joints should be masked with tape to prevent contamination of the substrates and to ensure a neat sealant line.Masking tape should be removed immediately after tooling.
Priming:Primers are not usually required on stone, concrete and masonry substrates. On nonporous substrates such as anodized aluminum, priming might be needed. It is recommended to carry out test on such substrates to assess the need for priming. A suitable primer on non-porous substrates is DOWSIL™ 1200 OS Primer. Allow at least half an hour between priming and sealant application. Please contact Dow’s technical service in case of doubt.
Back-up Materials: Where back-up material is required, open cell backer rod is recommended. Back-up materials provide back pressure and avoid three sided adhesion that limits sealant movement capability.
Finishing: The joint should be tooled within 5 minutes of application to ensure good contact between the sealant and the substrate. Tooling of the sealant also gives a smooth, professional finish.
Clean-Up: If sealant is misapplied to porous substrates, it should be left until it is just cured and then removed by peeling, cutting or other mechanical means. Care should be taken not to damage plastic or coated surfaces.
Usable Life and Storage
When stored at or below 32°C, DOWSIL™ 790 Silicone Building Sealant has a shelf life of 12 months from date of manufacture. Refer to product packaging for “Use By” date.
Limitations
This product is neither tested nor represented as suitable for medical or pharmaceutical uses.
