Dow Silastic E RTV Silicone Rubber

Dow Silastic E RTV Silicone Rubber Datasheet
  • Description for Dow Silastic E RTV Silicone Rubber

    Good tear resistance, low durometer, long working time, high elongation.

    *See Terms of Use Below

    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
    Cure Time (min) 1,440
    Viscosity (cPs) 55000 (mPa-s), Pourable
    Color White
    Key Specifications FDA (U.S. Food & Drug Administration) and/or CFIA (Canadian Food Inspection Agency): FDA 21 CFR 177.2600
  • Technical Data for Dow Silastic E RTV Silicone Rubber

    Overview
    • Application Type
    • 1 Part or 2 Part
      • 1 Part or 2 Part - 2 Part
      • Part A Name - Base
      • Part B Name - Curing Agent
    • Material Form
      • Liquid
    • Chemistry
    • Cure Method
      • Heat
      • 2-Part Cure - Base/Curing Agent
    • Color
      • White
    • Key Specifications
      • FDA (U.S. Food & Drug Administration) and/or CFIA (Canadian Food Inspection Agency): 177.2600 - FDA 21 CFR 177.2600
    • Brand
      • Silastic
    Specifications
    Cure Specs
    Cure Temperature (°C) 25 Test Method
    Cure Time (min) 1,440 Test Method
    Viscosity (cPs) 55000 (mPa-s), Pourable Test Method
    Linear Shrinkage (%) 0.10 Test Method
    Work / Pot Time (min) Long, 120 Test Method
    Mix Ratio 10:1 (by volume), 10:1 (by weight)
    Bond Strength
    General Bond Strength (psi) High
    Tear Strength (piw) 110 (ppi), Tear Resistance Test Method
    Tensile Strength (psi) 800 Test Method
    Hardness
    Shore A Hardness 37, 35 Test Method
    Elongation (%) 350, High Test Method
    Flexibility Flexible
    Other Properties
    Specific Gravity 1.140 Test Method
    Flash Point (°F) 212.0
    Business Information
    Shelf Life Details Silastic E RTV Silicone Rubber and its 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 E RTV Silicone Rubber

    *See Terms of Use Below

    1. Surface Preparation

      Patterns to be molded should be thoroughly cleaned to remove grease, oil and other surface contaminants. Certain contaminants sometimes used in moldmaking operations can prevent Silastic E RTV Silicone Rubber from curing. 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 place the original model or pattern in a light frame of cardboard, foil, wood or other material. Allow approximately 1/4-inch clearance on all sides and over the top of the pattern. Attach the pattern securely to the bottom of the frame so that it does not float. A pattern release agent should then be wiped or sprayed on the pattern. A light coat of release agent on the sides and underside of the top of the frame will facilitate release.

    2. Mixing

      Silastic E RTV Silicone Rubber base and its curing agent are produced in matched lots

      the two parts should be used in the kit form, as supplied. For the best curing results, use metal cans, clean glassware or unwaxed paper containers for mixing the base and curing agent. Silastic E RTV Silicone Rubber curing agent should be mixed into the base material just before use (with either manual or mechanical stirring) in the amount of one part curing agent to ten parts base by weight. Note: Varying the ratio of the Silastic E RTV Curing Agent will not hasten or slow the rate of cure. However, it will result in lowering the physical properties of the cured rubber.

    3. Deairing/Degassing

      Inclusion of air during mixing may cause voids 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 four to five 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.

      With the curing agent added, 0.45 kg (1 lb) of Silastic E RTV Silicone Rubber will produce 409.7 cubic centimeters (25 cubic inches) of rubber.

    4. Curing

      The cure of Silastic E RTV Silicone Rubber occurs by a reaction between the base polymer and the curing agent. This 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. The rate at which thick sections will set up depends on the size and shape of the piece.

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Cure Temperature Test Methods
Cure Temperature Cure Time Test Method
25°C CTM 0092A, Based on sample mass of one cubic inch.
Cure Time Test Methods
Cure Time Test Method
1,440 min CTM 0092A, Based on sample mass of one cubic inch.
Linear Shrinkage Test Methods
Linear Shrinkage Test Method Temp
0.10 % CTM 0157, 7 days, Based on sample thickness of 125 mils, cured 24 hours at 25°C (77°F). 25°C
Viscosity Test Methods
Viscosity Test Method Temperature
55000 (mPa-s) CTM 0050, Brookfield Viscometer Model HAF, spindle #6 at 5 rpm., As Catalyzed – 10:1 Ratio, by weight 25°C
Pourable
Work / Pot Time Test Methods
Work / Pot Time Test Method
Long
120 min CTM 0055, Time required to double initial catalyzed viscosity.
Tensile Strength Test Methods
Tensile Strength Cure Time Cure Temperature Test Method
800 psi 1,440 min 24°C CTM 0137 A
Tear Strength Test Methods
Tear Strength Cure Time Cure Temperature Test Method
110 (ppi) 1,440 min 24°C CTM 0159 A, Die B
Tear Resistance
Elongation Test Methods
Elongation Test Method
350 % CTM 0137A, Based on sample thickness of 125 mils, cured 24 hours at 25°C (77°F).
High Elongation Test Method
Shore A Hardness Test Methods
Shore A Hardness Shore Hardness Test Method Hardness Temperature
37 Hardness/Durometer Test Method
35 CTM 0099, Based on sample thickness of 125 mils, cured 24 hours at 25°C (77°F). 25°C
Specific Gravity Test Methods
Specific Gravity Temperature Test Method
1.140 25°C CTM 0022, Based on sample thickness of 125 mils, Based on sample thickness of 125 mils, cured 24 hours at 25°C (77°F).