Glues for NMR probes summary

From: Roger Kautz <rkautz_at_lynx.dac.neu.edu>
Date: Wed, 23 May 2001 17:48:10 -0700

Thanks to all who responded.

I would very much welcome any further information on epoxies or other
materials that can be formed into components in or near the coil.

In summary:

- Duco model airplane cement. Thinned with toluene.

- Teflon pipe tape: use to hold while glue dries, or in place of glue.

- Cyanoacrylates ("Super Glue", "Crazy glue").
   Brands vary widely in viscosity and somewhat in strength. Buy several
and test. Viscosity is important for whether it fills and supports gaps,
or runs deep into cracks. Most brands are thin. Devcon SuperGlue II is a
thick one. Apply with a glass whisker (pulled pipette). Hardware stores
will have several choices of SuperGlue (Devcon) and KrazyGlue
(Elmers). Loctite makes several (available from Small Parts, Inc), and 3M
is also in the market (e.g. "Pronto").

- Epoxy. Clear, slow-setting recommended. (5-minute epoxy may leave
un-crosslinked epoxy, which may cause background signal.).
Doty NMR used to sell an epoxy that was "susceptibility matched" (to
copper? Glass? Air?), but apparently wasn't worth the trouble for them to
repackage.

Papers from Sweedler's lab describe using superglue to hold down the
coils. In contact with samples a polyimide, which is cured by baking, is
mentioned in Subramanian et al. Anal. Chem. 71:5335.

                                        -- Roger




(Select specific responses follow)

----
> From: jim breeyear <jbreeyea_at_zoo.uvm.edu>
I have used Devcon Duco Cement. We used to call it airplane glue. Not
the plastic glue. Seemed to work ok. Use sparingly. There may be
something better on the market by now.
Jim
----
> From: "A. Scott Chesnick-" <chesnics_at_zeus.nhlbi.nih.gov>
Hello -
I saw your posting on Ammrl.
I use "Duco" model airplane cement thinned down with toluene.
Apply the thinned cement to the foil and then hold until solvent evaporates.
I sometimes use Teflon pipe tape to secure the foil while drying if my fingers are in the
way.  On some designs all I use is the Teflon pipe tape to secure the coil to the
glass. I do not use any cement at all and the fluorine of the TFE is all the NMR signal.
The excess cement can be removed with a solvent-soaked
pipe cleaner or, after drying, by scraping with a scalpel blade.
As far as Epoxies - I use the more expensive brands of clear 24 hour set.  Stay away
from the Duro brand five minute instant epoxies. The parasitic signal you are picking
up may be the residual epoxy that hasn't cross polymerized.
There is also on the market an "invisible" glass cement that sets in direct sunlight
or strong UV light. I have tried this on one or two coils with some success and I am
still experimenting with this.
Many years ago I also experimented with making a fully deuterated epoxy
and also using a glass cement known as "water glass" mixed with D2O.
This worked well enough but wasn't worth the effort.
Regards Scott
A.Scott Chesnick- Senior Scientist
Nuclear Magnetic Resonance Instrumentation and Biomedical Engineering
National Institutes of Health
In Vivo Center for Nuclear Magnetic Resonance Imaging Research
Building 10 Room B1D-513A
Bethesda, Md 20892
301-496-4282

Received on Wed May 23 2001 - 16:49:05 MST