I spent a few years working in a plastics extrusion factory.
and Polycarbonate (lexan) were two of the materials we extruded into tubes.
The notched Izod means that any scratch, scuff or point which the surface has been marred when flexed will yield a stress riser. To say that differently, any imperfection is where all the stress is focused.
A perfect unmarred piece of acrylic will withstand lots of pressure, jump on it, bend it over a table top and nothing happens. Take a box cutter
and pass it across the surface once and apply pressure... snap. A scratched piece of acrylic is as good as already cracked. Do the same thing to a piece of polycarbonate and you'll still be pushing and pulling tomorrow.
What we are saying is that acrylic is brittle. It does not give, it cracks. Drop an acrylic tube on a concrete floor and scuff it up, and cut it with a chop saw and it will explode. (Better be wearing some polycarbonate safety
glasses.) An unmarred tube right off the line will cut like butter.
Polycarbonate flexes, it is tough... tough... stuff. Grinding polycarbonate scrap is like grinding rocks. A three phase 5 horse power motor
spinning a massive foot wide, 10 inch diameter double bladed cutter
will spit 2 inch wide chunks back out, and take twice the time of anything else.
Another kink in the plan for incredible materials, is that the molecular structure of extruded sheet is oriented long ways. This means that the plastic is stronger when stretched in one direction than the other. Cast sheet, where the pellets have been heated to a high enough temperature that they "forget" their memory of being pellet, and cross link with each other randomly makes for a stronger average in all directions.
When plastic deformation happens with polycarbonate, it hazes over and turns white at the point that has deformed. Plastic deformation is where a material is stretched far enough that it does not return to the same shape when pressure is released. Polycarbonate cracks, along point loads that have caused plastic deformation.
I'm comfortable that a 1/2 inch piece of polycarbonate is stronger than the 1/4 inch of dry polyester laminate of mat and finishing cloth that is the side of my cabin!