Your Frequently Asked Questions
Below you’ll find answers to the questions we get asked the most about our products and services. If you still need help or advice then 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 of the RTV when it cures?
Depends on the cure system, but for instance;
- RTV100 Series, RTV15X Series, IS5628 etc.- Acetic Acid (vinegar)
- RTV16X Series (inc RTV133), RTV524X Series, TSE39X Series- Alcohol
- Other systems like Oximes give off Oxalic Acid, others Acetone.
It’s important to choose the grade with the end application in mind, especially if corrosion could occur.
How can I speed it up?
Place near high humidity. For example in an oven at 60’C with a pan of water. Others use steam irons or wall paper strippers.
Can I thin/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. These days we can offer materials with much lower viscosity without solvent, straight out of the tube.
How much will I get from a cartridge?
Depend on bead thickness. E.g. 3mm diameter = 40mtr long, 6mm dia = 10mtr
How long does it take to cure?
Depends on a number of factors. 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. Really 10-12mm is the limit.
- The humidity is lower
- There is little air or its sealed
- Temperature is low.
If it’s cold, what temperature can 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 temp 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 it withstand?
Continuous operation from -55C to +200C, with intermittent exposure to 260C except red high temp products. RTV106, RTV116 and RTV159 will function at up to 260C constant and 315C intermittent.
1 Component RTV-Heat cure grades
How are they different to moisture cure?
They are ‘addition’ cure, so don’t give off a by-product, don’t need humidity, just heat above 80c minimum. They can be cured fully sealed. They are susceptible to cure poisoning by certain chemicals (inhibition).
Why would I use them?
Speed up curing and gain adhesion in minutes, curing without moisture, or in a sealed box. Curing a number of similar materials in an assembly in one go. They work well on metals and plastics and can bond silicone to itself and other materials.
So once cured how do they differ from the moisture cure grades?
Not that much that you would notice. E.g. Red products work to +260’C plus, they are still silicone.
Does the temperature matter above 80’C?
Yes 80C 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 RTV
I heard there are two types of 2 pack silicones, what’s the difference?
Condensation cure (RTV11) type which give off alcohol during cure, are pretty fool-proof, but shrink more. Addition (RTV6XX) which liberate nothing, shrink very little can be heat cured but can be poisoned during cure (inhibited)
What’s the lowest application temp?
Like one components, it’s really got to be frost and damp free but actually it is less of an issue as the catalyst helps to cure.
How can I speed the cure up on the two part materials?
For the RTV 11 and all the condensation grades you can use a faster catalyst, e.g. STO or use mild heat <60C. For addition cure materials, such as RTV6XX/TSE3331 a 10C increase in cure temperature will halve the cure time, roughly. Addition cure grades can be cured at over 150’C if so desired.
What service temperature will these materials withstand?
Pretty much continuous 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’s the cure time of the materials?
Depends on the base chemistry
- 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.
– TSE3331-Minimum 80’C.
It’s best to check the individual data sheets.
General questions for silicones
I want to stick to a particular material, where do I start?
Probably a look at the New enquiry questionnaire may help. The one part silicones are designed to stick so it depends on what cure temperature you want to use (less than 100C, you should look at moisture cure). The other major factor is the materials to be bonded. If it’s PTFE, Polypropylene, Polyethylene or POM (polyacetal) then you have a problem, they are very difficult to bond too. Everything else is normally possible without a primer.
See the Primer compatibility chart
Another little known product range is our PSA (Pressure Sensitive Adhesives) which will bond silicone to itself and other materials like a contact adhesive with instant tack. Particularly good for lamination and sheets.
Why would I use a silicone versus a polyurethane or epoxy?
Depends on the application, But silicone offers some unique properties;
- High and Low Temperature – resistant to long term exposure and remains elastic
- Resists Ultra Violet light (UV), Ozone, and weathering for long term exterior use.
- Generally safe to use and is found in food contact and medical applications, when approved.
- Can be made, by design, to stick or release from most substrates as an adhesive or mould maker.
How can I stop silicones sticking?
A mould release such as petroleum jelly or Teflon (PTFE) based are good. Give us a call for further help.
Can I paint on silicones?
No. Paint first then apply silicone.
How do I remove silicone?
Depends what it’s on. Most times try and mechanically remove the majority of it. If the substrates allows (plastics are sensitive), try solvents like Toluene or Xylene. We have also got a Silicone Digester that eats silicone but is not harmful too many other materials.
Can I colour/pigment silicone?
Yes we carry a range of pigments. Give us a call