SPECIALTY ADHESIVES
PRESSURE SENSITIVE ADHESIVES are applied to a surface and permitted to dry. That surface will then adhere to most other materials on contact with pressure. Bonds may be temporary or permanent. These adhesives are usually made from natural or synthetic rubber.
SELF-SEAL OR COHESIVE (COLD SEAL) LATEX ADHESIVES - an adhesive that will adhere only to itself. Bond strength is variable and may be permanent or resealable. May be used as a protective coating that will not transfer to the material being coated.
HEAT SEAL ADHESIVES are waterborne resin heat seal adhesives. Heat seals are applied to one surface and dried. Adhesive is then activited for bonding by applying heat. Temperatures required vary from 175°to 300°F depending on adhesive.
FUGITIVE ADHESIVES form a temporary bond between two materials. The two materials may then be separated without damaging either surface. Made from natural rubber latex, it has no tack, dries clear, and is non-staining.
What is catalyst? The catalyst is what causes the RTV to cure or harden. It is either tin or platinum base. The tin base systems are much more user friendly and will harden against practically any surface.
What rubbers are compatible to pour over one another?
You can pour tin over tin base, platinum over platinum base and tin over platinum base. You can not pour platinum base over tin base as the tin will inhibit (not allow) the platinum to cure where it comes in contact with tin (mold surface).
Is there anything I can do to prolong the life of the mold?
Using mold release before pouring parts can double the life of your mold. Over time, the silicone oil will absorb into the silicone rubber mold to replenish some of the oil that has been lost during normal casting and demolding of your parts. The other option is to use a bake out process. A bake out process of the silicone rubber will help remove hardeners, plasticizers, and other materials that leach out of the casting resin materials that are on the molds surface. A slow gradual bake of 200 degrees F for 8 hours or 400 degrees F for 2 hours is recommended. This will also draw silicone oil within the rubber mold back to the surface to replenish what has been depleted. It is recommended to do this throughout the entire life of the mold rather than only when the mold dries out and is near the end of its life.
What is vacuuming and why should I do it?
Vacuuming: A vacuum pump is like a vacuum cleaner. A vacuum cleaner is designed to pick up things such as dirt off of carpet using suction or vacuum. A vacuum pump is identical to a vacuum cleaner, except it will have MUCH more suction. A vacuum system is measured in the amount of vacuum it will pull. In technical terms, it is measured in inches of mercury. A common household vacuum will pull 1-2 inches of mercury. A good vacuum pump will pull 29-30 inches of mercury. A vacuum pump is used to suck the air from the mixed silicone to assist in pouring air/void free molds. The concept is that when we mix the silicone we mix in tons and tons of air into the mix. Ideally, we want to remove the air from the mixed rubber so it doesn’t end up in our cured rubber mold and we’re really trying to avoid any air bubbles from sticking onto our original parts surface that would show up in our cured silicone rubber mold. When you put the mixed rubber that is full of tiny air bubbles under vacuum, it makes those air bubbles expand into big air bubbles which now have the buoyancy to float to the top and pop which removes them from your liquid rubber. If they remain small, they do not have the buoyancy required to float through the thick consistency of the rubber and get to the top. The thicker the rubber the harder it is for small bubbles to float and hence the need for the vacuuming rises. Vacuuming Silicone: Our QuickSet Silicone has a thin enough viscosity the majority of air bubbles will rise to the surface without a vacuuming system. Therefore, you must pull a vacuum to assure no air is entrapped. Once your vacuum reaches 29-30 inches of mercury, the rubber will foam up. You will need a container around 4 times the size of the amount of silicone you are mixing. Once the rubber has risen, it will break (meaning to fall quickly). After the silicone falls, you will want to keep it under vacuum for another 2-3 minutes. Then remove the material from the vacuum and pour the rubber over your master. You may want to pull a second vacuum after the mold has been poured. This will remove any air that you may have entrapped while pouring. Remember, once the rubber has risen and fallen, it will not rise again. Our Vacuum Chambers are 10” x 12”.
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