These products have a limited shelf life and should be used as soon as possible. This material should be stored and used at room temperature (73°F/23°C). This material may congeal if exposed to cold temperatures. To reconstitute, Part A & B must be heated to 90°F (33°C) then thoroughly mixed to an even consistency. This material is moisture sensitive, so relative humidity should be below 50%. Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Room size ventilation is necessary.
Applying A Release Agent – A release agent is necessary to facilitate demolding when casting into or over most surfaces. Use a release agent made specifically for mold making (Universal™ Mold Release or Mann’s Ease Release™ 200 available from Smooth-On or your Smooth-On distributor). A liberal coat of release agent should be applied onto all surfaces that will contact the material.
IMPORTANT: To ensure thorough coverage, apply release and brush with a soft brush over all surfaces. Follow with a light mist coating and let the release agent dry for 30 minutes.
Smooth-On silicone rubber molds usually do not require a release agent unless casting silicone into the mold. Applying a release agent will prolong the life of the mold.
Selecting A Mold Rubber – Pour into a urethane rubber mold (release agent required) or a silicone rubber mold. To prevent cure inhibition, post-cure newly made tin silicone molds for 8 hours at 60°C/150°F and let cool prior to casting. If you are unsure about surface compatibility, a trial casting should be made.
Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.
MEASURING & MIXING…
Liquid urethanes are moisture sensitive and will absorb atmospheric moisture resulting in bubbles in the cured rubber. Mixing tools and containers should be clean and made of metal or plastic.
Shelf life of product is drastically reduced after opening. Immediately replacing the lids on the containers after dispensing product will prolong the shelf life of the unused product. XTEND-IT™ Dry Gas Blanket (available from Smooth-On) will prolong the shelf life of unused liquid urethane products.
IMPORTANT: Pre Mix the Part B before using every time.
Hand Mixing – After weighing and dispensing the required amounts of Parts A and B into mixing container, mix thoroughly for at least 60 seconds making sure that you scrape the sides and bottom of the mixing container several times. Pour entire quantity into a new, clean mixing container and mix again as directed above.
Mechanical Mixing – drill mix using a Turbine mixer or equal for 30 seconds followed by careful hand mixing for 30 seconds as directed above. Then, pour entire quantity into a new, clean mixing container and repeat mixing procedure.
Be Aware – material pot life is 4 minutes at 73°F/23°C. Pot life at elevated temperatures will be less. Do not delay between mixing and pouring.
Although this product is formulated to minimize air bubbles when cured, vacuum degassing will further reduce entrapped air. A pressure casting technique using a pressure chamber can yield totally bubble free castings. Contact Smooth-On or your distributor for information about vacuum degassing or pressure casting.
Pouring – For best results, pour your mixture in a single spot at the lowest point of the containment field. Let the rubber seek its level A uniform flow will help minimize entrapped air.
Curing – Allow casting to cure for at least 2 hours at room temperature (73°F/23°C) before demolding. Do not cure rubber in temperatures less than 65°F/18°C. This material will reach full cure in 48 hours at 73°F/23°C.
Heat Curing – Allow casting to cure for 24 hours at room temperature (73°F/23°C). Heat cure casting at 140°F/60°C for 6 hours. Allow casting to cool to room temperature before handling.
Performance & Storage – Fully cured rubber is tough, durable and will perform if properly used and stored. The physical life of the rubber depends on how you use it. Contact Smooth-On directly with questions about this material relative to your application.