methylmetacrylate polymerization

From:Gayle Callis

Use sealed embedding molds to be air tight.   There are empty plastic
containers, used for formalin fixation/specimen collection that have O ring
lids, in many sizes, even small - very handy and easy to use.  If the bones
are huge, use Rubbermaid containers with a lid, OR Nalgene polypropylene
containers with lids that fit over outside of jar top.  

 IF you do not put MMA in a sealed container for final polymerization, the
monomer evaporates rather than polymerizing properly, it changes the amount
of monomer you have in your mixture and you still get a hard block, but it
usually cuts poorly. The block tends to look depressed in the top/middle,
and has a strange texture.  Been there, done that, and always used sealed
molds having problems with open air polymerization. You do not have to use
vacuum for polymerization, but Do not use a heated air incubator/oven, this
gives uneven heating. A waterbath is superior starting at 37C as rapid
polymerization and resulting bubbles should be avoided at all costs after
your lengthy PMMA protocol. Some people use glass vials, scintillation
vials (plastic)with lids.  Glass is messy since you have to shatter it -
dangerous unless wrapped in a towel, then have to pick out glass fragments.
 Plastic scintillation vials are easy, just cut the end off and push block
out.  

By dessication for MMA, what do you mean?  Draw a vacuum?? This implies
drying, rather than polymerization or curing (final step to get a hard PMMA
block).  

At 09:18 AM 11/13/02 -0500, you wrote:
>dear all
>For the last polymerisation step embedding in MMA, must the molds remain
air tight, or can we let the molds open in incubator ?
>does anyone have the protocole of dessication for MMA embedding ?
>Thank you for anyhelp.
>Myriam baali
>marseille
>France
>
>
>
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu




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