Violet Compositions for APCP

[Merl Milner]

Rocketry question from a research rocketry enthusiast.

I have made red flame plume, green flameplume, blue flame plume and white
flame plume propellants.

I even have a purple flame propellant composition (more like fuscia.

I have seen many fireworks displays where shells produced brilliant violet
to deep purple bursts.

One thing I have learned is the effects of chlorine donors and how some are
better than others for deepening a particular color.

I also know that the wavelength produced at atmosphere is very different
that what is produced under pressure in a composite rocket motor.

So here comes the question: Using Ammonium perchlorate composite propellant
(HTPB or PBAN binder) what chemicals compositions could be used to produce
the intense violet or deep purple that you folks seem to so effortlessly
produce in your shells?

Thanks in advance!

[Lloyd E. Sponenburgh]

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite
propellant (HTPB or PBAN binder) what chemicals compositions could be
used to produce the intense violet or deep purple that you folks seem
to so effortlessly produce in your shells?

First, ammonium perchlorate is an excellent chlorine donor, and needs no
others for deeply-saturated colors.

It is also a mistake to think that the pressure inside the motor has
anything to do with color. First, the color inside the motor is not
visible to the on-looker, and second, with a well-designed nozzle, the
pressure of the gasses outside the motor approaches atmospheric pressure.

Color has to do with what (usually chloride) species are in the flame
envelope, and at what temperature.

AP-based propellants without added aluminum tend to burn cooler than do
potassium perchlorate-based ones. For blues, that is a benefit, since
copper chloride exhibits a good blue only at relatively low flame
temperatures.

A decent blue propellant may be had by using black copper oxide as both
the colorant and a burn rate catalyst. A "deep purple" is only a good
blue with a touch of red, which may be had by adding strontium compounds.
Likely, strontium nitrate would be your best bet, since the carbonate
acts as a heat sink, and would slow your burn.

Adding aluminum to a motor increases the burn rate by increasing the
flame temperature. This, alone, reduces the quality of blue you'd
receive. Further, aluminum oxide is a refractory material that detracts
from your total impulse, since it is a solid at STP. And further yet,
aluminum oxides radiate a strong white light known as "black body
radiation", which will whiten and wash out a delicate color like blue.
Magnesium can increase the burn rate with less black body radiation and
thus a purer color, but magnesium doesn't play well with copper salts.
Very pure copper oxide is not water soluble, so it shouldn't be a
problem, but less pure technical grades may have soluble copper chloride
which reacts violently with Mg.

LLoyd


LLoyd

[Merl Milner]

Post by Lloyd E. Sponenburgh

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite
propellant (HTPB or PBAN binder) what chemicals compositions could be
used to produce the intense violet or deep purple that you folks seem
to so effortlessly produce in your shells?

First, ammonium perchlorate is an excellent chlorine donor, and needs no
others for deeply-saturated colors.
It is also a mistake to think that the pressure inside the motor has
anything to do with color. First, the color inside the motor is not
visible to the on-looker, and second, with a well-designed nozzle, the
pressure of the gasses outside the motor approaches atmospheric pressure.
Color has to do with what (usually chloride) species are in the flame
envelope, and at what temperature.
AP-based propellants without added aluminum tend to burn cooler than do
potassium perchlorate-based ones. For blues, that is a benefit, since
copper chloride exhibits a good blue only at relatively low flame
temperatures.
A decent blue propellant may be had by using black copper oxide as both
the colorant and a burn rate catalyst. A "deep purple" is only a good
blue with a touch of red, which may be had by adding strontium compounds.
Likely, strontium nitrate would be your best bet, since the carbonate
acts as a heat sink, and would slow your burn.
Adding aluminum to a motor increases the burn rate by increasing the
flame temperature. This, alone, reduces the quality of blue you'd
receive. Further, aluminum oxide is a refractory material that detracts
from your total impulse, since it is a solid at STP. And further yet,
aluminum oxides radiate a strong white light known as "black body
radiation", which will whiten and wash out a delicate color like blue.
Magnesium can increase the burn rate with less black body radiation and
thus a purer color, but magnesium doesn't play well with copper salts.
Very pure copper oxide is not water soluble, so it shouldn't be a
problem, but less pure technical grades may have soluble copper chloride
which reacts violently with Mg.
LLoyd
LLoyd

AP 200 30.0
AP 90 30.0
Magnalium -325 1.0
Strontium Nitrate 16.0
Strontium Carbonate 2.0
Black Copper Oxide 2.0
Copper Sulfate 3.0

R45 10.0
Tepanol 0.5
IDP 3.0
Castor Oil 0.5
HydroxyCure 1.89
Lecithin 0.2


My Magnesium & Magnalium is coated with potassium dichromate

This comp make fuscia. I can't get to a deep purple with this one.

[Lloyd E. Sponenburgh]

Post by Merl Milner
This comp make fuscia. I can't get to a deep purple with this one.

cut the strontium contribution by half, and try again.

You may have to increase the AP amount to adjust for the lower oxidizer
present after decreasing the strontium nitrate.

LLoyd

[Lloyd E. Sponenburgh]

Post by Merl Milner
This comp make fuscia. I can't get to a deep purple with this one.

Oh... the MgAl doesn't do your colors any good. It's there to increase the
flame temperature, but the aluminum in it will wash out the color.

LLoyd

[Andy Fox]

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite propellant
(HTPB or PBAN binder) what chemicals compositions could be used to produce
the intense violet or deep purple that you folks seem to so effortlessly
produce in your shells?

I'm interpreting "in your shells" to mean you want a purple star
composition, not rocket propellant? If that's the case I've had nice
results with copper benzoate and strontium carbonate (2:3 ratio). I
used hexamine as a chlorine doner and burning aid. Makes a nice
electric purple.

[Merl Milner]

No, I am trying to arrive at a truely purple flame plume rocket propellant.

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite propellant
(HTPB or PBAN binder) what chemicals compositions could be used to produce
the intense violet or deep purple that you folks seem to so effortlessly
produce in your shells?

I'm interpreting "in your shells" to mean you want a purple star
composition, not rocket propellant? If that's the case I've had nice
results with copper benzoate and strontium carbonate (2:3 ratio). I
used hexamine as a chlorine doner and burning aid. Makes a nice
electric purple.

[TONY S]

Post by Merl Milner
No, I am trying to arrive at a truely purple flame plume rocket propellant.

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite propellant
(HTPB or PBAN binder) what chemicals compositions could be used to produce
the intense violet or deep purple that you folks seem to so effortlessly
produce in your shells?

I'm interpreting "in your shells" to mean you want a purple star
composition, not rocket propellant? If that's the case I've had nice
results with copper benzoate and strontium carbonate (2:3 ratio). I
used hexamine as a chlorine doner and burning aid. Makes a nice
electric purple.

I make excelent blue with 73% Ap 25% binder and 2% CuO I would start
out trying adding strontium nitrate in equal proportions of CuO to
get purple, the binder i use for my APCP motors is plain old Bondo
brand fiberglass resin, Leave out the Aluminum when adding oxides or
the color will wash out as Lloyd stated. Ive never used Pban binder as
its too expensive. and just never got that involved "yet" with
composite motors.. but the fiberglass resin cures quickly and curing
can be controlled by adding more/less hardener .the stars I make with
this burns bright with no dross/residue and needs no primer as it can
be lit with even a touch from a cigarette . its just happens to be one
of the easiest formula's for stars and rocket fuel I've ever come
across.

[Merl Milner]

"Copper benzoate"

That is a new one on me.

Now my experience with benzoates has been of the sodium and potassium type.

Both I have seen commonly used to create whistling propellant, which in an
end-burning cardboard rocket motor is just fine.

I only know of one enthusiats that I have come across that could pull it
off in a 38mm reloadable motor. I am sure there are others.

The osilations that create the whisle are undesirable in a high power rocket
motor chamber in that they can easily create combustion instablility that
can lead to a CATO.

But again that is the Na & Kn type. Copper benzoate in combination with
strontium carbonate (what I commonly use as a burn rate moderator in my red
propellant comp) looks like an interesting candidate to work with.

Where can copper benzoate be obtained?

Post by Merl Milner
So here comes the question: Using Ammonium perchlorate composite propellant
(HTPB or PBAN binder) what chemicals compositions could be used to produce
the intense violet or deep purple that you folks seem to so effortlessly
produce in your shells?

I'm interpreting "in your shells" to mean you want a purple star
composition, not rocket propellant? If that's the case I've had nice
results with copper benzoate and strontium carbonate (2:3 ratio). I
used hexamine as a chlorine doner and burning aid. Makes a nice
electric purple.

[Lloyd E. Sponenburgh]

Post by Merl Milner
Where can copper benzoate be obtained?

Synthesize it, sir.

LLoyd

[Merl Milner]

Please detail the process for synthesizing Copper Benzoate.

Post by Lloyd E. Sponenburgh

Post by Merl Milner
Where can copper benzoate be obtained?

Synthesize it, sir.
LLoyd

[Bob]

Post by Merl Milner
Please detail the process for synthesizing Copper Benzoate.

If I knew it was going to be used in an ammonium perchlorate compo
like the one Andy Fox posted, then I would dissolve cuprous oxide in
ammonia water, mix it with benzoic acid, and recover and dry the
precipitate.

[Andy Fox]

Post by Merl Milner
Where can copper benzoate be obtained?

I purchased mine from Skylighter. They currently have it in stock @
$33/lb. Not cheap, I know, but a pound can go a long way. The formula
I used is:

Ammonium Perchlorate - 68
Copper Benzoate - 8
Strontium Carbonate - 12
Magnalium - 5
Hexamine - 7
Dextrin - +4

You'll probably need to play around with it a bit as I sacrificed
energy for color in this case. Anyway, hope it helps.

[Bob]

Post by Andy Fox
Ammonium Perchlorate - 68
Copper Benzoate - 8
Strontium Carbonate - 12
Magnalium - 5
Hexamine - 7
Dextrin - +4

I guess once you get into this area of formulation you have to accept
risks greater than normally encountered in pyrotechny.