Fillers to get a final sg of about 5?

[espresso51]

Hi,
I need to run a job in HTV Silicone rubber with an SG of about 5.
Any idea of fillers that I could use for this?
I will need something that is reasonably priced and freely available.
It will also need to run through my injection machine.

 

[GrahamBennett]

Are you sure about the SG needed? 5 is terrifically high for a rubber compound. In fact the highest SG compound I've ever developed was about 2.9 and that involved very high quantities of barium sulfate (SG = 4.1 or 4.2) and no softeners.

 

[espresso51]

We do need the sg of 5.
We have looked at using Soft iron powder as used in Sintered metal components(sg7.8)but the part should be non-metallic.

 

[Metten]

Lead oxide, magnesium oxide and zinc oxide are also high in SG.

Maybe you could use an insert to use a normal SG rubber, but the SG of the total part would be higher.

 

[RubberDog]

Magnesium oxide has specific gravity lower... ~ 3.6g/cm^3.
Zinc Oxide seens to be the least expensive... ~5.8g/cm^3.
Lead is much higher, but I would not use due the safety, toxicology, etc.
You may also try ferrite.. But even, with so high level of fillers, I don't believe the mechanical properties will be ok..

Is it possible to share why do you need so high specific gravity?
Sincere regards,

Daniel Cortarelli
Polymer Materials'Engineer

 

[espresso51]

It's for a mining application where they Ned to simulate ore densities.
I need to match the s.g.'s.

 

[RubberDog]

And it does need to be silicone? For what reason?
Just wondering due, as mentioned before, the physical properties...
If could be in other polymers, it would accept more fillers.

Daniel Cortarelli
Polymer Materials'Engineer

 

[GrahamBennett]

Even with 200phr of ZnO added to LSR, the SG calculates out at just less than 3.0 and the viscosity would be too high to mould properly.