brown MMA-a stupid question

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From:Linda Jenkins <>
Date:Wed, 25 Aug 1999 18:52:21 -0400
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Dear Sarah,
	Not a stupid question at all!  What I suspect that you are seeing
is the inhibitor in the methacrylate called hydroquinone.  Lots of MMA
recipes call for washing the methacrylate to remove the inhibitor.  This is
usually done in a separatory funnel where you pour equal amounts of methyl
methacrylate and 10% sodium hydroxide.  The first wash fumes and bubbles
and separates(like oil and water) into a clear liquid and a very dark brown
solution on the bottom half.  The dark brown solution is allowed to drain
and methyl methacrylate is washed a couple of more times with the sodium
hydroxide.  Each consecutive wash produces a lighter brown solution as the
hydroquinone is removed.
	Neil's recipe does not involve this messy method-YEAH!  He simple
overwhelms the inhibitor with the benzoyl peroxide which acts as a catalyst
to start polymerization.  The dimethylaniline is used as a plasticizer, if
I remember correctly.  The brown color does not interfere in the
microscopic viewing of the slide - just in the aesthetics of the block.
Linda Jenkins, HT
Clemson University
Department of Bioengineering
Clemson, SC

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