The following information represents, in general terms, the most frequent and common technical questions that are asked of our CSC department. As you consider this information, keep in mind that application details and circumstances can vary. For detailed information regarding specific applications, refer to Geocel's product technical data sheets and SDS.
What is the function of a sealant? A sealant prevents the elements (wind, rain, heat, cold, etc.) from penetrating the skin of a building. The appropriate sealant will maintain an impenetrable seal and will allow for thermally induced movement between dissimilar and similar substrates. Quality sealants must also be resistant to ultraviolet exposure and should be aesthetically pleasing and complement the building facade.
What is adhesive and cohesive failure? Cohesive failure refers to failure within the sealant itself. When the sealant fails it leaves behind residual sealant at the joint face or substrate. Adhesive failure refers to failure exhibited by the sealant pulling away clean from the substrate.
What is the difference between a one-component and a two-component sealant? One-component: no mixing required, no special equipment needed, requires exposure to atmospheric moisture, color produced during manufacture, limited shelf life, cures from exposed surface inward, and generally has a slower cure speed. Two-component: mixing required, bulk guns and mixing paddles needed, cures without exposure to atmosphere, color added at job site, extended shelf life, cures uniformly and generally has a faster cure speed.
What is the effect of temperature on typical architectural sealants? Most sealants will cure slower at lower temperatures and faster at higher temperatures. The ideal temperature range for most sealants is 50°F to 80°F.
Is priming required prior to applying sealant? Many sealants do not require priming. However, if field adhesion testing exhibits adhesive failure and cohesive failure is not achieved, then a primer should be utilized.
General Product Information
Coating Surfaces: We do not recommend that ANY of our products be used as a complete surface coating, only as repair products in smaller area applications.
All of our brushable products are solvent-based, so when they are used as a coating they do not let the substrate breathe. An example would be a brick chimney coated with 2310® Tripolymer Brushable Repair Coating or Pro Flex® Multi-Purpose Brushable Repair Coating. The sealant will trap any natural moisture that is in the brick and when temperatures are at or below freezing, the water molecules will expand. The stress caused by the expansion and contraction could crack the brick. Appropriate use for 2310 Coating or Pro Flex Multi-Purpose in this situation would strictly be to coat small cracks or the chimney cap only.
Multiple Coats: When using our brushable products, a second coat can usually be applied after 24 hours. We would recommend two thin coats instead of one thick coat. A thin coat would be 1/32", thick coat about 1/16".
Application on Rubber: GeoGreen 4500® Roof Bonding Sealant, 4515 Semi-self-leveling Repair Sealant, and Geocel ADVANCED RV EPDM® Roof Sealant are products suitable for use on rubber roofing. Examples of substrates include EPDM, TPO*, PVC*, Hypalon®, and Neoprene.
GeoGreen 4500 Sealant and Geocel ADVANCED RV Sealant are cartridge grade sealants that can be used as a lap adhesive or a scrim edge sealant for rubber. For a pourable sealant that works on black EPDM, TPO*, and PVC*, we recommend using 4515 Sealant.
*Primer required on TPO and PVC substrate applications. Geocel recommends using 45P Low VOC, TPO & PVC Primer.
Application on Styrofoam (polystyrene): The only products that will not harm Styrofoam® are our water-based sealants and adhesives. Anything that contains solvent will eat through Styrofoam.
Traffic Bearing Surfaces: For traffic bearing surface applications, we recommend using 1500SL Premium Self-leveling Concrete Joint & Crack Sealant or GeoGreen 4500 Sealant. For foot traffic, consider using 3300® Professional Grade Polyurethane Sealant or 3500 Roof Tile Adhesive/Sealant. 2315LRF Repair Coating, Instant Roof Repair Coating or Geobond Roof Repair Coating will handle intermittent foot traffic only.
Underwater Applications: We do not offer any products that will withstand constant underwater exposure. The most common places that people have asked to use our products are in birdbaths, fish ponds, fountains and swimming pools. We also receive occasional questions regarding water tanks and water troughs for animals. Typically, the products they want to use are our solvent-based sealants, which are NOT recommended for use in these applications. Customers with these types of questions should refer to pool supply stores or pet stores for acceptable sealants.
Rain/Water Resistance: Some of our products can be applied in the rain (2315LRF Repair Coating, Instant Roof Repair Coating, Geobond Roof Repair Coating, and GeoGreen Pro® Gutter Seal, for example). 2300 Sealant, Pro Flex Sealant, 2310 Sealant, and Pro Flex Multi-Purpose will withstand light rain immediately after application. All of our solvent-based and reactive products can withstand rain after 24 hours. All other water-based products need to be fully cured to withstand water as they are water soluble. Most of our products can be applied to damp surfaces, but not wet surfaces. An exception to this rule is many of our Scypolymer® products, such as GeoGreen 4500 Sealant and Pro Gutter Seal, which can be applied in ponding water situations.
Characteristics of Old Material: Ever have a situation where the product is difficult to work with, doesn't look quite right, or just won't stick to the substrate? The culprit may be product that is past its shelf life. Some characteristics to look for that will help determine if it is, in fact, old material include:
- Product will not come out of the tube or is hard to gun
- Product may gun, but is too thick to tool
- Product will not adhere to the substrate
- Product will not cure properly
If any of these characteristics arise, the best course of action is to complete the project using "fresh" product.
Out-gassing (bubbles forming in product after application): When bubbles form in a bead of product, or even under an area of brushable product, this is called out-gassing. This means that there is air or moisture trapped under the sealant. This usually occurs in sunny areas because the sun heats up the moisture and causes a vapor to form. Once it has turned to a vapor, it tries to escape, causing air pockets. An easy fix to this is to cut the bead open allowing the vapor to escape and then reapply the sealant.
Product Not Adhering: The most common reason a product won't adhere to a substrate is the presence of silicone from a previous application. In applications where silicone has previously been applied, no new sealant can be applied until all of the old silicone and its residue has been removed, and the area cleaned with a silicone remover. Silicones are not paintable and they will not stick to themselves.
Another possible reason is that the product is past its shelf life. Or, another reason could be the type of substrate. Most of our products do not stick well to new cedar or other exotic woods. These woods have oils in them that prevent our products from adhering. Old or weathered woods do not seem to cause this problem.
Odor Present During Cure: All of our solvent-based products have a strong odor during cure. 8125® 100% Silicone High Performance Acetoxy Cure Sealant has a vinegar smell during cure. Odor from these products will dissipate during cure and will disappear once they are fully cured. This usually happens in 5-7 days, depending on the product and ventilation. Any product that has these odors is not recommended for indoor use. If it is a situation where the product has been applied indoors, we recommend fresh air ventilation of the area, if possible. The odor may have short-term effects on those who are sensitive to these types of odors. There are no known long-term effects. Please refer to the product's technical data sheet for full and complete application specifications.
Shelf Life: Most of our products have a shelf life of one year from the date it was manufactured.
Application Temperature: The range (degrees) in which a sealant can be safely and properly applied without damage to the sealant's performance.
Service Temperature: The range (degrees) in which a sealant can perform safely and effectively. Though application and service temperatures overlap, they are distinctly different and important to understand. Service temperature is usually a wider range than the application temperature.
Twelve Factors to Consider When Designing a Joint Subjected to Movement
1. Sealants do not change their volume with compression or extension, only their shape.
2. With a given sealant and given conditions, the shape factor of the joint will determine its performance.
3. Bond breakers should be utilized with deep joint applications.
4. Both the structure and the sealant will expand and contract with temperature changes.
5. As the temperature falls, the force required to stretch the sealant increases. The lowest service temperature should be used as the basis for selecting the sealant.
6. Joint surfaces to be sealed should be dry, clean, and free of any contaminants such as dirt, grease, paint or laitance. Imperfect joint surfaces should be treated with an appropriate primer.
7. Differential coefficients of thermal expansion for various construction materials will affect joint size and spacing in all types of structures. As an example, aluminum will heat up, expand and then cool off and contract faster than concrete.
8. Elastomeric sealants should not be covered with rigid or brittle materials above or below because adhesion to these will prevent necking down of the sealant during extension. If the sealant is not allowed to bridge the widened joint by necking down, it will fail.
9. The hardness of the specified elastomeric sealant should be determined by service temperature, anticipated movement, and resistance to abrasion or traffic.
10. All joints subjected to movement should be kept in line, both vertically and horizontally.
11. Joints should be designed to be accessible for inspection and repair.
12. Quality workmanship in preparing surfaces and applying sealants is critical for success.