Silicone RTV Frequently Asked Questions

Below you'll find answers to the questions we get asked the most about our Momentive Silicone RTV products and services split into 1 component and 2 component grades. If you still need help or advice, please get in touch with a member of our Team who will be more than happy to help.

1 Component RTV Moisture Cure Grades

What comes out when 1 component RTVs cure?

It depending on the cure system used, but for example:

• RTV100 Series, RTV15X Series, and IS5628 - Acetic Acid (vinegar)
• RTV16X Series (including RTV133), RTV524X Series, and TSE39X Series - Alcohol
• Other systems like Oximes give off Oxalic Acid, others Acetone.

How long do 1 Component RTV-Moisture cure grades take to cure?

In general, a 3mm bead will cure in 24 Hrs at 25c/50% RH, but adhesion and final properties can take 4-7 days. These cure speeds can be extended by:

• The RTV cross section is thicker and further from humidity (10-12mm is the limit)
• The humidity is lower
• There is little air or its sealed
• Temperature is low

How can I speed up cure time?

Place near high humidity. For example, in an oven at 60°C with a pan of water. Others use steam irons or wallpaper strippers.

Can I thin or dilute the material?

If you use a solvent like Toluene, Xylene or White Spirit, it will thin. The more solvent you use, the more it will shrink during cure. We offer materials with much lower viscosity without solvent, straight out of the tube.

How much will I get from a cartridge?

The amount from a cartridge depends on the bead thickness, for example: 3mm diameter = 40mtr long or 6mm diameter = 10mtr.

If it's cold, what temperature should I apply the silicone at?

There is no low temperature as such, but the surface cannot have frost or condensation on it, or the bond won't work. Also, as the temperature drops and therefore the humidity. Below 30% RH (relative humidity) the cure rate slows and at freezing point there won't be any.

What temperature will 1 component RTVs withstand?

Continuous operation from -55°C to +200°C, with intermittent exposure to 260°C except red high temperature products. RTV106, RTV116 and RTV159 will function at up to 260°C constant and 315°C intermittent.

1 Component RTV Heat cure grades

How are they different to moisture cure RTVs?

They are 'addition' cure, so don't give off a by-product, don't need humidity, just heat above 80°C minimum, and can be cured fully sealed. Additionally, they are susceptible to cure poisoning by certain chemicals (inhibition).

Why would I use Heat Cure RTV Grades?

Benefits of using heat cure RTV grades include:

• Speeding up curing time and gaining adhesion in minutes
• Curing without moisture
• Curing in a sealed box.
• Curing several similar materials, in an assembly, in one go.
• They work well on metals and plastics and can bond silicone to itself and other materials.

Once cured, how do they differ from moisture cure grades?

They do not noticeably differ much, for example red products work to +260°C plus, but they are still silicone.

Does the temperature matter above 80°C?

Yes, 80°C is the bare minimum. Adhesion and cure speed improve dramatically above 100°C and really 130°C is optimum. You can cure up to 200°C if you want, with a hot air gun or heated press.

2 Component RTVs

What are the different types of 2 component RTVs?

Condensation cure (RTV11) type which give off alcohol during cure, are pretty fool proof, but shrink more.

Addition (RTV6XX) cure which liberate nothing, shrink very little, can be heat cured but can be poisoned during cure (inhibited).

What is the lowest application temperature?

Like one component RTVs, the substrate should be frost and damp free, but it is less of an issue as the catalyst helps to cure.

How can I speed the cure up on two-part materials?

For the RTV 11 and all the condensation grades you can use a faster catalyst, for example STO or use mild heat (60°C). For addition cure materials, such as RTV6XX/TSE3331 a 10°C increase in cure temperature will roughly halve the cure time. Addition cure grades can also be cured at over 150C if desired.

What service temperature will these materials withstand?

In generally they will withstand continuous temperatures from -55°C to +205°C except

• RTV31/RTV60/RTV88 withstands up to 260°C
• RTV511/RTV577/RTV655 -115°C to 205°C
• RTV560/RTV566 -115°C to 260°C.

What is the cure time of 2 component RTVs?

This depends on the base chemistry; it is always best to check the individual data sheets.

• RTV11,12,31 and 560 are condensation cure so its 24 hours at R.T.
• RTV6XX, TSE3062 are addition cure, and whilst most cure at room temperature in 24 hrs, others won't. For example, TSE3331 - Minimum 80°C.