chlorine free red flare/star

[dave321]

attached an interesting paper using amongst other alternatives, hexamine for a red flare/star
with no chlorine donor.

sabatini2015.pdf

[Lloyd]

Red is one color that requires no chlorine donor. Consider common road flares.

Lloyd

[richardh08]

I had always been led to understand (mainly by the many articles on the topic by the Kosankes) that the orange-red colour of a chlorine-free Sr-based composition was caused by emission from SrOH. However, this article says that the real culprit is SrO emission.

I took another look at Chapter 9 (by the Kosankes) of Pyrotechnic Chemistry. Table 12, a list of 'undesirable species', clearly states that SrOH emission is reddish orange (and that of SrO is 'orange'). In contrast, the earlier Table 9 shows that the strongest emission from SrOH is at a wavelength 682 nm, which is a slightly deeper red than that of the strongest emission of SrCl, at 674 nm (SrO isn't mentioned).

On the whole, I'm more inclined to believe Sabatini et al.

[Pyro]

The strontium monohydroxide emission gives ok red but not the blood red colour you can get from the more pure SrCl* emission and I guess it was from that perspective the Kosanke's were talking about what emitting species were undesirable or not.

For the military, and also for marine signaling flares, the red colour does not have to be very pure to be approved but it would not look good in fireworks unless that particular hue is wanted for a certain effect or combination of colours.

We have experimented a lot with improving the luminosity and colour of high magnesium content red flares and it is amazing how little chlorine donor is needed for an acceptable red colour if you just add a secondary fuel that can provide what is needed for both SrOH* and SrCl* emission. Hexamine works but guanidinium nitrate is much better.

[dave321]

i am assuming that the hexamine or guanidine nitrate, as well as being gas producers
and because of that also increase the flame envelope, which helps with the colour

[Pyro]

Yes they expand the flame and provide water vapor that is needed to create the monohydroxide.