Xiameter RTV 3481

High strength silicone moldmaking rubber

Applications

• XIAMETER® RTV-3481 Base is suited for the detailed reproduction of figures, art objects and similar items.

Description

XIAMETER RTV-3481 Moldmaking Rubber is a twocomponent material consisting of XIAMETER RTV-3481 Base which when mixed with a XIAMETER® RTV-3081 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.

How to use

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 XIAMETER RTV-3481 Base before use, as filler separation may occur upon prolonged storage. Weigh 100 parts of XIAMETER RTV-3481 Base and 5 parts of XIAMETER 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 XIAMETER RTV-3481 Base and XIAMETER RTV-3081 Curing Agent, then using a brush, painting the original with a 1-2mm 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 XIAMETER RTV-3481 Base and XIAMETER 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 XIAMETER RTV-3081 Curing Agent or XIAMETER® RTV-3081-VF 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.

Additional Information

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 >2mm. Leave to cure at room temperature until the material is
   tacky.
3. Prepare a new catalyzed mixture of XIAMETER RTV- 3481 and add 3% by weight ofXIAMETER 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 XIAMETER RTV-3081 Curing
   Agent or XIAMETER 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 XIAMETER RTV-3481 Base is XIAMETER RTV-3081 Curing Agent. For special requirements Dow Corning offers a range of additional curing agents:

• XIAMETER RTV-3081 Curing Agent for demolding after 6 hours.
• XIAMETER RTV-3081-VF Curing Agent for demolding after 2 hours.
• XIAMETER® RTV-3081-R Curing Agent for improved mold life with polyester casting resins.
• XIAMETER® RTV-3081-F Curing Agent and XIAMETER RTV-3081-VF Curing Agent are fast curing agents and give a shorter working time.

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 Dow Corning distributor for further advice.

Resistance to casting materials

The chemical resistance of fully cured XIAMETER RTV-3481 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: XIAMETER RTV-3481 is an industrial product and must not be used in food molding, dental and human skin molding applications.