Milkiness in carbon post cure

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#1

Hello all,

I have had a strange reaction with a part (many weeks post cure). There is some white milkiness that has appeared on a few parts. I have attached pictures of the problem areas.

The piece was made using epoxy, and wet lay.

One of the areas where there is milkiness, I attached a label using 5 min epoxy many days after the part was cured. I don’t think that has anything to do with it, since the reaction happened in other spots as well, where there was no secondary bonding.

In my readings I have come across something called amine blush; could this be it?

Any help is greatly appreciated.

#2

Have you tried washing it?

#3

If its in the resin and not a surface problem, milkiness is a contamination issue normally. Contamination can be water but is normally something else such as contamination on the mixing sticks when stirring or in mixing pot. Was this an infused part as it doesnt look like wet lay?

#4

He mentioned that it’s wet lay. I am leaning towards water contamination myself. Was it very cold or humid when you made these?

#5

Usually don’t see amine blush on the mold side.

#6

Is it a locally resin rich area?

A lot of composite resins can have a milky appearance when the thickness builds up sufficiently.

#7

Thanks for the replies.

Yes it is a wet lay. The humidity was ok, not the most humid of days. The other side of the peice is still perfect (each side was laid separately).

The only other thing I can think of is I might have used a damp cloth when I was applying the PVA to the mold, and since the half of the mold that produced a good finish on the part was done first, with a dry cloth, it was not affected.

#8

5min epoxy often creates milky surfaces because it is most times not mixed that accurate.
It than reacts with CO2 to carbamate.
If it is in the wet lay up resin it is humidity.

#9

I’ll chalk this one up as humidity, or water contamination.

I guess I will try reducing the humidity next time by having some hair dryers blowing towards the workspace, and having a gauge to monitor the humidity level.