Brand Silastic Application Type Mold-Making 1 Part or 2 Part 2 Part Material Form Fluid Substrate Casting plastics Manufacturer Dow Chemistry Silicone rubber Cure Method Heat, Base/Curing Agent Cure Temperature (°C) 25, 25, 52, 65, 93, 121, 149 Cure Time (min) 960, 960, 60, 30, 15, 7, 5.00 Viscosity (cPs) 90,000, Pourable Color Regal Blue Other Resistance Inhibition Cut Resistance Cut-growth
Technical Data for Dow Silastic M RTV Silicone Rubber
- Casting / Moldmaking - Mold-Making
1 Part or 2 Part
- 1 Part or 2 Part - 2 Part
- Part A Name - Base
- Part B Name - Curing Agent
- Liquid - Fluid
- Plastic - Casting plastics
- Silicone - Silicone rubber
- Dispenser - Automatic mixing equipment
- 2-Part Cure - Base/Curing Agent
- Blue - Regal Blue
Cure Temperature (°C) 25, 25, 52, 65, 93, 121, 149 Test Method Cure Time (min) 960, 960, 60, 30, 15, 7, 5.00 Test Method Viscosity (cPs) 90,000, Pourable Test Method Set Time (min) 30 Test Method Linear Shrinkage (%) 0.10 Test Method Work / Pot Time (min) 90 Mix Ratio 10:1 (by volume), 10:1 (by weight)
General Bond Strength (psi) High Tear Strength (piw) 90 (ppi), Tear Resistance Test Method Tensile Strength (psi) 650 Test Method
Other Resistance Inhibition
Cut Resistance Cut-growth Shore A Hardness 59 Test Method Elongation (%) 3 Test Method Flexibility Firm,Flexible
Specific Gravity 1.290 Test Method Flash Point (°F) 212.0
Shelf Life Details Silastic M RTV Silicone Rubber base and curing agent should be stored in closed containers at or below room temperature. The materials have a shelf life of 12 months from date of manufacture. Refer to product packaging for “Use By” date. Shelf Life Type from date of manufacture Shelf Life (mon) 12
Best Practices for Dow Silastic M RTV Silicone Rubber
Certain contaminants used in moldmaking operations can prevent Silastic M RTV Silicone Rubber from curing. Patterns to be molded should be thoroughly cleaned to remove grease, oil and other surface contaminants. Care should also be taken to ensure that corners, crevices and draws are free of dirt or particles of foreign matter. A light “blow over” with compressed air is advised when the pattern has convoluted draws or undercuts. Then, the original model or pattern should be placed in a light frame of cardboard, foil, wood or other material. There should be approximately 3/8-inch clearance on all sides and over the top of the pattern. The patterns should be attached securely to the bottom of the frame so it does not float. A pattern release agent should then be wiped or sprayed on the pattern. Spreading a light coat of release agent on the sides and underside of the top of the frame will facilitate release. A good pattern release agent can be made by combining 5 percent petroleum jelly and 95 percent solvent. Combine the materials and let stand overnight – then shake by hand to provide a good mix.
Automatic mixing equipment handles Silastic M RTV Silicone Rubber efficiently.
Silastic M RTV Silicone Rubber curing agent should be mixed into the base material just before use (with either manual or mechanical stirring) in the amounts of 10 parts base to one part curing agent by weight. For the best curing results, use metal cans, clean glassware or unwaxed paper containers for mixing the base and curing agent.
The product is deaired before shipment when packaged in drums.
Inclusion of air during mixing may cause avoids in the finished mold. Entrapped air may be removed by applying a vacuum of 28 to 29 inches of mercury. Under such a vacuum, the material will expand to three to four times its original volume. As the froth collapses, the mixture will recede to its original volume. The vacuum should be held one or two minutes longer before releasing. Pressure casting may be substituted with equal success.
The cure of Silastic M RTV Silicone Rubber occurs by a reaction between the base polymer and the curing agent. Polymerization requires 24 hours after the addition of the curing agent at room temperature. This material will not revert or depolymerize, even under conditions of elevated temperature and confinement. Vulcanization can be accelerated by heating the catalyzed material. However, this will increase the shrinkage from nil to 0.3 percent. A part 1/4-inch thick will set up within 30 minutes if the temperature is maintained at 150°F (65°C). The rate at which thicker sections will set up depends on the size and shape of the piece.
See Vendor Technical Data Sheet for more info.
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Cure Temperature Test Methods
|Cure Temperature||Cure Time Test Method|
|25°C||Based on sample mask of 1 cubic inch.|
Cure Time Test Methods
|Cure Time||Test Method|
|960 min||Based on sample mask of 1 cubic inch.|
Linear Shrinkage Test Methods
|Linear Shrinkage||Test Method|
|0.10 %||After 7 days|
Set Time Test Methods
|Set Time||Set Temperature|
Viscosity Test Methods
|90,000 cPs||Brookfield Viscometer Model HAF, spindle #6 at 5 rpm.||25°C|
Tensile Strength Test Methods
|Tensile Strength||Cure Time||Cure Temperature||Test Method|
|650 psi||1,440 min||25°C||Based on sample thickness of 125 mils, cured 24 hours at 77°F (25°C).|
Tear Strength Test Methods
|Tear Strength||Cure Time||Cure Temperature||Test Method|
|90 (ppi)||1,440 min||25°C||Based on sample thickness of 125 mils, cured 24 hours at 77°F (25°C)|
Elongation Test Methods
|3 %||Based on sample thickness of 125 mils, cured 24 hours at 77°F (25°C).|
Shore A Hardness Test Methods
|Shore A Hardness||Shore Hardness Test Method||Hardness Temperature|
|59||Hardness/Durometer Test Method||25°C|
Specific Gravity Test Methods
|Specific Gravity||Temperature||Test Method|
|1.290||25°C||Based on sample thickness of 125 mils, cured 24 hours at 77°F (25°C).|