Brand Silastic Application Type Mold-Making 1 Part or 2 Part 2 Part Material Form Liquid Manufacturer Dow Chemistry Silicone rubber Cure Method Heat, Base/curing agent Cure Temperature (°C) 25, 60, 20 to 25, 20, 25, 30, 35, 40, 50 Cure Time (min) Very Fast, 1,440, 120, 720, 840, 600, 420, 240, 120, 45 Viscosity (cPs) Low, 55,000 Chemical Resistance Inhibition
Technical Data for Dow Silastic T-2 Base / T-2 High Durometer Curing Agent
Cure Temperature (°C) 25, 60, 20 to 25, 20, 25, 30, 35, 40, 50 Cure Time (min) Very Fast, 1,440, 120, 720, 840, 600, 420, 240, 120, 45 Viscosity (cPs) Low, 55,000 Test Method Linear Shrinkage (%) <0.10 Test Method Work / Pot Time (min) 60, 180, 140, 105, 65, 35, 15 Test Method Mix Ratio 10:1 (by volume), 100:10 (by weight)
General Bond Strength (psi) High Tear Strength (piw) 120 (ppi), 130 to 140 (ppi) Test Method Tensile Strength (psi) 800, 800 to 1,000 Test Method
Chemical Resistance Inhibition
Shore A Hardness 50, 47 to 53, Medium, High Test Method Elongation (%) 3 Test Method Flexibility Flexible
Specific Gravity 1.120 Test Method Flash Point (°F) 212.0
Shelf Life Details SILASTIC T-2 Silicone Moldmaking Rubber base, and both of its curing agents should be stored at or below room temperature. The materials have a usable life of 12 months from date of production. Refer to product packaging for “Use By” date. Ensure that containers are tightly closed after use. Shelf Life Type from date of production Shelf Life (mon) 12
Best Practices for Dow Silastic T-2 Base / T-2 High Durometer Curing Agent
The surface of the original should be clean and free of loose material. When correctly mixed with either curing agent, SILASTIC T-2 Moldmaking rubber releases well from most substrates, a release agent or barrier coat may be needed to seal the surface before casting the silicone. Release coatings such as petroleum jelly or others can be used. Before casting the silicone rubber, it is advisable to verify that no adhesion has occurred between SILASTIC T-2 and the master mold or frame.
Pour the mixed base and curing agent onto the master, avoiding air entrapment.
Weigh out 100 parts of SILASTIC T-2 Silicone Rubber base with 10 parts of either curing agent in a clean container. Mix until the curing agent is completely dispersed in the base. Mix suitably small quantities to ensure thorough mixing of the base and curing agent and adequate working time.
Entrapped air should be removed in a vacuum chamber, allowing the mixture to completely expand and then collapse. After an additional five minutes, the vacuum can be released. A value increase of four to five times will occur upon vacuum de-airing of the mixture, so a suitably large container should be chosen. Pour the mixed base and curing agent onto the master, avoiding air entrapment. Some bubbles will remain in the material after the vacuum de-airing – these will rise to the surface and break during the working time.
The material should be allowed to stand for about 30 minutes at room temperature before heat curing. The catalyzed mixture will cure in thick sections to a flexible rubber, typically within 12 hours at room temperature, at which time the part can be demolded. Heat will greatly accelerate the cure. There may be some contraction upon cooling due to the coefficient of thermal contraction differences between the silicone rubber and the original. The higher the curing temperature, the greater the differences and dimensions.
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Linear Shrinkage Test Methods
|Linear Shrinkage||Test Method||Temp|
|<0.10 %||Cured 24 hours at 25°C (77°F)||25°C|
Viscosity Test Methods
|55,000 cPs||Mixed – 100 Parts Base to 10 Parts Curing Agent by Weight|
Work / Pot Time Test Methods
|Work / Pot Time||Temperature|
Tensile Strength Test Methods
|Tensile Strength||Cure Time||Cure Temperature|
|800 psi||1,440 min||25°C|
|800 to 1,000 psi||120 min||60°C|
Tear Strength Test Methods
|Tear Strength||Cure Time||Cure Temperature||Test Method|
|120 (ppi)||1,440 min||25°C||Die B|
|130 to 140 (ppi)||120 min||60°C||Die B|
Elongation Test Methods
|3 %||Cure 2 hours at 60°C (140°F)|
Shore A Hardness Test Methods
|Shore A Hardness||Shore Hardness Test Method||Hardness Temperature|
|50||Cure 2 hours at 60°C (140°F)||60°C|
|47 to 53||Cure 2 hours at 60°C (140°F)||60°C|
Specific Gravity Test Methods
|Specific Gravity||Test Method|
|1.120||100 Parts Base to 10 Parts Curing Agent by Weight|