How long should the color of HDPE parts last in the sun 2

[TCrawley]

I am having my product made in China (for now) and the samples from the production run were found to loose their color (bright orange) by about 30% in 5 days of being outside. They are supposed to have UV inhibitor in them, but how can you tell other than doing an outdoor test or an accelerated UV test? The broker that I am using is trying to tell me that it is the colorant that is failing. Wouldn't the UV inhibitor protect the color? Any help with helping me understant the possibilities of why this is happening would be greatly appreciated.

 

[patprimmer]

The UV inhibitor protects the polymer from degrading in the presence of UV light.

The orange pigment will react to sunlight, not just UV light. Particular pigments will have individual reactions. These reactions may be affected by the polymer and all additives to some extent, whether positively or negatively.

The pigment manufacturer can advise on the light fastness of their pigment in a particular polymer, and of any potential compatibility issues with the additive package.

Very bright pigments tend to have low light fastness.

Bright pigments can sometimes have better light fastness if they contain heavy metals, but then health issues are a problem.

Regards

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[TCrawley]

Thank you for your reply patprimmer.
The material is HDPE and it has a 5% talc content to make it more rigid.
Doesn't HDPE retain color for more than five days?
I cannot remember the Pantone # but it is one of the brightest oranges they have, kind of a super bright safety orange.
I was hoping to stick with the brighter colors, because they are eye catching.
A lot of my customers are going to have this product outdoors and I would like them to have a product that can retain it's color longer than five days.
Would other bright colors such as Pantone blue #072U, and Pantone green #354U have the same results in the sunlight?

Respectfully,

 

[patprimmer]

The polymer is not the source of the colour, the pigment is.

The polymer can at times interact with the pigment to affect it's stability, BUT the colour loss is due to degradation of the specific pigment.

I don't know what pigment was used. You don't even know what pigment was used.

I don't know what pigments can be used to match your colour. Colours cannot be matched by subjective description.

You need to contact colour suppliers, give them a fresh, unfaded moulding or colour chip, then take their advice on what colour fastness they can offer for that colour.

They may offer several options re cost and compromises on quality of the match.

Increasing the concentration of the pigment will increase the colour fastness.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TCrawley]

Thanks for the advise, it is much appreciated, and very helpful. I should have the information needed to get them on the right track.
Much obliged

 

[Demon3]

I just write to agree with Pat (the omniscient). The colour comes from the pigment and so the colour fastness depends entirely on the pigment used. Bright colours are often organic pigments which lose colour quickly in the sun. Inorganic pigments last much better but they are sometimes composed of heavy metals like cadmium and lead.

The best choice may be to ask Clariant or other skilled masterbatch supplier. They should be able to advise you on what to use.