Permatex Silicone

[MaximumMini]

I need a good, load bearing silicone that when cured, will help assist support a heavy load. Temperature will always be below 250F. It will not be subject to immersion, oil, grease or fuel.

AFAIK, Once fully cured, the RED Permatex Silicone is the sturdiest, hardest, most dense of the Permatex line of Automotive Silicone Sealants.

I need a silicone that can support substantial weight load without failing. Do you know of a better silicone in a tube that would be a better load bearing silicone?

Let's forget the specific application. It'll be insides the engine compartment. Who cares? All that is important here is which is the best at supporting a heavy load.

Thanks if you have any information.

 

[kschachn]

Interesting, why all the intrigue?

You need a high durometer elastomer. Good luck finding that, maybe you will. If it's really important then I'd try to use one that's already cured and available in sheet form.

 

[JohnnyG]

Take a look at DAP Auto/Marine sealant. But you'll have to do your own testing.

I found this one for you, but I'm sure there are many options:
https://www.mcmaster.com/products/s...-strength~14-day/reaches-full-strength~24-hr/

 

[kschachn]

Take a look at DAP Auto/Marine sealant. But you'll have to do your own testing.

I found this one for you, but I'm sure there are many options:
https://www.mcmaster.com/products/s...-strength~14-day/reaches-full-strength~24-hr/

Those structural sealants with a published durometer are a much better gamble.

 

[MaximumMini]

Folks at the Auto Parts Store said the GRAY is denser and stronger than the red for LOAD and TORQUE applications. While RED is better at higher temps. This is not a high temp scenario. Gray then maybe (if not one of the above?)

 

[wings&wheels]

I am a fan of 3M products for critical applications; boats, airplanes, sometimes vehicles. Does it have to be a true silicone? 3M 4000UV is a silane and one of my go-to's. 3m 5000 fast cure is my go to for permanent, high strength bonds with the emphasis on permanent.

 

[MaximumMini]

I am a fan of 3M products for critical applications; boats, airplanes, sometimes vehicles. Does it have to be a true silicone? 3M 4000UV is a silane and one of my go-to's. 3m 5000 fast cure is my go to for permanent, high strength bonds with the emphasis on permanent.

I checked into it. Looks pretty good, but it doesn't seem quite as dense and heavy load capable as Permatex Gray?
I need something as close to "Liquid Hard but flexible Rubber" as I can get.

 

[kschachn]

I checked into it. Looks pretty good, but it doesn't seem quite as dense and heavy load capable as Permatex Gray?
I need something as close to "Liquid Hard but flexible Rubber" as I can get.

Once again, if this mysterious application is that critical you’re better off with a cured sheet product. That will have a published durometer.

 

[Trav]

It would be a big help if you told us what it has to do, there are urethane, acrylics, seam sealer type products, etc that are much stronger than silicone.

 

[The Critic]

Look thru here and see if you can find something viable:
https://threebond.com/wp-content/uploads/Products-Guide_ver6-LOCAL.pdf

 

[wings&wheels]

I checked into it. Looks pretty good, but it doesn't seem quite as dense and heavy load capable as Permatex Gray?
I need something as close to "Liquid Hard but flexible Rubber" as I can get.

Grey is probably close to or a stronger material that 4000, however 5200 is much stronger than Grey bond wise, probably has the same flex or close, but it is very, very difficult to remove and not as resistant to chemicals. It is resistant to UV though.

Share the application, curious.

 

[The_Jeff]

I bet OP's filling in holes in his motor mounts.

If so, windshield urethane is the usual go-to.

 

[Nukeman7]

I bet OP's filling in holes in his motor mounts.

If so, windshield urethane is the usual go-to.

If he is filling/repairing motor mounts, street racers have also successfully used LOCTITE PL 3X Construction Adhesive to bolster the firmness of the elastomeric inserts.

 

[paulo57509]

Consider the substrate you're trying to bond. Some silicones produce Acetic Acid (vinegar smell) when curing and can be corrosive to the substrate. don't use these types of silicones around electronics.

Take a look at Dow-Corning silicones. At least they publish data sheets so you can compare durometer, etc.

 

[MaximumMini]

I bet OP's filling in holes in his motor mounts.

If so, windshield urethane is the usual go-to.

Windshield Urethane...hmmmm...that is some good stuff. That just might be better.

Yes, I'm weary of the motor mounts sagging after just a few months of replacement and the engineer in me believes this simple adjustment might greatly extend their life. Looking at them, I would almost say they are made to fail sooner rather than later judging by the amount of material used for suspension and the design.

Too soft and it doesn't help. Too firm and you'll feel the vibrations. It's a balancing act.

 

[dfarr67]

Ford International gray silicon.

 

[Exhaustgases]

I bet OP's filling in holes in his motor mounts.

If so, windshield urethane is the usual go-to.

When I saw the title its the first thing I thought of too. It is also a great glue, if your rear view mirror needs to be glued back on etc.
If it sticks so well to shiny glass what won't it stick to?

 

[Auto tech]

Silaprene solid seal. Comes in an orange and white tube. Bad ass stuff. Literally like a body putty in a tube, replaces welds and seals against anything

 

[meep]

There’s enough volume in the engine mounts that I don’t think you’ll need anything on the rigid side here. “Less is more” is probably going to go a long way. Remember, it’s replacing something that was liquid.

 

[MaximumMini]

After filling the cavities in the mounts with Gray Permatex, I'm finding that when you glob that stuff thick like that, the sealant towards the center has a hard time curing. On the outer edges it's curing just fine. But several days on, if I press an edge hard enough I can still get liquid gray permatex sealant to smear out. I'm wondering how long it will take to fully cure through and through (if it ever does).

You guys that suggested the Gray were right. That stuff gets really rigid when cured. Maybe too rigid as Meep suggested above?

May need to drill small holes through it to allow air with moisture in to promote curing?
It's gonna be interesting to see if that stuff withstands the pressures it'll be up against.