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Home  > Forum  > Coatings & raw material failures  > Yellowing in Auto OEM clearcoats

Sunday, 15 September 2019

Yellowing in Auto OEM clearcoats

2 Posts

Thursday 24 June 1999 1:00:00 am

We are suffering a yellowing problem in an automotive clearcoat formulation. The problem is shown mainly on the white basecoat. After full system E-Coat-Primer+Basecoat+Clearcoat. Without E-Coat and Primer the problem is reduced a lot means evaporation from previous coats (amines??) have an influence on this yellowing. I have some ideas how to solve the problem but unfortunately not defintives ones. Can anybody give ideas to improve clearcoat formulation to make it less sensitive to this yellowing!. Of course baking at hiher temperatures makes it worse.

Thanks

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Tuesday 29 June 1999 1:00:00 am

Hello Mr. Rey,
My experience is that the previous coats do not have very much influence on the yellowing. If you compare different clearcoats for this effect make sure you work with same dry film thicknesses.
I assume you have an SCA agent in the clear coat. As these materials contain urethanes and amines, the yellowing most probably comes from there. Check out your clear coat by leaving out the various ingredients one by one to find out which one is responsible.
Kind regards
Ralph Stange @ BASF Ludwigshafen, Germany

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Wednesday 30 June 1999 1:00:00 am

Dear Sir:
If you tell me about the polymer systems and the work you went through, especially to determine the source of the yellowing problem, I may help you.

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