Brand Silastic Application Type Mold-Making 1 Part or 2 Part 2 Part Material Form Liquid Substrate Porous substrates, Polyester resins, Rubber Manufacturer Dow Chemistry Silicone Cure Method Curing Agent Cure Temperature (°C) 20 to 25, 23, 23 Cure Time (min) 10,080, 1,440 Viscosity (cPs) 12,400 Chemical Resistance Excellent High Temperature Resistance (°C) Excellent
Technical Data for Dow Silastic 3498 Base / 98 Curing Agent
Cure Temperature (°C) 20 to 25, 23, 23 Cure Time (min) 10,080, 1,440 Viscosity (cPs) 12,400 Linear Shrinkage (%) 0.70 Test Method Work / Pot Time (min) Long, 122 Thixotropic High Mix Ratio 10:1 (by volume), 100:10 (by weight)
General Bond Strength (psi) High Tear Strength (piw) 145 (ppi), High, Tear Resistance Test Method Tensile Strength (psi) 536 (Cp) Test Method
Chemical Resistance Excellent High Temperature Resistance (°C) Excellent
Shore A Hardness 27 Test Method Elongation (%) 310, 316 Test Method Flexibility Flexible
Specific Gravity 1.240, 0.970 Test Method Flash Point (°F) 107.6
Shelf Life Details When stored at or below 32°C (89.6°F) in the original unopened containers, SILASTIC 3496, 3497 or 3498 have a usable life of 12 months from the date of production., SILASTIC 96 and 98 have a usable life of 12 months from the date of production. Shelf Life Type from the date of production Shelf Life (mon) 12
Best Practices for Dow Silastic 3498 Base / 98 Curing Agent
The surface of the original should be clean and free of loose material. If necessary, and in particular with porous substrates, use a suitable release agent such as petroleum jelly or soap solution.
Thoroughly stir SILASTIC 3496, 3497 or 3498 Base before use, as filler separation may occur upon prolonged storage. Weigh 100 parts of SILASTIC 3496 or 3497 Base and 10 parts SILASTIC 96 Curing Agent into a clean container. Likewise weigh 100 parts of SILASTIC 3498 and 10 parts SILASTIC 98 Curing Agent into a clean container. Mix together until the curing agent is completely dispersed in the base. Hand or mechanical mixing can be used, but do not mix for an extended period of time or allow the temperature to exceed 35°C (95°F). Mix suitable small quantities to ensure thorough mixing of base and curing agent.
It is strongly recommended that entrapped air be removed in a vacuum chamber, allowing the mix to completely expand and then collapse. After a further 1-2 minutes under vacuum, the mix should be inspected and if free of air bubbles, can then be used. A volume increase of 3-5 times will occur on vacuum de-airing the mixture, so a suitably large container should be chosen.
Caution: prolonged vacuum will remove volatile components from the mix and may result in poor thick section cure and non-typical properties.
Note: If no vacuum de-airing equipment is available, air entrapment can be minimized by mixing a small quantity of base and curing agent, then using a brush, painting the original with a thin layer. Leave at room temperature until the surface is bubble free and the layer has begun to cure. Mix a further quantity of base and curing agent and proceed as follows to produce a final mold.
Pour the mixed base and curing agent as soon as possible onto the original, avoiding air entrapment. The catalyzed material will cure to a flexible rubber and the mold can then be removed. If the working temperature is significantly lower than 23°C(73.4°F), the cure time will be longer. If the room temperature or humidity is very high, the working time of the catalyzed mixture will be reduced. The final mechanical properties will be reached within 7 days.
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Linear Shrinkage Test Methods
|Linear Shrinkage||Test Method||Temp|
|0.70 %||Cured for 7 days at 23°C (73°F)||23°C|
Tensile Strength Test Methods
|Tensile Strength||Cure Time||Cure Temperature|
|536 (Cp)||10,080 min||23°C|
Tear Strength Test Methods
|Tear Strength||Cure Time||Cure Temperature|
|145 (ppi)||10,080 min||23°C|
Elongation Test Methods
|310 %||Elongation Test Method|
|316 %||Elongation at break, Cured for 7 days at 23°C (73°F)|
Shore A Hardness Test Methods
|Shore A Hardness||Shore Hardness Test Method||Hardness Temperature|
|27||Cured for 7 days at 23°C (73°F)||23°C|
Specific Gravity Test Methods