Description
This silicone mold rubber is designed for high heat resistance, capable of withstanding temperatures up to 294°C (560°F). It has a low mixed viscosity and exhibits very low linear shrinkage once cured. The mix ratio is 100A:3B by weight, with a pot life of 40 minutes and a cure time of 24 hours. It is suitable for making foundry patterns, flat pattern reproductions, and casting low-melt metal alloys like tin and pewter.
Features
- High heat resistance up to 294°C (560°F)
- Low mixed viscosity
- Very low linear shrinkage
Technical Properties
- Mix Ratio By Weight: 100A:3B
- Pot Life: 40 minutes
- Cure Time: 24 hours
- Shore Hardness: 60 A
- Specific Gravity: 1.45 g/cc
- Specific Volume: 0.69 cm³/g (19.1 cu. in./lb.)
- Color: Red
- Tensile Strength: 2.74 MPa (398 psi)
- 100% Modulus: 2.28 MPa (331 psi)
- Elongation at Break: 132%
- Die B Tear Strength: 11.0 kN/m (63 pli)
- Useful Temperature Range: -54°C to 294°C (-65°F to 560°F)
- Dielectric Strength: >500 volts/mil
- Dielectric Constant, 100Hz: 3.4
- Dissipation Factor, 100Hz: 0.02
- Volume Resistivity: 9.0E+14 ohm/cm
- Thermal Conductivity: 0.347 W/m·K
- Shrinkage: 0.0015 mm/mm
- Mixed Viscosity: 20,000 mPa·s
Instructions
Preparation
Store and use materials at room temperature (23°C/73°F). Use products promptly due to limited shelf life. Wear safety glasses, long sleeves, and rubber gloves. Sulfur-based clays may inhibit curing, causing tackiness or incomplete curing. Test compatibility by applying a small amount of rubber to a non-critical area. If rubber remains gummy or uncured, inhibition has occurred.
Applying A Sealer / Release Agent
To prevent inhibition, apply a clear acrylic lacquer as a barrier coat and let it dry thoroughly. A release agent can ease demolding. Ease Release™ 200 is recommended for silicone molds. Lightly brush the release agent over all surfaces, then apply a light mist coating and let dry for 30 minutes.
Measuring & Mixing
Pre-mix Part A thoroughly. Weigh and mix parts A and B for 3 minutes, scraping the container sides and bottom. Vacuum degassing is recommended to remove air. Use a vacuum pump pulling at least 29 inches of mercury (1 Bar / 100 KPa). Allow room for material expansion. Vacuum until material rises, breaks, and falls, then continue for 1 minute.
Pouring / Curing / Post Curing
Pour mixture at the lowest point of the containment field, allowing it to flow uniformly. Ensure the liquid rubber levels at least 1.3 cm (1/2”) over the model's highest point. Cure for at least 24 hours at room temperature before demolding. Post cure for 4-5 hours at 65°C (150°F) to remove residual moisture and alcohol. Cool mold to room temperature before use. Do not cure below 18°C (65°F).
Decreasing Demold Time with Accel-T™ Silicone Cure Accelerator
Pre-mix Accel T™ with Part B before adding Part A. Note that working time is reduced, and library life of cured rubber decreases with more Accel-T™.
Using The Mold
New molds have natural release properties. Over time, mold lubricity may decrease, causing parts to stick. No release agent is needed for wax or gypsum. Use Ease Release™ 200 for polyurethane, polyester, and epoxy resins to extend mold life. For a dry matte finish, refer to Smooth-On’s FAQ for powder coating techniques. Improve low melt metal casting surface finish by dusting the mold cavity with talcum powder, brushing it on, and removing excess before casting. Use a dust mask when handling talc.
Mold Performance & Storage
Mold life depends on usage. Abrasive materials like concrete can erode detail, while non-abrasive materials like wax do not. Clean molds with soap solution and dry before storage. Assemble multi-part molds and store on a level surface in a cool, dry environment.
