Homebrew PCBs

Most peculiar.  I originally noticed this with denatured alcohol.  The 
denaturing agent is usually methanol.  I *THINK* I have seen the same effect 
with PGA ethanol, but now I am questioning my sanity.  I will do some 
experimenting down in the lab later today.

I did come across a mention of 0.37% solubility of polystyrene cup material 
in PGA, but not much else with a web search.

----- Original Message ----- 
From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, November 28, 2006 5:15 AM
Subject: Re: [Homebrew_PCBs] Isopropyl Alcohol 90%


> On Tue, 28 Nov 2006 06:43:34 +0100, Syd H. Levine
> <wireline@...> wrote:
>
>> Ethanol will most definitely attack polystyrene and its cousins.  If you
>> have not noticed it, it is because you have not been handling true
>> polystyrene.  It does not attack most other plastics.  My paper towel
>> dispensers in the shop are polystyrene, and if my fingers are wet with
>> ethanol, they will stick to the darn things and leave fingerprint marks.
>
> I just tried, with a solid polystyrene cup (marked), expanded polystyrene
> foam (marked), and ABS.
> None of these plastics shows any reaction whatsoever, when exposed for
> like a minute or so. I have rubbed the ethanol around with my finger and
> there was no stickyness, nor was there any surface disturbance after
> drying.
>
> So you are either mistaken (solvent not ethanol or towel holder not PS),
> or your ethanol is denatured with something agressive. I was told they
> used to denature it with petrol in some places.
>
> I'm sorry, but it's just not happening. I have used different brands of
> denatured ethanol here for at least 10 years, regularly on ABS and PS with
> no adverse effects. Some of my parts boxes are styrene plastic, and i
> remove obsolete markings all the time with ethanol.
>
>
> ST
>
>
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