RTV-2 Silicone (Two-Component)

What Is RTV-2 Silicone?

RTV-2 (Room Temperature Vulcanization, two-component) silicone is a liquid rubber system cured by mixing a base compound with a crosslinker or catalyst. Unlike RTV-1, which cures by moisture alone, RTV-2 cures throughout the entire mass simultaneously once the two components are thoroughly mixed, making it suitable for thick-section casting, precision mold making, and potting applications.

RTV-2 is available in two fundamentally different cure chemistries: addition cure (platinum-catalyzed) and condensation cure (tin-catalyzed). The choice between them determines shrinkage, by-products, cure speed, inhibition sensitivity, and ultimate application suitability.

Addition Cure (Platinum) RTV-2

Addition-cure RTV-2 is catalyzed by platinum through a hydrosilylation reaction. The key advantages are near-zero shrinkage (<0.1%), no by-product release, and the ability to cure in any section thickness without moisture dependency. These properties make addition-cure RTV-2 the standard for:

• Prototype and production mold making: High-fidelity reproduction of fine surface details with no dimensional distortion. Essential for jewelry casting, architectural heritage reproduction, and prototype tooling for injection-molded parts.
• Medical and food-contact casting: Clean extractable profile enables FDA and food-contact compliance when formulated with appropriate base polymers and pigments.
• Electronic potting: No by-product release prevents corrosion of copper traces and PCB components.

Inhibition sensitivity: Platinum-cured RTV-2 is sensitive to tin (from tin-cured silicone residues), sulfur (from latex, polysulfide, and some epoxy cure agents), nitrogen (from polyurethanes and amines), and some plasticizers. Contact with these inhibiting substances before cure can cause surface tackiness or complete cure failure. Clean tools and substrates are essential.

Condensation Cure (Tin) RTV-2

Tin-catalyzed condensation RTV-2 cures by a condensation reaction that releases a small molecule by-product — either acetic acid (acetoxy type), alcohol (alkoxy type), or acetone (oxime type). Key characteristics:

• Higher shrinkage than addition cure (typically 0.3–1.0%)
• Requires some atmospheric moisture to complete cure in thick sections
• Not sensitive to inhibition by sulfur, nitrogen, or other organic compounds
• Lower material cost than platinum grades
• Suitable for general mold making, casting, and potting where dimensional precision is not critical

Mix Ratio and Working Time

RTV-2 systems are supplied at mix ratios of either 1:1 (by weight or volume, for addition-cure systems) or 10:1 base-to-crosslinker (common for condensation-cure systems). Thorough mixing to homogeneity is critical — inadequate mixing produces soft spots or uncured regions. Working time (pot life) ranges from 20 minutes to 2 hours depending on formulation; cure time at room temperature is 4–24 hours for most grades. Elevated temperature (40–60 °C) accelerates cure significantly.

Shore Hardness and Tear Strength Selection

RTV-2 hardness spans Shore 5A (very soft, gel-like — used for flexible molds over rigid models) to Shore 60A (firm — used for rigid mold support structures). For mold-making, Shore 20A–40A is most common, providing flexibility for part demold while maintaining dimensional accuracy. For potting, Shore 30A–50A is typical.

Tear strength is the critical property for mold durability. Addition-cure grades with reinforcing fumed silica filler achieve tear strengths of 25–40 kN/m, enabling hundreds of casting cycles before mold failure.

Sourcing and Specification

When specifying RTV-2, define: cure system (addition or condensation), mix ratio, Shore hardness, working time, tear strength, transparency requirement, and certification requirements. For mold-making applications, request shrinkage data. For medical and food-contact applications, request extractable test reports and Declaration of Conformity.

Contact us to verify certification documents and request application-matched RTV-2 samples. Inquiries are routed to specialist suppliers in the silicon materials network.