epoxy yellowing without uv block varnish-alternatives?

[JuLia]

hi,

I don´t build or buy any boats, but I decided to ask here because you guys know so much about epoxy and other resins.

I produce beads and jewelry components with epoxy. I really want to polish them to a high shine. I love the cool surface and smoothness of polished items. Unfortunately some turned brownish/yellow with time Than I learned that epoxy tends to yellow soon. Now I do have to cover it with a uv block varnish but I don´t like any varnish on top of my epoxy...


help me pls, what to do? polyurethane seems to yellow also, polyester resin too. What alternatives do I have to epoxy? I need it in clear version to embed tiny things in it. It must not cloud or yellow in contact with water, chemicals or sunshine. Actually it has not to be a resin, something clear durable will do the job, but I don´t know what I could use..

many thanks

pls excuse my english its not my mother tongue.

[PAR]

Two part linear polyurethanes will eventually yellow, but it'll take much longer then single parts, varnish and epoxy alone. It also will not add color to the coating (like varnish does). Lacquer is an option as are some of the multi part automotive clear coats , but you're asking for a very difficult set of conditions to be served. There are also some water based products that are coming on line with clear coatings.

In the end, you'll have to do some serious research and start calling coating formulators asking for recommendations. This is because clear coating anything and desiring UV, water and chemical resistance is about the hardest thing a coating can preform.

[War Whoop]

20 Years back I shot Linear PU (Clear) over a White Gelcoat deck and it started to get a tinge after a couple years, I got sterling out to look at it,their lab got involved and it was on them, moral of the story is mix some solids into the clear ,they covered the job.

[bntii]

Years back one of my sisters cast items in resin with some success. I don't know what she used but I still have a few pieces and 30 years later they are still clear w/no yellowing.

A quick Google search yields this:

http://www.artmolds.com/product_deta...0Polyurethanes

"Clear Casting Resin is an optically clear polyurethane casting resin used where a hard, UV resistant, non-yellowing product is required. Clear Casting Resin is often used to encapsulate objects. Some of the most common uses of Clear Casting Resin are point-of-purchase displays, rapid prototypes, special effects, sculpture reproductions, giftware, etc."

"Clear Casting Resin provides a combination of performance properties including optical clarity, mechanical strength, hydrolysis resistance, gloss retention, and yellowing resistance."

It looks to me that these resins are seeing wide use by jewelry makers and artisans.

[gonzo]

I think that the choice of epoxy is crucial. If it has UV resistant additives, it will stay clear longer. A varnish coating will scratch and let areas yellow. Jewelery gets a rough treatment.

[CaptBill]

I think the epoxy formulated for the guys that pour bar tops nowdays is what you are after. Formulated with UV stability and outgassing performance (bubbles). Hopefully you wont need to polish as much because this stuff is optimized to dry to a wet/glassy finish. Try Epoxyproducts.com they are a good supplier. Here is a supplier from ebay.(search bartop epoxy)

http://cgi.ebay.com/ebaymotors/EPOXY...ssoriesQ5fGear


If memory serves me correctly, Epoxyproducts.com has an equivalent. I know these guys sell good stuff and have the best selection of 'fillers' around (you might find fun to experiment with. You gotta try some of their copper powder, really cool. I think they will send you samples if you ask). Just be warned, the web site will drive you crazy but everything about epoxy seems to be there, if you can just find it. Oh yeah you can't beat their prices plus these guys seem serious about selling you fresh goo (in case you don't use it all now you can expect longer storage time)

[Herman]

We have some of that stuff in NL, so that would be easy to ship to Austria. (Polytex resin)

However, Julia might be better off with casting acrylic. I believe Smooth-On has a suitable product.

[JuLia]

hi,

thank you so much.

@PAR what I am asking for, epoxy already eoes have, chemical ressistance, watersafe, cures hard except one thing: yellowing.
With varnish I meant that clear stuff that ladies put on her nails, lacquer ist the right word I think.

@War Whoop a couple of years sounds great, that would be a deal. Does polyurethane really gets yellow/tint/amber after years?

@bntii great stuff your sister used! wished yould know what it was. Many thanks for your research, this text I read before. I did many researches via Internet before I asked here. I am still collecting informations from more experienced people than me.

@gonzo I read, if it has uv blockers in it, it will just stay for a couple of weeks more clear. Not a long time. I thought the same today as I varnished my epoxy beads with uv blocker lacquer. What if it get scratches? oh damn it will yellow anyway

@CaptBill thank you for the link. Epoxyproducts.com : I knew this site and learned so much from it. Their help guide was very useful.

@Herman I will search for casting acrylic and Polytex resin through goggle. Although I seem to remember that acrylic comes only in white opaque color.

Here u can see that it started to tint:
these are my sanded and hand- polished beads, the half of the base is colored, the upper half is filled clear.

they transform into a necklace. This is clear epoxy with glitter embeded.

so that you get an idea what I am making.

[jim lee]

Here : "http://www.bjbenterprises.com/default.asp"

These guys make a water clear Urethane that is heat & UV resistant. It should last -much- longer than epoxy. Its also very tough (won't shatter) where as a polyurethane typically isn't. We use this for casting clear lights.

I can find the PN for the stuff we use if you want, when I get back to work tomorrow.

Hope this helps.

-jim lee

[CaptBill]

Nice work Julia.

I am sure you will find something to solve your coating issue. I did notice one disclaimer with the UV stable epoxies. It is not rated for direct sunlight exposure. There IS a second step that you can do for full UV ( from Max CLR specs) . Probably not a real issue with jewelry though. You should just test them all. Most of the places, I would imagine, do sample kits if you ask.

Let us know how it goes too. It's actually a great question around here.

[Herman]

http://www.smooth-on.com/Urethane-Pl...156/index.html

This is an option as well.

[JuLia]

hi

@jim lee thank you for the link.

@Herman thank you too.

Maybe Polyurethane is my next try, when my epoxy ends. I read in my document, where I paste all usefull informations about resins, that also others said that PU yellows slower. And so most of you did.

Perhaps PU is not so unhealthy than epoxy is. Need to read about it.

thank you for all your help

kind regards

[jim lee]

Polyurethane tends to be brittle, urethane is not.

[PAR]

Watch out for the toxicity of urethane. Polyurethanes are not considered toxic. Polyurethanes are chains of urethane groups. Polyurethanes can be formulated to be pretty much whatever you like. Urethanes are the base group of compounds and as such are fairly limited in what they can do, while the assembled at the sub molecular level polyurethanes, can be much more durable, harder, stronger, more elastic, etc.

There is a miss conception about epoxy being very toxic. It's really not. Naturally, you don't want to bath in it, rub it in your eyes, or eat it, but given the usual precautions, you'll have little difficulty with epoxy. The biggest issue with epoxy comes from sanding it. When sanded, the particulates can get into unprotected lungs, causing the typical difficulties, like COPD and black lung. If you sand epoxy that isn't fully cured, you are adding still reacting chemicals into your system, further causing issues with your health. A simple dust mask will solve these difficulties and if you work clean and use skin protection, no real worries.

[JuLia]

hi

I just know epoxy, polyurethan, polyester. But I heard of vinylesther resin and acrylic resin. Have to search for them. Actually I only wet-sand my stuff, and really have no good feeling about all the chemistry. OK I wear gloves but I don´t have a mask with filters ..it is so expensive, otherhands I really afraid. Sometimes my skin gets itchy. I heard of people that cant work with epoxy anymore because they got allergies.

but this gets off-topic hoping no mod will be angry.