Exothermic decomposition before melting at >200 °C
Ammonium perchlorate is an inorganic compound with the formula NH4ClO4. It is the salt of perchloric acid and ammonium hydroxide. All perchlorates are potentially powerful oxidizers, but ammonium perchlorate is especially labile.
It is produced by reaction between ammonia and perchloric acid, and is the driver behind the industrial production of perchloric acid. It also can be prepared by treatment of ammonium salts with sodium perchlorate. This process exploits the fact that the solubility of NH4ClO4 is about 10% of that for sodium perchlorate.
It crystallises in colorless rhombohedra.
Like most ammonium salts, AP decomposes before melting. Mild heating results in chlorine, nitrogen, oxygen, and water.
The combustion of AP is quite complex and is widely studied. Ammonium perchlorate crystals decompose before melting, even though a thin liquid layer has been observed on crystal surface during high pressure combustion processes. Strong heating may lead to explosions. Complete reactions leave no residue. Pure crystals cannot sustain a flame below the pressure of 20 bar (2 MPa).
AP is a Class 4 oxidizer (can undergo an explosive reaction) for particle sizes over 15 micrometres and is classified as an explosive for particle sizes less than 15 micrometres.
When AP is mixed with a fuel (like a powdered aluminum and/or with an elastomeric binder) it can generate self-sustained combustion also far under atmospheric pressure. It is an important oxidizer with a decades-long history of use in solid rocket propellants-- space launch, military, amateur, and hobby high powered rockets--as well as in some fireworks.
Some "breakable" epoxy adhesives contain suspensions of AP. Upon heating to 300 °C, the AP degrades the organic adhesive, breaking the cemented joint.
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