For some element samples of mine which I wish to seal up very well for safety reasons. I have seen in various places element samples in an ampule,
which is then embedded in some sort of plastic. I wish to do this, but I am not sure what this plastic stuff is, it it epoxy or something else?
If anyone can recommend a product, that would be great!Xenoid - 31-5-2008 at 19:54
Probably a good idea to get some custom molds and/or release agent.
[Edited on 1-6-2008 by Xenoid]argyrium - 31-5-2008 at 20:46
I am unsure with what you may have seen but am familiar with many epoxies used in the field of conservation. In an epoxy for ceramics/vitreous
materials you will want one with a relatively low viscosity, low rate of yellowing (ALL will yellow to some degree over time) and Tg that is not too
high. The exotherm during cure may or may not be a consideration for your ampules depending on the quantity cast and into what sort of "mold"
(insulated or conductive) you choose.
I am relatively unfamiliar with polyesters and so can't comment on them other than as a class of thermosets, their use in conservation is very
limited.
Two optical grade epoxies I routinely use are Epotek 301-2 and HXTAL NYL-1. There are others made by Ciba-Geigy and I'm sure many others, but I have
only read the long term studies on these.
The Epotek 301-2 is a 100/35 (w/w) mix and is not very forgiving for inaccuracies on the scale. Pot life depends on mass and ambient T. Sets up
overnight in thin sections. The numbers may be found at: http://www.epotek.com/categories.asp?ID=3
Unfortunately don't have anything at hand on the HXTAL. It is a bit more viscous than the Epotek and can take a several days for a moderate cure (it
will pour/run slowly next day in the lab) and has a very low exotherm.
They are both expensive but have their place.
It would be prudent to test whatever material you settle on in a scaled mock-up to see what sort of exotherm and pot life to expect before taking a
chance with your ampouled specimens. Bubbles entrained in the resin can be frustrating to deal with and may require the pre-wetting (paint brushed)
the surface of the ampoule and/or pulling a vacuum on the potted assembly.
Good luckPanache - 17-6-2008 at 04:21
don't use polyester's, even though they are cheaper you will be sanding it for days to get the surface clear so you can see your sample nicely.
Epoxy's on the other hand cure with a gloss surface so if you are happy it may require little additional polishing.
Epoxies shrink unappreciably when curing whereas polyesters shrink around 5% and this can be tricky on long samples as the sample is not shrinking
All resins generally have about a 1-2 cm casting thickness limit, if you cast any thicker they will crack, so you build up the layers, casting the
next one before the surface is cured on the previous.
Important if appearance matters is a dust free enviroment.
Don't bother using mold release agents on simple molds use instead polyethylene film (as in the stuff you wrap sandwiches in. It will leave your
surface perfectly clean and no additional polishing.
I did this as a hobby for a couple of years, i found any avoidance of sanding was important hence the tack of replies.
Looking forward to seeing them!!
oh yes epoxies will yellow over time unfortunately a major drawback to their use in 'desighner' applications, lol i don't think that the yellow
tinge bothers the raptor pilots though.
[Edited on 17-6-2008 by Panache]
[Edited on 17-6-2008 by Panache]Phosphor-ing - 17-6-2008 at 06:01
I thought the resin was Acrylic?Panache - 18-6-2008 at 15:42
Quote:
Originally posted by Phosphor-ing
I thought the resin was Acrylic?
trying to get your number of posts up?
I'm only joking but that was pretty lame, don't be offended i'm truely smiling.
