The Smooth-Cast™ Semi-Rigid line of low-cost semi-rigid urethane casting resins cure quickly to semi-rigid plastics that offer excellent impact resistance. These plastics are easy-to-use (mix ratio is 1A:1B by volume) and have low viscosities for minimal bubble entrapment. Vibrant colors are possible by adding SO-Strong™, UVO™ or Ignite™ colorants.
These semi-rigid plastics are good for making impact resistant prototypes, models, toys, props, climbing holds, etc.
Smooth-Cast™ 66D is a grey resin with a 7 minute pot life and 60 minute demold time.
NOTE: Do not use Smooth-Cast™ 66D for roto casting.
Safety - Materials should be stored and used in a warm environment (73° F/23° C). These products have a limited shelf life and should be used as soon as possible. All liquid urethanes are moisture sensitive and will absorb atmospheric moisture. Mixing tools and containers should be clean and made of metal, glass or plastic.
Mixing should be done in a well-ventilated area. Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk.
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 plastic.
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.
IMPORTANT: Shelf life of product is reduced after opening. Remaining product should be used as soon as possible. Immediately replacing the lids on both containers after dispensing product will help prolong the shelf life of the unused product. XTEND-IT™ Dry Gas Blanket (available from Smooth-On) will significantly prolong the shelf life of unused liquid urethane products.
MEASURING & MIXING...
Liquid urethanes are moisture sensitive and will absorb atmospheric moisture. Mixing tools and containers should be clean and made of metal, glass or plastic. Materials should be stored and used in a warm environment (73°F/23°C).
The components (Parts A and B) should be at room temperature (73°F/23°C). Combine equal amounts of Parts A & B by volume in a mixing container. Make sure that you scrape the bottom and sides of your container several times. Do not delay between mixing and pouring. Also, the higher the mass concentration, the faster the material gels and cures.
Pouring - For best results, pour your mixture in a single spot at the lowest point of the containment field and let the mixture seek its level. This will help minimize air entrapment.
For Best Results - Best results are obtained using a pressure casting technique. After pouring the mixed compound, the entire casting assembly (mold, dam structure, etc.) is placed in a pressure chamber and subjected to 60 PSI (4.2 kg/cm2) air pressure for the full cure time of the material.
Curing - Warning: Fumes, which may be visible as this product starts to “gel” and cure, will dissipate with adequate ventilation. Only use this product with room size ventilation and do not inhale/breathe fumes. Castings will be extremely hot immediately following cure and may burn the skin. Let cool to room temperature before handling.
Performance - Cured castings are durable. They resist moisture, solvents, moderate heat, dilute acids and can be machined, primed/painted or bonded to other surfaces (any release agent must be removed). If machining cured material, wear dust mask or other apparatus to prevent inhalation of residual particles. Castings can be displayed outdoors after priming and painting. Unpainted castings will yellow over time - more quickly when exposed to ultra-violet light.
Because no two applications are quite the same, a small test application to determine suitability is recommended if performance of this material is in question.