PowerLabs Deflagrants Page

•  Introduction:

 The word "deflagrate" comes from Latin "deflagrare", from de- + flagrare to burn. The dictionary defines it as "to burn rapidly with intense heat and sparks being given off". Simply put, deflagrating reactions are chemical reactions between very finely divided fuel and oxidizer particles. The fuel and/or oxidizer can be in either solid, liquid or gaseous state. Gaseous mixtures have a lower energy density per volume, and liquid mixtures are far more likely to undergo detonation than they are to deflagrate so this page will mostly deal with solid state deflagrants. The oxygen percentage per weight of the oxidizer, its decomposition temperature, the fuel ignition temperature, its caloric output, and specially, the grain size of both the fuel and the oxidizer particles will allow affect how quickly the flame travels through the mixture. Some deflagrants can be spectacularly exothermic, such as Aluminium/Potassium Perchlorate flash powder, which will put out 2.2kilocalories per gram, incredibly brilliant, as in U.S. Type III Flash Powder (Potassium Perchlorate/Barium Nitrate/Aluminium) which produces 0.82 billion candlepower for 40 milliseconds at 31.9 million candlepower/second in a 60pound charge. Other mixtures can also be surprisingly violent, such as thermite mixtures utilizing Silver Oxide as an oxidizer, or mixtures that employ Red Phosphorous as a fuel, which combust at supersonic velocities and explode even when unconfined.
 My interest in deflagrants lies in their usefulness as high performance rocket propellants, which is their number one use right now. Other uses include high altitude night photography and blasting for mining applications, although high explosives have taken over in this field over the years.

•  A brief overview of the components in a deflagrating mixture:

 Fuel:

 The fuel in a deflagrating mixture will determine its properties to a very great extent. Fuels with very high caloric outputs, such as metals, will result in very hot and bright deflagrations. Fuels with very low ignition points such as Phosphorous and Sulfur will result in mixtures which are very sensitive to ignition, and that once ignited burn extremely fast and often explode without the need for any confinement. Sometimes fuels are mixed so that the best properties of the two can be achieved in the mixture, such as in the case of black powder, where Carbon provides a reasonably high caloric output, but burns slowly, and sulfur burns fast but with less energy, so by mixing the two a hot, easily initiated and reasonably fast burning deflagrant can be obtained.

 Oxidizer:

 The oxidizer in a deflagrating mixture provides oxygen by decomposing under heat. Nitrates, Chlorates, Perchlorates, Permanganates, transition metal Oxides, Peroxides, and other unstable, high oxygen content molecules can all be used. One example would be Potassium Nitrate (KNO3), the oxidizer used in black powder. On heating it decomposes to yield oxygen and potassium nitrite. The ease with which the oxidizer decomposes will determine to a large extent the sensitivity and combustion rate of the mixture; formulas utilizing peroxides, permanganates, and some of the more unstable Chlorates will often be shock sensitive and typically burn fast enough to explode when ignited. Formulas utilizing Perchlorates and Nitrates are safer to handle but do not burn as violently.

 Mixture properties:

 Regardless of what makes up the deflagrating mixture, the more finely divided the oxidizer and the fuel are, and the more intimately mixed they are, the faster it will burn. A coal briquette will not burn to any great extent if it is sitting on top of some potassium nitrate, but if both the KNO3 and the coal are pulverized combustion can take place at a couple hundred meters per second.
 Deflagrating mixtures are not capable of Detonation to any appreciable degree. Detonation *can* be induced on some special mixtures employing blasting caps on atomized fuels and oxidizers, but these are very special cases and initiation is provided by a high explosive blasting cap. In general, if ignited, a deflagrating mixture will not yield a shockwave. This, however, does not mean that it can not explode; any deflagrating mixture is capable of self confining; if 50 grams of commercial flash power are ignited out in the open, the pressure produced by its combustion will result in supersonic expansion of the exhaust gases and the pile will explode with considerable force. Some mixtures require far less than 50 grams to self confine, whilst others will not self confine at all. Adding any kind of confinement to a deflagrating mixture will result in increased combustion pressures and thus increase the chances of an explosion. Firecrackers are nothing more than a fraction of a gram of flash powder inside a cardboard tube sealed on both ends. When the flash powder burns it produces a very quick burst of pressure which ruptures the casing and causes a supersonic gas expansion. Even a small firecracker with under one gram of pyrotechnic mixture will be able to blow fingers off, and their manufacture is strongly discouraged by the author of this page.

•  PowerLabs deflagration demo:

 I have experimented with Carbon, Sulphur, Epoxies, Rubbers, Sugars, Magnesium, Zinc, Iron, Aluminium and plastics as fuels, and used Peroxides, Oxides, Nitrates, Perchlorates, Permanganates, Chromates, Dichromates, Bromates and Iodates as oxidizers. Of my countless experiments with oxidizers, a few stand out from the rest by their unexpected results, such as the time when I attempted to make flash powder using Sodium Peroxide as the oxidizer. I pulverized some Na2O2 pellets, mixed them with Sulphur and Aluminium powder and started rolling the mixture backwards and forward on a sheet of paper (the safe, correct method of mixing powders). Immediately I noticed that the mixture was clumping together around the oxidizer granules. I didn't even have time to figure out what that meant because within seconds of having been mixed the mixture exploded and burned a hole on the table I was working on. When mixing energetic fuels with unstable oxidizers one must be aware that the unexpected can and will happen, and must be prepared for such an event. On my case I had goggles and a lab coat on, and the mixture I was working with was on the centre of a large sheet of paper, and did not consist in a dangerous amount, therefore no harm was caused.
 Chromium Trioxide exploded in a similar fashion with Magnesium Powder. The mixtures are too many to describe, but I have compiled a list of some formulas I have attempted, and some I am aware off on the bottom of this page for informational purposes.

 One mixture I have always been fond of is the Potassium Bromate/Sulphur/Mannitol deflagrant. I came up with this formula myself after some experimentation. Potassium Bromate is similar to KNO3 as an oxidizer, but because of the larger Bromine molecule holding on to the Oxygen it is more unstable and therefore results in a more violent reaction. Similarly, Mannitol being a light sugar combusts spectacularly fast. The Sulphur helps yield a mixture that is even faster burning. This mixture is, as one would expect, friction, impact and heat sensitive and shouldn't be used for anything other than small demonstrations. Nonetheless, it is quite possibly *the* fastest burning deflagrant mixture I have ever experimented with that does not involve ultra fine metal powders, burning faster than even some commercial flash powder grades.

The reactants were all finely pulverized and than thoroughly mixed together by rolling backwards and forwards on a large sheet of paper. I can't find the correct proportions since I've lost my notes for this experiment. As I recall, I arrived at the ideal proportions by varying the fuel/oxidizer ratio and analyzing the combustion products: If there was any molten Potassium Bromate on the watch glass I would add more Mannitol in order to balance out the oxygen surplus. If there were carbon stains on the watch glass that meant that there was not enough oxygen to fully combust the Mannitol and I would add more KBrO3. It is easy to notice when the mixture is optimal because it will combust extremely fast when that happens.
 Once the mixture had been prepared it was placed on an watch glass and a glass rod was dipped in 98% Sulphuric acid. The mixture deflagrates violently with a puff of smoke when touched by the Sulphuric Acid.

 The picture to the left shows a still frame capture from the video at the moment the mixture deflagrates. Notice the intense purple light from the Potassium in the oxidizer. Also notice the incredibly large amount of smoke (Mostly water vapor, with some CO2, KBr and SO2) it produces for such a small amount.

 Click on the picture to watch the video. It is quite small (only 122K, MPEG format) but definitely worth watching!

•  A Few more examples of Deflagrating mixtures:

 Chlorate Mixtures:

 Chlorates are very unstable and powerful oxidizers. They have generally been replaced by perchlorates in most commercial formulas as those are just as powerful and more stable. Some older formulas list chlorates with sulfur. This extremely dangerous practice has lead to countless accidents due to the fact that the sulfur will gradually convert into sulfuric acid in the presence of moisture and this will lead to the generation of Chlorine Trioxide, an extremely unstable gas that causes the mixture to ignite spontaneously. Chlorate explosives must also not be stored together with ammonium nitrate explosives, since ammonium chlorate which is formed when these two substances are brought in contact causes them to explode. Chlorate mixtures containing Sulphur are listed here for curiosity purposes only and should not be attempted!
General formula:  KClO₃ + 2 Al  -->  KCl + Al₂O₃ + energy

 Perchlorate mixtures:

 Potassium Perchlorate is the standard today at the fireworks industry. Very powerful, and safer than most other mixtures.
3KClO₄ + 8Al  -->  3KCl + 4Al₂O₃ + energy

Comments: This energetic burst charge can be used for small shells, but is unsuitable for the smallest diameters (2...3 inch). It is much safer to handle than the H3 bursting charge since it contains no chlorates.
Preparation:

Potassium perchlorate.............................70
Hemp coal (or Paulownia coal).....................18
Sulfur............................................12
Glutinous rice starch.............................+2%

Comments: Shimizu lists this composition as �burst charge No. 44�. The potassium bichromate catalyses the decomposition of the potassium perchlorate. This composition�s sensitivity is quite low, although higher than that of black powder. The explosive force of this composition is lower than that of the �Potassium perchlorate bursting charge #1�. This burst charge is often used in shells of middle and large diameter (6...10 inch).
Preparation:

Potassium perchlorate.............................70
Hemp coal (or Paulownia coal).....................30
Potassium bichromate..............................5
Glutinous rice starch.............................+2%

Purple Flash
Source: rec.pyrotechnics
Comments:
Preparation:

Magnesium.........................................10
Potassium perchlorate.............................10
Cupric oxide......................................3
Strontium nitrate.................................3
PVC...............................................1

Green flash
Source: rec.pyrotechnics
Comments:
Preparation:

potassium perchlorate.............................6
barium nitrate....................................3
Aluminum powder...................................5

Whistle mix #1
Source: rec.pyrotechnics. Composition from Ellern[4].
Comments:
Preparation:

Potassium perchlorate.............................72.5
Sodium salicylate.................................27.5

Whistle mix #2
Source: rec.pyrotechnics. Composition from Ellern[4].
Comments:
Preparation:

Potassium nitrate.................................30
Potassium dinotrophenate..........................70

Whistle mix #3
Source: rec.pyrotechnics. Composition from Ellern[4] and Shimizu[1].
Comments:
Preparation:

Potassium perchlorate.............................70
Sodium benzoate...................................30

Whistle mix #4
Source: rec.pyrotechnics. Composition from Oztap
Comments:
Preparation:

Potassium chlorate................................40
Sodium chlorate...................................10
Potassium nitrate.................................30
Sodium salicylate.................................10
Paraffin oil......................................10
Ferric oxide......................................+0.2

Whistle mix #5
Source: rec.pyrotechnics. Composition from Lancaster[2].
Comments: This mixture is quite sensitive to friction and shock.
Preparation:

Potassium chlorate................................75
Gallic acid.......................................25

 Synthesis produced by POWERLABS.

 Last update 11/02/10