micro-balloons etc

[Gray E Fowler]

Tom

Sounds like Cab-O-Sil fumed silica.  First off it is amorphous so no 
silicosis problems.  It is quite different than microballons, as it does 
not increase volume or reduce the density of the "mix".  It also does not 
affect the cured properties very much at all. Some will say that makes it 
, tougher, harder, or harder to sand etc. but you can only add about 6% by 
weight, so the properties of the epoxy are not really affected. It is hard 
to mix properly, because it really needs to be high shear mixed , which 
cannot be done with a stick. Poor mixing can weaken the epoxy and hurt the 
wet out properties, hence the real reason people percieve that it changes 
the properties.  You can use it for corner fill in the mold, but you must 
be aware that you easily add 100-125 grams of dead weight to the plane. 



Gray Fowler
Principal Chemical Engineer
Composites Engineering




"Koenig, Tom" <Tom.Koenig at actewagl.com.au>
Sent by: discussion-request at nsrca.org
05/18/2003 07:40 PM
Please respond to discussion

 
        To:     "'Discussion'" <discussion at nsrca.org>
        cc: 
        Subject:        micro-balloons etc



Help.....please

Gray, Matt, Lance.... anyone.

I have a huge tub at home that is a white fluffy powder, which weighs
nothing...( Nooooo....not that sort of powder<VBG>) I dont know wether it 
is
micro balloons or cabosil, or whatever.
When I mix it with epoxy it sort of forms the white stuff which you 
commonly
see in the corners of layups ( to help lay the glass), but it isnt quite 
the
same, it seems to be more translucent.
Am I not mixing properly? It seems that when I keep adding more powder it
becomes too dry and unworkable. It also doesn't seem that light which 
makes
me think it isnt micro balloons. Is it the resin I'm using ( LC 3600)?

Sorry for the moronic question...but how can I tell what I've got? Also 
what
exactly is used as the fillers in the ZN kits, Bollys etc ? Do they use a
thixotropic additive in the resin when they form the fillets etc.

Thanks guys

Tom

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