RE: Need help finding portable vacuum desiccator


Can not add a thing to what Gayle has said in her e-mail.  I think she
covered everything.  Unless you are using a combination of GMA and MMA it
will not polymerize in the cold with or without vacuum.
Good Luck!!  Pam Marcum

> -----Original Message-----
> From: Gayle Callis []
> Sent: Monday, August 12, 2002 11:04 AM
> To: Bernard Ian R SSgt 59 CRES/MSROP;
> Subject: Re: Need help finding portable vacuum dessicator
> If you are doing PMMA work, a dessicator under vacuum in the refrigerator
> basically doesn't work.  It is best to vacuum before putting into the
> refrig for 4 hours or so,  then release vacuum, tightly cap the
> jar and put
> that into the refrigerator.
> Having been through this, I tried vacuuming, going into refrig, and it was
> a bust. Besides that, the grease you use seizes up and you can't get the
> lids off after letting them sit for a day or so! I do not know what the
> physical explanation is, but I am not sure that the vacuum draws very well
> under cold temperatures, and you would need to put the vacuum pump in a
> HOOD! to avoid methacrylate fumes.
> As for dessicators, you can buy any kind from Fisher, VWR, etc.  make sure
> they are glass, MMA monomer fumes will eat plastic dessicators.  You can
> also buy O ring dessictors, Wheaton, to avoid using grease. The O ring
> expands in presence of fumes, you need extra O-rings which can be hung
> inside a hood to go back to normal size.  These dessicators will
> not hold a
> vacuum after a time due to O-ring expansion, but are wonderful for a days
> work under vacuum at RT, no more messy vacuum grease. The same
> goes for the
> stopcock area, these are ground glass surfaces, and need to be kept clean
> in order to turn.
> Ground glass dessicators must be cleaned of grease more often than we
> wanted to deal with - acetone and xylene will do that job, but if grease
> sets up like hard, concrete like glue on the ground glass area, you will
> have a mess trying to get it open. Been there, done that, had to shut the
> door from bad language!
> YOu also need to have a dessicator cage or plastic guard in case the glass
> desiccator explodes, rather implodes.  Dessicator sits in this cage while
> drawing vacuum and under vacuum.
>  and At 06:48 PM 8/11/02 -0500, you wrote:
> >I need a purchase source for a good vacuum dessicator that has a control
> >stop cock to allow pressure in and shuts it off to maintain
> pressure.  This
> >dessicator will then be place in a 4 deg C fridge for a number
> of days.  I
> >hope to maintain the same vacuum pressure all through out while in the
> >refrigerator.  Any ideas? (a source will be nice).
> >
> >Boring a hole in the fridge to maintain pressure is not an
> option.  I will
> >be using a plastic/monomer organic solvent(Methyl Methacrylate) in the
> >dessicator.  It needs to be under vacuum pressure.
> >
> >Thanks histonetters(especially in plastic)
> >
> >
> >
> Gayle Callis
> Research Histopathology Supervisor
> Veterinary Molecular Biology - Marsh Lab
> Montana State University - Bozeman
> 19th and Lincoln St
> Bozeman MT 59717-3610

<< Previous Message | Next Message >>