perspex vrs lexan how to tell

**bollie7** · 28th May 2015, 09:41 PM

G'day All.
Though this is not directly metal related it is indirectly so I hope someone can help me. Mods -if you think this is unsuitable, my apologies and please do what you have to.
So - I have a small plastic case ( about 350L X 230 W X 60 D) from something that I intend to put some dividers in to use it to store some of my fastener assortment. I have what I thought was a piece of 3mm perspex which is a bit scratched so I thought "that will do for dividers" Went to break some strips off using the score both sides and snap method that has always worked in the past only to find that it wont break. Well I managed to break one bit off but it only followed the score for about half before heading of on its own.
So now I'm thinking it might be a lexan. (it as in the shed of my late FIL so I have no idea what it is)
Can anyone tell me an easy way to identify what it is (if thats possible)?
The reason I've started down this path in the first place is I have a number of old Champion Ruby tobacco cans that an old bloke gave me when I was an apprentice. I spotwelded the lids to the bottoms to end up with a stack all joined together. Great for small screws etc. That was fine 37 years ago, now though, I'm getting arthritus in my hands and found out tonight that they are getting a bit difficult to open. Time for a change I think.
I'll end up buying a few more plastic containers with dividers but they are not that cheap anymore when you start buying them in any quantity. Hence trying to use stuff I already had.

thanks
bollie7

**BobL** · 28th May 2015, 10:07 PM

If its a small strip and it snaps it's perspex whereas Lexan or Polycarbonate will bend even when it is cold.

**Big Shed** · 28th May 2015, 10:10 PM

Lexan or polycarbonate stress cracks when in contact with higher aromatic content solvent such as Mineral Turps but not with White Spirit.

Plexiplas or perspex is affected by solvents like acetone (it makes a good glue for it).

Put some turps on it and see what it does, if nothing put some acetone (or your wife's nail polish remover) on it if it affects it you have perspex.

**BobL** · 28th May 2015, 10:16 PM

There is also a burn test.

Perspex will continue to burn slowly after the flame has been removed, burn flame is yellow with blue tip
PC will self extinguish after the ignition flame is removed, burn flame is orange with black soot

**BobL** · 28th May 2015, 11:05 PM

Here is a link to a plastics burn test chart.
http://www.boedeker.com/burntest.htm

**bollie7** · 29th May 2015, 08:49 AM

Thanks for the replies. I'll look at this further over the weekend. I'm fairly confident its not Lexan. I've worked with that before and have actually made some guards from it where we put 90 deg bends in it using a pan brake. That particular time the stuff we were using was about 2mm thick.
I've never come across perspex like this before. Its been my experience that once it gets a bit old it becomes a bit more brittle and thus easier to break. Maybe I'm just losing it

bollie7

**chambezio** · 29th May 2015, 09:35 AM

Hi Pete
Rather than scoring and snapping put a fine blade on your table saw and just cut it that way. I usually put a thin piece of MDF under the clear sheet and cut the 2 together. The MDF just supports the clear sheet enough so it won't shatter. Once cut your pieces just need an arris and they are ready to use

**bollie7** · 29th May 2015, 02:17 PM

Rod
Unfortunately my table saw is buried under a pile of portable scaffolding atm. This was only going to be a 5 minute job

. Somewhere in my stuff I have some strips of fibre insulating board that I scabbed from a dump bin 30 years ago. I might dig then out and use them. Just have to remember the safe place I put them in.
bollie7

**pippin88** · 30th May 2015, 11:47 PM

Cast vs extruded perspex behave a bit differently so it may the one you aren't used to?

**Theberylbloke** · 31st May 2015, 11:33 AM

Greetings bollie7,

A long time ago, street light covers were made from perspex which was susceptible to vandalism from thrown rocks. Lexan or polycarbonate was found to be susceptable to bullets but not rocks. The perspex was clear/milky when viewed on edge and the polycarbonate was a medium green. There maybe variations in current plastics, that was a long time ago.

Cheers

The Beryl Bloke

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