Plexiglass and Acrylic Are They Identical
Been getting this question for 20 years. Short answer, yes. Same stuff. PMMA. Poly methyl methacrylate if you want to sound smart at the supply house.
Plexiglass was a brand name from Rohm and Haas way back. Kleenex situation. People called all acrylic plexiglass and it stuck. Rohm sold to Arkema, brand changed hands a few times. Nobody cares anymore. You walk into any shop and say plexiglass or acrylic, guy behind the counter knows what you need.
Now here's where it actually matters.
Cast vs Extruded
This is the real difference nobody talks about when they're asking about plexiglass vs acrylic. Cell cast and extruded are not the same animal.
Cell cast, they pour liquid monomer between glass plates and bake it. Takes forever. Costs more. But the material machines like butter. I can rout cell cast Acrylite all day, edges come out clean, no stress cracks six months later.
Extruded they push pellets through heated rollers. Cheaper, faster, fine for a lot of jobs. Bend it, thermoform it, no problem. But try to drill near an edge without annealing first. Cracks. Every time. Learned that one the hard way on a $400 aquarium panel back in 2008.
Brand Names
Acrylite from Roehm. Lucite from whoever owns it this year. Optix is the Plaskolite house brand. Perspex if you're talking to someone from UK.
Here's the thing. Plaskolite bought a bunch of these companies. Half the stuff comes out of the same plant in Ohio now. The old timers swear cell cast Lucite from the 90s was better. Maybe. Can't prove it. What I can tell you is I stopped buying no-name import sheet after a job in 2019. Customer wanted cheap, I sourced cheap, laser cut edges yellowed in under two years. Outdoor application. Should have known better.
Domestic cell cast, you pay the premium, you get consistency. Taiwan extruded is fine for indoor signage. Chinese sheet is a gamble. Sometimes great, sometimes internal stresses so bad it warps sitting on the rack.
Machining Notes
Carbide spiral upcut, single flute, 18000 rpm minimum, feed rate depends on your spindle but I run around 150 ipm on quarter inch. Go slower than you think. Chip load matters more than speed.
Laser, we run a 150 watt Epilog for most jobs. Half inch needs multiple passes or you get melt back. Edge comes out polished if you dial it in. Too fast, edge is frosted. Too slow, you're vaporizing too much material and the fumes will gunk up your optics. Our exhaust fan runs 24/7 during cutting.
Flame polish. Forget hydrogen oxygen unless you like explosions. We use MAPP gas. Used to use propane but MAPP runs hotter, faster passes, less chance of overheating. Keep the torch moving. Soon as you see the edge go glossy, you're done. Linger and you'll watch six inches of edge bubble up and turn white.
Cementing
Weld-On 4 for thin joints. Weld-On 16 for gap filling. Scigrip if you can get it in your area.
Capillary method, hold pieces together, run the cement along the joint with a needle bottle, capillary action pulls it in. Sounds easy. Takes practice. Cement goes where it wants to go if your surfaces aren't flat and clean. Every scratch shows after. Ask me about the display case I had to remake three times.
For structural joints I like Weld-On 40, two part, sets up thick. Gives you working time. Costs more per tube but cheaper than redoing a job.
The Scratch Problem
Glass doesn't scratch. Acrylic scratches if you look at it wrong. Customers never understand this until they wipe their new sneeze guard with a paper towel. Then they call you.
Novus plastic polish, three step system. Actually works for light scratches. Deep gouges, you're sanding with wet 800 grit and working your way up. Or you're cutting a new piece.
Hard coat acrylic exists. Costs twice as much. Scratches about half as easily. Still not glass.
Static
Acrylic generates static like crazy. Fresh cut piece will grab every dust particle in the shop before you get it to the packing table. Anti-static spray helps some. Pink poly sheeting for packaging. We switched to that two years ago and returns for dust contamination dropped to almost zero.
One More Thing
Polycarbonate is not acrylic. Lexan is not plexiglass. Different polymer entirely. Higher impact, yellows faster, scratches easier, needs different cement, different feed rates, smells different when you cut it. If someone calls asking for bullet resistant plexiglass, they want polycarbonate. If they want a 20 year outdoor sign that stays clear, they want acrylic.
People mix these up constantly. Even purchasing agents at companies that should know better.
That's the rundown. Both names, same material, real differences are in how it's manufactured and who made it.
