RE: [Killietalk] WEld-on??

[Chris <cgraseck at optonline_net>]

Knowing me, I probably used 91% Isopropyl.  As the alcohol evaporated
the acrylic cracked (many cracks up to an inch long, along the entire
edge).  We noticed the same thing in the machine shop where I used to
work. We replaced a window on a CNC machine with acrylic.  It cracked
all along the edges when exposed to the coolant.  Changing the window to
polycarbonate solved the problem.

Perhaps using 71% alcohol would be O.K. but most of the store bought
stuff contains some sort of contaminant which is left as an oily residue
when the alcohol evaporates.


In a message dated 4/7/04 1:39:57 PM, cgraseck at optonline_net writes:

<< My experience is that one should never use alcohol of any sort on
acrylic.  >>

Solubility parameters of acrylic (poly methyl methacrylate or PMMA) are 
unusual in water/alcohol mixtures. I did a study once that showed that
100% ethyl 
alcohol was not a good solvent for PMMA, but 90/10 ethyl alcohol/water 
dissolved a significant amount of PMMA. However, at less than about 80%
alcohol in 
water mixtures, it was a non solvent. Ternary phase diagrams represent
these 
solubility relationships remarkably well. I cannot  remember the exact
details but 



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