coloring LDPE

I am looking for a way to permanently color a finished product made from low density polyethylene. I am working with 1.25" thick sheets of LDPE,
sort of a milling process, and I can only find it in white.
Is there a dye or some coloring process I can use? I assume it is tough (even if possible) as my attempts to use "indelible" markers have ultimately proved fruitless. I'd like to be able to put the pieces in a small tub of the color and then fish them out - like coloring Easter eggs.
(If there is a different newsgroup where I might find an answer to this question, suggestions welcome on that, as well.)
TIA. -- Igor
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You probably have to use some sort of pretreatment, either a chemical (primer) or a physical (plasma, flame treatment) one.
Oliver
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Put them in hot tomato sauce for a few hours ;)
Most of the FD & C dyes are water soluble, but a few are oil soluble. There are also natural colorants such as lycopene (see above) and tumeric that might work well too.
John
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On 11 Oct 2004 05:42:27 -0700, snipped-for-privacy@aspenresearch.com (John Spevacek) wrote:

Thanks. I guess I should have mentioned that the finished product does not have to be food safe, if that is what the FD&C concern is. It does have to be safe to touch.
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If that is the case (I went with the most conservative approach initially), then you can try looking for D & C dyes, which should cost less. There are also non- D & C dyes that could work too.
John
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On 12 Oct 2004 05:37:18 -0700, snipped-for-privacy@aspenresearch.com (John Spevacek) wrote:

John -- Thanks. Unfortunately, I don't know nuthin' about dyes - for LDPE or any other material, except maybe for stains at the local hardware store and clothes dyes at the supermarket. It would be great if you could provide some additional info, such as where to get such dyes (in relatively small quantities) and how I determine what to mix them with to get them to take to the LDPE. Or, do they already come suspended in solution? Even so, what would I ask for? Again, thanks. -- Igor
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(John

Dyes are colorants that are dissolved in a liquid/solid. At a molecular level, the dye molecules are spread out evenly and you could theoretically get to the point where each of the molecules are separate from each other, no clumpiness. A dyed liquid is colored, but clear, such as in wine, beer or whiskey, or more to your case, wood stains and cloth dyes.
Pigments are colorants that are dispersed/suspended in a liquid/solid, and need to be clumpy in order for the color to be seen. You cannot see through a pigmented liquid. Paint is an example (although it is also an emulsion, which complicates the issue too much for discussion here).
A couple of companies to contact: Organic Dyestuffs http://www.organicdye.com/about.asp and also Noveon Hilton Davis (no website to speak of, except for Noveon, the parent company. Back when they were Hilton Davis, their number was 1-800-333-0335. Maybe it still works.) The technical service people should be able to help you much more than I can, and they can easily supply small sample sizes. Dyes and pigments can be extremely expensive, in some cases over $2000/lb. Fortunately, a little goes a long ways.
John
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On 13 Oct 2004 06:38:46 -0700, snipped-for-privacy@aspenresearch.com (John Spevacek) wrote:

That is a great help. The dye companies should know what they can dye. Makes sense to me. Thanks.
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If all you are trying to do is color the PE to an opaque color, I wouldn't use a dye at all. I would suggest using an inorganic pigment. It typically only takes about 1-2% of the pigment to do the trick. I've used Americhem here in the U.S. for my needs, but a quick google search on inorganic pigments popped up several suppliers across the globe.
Larry Effler

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I don't think you are likely to be successful trying to dye 1.25" thick p'e, can't you change to high molecular wt HDPE where you can easily obtain this thickness of sheet in a wide range of colours. If you have to dye them, then nylon is relatively easy to surface dye using hot water soluble dyes
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On 16 Oct 2004 11:58:36 -0700, snipped-for-privacy@smile-plastics.co.uk (colin) wrote:

I wish I could switch materials -- for a number of reasons, incl cost and availability. And colors. Can't. I need the flex/friction attributes of LDPE. Thanks.
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