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RE: Measurement of Viscosity

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I guess the problem I have is that whereas the specified requirement for
viscosity for this injection resin (according to ASTM D 1638) is shown in
"cps", the actual product being submitted for approval claims a viscosity of
"< 3 mPa.s".

Now, if I'm doing my conversions right, 1 mPa*s should be exactly 1 cP (or
"cps" if you prefer).  So what it's say is that the viscosity is so low it
sounds like it's a plasma or something!!! Probably only achievable in a
particle accelerator or some such exotic place.

Since I'm not used to dealing very much with "viscosity" It's hard to have
an intuitive feel for it.

As it stands, it sounds like this product manufacturer shouldn't have used
"millipascal-seconds" but something like "decipascal-seconds".

Or, put another way, the product probably has a viscosity of "< 300 mPa*s",
not "< 3".

Anyway, that's just to give you some idea whence comes my confusion.


William L. Polhemus, Jr. P.E.
Polhemus Engineering Company
Katy, TX, USA
Phone (281) 492-2251
FAX (281) 492-8203
email bill(--nospam--at)polhemus.cc

-----Original Message-----
From: Christopher Wright [mailto:chrisw(--nospam--at)skypoint.com]
Sent: Friday, January 11, 2002 12:28 PM
To: ?
Subject: RE: Measurement of Viscosity

>The particular substance that is supposed to have a
>viscosity of "between 250 and 400 cps" is an ULTRA-LOW VISCOSITY
>Polyurethane injection resin.
I couldn't follow you on why the viscosity couldn't be 200 centipoise.
Anyway the ISO practice on defining units would be lost on most plastics
suppliers. The 'ultra-low viscosity' designation probably means ultra low
for a polymer, which would be a lot higher than water or diesel. As I
recollect a few days I spent in a fiberglass plant the polyester resin
has a consistency between paint and warm honey (greater than crude oil
but less than glycerine, I figure) which would put it in the same range
as your resin. You need the stuff to be light enough to saturate glass
mat, but not so light to splatter and run out. If your urethane is the
stuff used to patch concrete, it'd seem that you'd need something fairly
stiff to keep it from simply flowing through the crack.

I did a little sniffing around and kept running into the 'cps' units for
viscosity. I'd be happier if they'd use standard terminology, but
plastics suppliers' are notoriously imprecise about engineering
properties. They like property scales like NG, OK and GOOD more than
actual numbers. My guess is that cps means centipoise. If you're still
not sure I'd call up the nearest university with a materials science
department.



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