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Ecoflex™ 5

Ecoflex™ 5 vs. Smooth-Cast™ 325 vs. Smooth-Cast® ONYX™ FAST

Super-Soft, Addition Cure Silicone Rubber

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Smooth-Cast™ 325

Ecoflex™ 5 vs. Smooth-Cast™ 325 vs. Smooth-Cast® ONYX™ FASTEcoflex™ 5 versus Smooth-Cast® ONYX™ FAST

Ultra Low Viscosity Liquid Plastics

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Key Differences

Product Type
  • Silicone Rubber - Platinum Cure
  • Urethane Resins
  • Urethane Resins
Mixed Viscosity13,000 cps100 cps100 cps
Pot Life1 minute2.5 minutes2.5 minutes
Cure Time5 minutes15 minutes10 minutes
Shore D Hardness8072
Shore A Hardness5
ColorTranslucentBlackClear Amber
Tensile Strength350 psi5,840 psi3,170 psi
Elongation @ Break1,000 %4 %10 %
Disclaimer
Although we do our best to ensure the accuracy of this Compare Tool, Smooth-On offers no warranty either expressed or implied as to the reliability of the information contained herein. Smooth-On assumes no liability for loss or damage associated with use of the Compare Tool. If this is a critical project, we encourage you to review all of the technical data below and contact our Technical Service department with any questions or concerns.

All Technical Data

Ecoflex™ 5Smooth-Cast® ONYX™ FASTSmooth-Cast™ 325
Product Type
  • Silicone Rubber - Platinum Cure
  • Urethane Resins
  • Urethane Resins
Mixed Viscosity13,000 cps100 cps100 cps
Mix Ratio By Volume1A:1B100A:100B1A:1B
Mix Ratio By Weight1A:1B120A:100B115A:100B
Pot Life1 minute2.5 minutes2.5 minutes
Cure Time5 minutes15 minutes10 minutes
Shore D Hardness8072
Shore A Hardness5
Specific Gravity1.07 g/cc1.09 g/cc1.07 g/cc
Specific Volume25.8 cu. in./lb.27.7 cu. in./lb.25.9 cu. in./lb.
ColorTranslucentBlackClear Amber
Die B Tear Strength75 pli
Tensile Strength350 psi5,840 psi3,170 psi
Tensile Modulus246,000 psi140,000 psi
Elongation @ Break1,000 %4 %10 %
100% Modulus15 psi
Compressive Strength8,760 psi3,500 psi
Compressive Modulus77,400 psi36,500 psi
Flexural Strength8,280 psi3,690 psi
Flexural Modulus246,000 psi101,000 psi
Shrinkage<.001 in. / in.0.010 in. / in.0.01 in. / in.
Heat Deflection Temp120 °F
Useful Temperature (min)-65 °F
Useful Temperature (max)450 °F
Heat Deflection With Post Cure250 °F

Product Description

Ecoflex™ 5

Ecoflex™ rubbers are platinum-catalyzed silicones that are versatile and easy to use. Ecoflex™ rubbers are mixed 1A:1B by weight or volume and cured at room temperature with negligible shrinkage.  Low viscosity ensures easy mixing and de-airing. Dispense using our convenient dispensing cartridges. Cured rubber is very soft, very strong and very “stretchy”, stretching many times its original size without tearing and will rebound to its original form without distortion.

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Smooth-Cast® ONYX™ FAST

Smooth-Cast® ONYX™ is a mercury-free urethane resin that cures at room temperature to a deep black, solid plastic. ONYX™ resins offer the convenience of a 1A:1B by volume mix ratio and have very low viscosities, so they are easy to mix and pour. ONYX™ resins have an ultimate Shore hardness of 80D and offer higher physical properties and higher heat resistance vs. other general purpose resins.ONYX™ FAST resin has a pot life of 2.5 minutes and a cure time of 10-15 minutes. ONYX™ FAST is a good choice for creating fast cold cast bronze, brass, copper, nickel/silver, etc. effects.

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Smooth-Cast™ 325

The Smooth-Cast™ 325, 326 & 327 ColorMatch™ Series plastics are urethane resins that were developed specifically for adding color pigments and fillers to achieve true color representation or filler effect. The ColorMatch® Series is formulated “color neutral”. Small amounts of pigment will yield accurate, vivid colors from cured castings using So-Strong™ tints UVO™ pigments or Ignite™ color pigments. The ColorMatch™ Series offers the convenience of a 1A: 1B mix ratio by volume and has a very low viscosity. Demold times range from about 10 minutes to 2-4 hours (depending on product, mass and mold configuration). Note: Large mass castings will get very hot and shrink more, depending on mold configuration.

The ColorMatch™ Series also readily accept fillers (such as URE-FIL™ 3 from Smooth-On). Because of its neutral color, Smooth-Cast™ 325 is ideal for creating marble and wood grain casting effects, or duplicating the look of real metal by adding bronze, brass or other metal powder. Applications for the ColorMatch™ Series plastics include making pigmented prototype models or figures, special effect props, reproducing small to medium size sculptures, decorative jewelry, etc.

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