Urethane RTV Rubber
RU-420 (20A Shore)
RU-420 A/B Two-Component, 100% solids (20A) Urethane Elastomer RTV developed for its Softness (Low Durometer), High Flexibility and Elongation properties. This Softer RTV provides High Stretch and High Tear Resistant properties that can be used for making molds or rubber parts. Molds can be used to cast gypsum cement, plaster and wax parts.
Features:
*High Stretch and Tear Resistance Properties
*Low Viscosity for Improved Detail Definition
*Soft Urethane RTV
Typical Physical Properties:
(For Components)
Component A Component B
Viscosity (cps): 2000 1000
Mix Ratio, By Weight: 50 100
Color: Yellow/Clear White
(For Cured Material)
Hardness: 20 A
Tensile Strength (psi) 549
Elongation %: 847
Tear Resistance (psi): 125
Reactivity Data:
Gel Tme: 20 minutes
De-Mold Time: 16 – 24 hours
Preparation of Master
Urethane elastomers will adhere to most surfaces. A proper mold release must be used on all surfaces-- MR-150 or ER-2300 is recommended. Wood, plaster, stone, pottery, masonry, or any porous surface must be sealed with lacquer or clear shellac prior to applying release. Partall Film #10 or shellac is suitable for sulfur & water based clays. Allow 24 hours to dry before preparing master with mold release. Plaster masters can release air when pouring larger molds due to some heat generated. Venting the base of your master by (drilling several ¼” holes) will release the air downward to avoid air release into mold cavity. Urethane RTV cures to a flexible rubber in above cure times. These products are safe to use as directed, check MSDS for safety information.
Mixing and Curing
Before adding A to B, part B should be stirred or shaken for 1 minute to assure that any separated material is remixed. Select a clean, dry container for mixing. Avoid using wood or paper products, which could cause cure problems. Weigh the proper ratio A to B and mix well. Two containers may be used to assure that all materials are thoroughly mixed.
Pour mixture over master slowly allowing material to fill void and push air out of cavity. A vacuum chamber can be used to remove excess air bubbles before pouring. After mixture is poured a light mist of ER-2300 can be sprayed on top surface to break tension bubbles. Urethane RTV will cure to solid rubber at above cure time. Urethane rubber that is colder than 75°F will cure slower. During colder weather material may be heated in a hot water bath (place container in plastic bags first) and the master model should be warmed. Accelerated cures can be reached by heating the mold and material at 100-150°f for 4 to 6 hrs. Cold weather or off-ratio material can produce unacceptable rubber results.
Using Mold
The use of a release aids demolding and is recommended prior to each casting. Release selection is based on material that is to be cast. R-100-50 is recommended for casting concrete. No release necessary for wax or plaster products.
Storage
Un-mixed material should be stored in warm, dry area with lids secured tightly. Once containers are opened, material should be used in a short time period. Pre-test any aged material before using. Molds or parts should be cleaned with a soap solution and completely dried prior to storing them in a dry, cool environment. Avoid stacking or exposing them to environmental elements—UV and moisture.
The information and data contained herein are based on information we believe reliable. Each user of the material should thoroughly test any application and independently conclude satisfactory performance before commercializing. Suggestions of uses should not be taken as inducements to infringe on any particular