Peter, that sounds like it could be an interesting student project...
Investigate the shock sensitivity and critical diameter of "pristine" AP
crystals, and then heat treat them to produce the strange porous crystals
we are talking about. What do you think? I still have a good relationship
with my previous employer, perhaps we could come up with a plan, I can
contact them and we could do some research into the matter.
On 23 July 2015 at 13:55, Peter Fairbrother <zenadsl6186@xxxxxxxxx> wrote:
On 23/07/15 11:39, James Padfield wrote:
Peter: I helped with a student project a couple of years ago at the
university I was working at. She was examining baking AP (I don't
recall the initial particle size) at fairly high temperatures (200,
maybe 220 degC) to alter the particle porosity. As you say, some mass
is lost, 30% sounds about right, and the resulting particles are no
longer regular crystals, but porous. She took some nice Scanning
Electron Microscope photos of the particles. She then formulated them
(IIRC) with PVC/DOA binder system (easier than mucking about with a
curable HTPB/IPDI system). Don't recall how far she progressed with the
project, I don't believe it got as far as measuring burnrates...
James: What I'd really like to know is how the detonatability changes. The
product has submicron particles, which would be easy to detonate if they
were normal crystals - but they aren't, and I don't know what happens.
IMO this could be very significant, for AP in fires ..
John: Thinking again about AP flowing. while it does not melt in bulk, it
may flow as a bulk powder in some circumstances. If it is for instance on
top of and reacting with tarmac or polythene, the reaction will produce
lots of gas, at a prodigious rate.
This effusion of gas may be fast enough to fluidise any overlying AP
powder, which would then flow almost like a liquid.
-- Peter Fairbrother
