Small Optically clear fluoropolymer beads w RI ~1.36
Small Optically clear fluoropolymer beads w RI ~1.36
(OP)
Hello,
Am new to this board. Looking for a source for small (~0.200mm), optically clear plastic beads with a refractive index ca. 1.36, which I assume would probably be a fluoropolymer. For example, Norton FEP would be OK, but seems to be supplied only as powder or film?
Jonathan
Am new to this board. Looking for a source for small (~0.200mm), optically clear plastic beads with a refractive index ca. 1.36, which I assume would probably be a fluoropolymer. For example, Norton FEP would be OK, but seems to be supplied only as powder or film?
Jonathan






RE: Small Optically clear fluoropolymer beads w RI ~1.36
Nafion beads are a bit too expensive for this application, but would like the beads to be wettable by an ethanol-water solution. Teflon AF seems not to be wettable...CYTOP might work?
RE: Small Optically clear fluoropolymer beads w RI ~1.36
Maybe it is still available somewhere.
PMMA is very clear and a lot easier to wet than are Fluorocarbon based polymers. I think it's refractive index is about 1.36. I know it is somewhat higher than glass as lenses made from it can be thinner for the same power.
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RE: Small Optically clear fluoropolymer beads w RI ~1.36
This looks promising as it says fluoroacrylates will work (I checked and PMMA is too high at 1.49).
http://weekoflearning.pstc.org/papers.php
"Electro-Optical Light Management Material: Low Refractive Index Adhesive
Eng-Pi Chang
Principal Scientist
Avery Dennison
A prototype pressure sensitive adhesive, which has a low refractive index (< 1.36) and is optically clear, has been developed. The refractive index is a key feature in the application of optical polymers and this pressure sensitive adhesive is particularly useful for light transmitting devices. This pressure sensitive adhesive is a fluorosubstituted monoacrylate adhesive. Fluoropolymers are known to have low refractive index, but typically the fluoropolymers are not sticky and are opaque due to crystallinity. The design of this novel fluorosubstituted monoacrylate adhesive polymer is based on the rheological marriage of fluoropolymers and pressure sensitive adhesives."
You would still have the wetting problem though so why not add a tiny amount of surfactant? The best one I know of for wetting low energy surfaces is Dow Corning Additive 67. It's silicone based.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
in about this size by the lb-s. Wouldn't it do?
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RE: Small Optically clear fluoropolymer beads w RI ~1.36
Am trying to find a combo of spheres and liquid for which the spheres in the liquid would be invisible, i.e. matched RI's. This for imaging sub mm delicate museum specimens normally stored in 75% EtOH (~1.36).
Specimens tend to float in liquids near 1.474 (e.g. glycerol), and, anyway, would be best to leave them in the EtOH.
Hence the search for beads of low refractive index, which probably will have to be a fluoropolymer.
My problem is unfamiliarity with FP's and their appearance and the forms in which they are supplied, e.g. clear and ~0.2mm, would be best.
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
The full context is that I work for the Smithsonian, and we have embarked on a very large project to image our most valuable biological specimens. Many of these are stored in 75% EtOH and are small (~500um). It is difficult to take decent pictures of small things submerged in liquids. For the photos to be useful scientifically, the specimens must be posed in individually idiosyncratic ways. The informal solution has been to pose them in plain sand (i.e. partially submerged or nestled), but sand as a background is aesthetically inferior.
Thus the quest for clear, "sand-like" particles immersed in a liquid of matching refractive index. Spheres are the optimal shape.
The lowest glass RI's are ~1.45-1.474, but liquids that match are not particularly compatible with 75% EtOH, are oils, or toxic, etc. It's do-able, but not ideal.
So rather than high-tech liquids, how about high-tech spheres? Hence the question about fluoropolymer beads w RI ~1.36?
The component in the adhesive mentioned above in the abstract sounds good, but it's from an abstract at a meeting given by a corporate chemist reporting R&D--likely proprietary and probably unavailable.
Nafion reportedly would work, but it is extremely expensive. Other optical fluoropolymers seem to come in bars or films, and there are thousands of them.
I thought someone reading this forum might happen to know of some promising leads.
RE: Small Optically clear fluoropolymer beads w RI ~1.36
It's not so much that we can't stop motion w strobes, it's that a moving specimen drifts out of the plane of focus, and we are using 3D image 'stacking' technology to produce composite photos with great depth of field.
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
RE: Small Optically clear fluoropolymer beads w RI ~1.36
First have a look at this, it's Teflon AF from DuPont. It's amorphous and therefore transparent.
http://
The curve of refractive index versus temperature is here:
http://ww
It seems to be in the right range for your application.
Of lowest RI of any hydrocarbon polymer (non fluoro) is TPX® Polymethylpentene with 1.46
http://www.boedeker.com/tpx_p.htm
Here's a nice document of refractive index matching for LEDs. They use silicones (RI 1.40)and fluorosilicones (RI 1.38) and silicone thermosets (RI 1.38 – 1.57).
http
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
[PDF] Teflon(R) FEP 160, technical informationFile Format: PDF/Adobe Acrobat
FEP 160 is supplied as pellets and is. available in 55-lb (24.9-kg) multilayer kraftbags. with an integral polyethylene liner. U.S. Freight Classification ...
www2.dupont.com/Teflon_Industrial/ en_US/assets/downloads/h26581.pdf - Similar pages
[ More results from www2.dupont.com ]
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
Some time ago I spoke to the NuSil folks, who were kind enough to send me a sample, but the stuff cured to a rather rubbery, sticky solid, which I milled to small particles, but they stay sticky, even when wet. Can't have sticky. It may be that the hardener didn't properly mix. But you're right, NuSil is another promising technology.
Have been measuring the temp--it's gone up from 26 to 29C in about two hours, due to fiber optic lighting of EtOH bath.
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36
RE: Small Optically clear fluoropolymer beads w RI ~1.36
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Small Optically clear fluoropolymer beads w RI ~1.36