Author Topic: How conductive is lexan?  (Read 6399 times)

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Offline zeos

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How conductive is lexan?
« on: May 11, 2015, 02:03:57 am »
I bought a sheet of lexan to stick some breadboard on and have some extra space to put raspberry pi, arduino, etc. on.  Is it safe to do this or should I put some of that pink foam that sometimes comes in computer motherboard packaging?
 

Online Monkeh

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Re: How conductive is lexan?
« Reply #1 on: May 11, 2015, 02:07:41 am »
If you can't measure it..
 

Offline babysitter

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Re: How conductive is lexan?
« Reply #2 on: May 11, 2015, 06:49:05 am »
you might google it, but short: you can consider it to conduct at the "Not at all" level. High voltage breakdown needs some kV per mm thru it, resistance is better written as a number with exponent. Thats the clean, clear product, intense colors might get the resistance down.
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Offline Psi

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Re: How conductive is lexan?
« Reply #3 on: May 11, 2015, 06:52:51 am »
The pink foam will be orders of magnitude more conductive than the lexan
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Offline T3sl4co1l

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Re: How conductive is lexan?
« Reply #4 on: May 11, 2015, 06:57:21 am »
Indeed, your question is the wrong way around -- the pink stuff is millions to trillions of times more conductive than most plastics!  It's used to ship and store unpowered electronics.  Though almost everything will be okay operating in contact with it, anyway -- despite the difference, its resistivity is still usually measured in exponents too.  So the in-circuit resistance between points touching the stuff will be in the gigaohms -- something no digital circuit would notice.

I have a very different caution for you, actually -- be very careful cutting that stuff, it likes to crack like nobody's business.  Or is that acrylic, or both?  Both like to melt and gum up high speed cutting tools, too (drills, saws, etc.).

Have fun,

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Offline SL4P

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Re: How conductive is lexan?
« Reply #5 on: May 11, 2015, 07:01:22 am »
I suspect the pink foam you're referring to is conductive!
(megohms per inch) for dissipating static buildup.
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Offline Psi

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Re: How conductive is lexan?
« Reply #6 on: May 11, 2015, 07:21:28 am »
I have a very different caution for you, actually -- be very careful cutting that stuff, it likes to crack like nobody's business.  Or is that acrylic, or both?  Both like to melt and gum up high speed cutting tools, too (drills, saws, etc.).

Acrylic is the one that cracks when you look at it funny.  Lexan/polycarbonte does like to melt and gum up the cutting tool though, as you say.
Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline electr_peter

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Re: How conductive is lexan?
« Reply #7 on: May 11, 2015, 07:27:26 am »
Don't worry about plastic, there will be no issues at all.
I add small rubber feet stickers (used on furniture) on the bottom of the development boards so it does not scratch surfaces and does not short out on metal surfaces. It adds some bounciness and friction/resistance to forces from cables too.

I have a very different caution for you, actually -- be very careful cutting that stuff, it likes to crack like nobody's business.  Or is that acrylic, or both?  Both like to melt and gum up high speed cutting tools, too (drills, saws, etc.).
Be aware with transparent acrylic materials. Acrylic will crack on contact with any (!) chemical unless it is water or substance designed to be used on acrylic. This includes almost all types of glue, alcohols, loctites, etc (that is - anything other than water). Do not ask how I know...
 

Offline OldNeurons

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Re: How conductive is lexan?
« Reply #8 on: May 11, 2015, 08:27:33 am »
Certainly no problem at all with resistivity which is in the range of 10E16 Ohms-cm. http://www.associatedplastics.com/forms/pc_lexan_9034.pdf
I would be more cautious about static charges.
 

Offline mzzj

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Re: How conductive is lexan?
« Reply #9 on: May 11, 2015, 09:58:34 am »
I have a very different caution for you, actually -- be very careful cutting that stuff, it likes to crack like nobody's business.  Or is that acrylic, or both?  Both like to melt and gum up high speed cutting tools, too (drills, saws, etc.).

Acrylic is the one that cracks when you look at it funny.  Lexan/polycarbonte does like to melt and gum up the cutting tool though, as you say.
IMO Polycarbonate is very nice to work with sharp tools and wont melt easily. 12mm PC plate will cut easily with small handheld circular saw with good finish and drills nicely without worry of cracking.
Acrylic (PMMA) is cracked easily and melts reasonably easily.
Polystyrene is the royal pain in a..  will ether crack or gum on tooling, sometimes crack AND gum in the same time..  :-//
 

Offline f5r5e5d

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Re: How conductive is lexan?
« Reply #10 on: May 11, 2015, 10:21:33 am »
actually polycarbonate is worse for solvent crazing than acrylic - keep ketone solvents far away unless you want a pile of chips

http://www.theplasticshop.co.uk/plastic_technical_data_sheets/chemical_resistance_guide_polycarbonate_sheet.pdf

 

Offline zeos

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Re: How conductive is lexan?
« Reply #11 on: May 11, 2015, 02:09:56 pm »
Thank you for the info.  I like the idea of adding feet.
 

Offline macboy

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Re: How conductive is lexan?
« Reply #12 on: May 11, 2015, 02:14:44 pm »
I suspect the pink foam you're referring to is conductive!
(megohms per inch) for dissipating static buildup.

Many here assuming pink foam is conductive; it is not. It is "non static charge generating", meaning that it does not readily take on or give off electrons when rubbed against other things. This  prevents static buildup which destroy electronics, but it is not conductive, and won't actually dissipate static charge like conductive products will. The shiny metalized (or black) plastic bags are conductive, the black open-cell foam that you stick dip ICs into is conductive, but pink bags and foam are not.
 

Offline KJDS

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Re: How conductive is lexan?
« Reply #13 on: May 11, 2015, 02:28:35 pm »
I do know that a brand new instrument, only one working in the world was about to be sent to the US and I saw that the screen was dirty so gave it a quick wipe with acetone.

I then had a mad half hour finding and replacing the screen after it had completely frosted.

Don't put any volts across black conductive foam. Actually, do put volts across it, but do that outdoors for fun, it combusts well.

Offline LabSpokane

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Re: How conductive is lexan?
« Reply #14 on: May 11, 2015, 03:19:15 pm »
actually polycarbonate is worse for solvent crazing than acrylic - keep ketone solvents far away unless you want a pile of chips

http://www.theplasticshop.co.uk/plastic_technical_data_sheets/chemical_resistance_guide_polycarbonate_sheet.pdf

Add ammonia-based cleaners to the list - in particular spray window cleaners.

Polycarbonate is tough on cutting tools. Stick to carbide-tipped if you can. Also keep the cutting speeds down to reduce melting.
 

Offline jobog

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Re: How conductive is lexan?
« Reply #15 on: May 11, 2015, 09:44:33 pm »
I cut a lot of lexan sheet while working at Lowes part time.  The best way is to score the sheet several times with a sharp knife and then snap the sheet, hold down one side and put pressure on the other, over the sharp corner of a board or table.  Even the 1/4" stuff breaks very clean this way.
 

Offline CatalinaWOW

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Re: How conductive is lexan?
« Reply #16 on: May 11, 2015, 10:19:32 pm »
I suspect the pink foam you're referring to is conductive!
(megohms per inch) for dissipating static buildup.

Many here assuming pink foam is conductive; it is not. It is "non static charge generating", meaning that it does not readily take on or give off electrons when rubbed against other things. This  prevents static buildup which destroy electronics, but it is not conductive, and won't actually dissipate static charge like conductive products will. The shiny metalized (or black) plastic bags are conductive, the black open-cell foam that you stick dip ICs into is conductive, but pink bags and foam are not.

Many, perhaps most, of the "pink foams" and static control plastics ARE static dissipating.  They are often, perhaps always, not-conductive by EIA-541 definition of < 10^4 ohms, but many manufacturers claim static dissipating qualities which means resistance in range of 10^5 to 10^12 ohms per EIA.

If you are really concerned about these qualities you need to know the vendor of your example of pink foam, and know what that vendor claims about their material.  Whatever the theoretical arguments, I have had no known ESD issues with devices that have been shipped in, stored in or worked on pink foam.   Can't say the same about devices that have had no ESD protection.
 


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