Query on PA66+GF15% - Color variation (Natural to Yellowish) problem

[vivkrish]

Hi All,

I Have a question..!

We are using PA66+GF15% for one of our product. We are facing color variation (Natural to Yellowish) problem on that. I heard information that, while that product stocking for 10-15 days from the injection gets color change on it.

Is there any possible of absorbing moisture while stocking 10-15 days in Poly Amide filled with Glass fiber?

When absorbing moisture really it changes the color of the product.?

Anyone help me to overcome this issue...!


Thanks,
Vivkrish.

 

[Golfman25]

A couple of things.

First, how does it come in and is stored, ie; sealed foil lined bags?

Second, are you sure it is fresh form you vendor?

Third, where do you notice the color change. It could be from your drying.

Fresh material should be good for a long time if stored properly.

 

[Miner]

It's been awhile since I have worked with PA66, but the biggest problem I encountered was drying out and becoming brittle. The supplier of the fastener in the picture would pour 12 ounces of water in the plastic bag containing these in order to prevent them from snapping on assembly. Another product that I dealt with we had to store in a special room with 95% humidity until we had to ship them to prevent dryout and embrittlement. In the final application, they had coolant running through it and it was no longer an issue once installed.

Is there any chance that the discoloration is caused by the heat exposure during molding?

 

[Miner]

Just found the following technical information.

 

[Ronen E]

PA will readily absorb moisture from its environment, regardless of GF content, and may change properties as a result. Not necessarily a bad thing as long as you account for it.
Yellowing could occur due to various reasons. To track down the root cause carefully check the source and what you actually get, then all stages of handling, pre-, during and post-injection moulding.

 

[vivkrish]

A couple of things.

First, how does it come in and is stored, ie; sealed foil lined bags?

Second, are you sure it is fresh form you vendor?

Third, where do you notice the color change. It could be from your drying.

Fresh material should be good for a long time if stored properly.

Hello Golfman25,

The injected parts stored in our vendor end as a open condition (Not in sealed pack).

vendor itself it has been stored for 10-15 days. (Now we have suggested to 2-3 days).

We are preheating before painting on it. While preheating the color change noticed.

Our vendor statement is While stocking for a while, it changes to Greenish. Then while preheating before Painting it changes to Greenish to Yellow.


Thanks,
Vivkrish.

 

[vivkrish]

PA will readily absorb moisture from its environment, regardless of GF content, and may change properties as a result. Not necessarily a bad thing as long as you account for it.
Yellowing could occur due to various reasons. To track down the root cause carefully check the source and what you actually get, then all stages of handling, pre-, during and post-injection moulding.

Hello Ronen E,

Yep, I agree with your statement before injection while stored as a granules(Without proper storage) it absorbs moisture. But after injection is it possible?
I have verified all the stages. Injected parts has uncolored only. After stocking of some days only it changes its colors.

Thanks,
Vivkrish.

 

[Ronen E]

But after injection is it possible?

Yes, it’s possible and likely due to PA’s chemical structure.

 

[vivkrish]

Yes, it’s possible and likely due to PA’s chemical structure.

Okie Thank you...

 

[vivkrish]

It's been awhile since I have worked with PA66, but the biggest problem I encountered was drying out and becoming brittle. The supplier of the fastener in the picture would pour 12 ounces of water in the plastic bag containing these in order to prevent them from snapping on assembly. Another product that I dealt with we had to store in a special room with 95% humidity until we had to ship them to prevent dryout and embrittlement. In the final application, they had coolant running through it and it was no longer an issue once installed.

Is there any chance that the discoloration is caused by the heat exposure during molding?

Hello Minor,

Here its not a problem. After injection while stored for sometime it changes the color. Because we can observe the discoloration after completion of injection itself. We didn't find any discoloration immediate after injection.

Thanks,
Vivkrish.