This was a response to another thread on the CCO forum about something similar:
"Bob,
after reading my post over again, oops.
I was referring to damage to the acrylic. I saw a video of a guy who flame polished the edge of a 3/8" square, let it cool and then poured isopropyl alcohol over it. within seconds it produced fracture lines all through the edges. It looked like the flame polishing produced a mechanical stress within the material and then the -OH weakened the bonds allowing for stress fractures.
"
Watch the video, and you can see how this probably happened.
Bob