Dow Silastic RTV 3481 is a high strength silicone moldmaking rubber.
High strength silicone moldmaking rubber
SILASTIC™ RTV-3481 Mould-Making Rubber is a two-component material consisting of
SILASTIC RTV-3481 Base which when mixed with a SILASTIC™ RTV-3081 Mould-Making
Curing Agent, cures at room temperature by a condensation reaction. A range of materials
can be cast into the cured silicone mold: plaster, polyurethane and polyester resins are
materials typically used.
Substrate Preparation
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.
Mixing
Thoroughly stir SILASTIC RTV-3481 Base before use, as filler separation may occur upon
prolonged storage. Weigh 100 parts of SILASTIC RTV-3481 Base and 5 parts of SILASTIC
RTV-3081 Curing Agent in 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 suitably
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 can be used if free of air bubbles. 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 SILASTIC RTV-3481 Base and SILASTIC RTV-3081 Curing
Agent, then using a brush, painting the original with a 1–2 mm 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.
Pouring The Mixture And Curing
Pour the mixed SILASTIC RTV-3481 Base and SILASTIC RTV-3081 Curing Agent as soon
as possible onto the original, avoiding air entrapment. The catalyzed material will cure to a
flexible rubber within 24 hours (or faster when SILASTIC RTV-3081 Curing Agent or
SILASTIC™ RTV-3081-VF Mould-Making Curing Agent are used) at room temperature (22–
24°C/ 71.6–75.2°F) and the mold can then be separated from the material. If the working
temperature is significantly lower, 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 of the mold will be reached within 7 days.
Reproduction of vertical surfaces if a skin mold is required of a vertical object or surface and
cannot be made by normal pouring techniques, the catalyzed mixture can be made
nonflowable by the addition of XIAMETER™ RTV-3011 Thixo Additive.
1. Prepare the original as described earlier.
2. Brush the original with a thin layer of catalyzed mixture. Repeat the operation when the
first layer has started to cure, to achieve a coating thickness of > 2 mm. Leave to cure
at room temperature until the material is tacky.
3. Prepare a new catalyzed mixture of SILASTIC RTV-3481 Base and add 3% by weight
of XIAMETER RTV-3011 Thixo Additive and mix thoroughly until a paste consistency is
reached. De-airing of the mixture is not required.
4. Using a spatula, cover the coated original with the thixotropic coating until all undercuts
are filled; leave to cure for 24 hours, or less if SILASTIC RTV-3081 Curing Agent or
SILASTIC RTV-3081-VF Curing Agent are used, at room temperature.
5. Construct a support mold using polyester resin or plaster and allow to set in contact
with the silicone coating. Carefully remove the support mold. Peel the rubber off the
original and place in the support mould.
Other Curing Agents
The standard curing agent for SILASTIC RTV-3481 Base is SILASTIC RTV-3081 Curing
Agent. For special requirements we offer a range of additional curing agents.
Use At High Temperatures
Some molds produced from condensation cure silicone rubbers can degrade when exposed
to temperatures above 150°C (302°F) over a period of time or when totally confined in
storage at high ambient temperatures. This can result in softening and loss of elastic
properties.
Please contact a distributor for further advice.
Resistance To Casting Materials
The chemical resistance of fully cured SILASTIC RTV-3481 Base is excellent, and similar to
all condensation cure silicone elastomers. It should be noted however that ultimately, resins
and other aggressive casting materials will attack silicone molds, changing physical
properties, surface release and possibly mold dimensions. Molds should be checked
periodically during long production runs.
Note: SILASTIC RTV-3481 Base is an industrial product and must not be used in food
molding, dental and human skin molding applications.
PRODUCT SAFETY INFORMATION REQUIRED FOR SAFE USE IS NOT INCLUDED IN THIS DOCUMENT. BEFORE HANDLING, READ PRODUCT AND SAFETY DATA SHEETS AND CONTAINER LABELS FOR SAFE USE, PHYSICAL AND HEALTH HAZARD INFORMATION. THE SAFETY DATA SHEET IS AVAILABLE ON THE DOW WEBSITE AT WWW.CONSUMER.DOW.COM, OR FROM YOUR DOW SALES APPLICATION ENGINEER, OR DISTRIBUTOR, OR BY CALLING DOW CUSTOMER SERVICE.
Product should be stored at or below 32°C (89.6°F) in original, unopened containers.
This product is neither tested nor represented as suitable for medical or pharmaceutical
uses.
To support customers in their product safety needs, Dow has an extensive Product
Stewardship organization and a team of product safety and regulatory compliance specialists
available in each area.
For further information, please see our website, www.consumer.dow.com or consult your
local Dow representative.
To request any type of technical sheet or safety sheet.
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