Rubber blooming on end product

[Julia Mahir]

I'm trying to understand the nature of blooming that appear on our products but cannot really understand these I got from internet:

1. Is the color change light induced? (mask part of sample for reference)
Grey/Brown - amine antioxidant
Pink - phenolic antioxidant

2. Is the color change heat induced?
If yes with stickiness/embrittlement - oxidative degradation
If yes without stickiness/embrittlement - amine antioxidant


What does light induced and heat induced mean?
Do I know to apply light/heat on products?

Thanks in advance.

 

[GrahamBennett]

"Light induced" means that if you expose your rubber part to e.g. sunlight for any length of time then there is a colour change.

"Heat induced" means exposing the rubber part to heat.

Many cases of blooming are due to an excess of sulfur in the formulation, however. This appears as a white discolouration that can be easily removed with a solvent wipe but will recur over a relatively short space of time.

forumtowers.com

 

[Julia Mahir]

I also would think Sulphur is the culprit, as usual...
But could sulphur less than 1.5phr also "helps" in case of blooming.

Yes, as said... it blooms, and we washed with silicon and water and then when it reaches our oversea customer (after some time)...it blooms again..

 

[GrahamBennett]

You are quite correct. In fact sulfur levels above about 1.3phr will bloom on the final product if it hasn't all been consumed during vulcanisation. You should inform your customer that this blooming will not affect the performance of your parts as it is a cosmetic effect only and they could remove it as you do.

To help you to eradicate the bloom altogether I would need to see your formulation but I suspect you will not be able or willing to divulge this on an open forum.

forumtowers.com