Ammonium perchlorate products

We and others have reported a series of studies in ammonium perchlorate production workers who are exposed intermittently to perchlorate, resulting in urine perchlorate values of up to 40 mg daily, and in normal volunteers given 3—3 5 mg perchlorate daily for 2 weeks or 0.5 and 3mg daily for 6 months (Lawrence et al, 2000, 2001 Greer et al., 2002 Gibbs et al., 1998 Braverman et al, 2005, 2006). Thyroid function studies, including serum TSH, thyroxine (T4), free T4, and total triiodothyronine (T3), were not affected by perchlorate exposure in the plant or perchlorate administration to normal volunteers, despite a decrease in the thyroid uptake of at the higher exposures. Despite a mean exposure of 3 years to high levels of perchlorate in the production workers, no abnormalities of the thyroid evaluated by ultrasound were detected compared to a nonexposed local population (Braverman etal., 2005). 

Fig. 1. The postulated flame stmcture for an AP composite propellant, showing A, the primary flame, where gases are from AP decomposition and fuel pyrolysis, the temperature is presumably the propellant flame temperature, and heat transfer is three-dimensional followed by B, the final diffusion flame, where gases are O2 from the AP flame reacting with products from fuel pyrolysis, the temperature is the propellant flame temperature, and heat transfer is three-dimensional and C, the AP monopropellant flame where gases are products from the AP surface decomposition, the temperature is the adiabatic flame temperature for pure AP, and heat transfer is approximately one-dimensional. AP = ammonium perchlorate.

Oxidizers. The characteristics of the oxidizer affect the baUistic and mechanical properties of a composite propellant as well as the processibihty. Oxidizers are selected to provide the best combination of available oxygen, high density, low heat of formation, and maximum gas volume in reaction with binders. Increases in oxidizer content increase the density, the adiabatic flame temperature, and the specific impulse of a propellant up to a maximum. The most commonly used inorganic oxidizer in both composite and nitroceUulose-based rocket propellant is ammonium perchlorate. The primary combustion products of an ammonium perchlorate propellant and a polymeric binder containing C, H, and O are CO2, H2, O2, and HCl. Ammonium nitrate has been used in slow burning propellants, and where a smokeless exhaust is requited. Nitramines such as RDX and HMX have also been used where maximum energy is essential. 

The ammonium perchlorate solution is spray-dried to the desired crystal size at air temperatures below 150°C and crystal temperatures of about 110°C. This procedure provides a pure product having a controlled grain size. Prior mechanical and thermal treatment affects the isothermal... 

Ammonium Perchlorate. The commercial AP product is manufactured by the double-exchange reaction of sodium perchlorate and ammonium chloride (102,103). 

Ammonia, hydrochloric acid, and sodium perchlorate are mixed and the reaction mixture crystallised in a vacuum-cooled crystalliser. Ammonium perchlorate crystals are centrifuged, reslurried, recentrifuged, and then dried and blended for shipment. Mother Hquor is evaporated to precipitate sodium chloride and the depleted mother Hquor is recycled to the reactor. The AP product made by this method is 99% pure and meets the specifications for propeUant-grade ammonium perchlorate. The impurities are ammonium chloride, sodium perchlorate, ammonium chlorate, and water insolubles. 

The U.S. domestic capacity of ammonium perchlorate is roughly estimated at 31,250 t/yr. The actual production varies, based on the requirements for soHd propellants. The 1994 production ran at about 11,200 t/yr, 36% of name plate capacity. Environmental effects of the decomposition products, which result from using soHd rocket motors based on ammonium perchlorate-containing propellants, are expected to keep increasing pubHc pressure until consumption is reduced and alternatives are developed. The 1995 price of ammonium perchlorate is in the range of 1.05/kg. Approximately 450 t/yr of NH ClO -equivalent cell Hquor is sold to produce magnesium and lithium perchlorate for use in the production of batteries (113). Total U.S. domestic sales and exports for sodium perchlorate are about 900 t/yr. In 1995, a solution containing 64% NaClO was priced at ca 1.00/kg dry product was also available at 1.21/kg. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

The products of equation 11 are separated by controlled crystalLi2ations to produce high purity crystalline anhydrous ammonium perchlorate and sodium chloride. The main use for ammonium perchlorate is as an oxidi2er in the propellant of rockets and missiles (see Explosives and propellants). 

May 4, 1988, explosions leveled a Pacific Engineering Production Co. (PEPCO) plant, at Henderson, NV, one of only two U.S. plants producing 20 million lb/ year (maximum of 40 million Ib/year - see Table 7.1-2) ammonium perchlorate for solid rocket fuel. It was the principal supplier for the space shuttle and sole supplier for the Titan rocket and several military missiles. 

The Space Shuttle uses aluminum metal and ammonium perchlorate in its reusable booster rockets. The products of die reaction are aluminum oxide, aluminum chloride, nitrogen oxide gas, and steam. The reaction mixture contains 7.00 g of aluminum and 9.32 g of ammonium perchlorate. 

Heath and Majer (H3) have recently used a mass spectrometer to study the decomposition of ammonium perchlorate. Decomposition was detected in the range from 110° to 120°C. At this temperature, there were ions in the mass spectrum caused by NH3, HC104, Cl2, HC1, nitrogen oxides, and 02. The appearance of the species NO, N02,02, and Cl2 in the decomposition products under very low pressure (i.e., in the absence of gas-phase molecular collisions) indicates that the principal decomposition reactions take place in the crystal and not in the gas phase. 

Accumulatory pressure measurements have been used to study the kinetics of more complicated reactions. In the low temperature decomposition of ammonium perchlorate, the rate measurements depend on the constancy of composition of the non-condensable components of the product mixture [120], The kinetics of the high temperature decomposition [ 59] of this compound have been studied by accumulatory pressure measurements in the presence of an inert gas to suppress sublimation of the solid reactant. Reversible dissociations are not, however, appropriately studied in a closed system, where product readsorption and diffusion effects within the product layer may control, or exert perceptible influence on, the rate of gas release [121]. 

One spectacular example of the oxidizing ability of perchlorates is their use in the booster rockets of space shuttles. The solid propellant consists of aluminum powder (the fuel), ammonium perchlorate (the oxidizing agent as well as a fuel), and iron(III) oxide (the catalyst). These reactants are mixed into a liquid polymer, which sets to a solid inside the rocket shell. A variety of products can form when the mixture is ignited. One of the reactions is... 

It is possible in both the above processes to add oxidisers such as ammonium perchlorate so as to give propellants which combine the properties of the composite propellants and the more conventional double base type. It is claimed that the product can have an ultimate tensile strength of 800 kPa with an elongation of roughly 30%. These properties must, however, be sacrificed to some extent if the highest propellent performance is required. 

Polymers which give mouldable propellants are mixed with the oxidiser in a similar manner, but the product is usually worked mechanically between rolls and evacuated to remove air bubbles. The powder is then moulded by pressure into the metal casing. Alternatively, such plastics can give a propellant which can be extruded into charges which are afterwards cut and machined to suitable shape. The Rocket Propulsion Establishment at Westcott has used ammonium perchlorate and polyisobutene to produce a propellant of putty-like consistency. 

The burning mechanism of composite propellants differs from that described above. There is no exothermic reaction which can lead to a self-sustaining fizz zone. Instead, the first process appears to be the softening and breakdown of the organic binder/fuel which surrounds the ammonium perchlorate particles. Particles of propellant become detached and enter the flame. The binder is pyrolysed and the ammonium perchlorate broken down, initially to ammonia and perchloric acid. The main chemical reaction is thus in the gas phase, between the initial dissociation products. 

Though the chemical potentials of ammonium perchlorate and potassium perchlorate are high compared with those of other oxidizers, hydrogen chloride is formed as a combustion product. Hydrogen chloride is known to generate hydrochloric acid when combined with water vapor in the atmosphere. The chemical potentials of crystalline oxidizers are dependent on the fuel components with... 

When a composite propellant composed of ammonium perchlorate (AP) and a hydrocarbon polymer burns in a rocket motor, HCl, CO2, H2O, and N2 are the major combustion products and small amounts of radicals such as OH, H, and CH are also formed. These products are smokeless in nature and the formation of carbon particles is not seen. The exhaust plume emits weak visible light, but no afterburning occurs because AP composite propellants are stoichiometrically balanced mixtures and, in general, no diffusional flames are generated. 

Mixtures of ammonium perchlorate with fuels can produce high temperatures when ignited, and the hydrogen chloride (HCl) liberated during the reaction can aid in the production of colors. These two factors make ammonium perchlorate a good oxidizer for colored flame compositions (see Chapter 7). 

A solid oxidizer Ammonium perchlorate (NH C10 ) is the current favorite due to the high percentage of gaseous products it forms upon reaction with a fuel. 

Perchlorate is the oxidation product of chlorate. It forms a variety of compounds, including ammonium perchlorate, potassium perchlorate, sodium perchlorate, and perchloric acid. Perchlorate is highly reactive in its solid state, and as ammonium perchlorate it is used as the oxidizer in solid rocket fuel. Because of its limited shelf life, it must be periodically washed out of the country s rocket and missile inventory and replaced. Large volumes of the chemical have been disposed of since the 1950s, and perchlorate has been detected in large concentrations in both groundwater and surface water. Perchlorate has also been used in the manufacture of matches, munitions, fireworks, and in analytical chemistry. 

Figure 3. Change in concentration of reactants and products at 60°C. (140°F.) for agitated propionic acid (0.5M), 1 -benzoyl-2-ethylaziridine (0.5M) in toluene solution with 18.5% ammonium perchlorate and 0.5 wt. % ZrAA...

Propellant Aging. Three structurally different chemicals and mixtures of these materials have been used to cure CTPB propellants. These are MAPO, other aziridines which do not contain the P—N bond, and epoxides. As stated in the discussion of curing agents, the aging behavior of CTPB propellants prepared with these materials is distinctly different, owing to the behavior of these compounds and their reaction products in the presence of ammonium perchlorate and at elevated temperatures. 

Ammonium perchlorate is a monopropellant which is exothermic in its decomposition to the extent of 270 cal./gram (1, 30, 54), based on measured decomposition products, and has a measured adiabatic flame temperature of 950°C. (1, 54) (see Table I). The dissociative sublimation step is zero order and is endothermic to the extent of 500 cal./gram... 

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