[PSUBS-MAILIST] alternative syntactic foam

[Alan via Personal_Submersibles]

Hank,
I have just looked at some figures on the 3M 5500 psi glass micro spheres  on Ebay.
They are talking about a 50/50 ratio of spheres to epoxy resin. I don't know if you can
use less resin than this.
Resin weighs 1.1 grams per cubic centimetre, spheres are .38, so in a 50/50 mix you get 
.26 gram buoyancy per cubic centimetre, or 260 grams per cubic litre. 
You need to be 550 lb. buoyant, or 256kg. You would need 100 litres of mix to get this.
In a 50/50 mix that would cost 50 x $18:72 = $936 for the spheres & based on a price
of $400- for a 16 litres pack of epoxy, ($25 per litre) it would cost 50 x 25 = $1250
for the resin. Total of $2186.
You might be able to get the price down buying in bulk.
Cheers Alan



Sent from my iPad

> On 19/06/2017, at 1:51 PM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hank,c 
> have you had a look at this stuff...
> http://www.ebay.com/itm/MICROSPHERES-GLASS-BUBBLES-LOW-DENSITY-EPOXY-SYNTACTIC-FOAM-FILLER-1-GAL-1-5-KIT-/220528963762
> One gallon in volume for $18:72. It says it crushes to 90% of it's volume at 5500 psi.
> And yes, enjoy a bit of detective work.
> Cheers Alan
> 
> Sent from my iPad
> 
>> On 19/06/2017, at 12:19 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> Hi All,
>> Just been thinking  about low cost ways to make foam.  I am sure at the end of the day, I will make my foam the standard way, but it is still an interesting subject to explore.  I have learned that microspheres are added to many things, even concrete.  That got me thinking, if the compressive strength is there, the best product to reinforce the spheres should be the lightest possible material.  Polypropylene is very light and has a compressive strength of 6,000 psi.  The fun part about Polypropylene is, it can be recycled from bottle lids etc.  I don't think it would take to much imagination to build an oven with a mixer inside and a microsphere injection port.  Polypropylene has a specific gravity in the neighbourhood of .7g\cc that means a light weight foam can be made with microspheres and no macro spheres.    I don't know about the water absorption properties yet.
>> Hank
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