Platinum Cure

[Ahmad Uzair]

Our Customer are demanding to use their Platinum Cure Silicone rubber for their part.
However after few days the rheometer MH for the platinum cured silicone decreases.
Until 3 month the rheometer MH just flat and the part doesn't cured at all.

Because of that I made development by put peroxide cure to it.
After I add C8A peroxide cure for the silicone, the properties back to normal.

Due to the part use was for medical product, they didn't want to use this improvise silicone.
A piece of advice for those who used to the platinum cured silicone are appreciated.

Regards

 

[Metten]

We use small amounts of platinum cured silicones, but do not see the same phenomenon.
Store it cool and away from contamination (sulphur and other vapours).

 

[btrueblood]

Sulfur is a catalyst poison; there are others. Keeping the container well sealed and stored cool as Metten suggests would help. But 3 months? Sounds more like contamination in the rheometer itself - if the rheometer gets used for other compounds using sulfur cure systems then traces of those could halt the cure the way you said.

from this website:

https://www.mositesrubber.com/technical/technical-info/silicone-rubber/

3rd or 4th paragraph in the introduction:

" The RTV system often utilizes a platinum catalyst. This type of cure system is very sensitive to sulfur, some organic rubber, certain tooling waxes, and machine oil. If an RTV silicone part is contaminated by any of these substances it will not cure and this reverted surface can cause problems."

 

[Ahmad Uzair]

I know it sound unbelievable but that what happen.
Even the molded part didn't cure during the production run.
The compression mold was use for silicone only but still didn't cure.
We store the silicone
>inside air conditioner room
>control temp 20`30 Celsius.
>Inside its own box

Here are our monitoring rheometer result.

https://files.engineering.com/getfi...-46c7-b029-2b7dda18ea3e&file=Rheo_problem.png

And here what happen after we add peroxide cure.

https://files.engineering.com/getfi...6c51-4177-baaa-4a04561069e0&file=rheo_C8A.png

From observation: The part didn't harden but back to its silicone property (soft)
But btrueblood mentioned that sulfur are catalyst poison. Does it means it kills the platinum catalyst function?


“I have no special talents. I am only passionately curious.”?—?Albert Einstein

 

[GrahamBennett]

But btrueblood mentioned that sulfur are catalyst poison. Does it means it kills the platinum catalyst function?

Yes.

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