RTV-1 vs. RTV-2 Silicones: The Complete Comparison
When selecting the right silicone for technical applications, one is often faced with the fundamental question: RTV-1 or RTV-2? The designation RTV stands for "Room Temperature Vulcanization" and describes silicones that cure at room temperature. However, there are significant differences between one-component and two-component systems in terms of processing, properties, and areas of application.
What are RTV silicones?
RTV silicones are elastomers based on polydimethylsiloxane (PDMS) that cure at room temperature between 15 and 30°C. Unlike high-temperature vulcanizing silicones (HTV), which require temperatures of 120 to 200°C, cross-linking in RTV systems occurs through chemical reactions at ambient conditions.
RTV-1 (single-component): Ready-to-use silicones that cure by reacting with moisture in the air. They cure from the outside in. Typical curing speed: 2-3 mm per 24 hours.
RTV-2 (two-component): Consists of a base and hardener (catalyst) that must be mixed before use. Cross-linking occurs evenly throughout the entire volume, regardless of the layer thickness.
networking mechanisms
condensation cross-linking
In condensation cross-linking, silicone chains are linked together with the elimination of small molecules (acetic acid, alcohol, oxime, or amine). This mechanism is used in all RTV-1 and some RTV-2 systems.
- Acetate system: Releases acetic acid (characteristic odor). Fast curing, good adhesion to glass and ceramics.
- Alkoxy system: Splits off methanol. Neutral cross-linking, corrosion-free, ideal for sensitive substrates.
- Oxime system: Splits off butanone oxime. Good deep curing, suitable for thicker layers.
Addition crosslinking (platinum-catalyzed)
In addition cross-linking, vinyl and hydride groups are linked under platinum catalysis without the separation of by-products. This mechanism is used exclusively in RTV-2 systems.
- No shrinkage (no by-products)
- Precisely controllable pot life and curing times
- Food-safe and skin-friendly possible
- Sensitive to catalyst poisons (sulfur, amines, tin)
Comparison table: RTV-1 vs. RTV-2
| property | RTV-1 | RTV-2 |
|---|---|---|
| components | 1 (ready to use) | 2 (base + hardener) |
| networking | Due to humidity | By mixing the components |
| network type | condensation | Addition or condensation |
| curing depth | Limited (0.8–1.2 inches/24 hours) | Unlimited (through-hardening) |
| shrinkage | 0.5-2% (breakdown products) | Addition: <0.1%, Kond.: 0.5-1% |
| Shore hardness | 15-50 Shore A | 0-70 Shore A |
| tear resistance | 2-6 N/mm² | 2-12 N/mm² |
| temperature range | -50 to +200°C | -60 to +300°C |
| pot life | Ready for immediate use | 5 minutes to several hours |
| mixing ratio | Not required | Typically 1:1 or 10:1 |
| processing equipment | cartridge press | Scale, mixer, vacuum |
| Typical application | Sealing, bonding, grouting | Mold making, precision parts |
| Maximum layer thickness | 10-15 mm | Unlimited |
| storage stability | 6-12 months | 12-24 months (separated) |
| food contact | Rare | Yes (addition systems) |
| Price per kg | $15–40 | $25–80 |
| color selection | Limited (transparent, white) | Can be dyed as desired |
When to choose RTV-1?
- Sealing and joints: Thin beads and layers up to max. 10 mm
- Bonding: glass to metal, plastic to ceramic
- Electronics encapsulation: Thin protective layers on circuit boards
- Repairs: Fast on-site applications without mixing equipment
- Prototyping: Fast, uncomplicated sealing
When to choose RTV-2?
- Mold making: Flexible silicone molds for casts in synthetic resin, plaster, concrete
- Technical components: Precision seals, diaphragms, buffers
- Potting compounds: Complete embedding of electronics and sensors
- Food contact: baking tins, dosing valves, seals
- Medical technology: Skin-compatible components, prosthetic elements
- Large volumes: Parts with any layer thickness
Processing tips
Processing RTV-1 correctly
- Substrates must be clean, dry, and free of grease.
- For thick layers (>6 mm): Apply in several layers.
- Optimal conditions: 23°C, 50% relative humidity
- Use primer for difficult substrates (PE, PP, PTFE)
Processing RTV-2 correctly
- Strictly adhere to the mixing ratio (use precision scales).
- Mix thoroughly (2-3 minutes), scraping down the sides and bottom of the bowl.
- Evacuate after mixing (vacuum chamber, 20-50 mbar)
- Apply release agent to the model (petroleum jelly or special silicone release agent)
- Pour slowly and without creating bubbles.
Frequently Asked Questions
Conclusion
RTV-1 and RTV-2 silicones each have clear strengths. RTV-1 is the first choice for fast, uncomplicated sealing and bonding in thin layers. RTV-2 is superior for mold making, technical components, and wherever precision, mechanical strength, and thorough curing are required regardless of layer thickness.
Not sure which RTV system is best for your application?
Our application engineers at SILITECH will be happy to advise you. We stock both RTV-1 and RTV-2 silicones from Bluesil and SILISIL and will find the optimal solution for your requirements.
RTV-1 vs. RTV-2 Silicones: The Complete Comparison
When selecting the right silicone for technical applications, one is often faced with the fundamental question: RTV-1 or RTV-2? The designation RTV stands for "Room Temperature Vulcanization" and describes silicones that cure at room temperature. However, there are significant differences between one-component and two-component systems in terms of processing, properties, and areas of application.
What are RTV silicones?
RTV silicones are elastomers based on polydimethylsiloxane (PDMS) that cure at room temperature between 15 and 30°C. Unlike high-temperature vulcanizing silicones (HTV), which require temperatures of 120 to 200°C, cross-linking in RTV systems occurs through chemical reactions at ambient conditions.
RTV-1 (single-component): Ready-to-use silicones that cure by reacting with moisture in the air. They cure from the outside in. Typical curing speed: 2-3 mm per 24 hours.
RTV-2 (two-component): Consists of a base and hardener (catalyst) that must be mixed before use. Cross-linking occurs evenly throughout the entire volume, regardless of the layer thickness.
networking mechanisms
condensation cross-linking
In condensation cross-linking, silicone chains are linked together with the elimination of small molecules (acetic acid, alcohol, oxime, or amine). This mechanism is used in all RTV-1 and some RTV-2 systems.
- Acetate system: Releases acetic acid (characteristic odor). Fast curing, good adhesion to glass and ceramics.
- Alkoxy system: Splits off methanol. Neutral cross-linking, corrosion-free, ideal for sensitive substrates.
- Oxime system: Splits off butanone oxime. Good deep curing, suitable for thicker layers.
Addition crosslinking (platinum-catalyzed)
In addition cross-linking, vinyl and hydride groups are linked under platinum catalysis without the separation of by-products. This mechanism is used exclusively in RTV-2 systems.
- No shrinkage (no by-products)
- Precisely controllable pot life and curing times
- Food-safe and skin-friendly possible
- Sensitive to catalyst poisons (sulfur, amines, tin)
Comparison table: RTV-1 vs. RTV-2
| property | RTV-1 | RTV-2 |
|---|---|---|
| components | 1 (ready to use) | 2 (base + hardener) |
| networking | Due to humidity | By mixing the components |
| network type | condensation | Addition or condensation |
| curing depth | Limited (0.8–1.2 inches/24 hours) | Unlimited (through-hardening) |
| shrinkage | 0.5-2% (breakdown products) | Addition: <0.1%, Kond.: 0.5-1% |
| Shore hardness | 15-50 Shore A | 0-70 Shore A |
| tear resistance | 2-6 N/mm² | 2-12 N/mm² |
| temperature range | -50 to +200°C | -60 to +300°C |
| pot life | Ready for immediate use | 5 minutes to several hours |
| mixing ratio | Not required | Typically 1:1 or 10:1 |
| processing equipment | cartridge press | Scale, mixer, vacuum |
| Typical application | Sealing, bonding, grouting | Mold making, precision parts |
| Maximum layer thickness | 10-15 mm | Unlimited |
| storage stability | 6-12 months | 12-24 months (separated) |
| food contact | Rare | Yes (addition systems) |
| Price per kg | $15–40 | $25–80 |
| color selection | Limited (transparent, white) | Can be dyed as desired |
When to choose RTV-1?
- Sealing and joints: Thin beads and layers up to max. 10 mm
- Bonding: glass to metal, plastic to ceramic
- Electronics encapsulation: Thin protective layers on circuit boards
- Repairs: Fast on-site applications without mixing equipment
- Prototyping: Fast, uncomplicated sealing
When to choose RTV-2?
- Mold making: Flexible silicone molds for casts in synthetic resin, plaster, concrete
- Technical components: Precision seals, diaphragms, buffers
- Potting compounds: Complete embedding of electronics and sensors
- Food contact: baking tins, dosing valves, seals
- Medical technology: Skin-compatible components, prosthetic elements
- Large volumes: Parts with any layer thickness
Processing tips
Processing RTV-1 correctly
- Substrates must be clean, dry, and free of grease.
- For thick layers (>6 mm): Apply in several layers.
- Optimal conditions: 23°C, 50% relative humidity
- Use primer for difficult substrates (PE, PP, PTFE)
Processing RTV-2 correctly
- Strictly adhere to the mixing ratio (use precision scales).
- Mix thoroughly (2-3 minutes), scraping down the sides and bottom of the bowl.
- Evacuate after mixing (vacuum chamber, 20-50 mbar)
- Apply release agent to the model (petroleum jelly or special silicone release agent)
- Pour slowly and without creating bubbles.
Frequently Asked Questions
Conclusion
RTV-1 and RTV-2 silicones each have clear strengths. RTV-1 is the first choice for fast, uncomplicated sealing and bonding in thin layers. RTV-2 is superior for mold making, technical components, and wherever precision, mechanical strength, and thorough curing are required regardless of layer thickness.
Not sure which RTV system is best for your application?
Our application engineers at SILITECH will be happy to advise you. We stock both RTV-1 and RTV-2 silicones from Bluesil and SILISIL and will find the optimal solution for your requirements.
