[AR] Re: A perfect hybrid rocket fuel ?
- From: James Padfield <james.padfield@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 7 Apr 2014 12:58:44 +0100
On 28 March 2014 22:41, UC3 NAUTILUS <uc3nautilus@xxxxxxxxxxx> wrote:
> Dear rocket experts...
>
>
> It may seem like a very small problem, since there is much less
> requirements for a hybrid fuel than for say a solid propellant fuel -
> binder.
> But being practical the selection of hybrid fuels is a little more
> complex.
>
> "Best" fuel is therefore not a simple term.
>
> But - N20 has a lousy density impulse, and its polyurethane rubber fuel is
> cast using a curing agent that is toxic. And by toxic I mean hydrazine
> level toxic. The MDI curing agent
> is nasty, and skin contact may cause severe acute problems and ultimately
> cancer. This same thing makes HTPB a bad choice, and HTPB also has very low
> availability in Europe.
>
> Any comments or smart ideas worth sharing ?
>
> All the best,
>
> Peter Madsen
>
Peter,
Yes, MDI used to cure HTPB is pretty nasty. However, there are alternative
isocyanates that are much less unpleasant to work with. Isophorone
diisocyanate (IPDI) is the standard in composite rocket propellants and
polymer-bonded explosive (PBX) compositions for the military; it is still
toxic and potentially a skin sensitiser, but like I said much less so than
MDI. Check out Bayer's range of polyisocyanates; they manufacture some
polymeric isocyanates that we have experimented with with great success;
Bayer uses the tradenames Desmodur N100, N3200, for example. They have
much lower vapour pressures than small molecules like IPDI and MDI, and so
are much safer to work with.
And yes, R45M is hard to get hold of in Europe, but have you tried the
Liquiflex P or Liquiflex H polybutadienes from Petroflex in Brazil? We
have got hold of these and found them to be satisfactory for making PBXs.
It may be easier to get hold of them since as you say R45M is export
controlled by the US...
James.
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