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RE: GSBN:Siloxane, Oligomeric Polysiloxanes, Silanes and You

Sorry for not replying sooner Rob.
I agree geometry is always better than chemistry.  But there are situations
where the compromise of relying on chemistry is acceptable IMO.  Hence we
had better get to know what our optins are.

a) is it safe to drink?  Probably safer than drinking lime, cement, or even
significant dosages of earth plaster.  Is it harmful to health?  The
silioxane itself is quite inert, and is simply a precursor to silicone.  The
solvents may be harmful -- some are mineral solvents like alcohol and
petroleum distillates while others are mostly water borne.  You can choose
your poison
b) I tested a 5%wt solution of polymeric siloxane from Sika, the normal
concentration recommended for walls. Most manuf supply  5 and 10% versions,
the latter for bridge decks. I would suggest that 5% is the minimum quantity
we should presently consider.
c) I don't know enough to recommend brand names, but the product is fairly
similar across manuf - so long as 5%wt sloxane.  Xypex is NOT a siloxane, it
is apore-blocking crystal former, not vapour permeable.
d) Siloxanes are considered the best in highly alkaline environments like
fresh plaster and is the reason they were tested. Silanes have a slightly
smaller molecule and greater penetrating power but are higly volatile and
often evaporate away before fixing and stuccos tend to be rather porous
anyway 9unlike dense concrete, which may require the use of silanes over
siloxanes). BTW oligomeric polysiloxanes are simply a class of siloxanes,
the other being polymeric siloxanes. The latter is more common and has more
predictable and higher performance.  Some of the o-siloxanes are pretty bad
(e.g., those with only one or two functional alkyl groups for the chemists
on the list).
e) I don't think I can actually answer all the questions, but I can frame
the answer within narrower bounds.  Ransom is not my style, I prefer violent

John Straube
Civil Engineering Dept and School of Architecture
University of Waterloo
T: 519 888 4015 		F: 519 888 6197

-----Original Message-----
From:	Rob Tom [mailto:rw_tom@hotmail.com]
Sent:	Wednesday, February 07, 2001 6:27 PM
To:	GSBN@...
Cc:	martin.oehlmann@wxs.nl; jfstraube@...
Subject:	GSBN:Siloxane, Oligomeric Polysiloxanes, Silanes  and You

on 6 Feb 2001  blackrange@... wrote:

>recent Canadian test report on stucco -- they endorsed a >product called

I'm a Canadian but have never used the stuff in the belief that is probably
more prudent to rely upon geometry rather than chemistry to protect a
building from moisture ... probably due in large part to my not knowing what
exactly the chemistry is and in another part, an innate fear of chemistry,
period . (Like, too many bum trips in the past, man.)

A number (well, three anyway) of questions arise .

(a) Is the stuff safe enough to drink (or indirectly
    absorbed into the body when handling the stuff)?
    I suspect not, but just how safe or dangerous is the
    stuff compared to say, driving on an LA freeway in a
    democrat ?
     (aka "horse & buggy" for non Waterloo County folk)

    Silicone sealers usually have a skull and crossbones
    on the can so I'm guessing that siloxane sealers
     wouldn't be cat tea ?

(b) It appears that different manufacturers supply
   products of different concentrations.
    What solution is best for the job of sealing plaster
    on SB walls ?
     Would 6% do or should one use 15% solution only ?
   ( ie Does concentration matter ?)  Obviously the task
    of sealing pavement which sees heavy traffic will
    have  different criteria than the task of sealing a
    wall surface .

(c) Are some brand names preferable to others or is
    checking the solution a good enough assurance that
     the product will provide the protection desired ?
     ie A person recently asked if Xypex was a siloxane.

(d) Of the three (siloxane, oligomeric polysiloxanes,
     silanes) do we assume that siloxane is the better
     choice in terms of performance and environmental
     friendliness (and cost, I suppose) ?
     If not, is there some reason (other than lack of
    funding) why the other two  weren't considered for
    testing  ?

(e) Is WatJohn the only person on this List who can
    answer these questions ? If so, looks like WatJohn
    could make some pretty serious ransom demands here.

  --- * ---
Robert W. Tom
Kanata, Ontario, Canada        rw_tom@...
please visit:  http://www.theHungerSite.com daily

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