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  #1  
Old 08/05/2003, 05:36 PM
schrader mo schrader mo is offline
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Location: Carthage, MO
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reef safe?

I got about 20 3'x2' sheets of acrylic today and it has LExan MR-4000 stamped on it.Is it safe to use?
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  #2  
Old 08/05/2003, 05:41 PM
GeorgiaSalt GeorgiaSalt is offline
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NICE!!!

VERY reef safe...Lexan is high grade acrylic (ok acrylics or Zepherant you can fill in the specifics ) and is perfectly reef safe.

It is what some bulletproof windows are made of and for the average DIY project is super expensive. So if you got these cheap or free I would say you got a GREAT deal...I don't know the specifics on the stuff, but I am sure the guys who do will chime in, but it is much stronger than your basic acrylic.

You may need special cement to glue it..once again I am sure they can tell you this...and I have read you can use thinner lexan than acrylic for projects because it is stronger.

Congrats on your acquisition,
GS
  #3  
Old 08/05/2003, 05:48 PM
schrader mo schrader mo is offline
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Cool I got it for free.I think it is about 3/8" thick.I would like to here some ideas about what to use it for and what kind of cement it takes to glue it together>
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  #4  
Old 08/05/2003, 05:50 PM
GeorgiaSalt GeorgiaSalt is offline
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HEH

Send some to me and I'll test it for you

just kidding

I am sure Acrylics or Zepherant (sp?) will be able to tell you what to use to glue it. They are the acrylic gurus around here from wht I have seen.

Oh, and you could make 4 90 gallon tanks with it if it is 3/8" thick. (need 5 sheets per tank 36"long, 24" wide, 24" tall)
GS
  #5  
Old 08/05/2003, 06:03 PM
Acrylics Acrylics is offline
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Re: reef safe?

Quote:
Originally posted by schrader mo
I got about 20 3'x2' sheets of acrylic today and it has LExan MR-4000 stamped on it.Is it safe to use?
What's the thickness?
Lexan MR is not acrylic at all but "mar resistant" polycarbonate. The mar resistance is essentially a micro thin silica coating that is virtually impervious to chemicals including solvents. To glue it one must remove this coating either by machining or sanding. Then either glue by using methylene chloride (Weld-on 3 is ok) or tetrahydrafuran (THF is one of the active ingredients in PVC pipe cement).
While very reef safe, IMO the uses are somewhat limited due to the nature of polycarb itself and the coating.
Although water-tight joints can be made, it is extremely difficult to get them to last long term. Also, since the material is so soft, it will bow alot more than acrylic possibly cracking the MR coating, at which point it will start to sluff off in rather large flakes.
If you decide to make something out of it, be EXTREMELY careful when routing, the material is very soft and routers can "grab" it and take you for a ride you would wish to forget or shoot pieces into either you or anything nearby.
I really do not wish to scare you away from the stuff but it can be downright scary even for experience professionals, so just be - well you know.
Sell it to someone iff you can, it goes for about $8-10/sq ft. so it might be worth a few $$ to someone.

Hope this is somewhat helpful
James
  #6  
Old 08/05/2003, 08:49 PM
GeorgiaSalt GeorgiaSalt is offline
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Acrlylics

Thanks for the information, you always enlighten me about these things. So it is softer than acrylic? Interesting, is that just this sub type of lexan or lexan in general. I was under the impression it is stronger than acrylic...is that true?

So the lexan used in bulletproof applications has a different coating I assume.

You said this lexan would bow alot, and would flake off where it bows. Does this reduce the strength in the bowed area?

Glad someone who knows this stuff is around here...there is alot of misinformation on the internet. I will have to track down the link on another forum where someone talks about using it to build a tank and that you could use thinner lexan than acrylic.

What exactly are the benefits of lexan, i.e. why is it sooooo much more expensive than even cast acrylic (thickness for thickness that is)

Thanks,
GS
  #7  
Old 08/05/2003, 11:38 PM
Acrylics Acrylics is offline
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Re: Acrlylics

Quote:
Originally posted by GeorgiaSalt
So it is softer than acrylic? Interesting, is that just this sub type of lexan or lexan in general. I was under the impression it is stronger than acrylic...is that true?
Polycarb is softer, this is what gives impact resistence. Look at like; glass is harder than acrylic, less prone to scratching, more rigid, but because of these properties will break first. Well acrylic is harder than polycarb, less prone to scratching, more rigid, but because of these properties will break first...while not the perfect analogy - you get the picture.
In most respects it is stronger. General Electric (mfr of Lexan) has a warranty on it not to break for 5 yrs under "normal operating conditions". It's kinda like "bend but don't break". It does have some fairly unique characteristics especially for transparent plastics like it's very resistant to gamma rays which basically shatter acrylic (fun to watch) and is very impact resistant which leads to the following:
Quote:

So the lexan used in bulletproof applications has a different coating I assume.
Bullet resistant Lexan or "LexGuard" is made by laminating the material together alternating it's extrusion poles. The thinnest Lexguard is 3/4" made by laminating 1/8", 1/4", 1/4", 1/8" each time turning the extrusion or "ripple" orientation. You can get LexGuard either coated or not, has little to do with it's mechanical properties. You can also get the stuff laminated with glass on each side to 'shroom out the bullets prior to actual penetration. Comes up 4.25" thick which we used to supply to the various governments - will stop 50 cal. bullet.

Quote:

You said this lexan would bow alot, and would flake off where it bows. Does this reduce the strength in the bowed area?
No, the mechanical properties are unaffected by the coating or the loss of it.

Quote:

...someone talks about using it to build a tank and that you could use thinner lexan than acrylic
Good luck

Quote:

What exactly are the benefits of lexan, i.e. why is it sooooo much more expensive than even cast acrylic (thickness for thickness that is)
It's not that much more expensive until you get to 3/8 - 1/2" but does jump from there. Lexan is fairly unbreakable so makes for great windows in fact all train windows are Lexan MR, machine guards, twin wall polycarb makes greenhouse material, some use it for skylights, even drinking glasses, tons o' other stuff not often thought about like CDs and DVDs are made from polycarbonate coated with aluminum and acrylic.

James
 

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