Will silicone sealant stand 80C (ish)?

[brass monkey]

I need to fill a few draught holes where the CH pipes come through the ceiling (bungalow). The sheds don't seem to list the upper temp of their silicone sealants. TIA.

[Dave Baker]

It withstands the 100C plus temperature of the engine sumps and other engine parts I've used it on for 20 years.

[fred]

In article , brass monkey writes

Bog standard silicone sealant should be good for 120degC, some go to 200 & high temperature rated goes to 300degC.

Watch put for acrylic sealant pretending to be silicone which may not be rated above 80 and specialist silicone, I've just seen some for glazing that they say is only good to 50.

The benefit of the acrylic would be that it is paintable, whereas silicone is not.

[dennis]

I use silicone rubber kitchen bakeware and they can be baked at 220C without problems.

[The Natural Philosopher]

Temp no prob but acrylic sealer - decorators caulk - is better. It paints!

[ScrewMaster]

Use high temperature silicone to be on the safe side. You'll have to go to a plumbers merchant rather than B&Q to get it.

[Dave Plowman (News)]

My local exhaust place uses it - I suppose a special high temperature version? They said it was quite expensive, but far better than any other exhaust sealer. Although I'd always thought a good exhaust properly fitted with the correct gaskets etc wouldn't need sealer.

[Dave Baker]

Silicone sealant is the in-thing for exhaust systems nowadays. Everyone who tries it swears by it. I never got on very well with those old exhaust pastes and putties you could buy anyway. They set rock hard and then just chip off. I never managed to cure a leak at a sleeve joint with them. Their main effect seems to be just to make it impossible to dismantle anything again.

Normal DIY silicone will withstand at least 100C if it's the low modulus stuff and up to 200C if it's the high modulus acetoxy cure type so any of them are fine for hot water heating systems or general engine gaskets like sumps and rocker covers. High temp RTV usually runs from about 260C up to as much as 350C. It is expensive though. A 310 ml tube of ordinary domestic silicone is about 3 quid and if you buy enough of it maybe as low as £1.25 or so. A 95g tube of high temp sealant is over a fiver so about six times the price per gram. It's still a lot cheaper than buying the gaskets though. I think the shim gasket for the joint between the manifold and cat on my Focus is £6 from Ford for a wafer thin bit of metal about 4 inches square. Sod that for a game of soldiers.

Luckily I have a mate who works in a huge industrial complex, I'd better not say which one, and they seem to have a need to stock just about every type of industrial consumable you could ever imagine. Loctite in various grades, greases, gloves, goggles, WD40 to name a few of the things he's acquired for me. The last delivery was a tube of Loctite 598 catalyst safe high temp RTV silicone because I have to change my exhaust manifold soon. It's listed to be ok up to 260C but apparently doesn't mind the fact that exhausts get much hotter than that.

[Dave]

If I remember rightly, it will stand temps up to about 300 C.

Dave

[geoff]

There is no single silicone sealant, the stuff you use to seal a bath is completely different to that which is used for gaskets

If you get some high modulus silicone from a central heating merchant, it should withstand the temperature

[Dave]

Many thanks for that. I am used to working in the aerospce industry usung Dow Coring stuff. RTV etc.

Dave

[geoff]

Glueing eurofighters together ?

Just get some high mod silicone from a CH merchant

... I cannot believe that Dow Corning do not publish data sheets for silicone used in aerospace applications

Smuggle some out between your bum cheeks - just tell them that you've been playing squash

[Dave Baker]

There's no silicone sealant ever made that can't withstand the sub 100C temperatures of a domestic hot water system. Low modulus, high modulus, cheap, dear, clear, coloured - they'll all cope with at least 100C. Given the caution the manufacturers will display in their spec sheets to avoid being sued you can bank on them coping with a lot more than that too as I've found over the years with engines. Oil temps and therefore block and sump temps exceed 100C by a considerable margin but no silicone sealant I've ever used has failed to work other than perfectly reliably in such an environment and I've only ever used cheap standard domestic stuff for £3 a tube rather than the many times dearer automotive types.

[Dave]

No they were taken out of the hands of the long standing team of develoment and given to the yes men and a new department was formed as a result.

I have worked on Lightnings, Jaguars, Victor tankers, Canbera PRA, Hawks and otheres that I can't mention. This is where I learned about bonding and various bonding substances.

Dave

[Dave]

I have to agree with you here. The silicone I worked with had an upper temp of about 300 to 350 degree C before it broke down.

Dave

[geoff]

'Kin good ACS on them, though

(insert smiley here)

The fighter who shall not be named

Outward bound course, eh ?

[Dave]

Stealth?

Dave