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Subject:
From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 14 Sep 2011 09:46:49 -0500
Content-Type:
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text/plain (358 lines)
Yeah, what he said.  I know from our past internal studies that we get 
static electricity generation that are in high levels with things like 
silicone adhesives or urethane adhesives dispensed as staking compounds. 
And when you have components that can be damaged by as little as 50 volts, 
that is a reliability hazard.  We have air ionizers going in such 
applications, along with properly grounded ESD mats and wrist straps for 
the operators.

Inge, there is not enough Diet Mt. Dew in Iowa for me to even try to 
figure out the physics behind triboelectric charging mechanisms between a 
liquid insulator and a solid insulator.

The issue that we have, which prompted my original question, is that much 
of our conformal coating is done by hand (don't ask why).  The acrylic 
coating used has a high solvent load with a relatively fast evaporation 
rate.  Besides the pneumatic syringes, we have small open containers of 
conformal coating.  The air ionizers blowing across the coating booth has 
a tendency to evaporate the solvent, making the coating very stringy and 
viscous.  Leads to a lot of waste.  It makes the operators jobs harder. 
And of course, our managers do not want to incur the cost of putting an 
air ionizer in every booth.  Static dissipative materials would be the 
preferred route to eliminate the charging in the first place.  The 
operators did not like the black carbon loaded ones that we use because 
they cannot see how much coating is left in the tube as they can with a 
translucent body.  Some programs re-use syringes, some do not.  Static 
dissipative syringe bodies are expected to be more expensive, so 
Enterprise Sourcing (or as we call them, The Enemy) will have a conniption 
fit over increased costs and so some sort of sleeving device would be a 
desired alternative from their perspective.  The last time we looked, our 
existing vendors wanted very large minimum orders for these and did not 
really have them as stock items for off the shelf purchase.

Which is why I originally went to this forum to see what solutions you 
guys were using.  Still looking for something along the lines of "we use 
Bob's House O' Syringes, part number BR-549".  I do have a call in to 
Ellsworth Adhesives, one of our suppliers, as was suggested.

Doug Pauls



"Stadem, Richard D." <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
09/14/2011 08:15 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Stadem, Richard D." <[log in to unmask]>


To
<[log in to unmask]>
cc

Subject
Re: [TN] Pneumatic Syringes and ESD






Okay. Gotta tell you.
ESD generation of fluids of all types has always been a major issue in 
many manufacturing fields, especially in the automotive, boat, metal 
furniture, etc. epoxy paint applications and very especially the medical 
profession.
So yes, there are dissipative syringes, tips, and special holders that 
ground the syringe back to the machine's electrical ground. 
Just so you know, the Navy recently expressed a concern with ESD charges 
occurring from epoxy application. They reviewed our process, but I only 
use the dissipative syringes, so no issues. However, I do know that there 
has been a major push away from the poly syringes to dissipative within 
the industry.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Wednesday, September 14, 2011 6:33 AM
To: [log in to unmask]
Subject: Re: [TN] Pneumatic Syringes and ESD

Inge,

I have seen many materials that 'string' like crazy when dispensing -
conductives and non-conductives.  I've always used localized ionized 
blowers
in situations where stringing is observed, in the belief that 'stringing'
was related to charge generation - and for the most part, this has greatly
reduced the stringing.  While not scientific 'proof' of charge generation,
it might support the concept. 

When the dispensed material's tail separates from the dispense needle, it
can take off large distances in any horizontal direction.  Some materials
seem to throw a string equal in length to the dispense height. 

Even the conductive paste materials have a large percentage of
non-conductive resins involved.  Some silicones can be even more messy.

Could charge generation be related to a shearing effect as the material is
extruded through a needle, or past the brush hairs in Doug's case?  Could
the repeated time pressure pulse of a dispenser's compress and release of
the material within the syringe to the extent that charge generation is
taking place within the bulk of the material [on a molecular scale]??? 

And possibly what I call 'stringing' has nothing to do with charge
generation...

Personally, I believe that an antistatic syringe barrel and piston is less
effective than a well controlled workstation.  Even if the barrel and 
piston
are antistatic, are static dissipative needles available?  What about the
vinyl hose coming from the dispenser to the barrel adapter at the syringe
end of the hose?  Is that antistatic as well?  What about the plastic
fitting on the end of the vinyl hose going into the plastic fitting on the
face of the dispenser unit?

Be interesting to hear comments.

Best regards,

Steve 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Wednesday, September 14, 2011 6:33 AM
To: [log in to unmask]
Subject: Re: [TN] Pneumatic Syringes and ESD

Doug,

Triboelectric means adding or stealing electrons through friction. How can 
a
uncured glue (liquid with a high viscosity) move electrons from your 
nozzle?
I've been in the game for decades and not heard about such things. I've
participated in p-p courses, glue courses, read lots of articles etc, but
missed what you insist.

Human and dry hair has a molecular crystal-like surface, and via the Fermi
level you can move electrons from the orbit. However, if your hair is fat,
there will be no charge movements, because the fat has no specific surface
for that purpose. Likewise, I thought uncured glues were no aspirants
either.

Well, never too late to learn something new.

Inge

 Relationship between *triboelectric* charging and surface *...*
<
http://search.mywebsearch.com/mywebsearch/redirect.jhtml?qid=62bac059e5f09c

b4c1291b201f0024f4&searchfor=kinetic+explanation+of+triboelectric+charges&ac
tion=pick&pn=1&n=77decd8b&ptb=naCNCR5Azm75RkmBmXss1w&ptnrS=ZRxdm784YYSE&ss=&
st=hp&cb=ZR&pg=GGmain&ord=4&tpr=hpsb&redirect=mPWsrdz9heamc8iHEhldEWVlFOy8LX
VdR6PzojpERxbLlEmRQOowS8Qj5BmJGVqQkswtwN%2FH7EAkxVp0REdxDZ8QU9G9gHdhVQrRQ2vn
%2FnU%3D&ct=AR>
bleaching, and oxidative dyeing has only a small effect on
*triboelectric*charging. Measurements of the
*kinetics* of *charge* decay indicate that none of these *...*
http://journal.scconline.org/pdf/cc1985/cc036n03/p00189-p00212.pdf -
Cached<
http://search.mywebsearch.com/mywebsearch/redirect.jhtml?redirect=GGc
ached.jhtml&action=click&searchfor=kinetic%2Bexplanation%2Bof%2Btriboelectri
c%2Bcharges&curl=http%3A%2F%2Fjournal.scconline.org%2Fpdf%2Fcc1985%2Fcc036n0
3%2Fp00189-p00212.pdf&isDirResults=false&tpr=hpsb&cid=KYJrE_TQtsAJ&ptnrS=ZRx
dm784YYSE&st=hp&ptb=naCNCR5Azm75RkmBmXss1w&ct=GC&pg=GGmain&n=77decd8b>




On 13 September 2011 20:06, Douglas Pauls
<[log in to unmask]>wrote:

> The coating is insulative in its liquid state as well.
>
> Doug Pauls
>
>
>
> "Mike Fenner" <[log in to unmask]>
> 09/13/2011 12:48 PM
> Please respond to
> <[log in to unmask]>
>
>
> To
> "'TechNet E-Mail Forum'" <[log in to unmask]>, 
<[log in to unmask]>
> cc
>
> Subject
> RE: [TN] Pneumatic Syringes and ESD
>
>
>
>
>
>
> You would have to check with supplier, or verify it yourself; but though
> the
> coating is insulating when cured it may well not be uncured in liquid
> form.
>
> Regards
>
> Mike
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
> Sent: Tuesday, September 13, 2011 4:53 PM
> To: [log in to unmask]
> Subject: [TN] Pneumatic Syringes and ESD
>
> Good morning all,
>
> Time for a silly question.  The question has been raised internally as 
to
> the risk of ESD generation when an acrylic conformal coating (an
> insulative material) is applied using pneumatic syringes (also an
> insulative material), through a nylon brush (a third synthetic 
material).
>
> 1.  Do you know of any studies done benchmarking static generation 
levels?
>
>  We have done some here, but want to do a sanity check.
> 2.  If you have such devices in your facilities, what are your 
mitigation
> efforts?  Air ionizers, grounded tubes?
> 3.  Does anyone use, and can recommend, ESD safe syringe bodies and 
caps?
>
> Many thanks in advance.
>
> Doug Pauls
> Rockwell Collins
>
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