RTV Silicone – A Comprehensive Overview and Product Guide

When it comes to choosing types of silicone, RTV remains a popular option in modern industry.

A reason this guide explores some fundamental facts about RTV silicone – from benefits, properties, components, applications to manufacturing process.

So, before choosing this silicone for your next project, read this guide.

What is RTV Silicone?

Room temperature vulcanizing silicone or RTV silicone is a unique silicone rubber type that easily cures at room or normal temperature.

RTV silicone mostly comes in two parts – the ready-to-use part and the other part that requires you to mix before use.

Silicone Rubber Structure
Silicone Rubber Structure

When it is applied, it goes through a specific chemical reaction which makes it vulcanize – therefore creating a flexible and strong material.

Benefits of RTV Silicone

Below are the major benefits that come with using RTV Silicone:

  • Highly flexible and maintains flexibility no matter the temperature range.
  • Can withstand compressing and stretching without getting lost.
  • It is durable and is resistant to weathering and aging in various environments.
  • Resistant to moisture and offers excellent sealing for both outdoor and indoor environments.
  • Comes with excellent electrical insulation characteristics.
  • Has adhesive characteristics that are strong to various material ranges such as glass, ceramics, metal, and plastic.
  • Very easy to use.
  • Versatile
  • Non-toxic and safe for consumer product use. There are even low VOC types available.
  • Resists UV radiation, which makes it ideal for external use.
  • Will not corrode metals or materials they come into contact with.

Properties of RTV Silicone

Curing RTV Silicone
Curing RTV Silicone

·         RTV Silicone Cure Time

Curing timings are different most times based on the part that is being used:

For one-part RTV Silicone the following should be noted:

  1. Formation of skin – This happens mostly within 5 to 30 minutes based on temperature and humidity.
  2. Complete cure – Mostly happens within 24 to 48 hours for sections that have thickness of up to 3 mm. Sections that are thicker might take some days to cure.

For the two-part RTV Silicone the following should be noted:

  1. Pot life – The window time to have mixture applied after mixing components will range mostly from some minutes to some hours.
  2. Setting initially – Mostly takes place within 30 minutes or can increase to some few hours.
  3. Complete cure – Mostly happens within 24 hours. However, the timing can vary depending on ideal formulations and conditions environmentally.

Waterproof

Below are the waterproof properties of RTV Silicone:

  1. It inherently waterproof and also have great sealing characteristics against water ingress and moisture.
  2. Is able to maintain its properties of waterproofing over a time period.
  3. Can resist degradation from being exposed to water for long.

Adhesive Properties

Some adhesive properties of RTV Silicone includes:

  1. Bonds perfectly with different materials such as glass, different metals, ceramics, wood, concrete, plastics, etc.
  2. Some materials might necessitate primer to make adhesion more. This works even more for surfaces that are non-porous.
  3. Adhesion for structural and non-structural applications provided is strong.

Thermal Stability

  1. Resists temperature from 60°C to 200°C. Some specialized silicones can withstand more.
  2. It has low coefficient of thermal expansion meaning reduced size changes with fluctuations in temperature.

Mechanical Properties

  1. Elongation stretch from 100 to 600% of its actual length before it breaks down.
  2. Tensile strength range from 2 to 5 MPa based on ideal formulations.
  3. Hardness is ideally between 20 to 70 Shore A.

Chemical Resistance

  1. Resists oils, acids, bases and oils.
  2. Doesn’t resist strong alkalis, acids, etc.

Electrical Properties

  1. Has dielectric strength of almost 500 to 700 V/mil, which is high.
  2. Comes with about 10^14 ohm-cm to assure electrical flow resistance is high.

Main Components of Room Temperature Vulcanizing Silicone

Some main components of room temperature vulcanizing silicone include:

  • Base or silicone polymer
  • Crosslinking agents like acetoxysilanes, alkoxysilanes, oximesilanes, and amino silanes.
  • Catalysts for curing like air moisture and tin or platinum for RTV-1 and RTV-2 respectively.
  • Fillers such as silicon dioxide or silica, alumina trihydrate, and calcium carbonate.
  • Plasticizers serving as plasticizing agents.
  • Additives such as silane coupling agents, colorants, UV stabilizers, flame retardants, and thixotropic agents.
  • Solvents such as toluene and xylene, but most RTV silicones come without solvents.
  • Moisture absorbers

RTV Silicone Manufacturing Process

Below is the manufacturing process of RTV Silicone:

Step 1 – Choose Raw Materials

Some raw materials include:

  • Base polymer like polysiloxane or high-quality silicone polymer
  • Crosslinkers (choose based on the RTV Silicone type) like acetoxy, alkoxy, amino silanes, or oxime.
  • Choose ideal catalysts such as platinum or tin compounds.
  • Choose additives like adhesion promoters, plasticizers, and colorants.
  • Choose fillers like calcium, carbonate, and silica).

Step 2 – Measure

Measure specific amounts of every raw material based on forming necessities.

Step 3 – Mix

  • Begin by mixing base polymers with fillers and plasticizers. Mix to have a mixture that is homogeneous.
  • Use a high-shear mixer to completely blend components. This ensures even distribution of additives and fillers all through the silicone base.

Step 4 – Add Crosslinkers

Add crosslinkers to the fully mixed blend in a manner that is controlled to setup for vulcanization.

Step 5 – Add Catalysts

For RTV-2 silicone, you will have to mix catalysts differently and then add with the base mixture before you package.

Step 6 – Vacuum Deaeration

Take the mixture through vacuum deaeration. This takes out all air bubbles trapped in it. Ensure this process is undergone to have a final product with no defects and lumps.

Step 7 – Quality Control Test

  • First check the viscosity for its ideal use.
  • Test curing time to be certain.
  • Test its mechanical properties like elongation, tensile strength, etc.

Step 8 – Package

  • One part systems can be packaged in tubes, cartridges, etc that do not welcome moisture ingress. Thus way curing is not initiated.
  • Twp part systems should be packaged into separate containers or dual-component cartridges.

Step 9 – Store

Needs to be stored in conditions that are controlled to keep product stability as well as shelf life higher.

RTV-1 Silicone vs. RTV-2 Silicone

Area RTV-1 Silicone RTV-2 Silicone
Part One part system Two part system
Curing time Cures faster from 24 to 48 hours Full curing is about 24 hours
Cure Mechanism Cures when exposed to moisture of the atmosphere Cures through chemical reactions
Ease of use Pre-made to be used from container A two part mixture is needed before use
Storing Store in a container that is moisture proof Store parts separately to prevent curing prematurely
Adhesion Doesn’t require primers to achieve ideal good adhesion Has higher level of adhesion but is made better with primers
Temperature resistant Can withstand temperature ranges from -60°C to 200°C. Formed for a wider temperature range or exact thermal needs
Durable Excellent UV, chemical, and weather resistance Excellent durability

 

RTV Silicone vs. Regular Silicone

Area RTV Silicone Regular Silicone
Curing method Room temperature curing Heat curing and cures at higher temperature
Curing time Cures faster from 24 to 48 hours Cures slowly, can take several days or heat curing
Parts Avail in one- and two-part systems Mainly one-part systems requiring heat curing
Flexible nature Very flexible and elastic after curing Not as flexible as RTV silicone
Waterproof Excellent waterproofing properties Good waterproofing properties, however, formulation varies
Resisting chemicals Highly resistant levels to solvents, oils, bases, and acids Has good resistant but varies with formulations
Temperature resistant Can withstand temperature ranges from -60°C to 200°C. Variable with ranges that are similar available
UV resistance Excellent UV resistance Can degrade over a period if it is not UV stabilized
Durability Lasts long and durable Not so durable since it cannot withstand harsh conditions
Use environment Ideal for outdoor use Ideal for indoor use mostly
Electrical insulation features Has excellent dielectric features Based on formulation, insulation properties varies but are basically good
Odor Low odor, particularly in its neutral cure form Strong odors during heat cure process

 

RTV Silicone vs Silicone

Area RTV Silicone Silicone
Method of curing Cures at room temperature Has different curing methods like UV light, heat, etc.
Parts Avail in two parts (RTV-1 and RTV-2) systems Avails in one or multiple-part systems based on type and use
Curing time Cures faster Doesn’t cure as fast as RTV silicone
Ease in use Easy to use Not all silicone types are easy to use
Electrical insulation Has excellent insulation properties Not all silicones come with this feature
Resistance to temperature Ideal in different temperature ranges from -60°C to 200°C. Not all silicones can resist temperature. However, some can withstand up to 300°C.

RTV Silicone Uses

RTV Silicone Structure
RTV Silicone Structure

Below are some uses of RTV Silicone:

  • It is used as an adhesive to bond materials like metal, glass, ceramics, and more.
  • Ideal for automotive gaskets, plumbing fixtures, and construction sealings.
  • Used for parts in electrical devices and circuits for electrical insulations and safety.
  • Can be used to create molds that are flexible to cast chocolates, resins, etc.
  • To fix leaking windows, roofs, and more.
  • Creating molds and seals in manufacturing medical devices.
  • Make molds for sculptures, confectionery, baking and other artistic works.

FAQs

Is RTV Silicone better than Standard Silicone?

RTV silicone and standard silicone both come with their unique benefits. So, based on your need or requirements, you will need to choose the type that will meet that need.

When should you use RTV Silicone?

RTV silicone can be used on gasket corners, on stepped casting environments that have gaps, or when flexible and/or room temperature curing sealants are needed. They can be used for electrical insulations too.

Conclusion

As the names suggests, room temperature vulcanizing silicone is a unique material that cures at room temperature. Depending on your unique application requirements, you can use it a single component or two component.

At LEGENDAY, we help you get silicone products made from high grade materials. For any inquiries, contact us now.

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