Plexiglass in high voltage applications
It's not unusual for someone to select Plexiglass (tm) or other
acrylics for use in high voltage applications such as a high voltage
power supply. It does, after all have a good dielectric strength
rating. Plus it is inexpensive and it is transparent, which can come
in very handy in some systems. However, there are better choices,
primarily because Plexiglass is flammable, and brittle. In addition,
cracks can occur due to stressing or due to exposure of the vapors of
some solvents. I've heard of Plexiglass catching on fire in high
voltage power supplies.
A good material to consider instead would be Lexan (tm). There are
other possibilities, as well, but Lexan is a good place to start.