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The burning rate of AP/HTPB composite propellant increases with increasing AP content and with decreasing AP size. In addition, the burning rate can be enhanced with the addition of Fe2O3. The burning characteristics and thermal decomposition behavior of AP/HTPB composite propellant using coarse and fine AP particles with and without Fe2O3at various AP contents were investigated to obtain an exhaustive set of data. As the AP content decreased, the burning rate decreased and the propellants containing less than a certain AP content self‐quenched or did not ignite. The self‐quenched combustion began at both lower and higher pressures. The lower limit of AP content to burn the propellant with coarse AP was lower than that with fine AP. The lower limit of AP content to burn was decreased by the addition of Fe2O3. The thermal decomposition behavior of propellants prepared with 20–80 % AP was investigated. The decrease in the peak temperature of the exothermic decomposition suggested an increased burning rate. However, a quantitative relationship between the thermochemical behavior and the burning characteristics, such as the burning rate and the lower limit of AP content to burn, could not be determined.

Usually, a plasticizer is a relatively low‐viscosity liquid ingredient that is added to improve the mechanical properties and the processing properties of a propellant, such as a lower viscosity for casting or a longer pot life of the mixed, but uncured propellant. The effects of many plasticizers on the performance of the composite propellant have been studied in detail. Glycerin is a triol, a low viscosity material, and inexpensive. It seems that the processing properties and the mechanical properties of the HTPB binder would be improved by the addition of glycerin. The curing behavior, the mechanical properties, and the thermal decomposition of a glycerin/HTPB blend have been investigated in this study. The viscosity of the glycerin/HTPB blend and the increasing ratio of the viscosity versus the elapsed time are lower than those of only HTPB. The mechanical properties are improved by the addition of glycerin, even for a low quantity of glycerin. The thermal decomposition behavior of the blend occurs at lower temperatures when compared to that of HTPB.

Ammonium nitrate (AN)‐based composite propellants have attracted much attention, primarily because of the clean burning nature of AN as an oxidizer. However, such propellants have some disadvantages such as poor ignition and low burning rate. Ammonium dichromate (ADC) is used as a burning catalyst for AN‐based propellants; however, the effect of ADC on the burning characteristics has yet to be sufficiently delineated. The burning characteristics of AN/ADC propellants prepared with various contents of AN and ADC have been investigated in this study. The theoretical performance of an AN‐based propellant is improved by the addition of ADC. The increase in the burning rate is enhanced and the pressure deflagration limit (PDL) becomes lower with increasing amount of ADC added. The increasing ratio of the burning rate with respect to the amount of ADC is independent of the AN content and the combustion pressure. The optimal amount of ADC for improving the burning characteristics has been determined.

In this study, the kinetics of the thermal decomposition of aminoguanidinium 5,5′‐azobis‐1H‐tetrazolate (AGAT), which is one of the promising fuel candidates of the new gas generating agents for airbags, was investigated. The kinetic model that fits the main decomposition of AGAT was examined, and the activation energy was obtained. The main decomposition of AGAT was a single elementary process according to the result of mass spectrometry. The recommended kinetic model for the main decomposition of AGAT is Avrami–Erofeev equation (n=4). The activation energies for the main decomposition obtained under helium by non‐isothermal analysis and isothermal analysis were 207 and 209 kJ mol−1, respectively.

Bubble contamination in an ammonium perchlorate (AP)‐based composite propellant has a positive effect on the burning rate. However, the quantitative effect of the bubble contamination on the burning rate has never been revealed. In order to clarify the relationship between the increase in the burning rate and the void fraction of the propellant, propellants were prepared with fine porous AP particles (PoAP) or fine hollow AP particles (HoAPs), and their burning rate characteristics were investigated. The voids inside AP particles have the effect of increasing the burning rate. The increase in the burning rate is enhanced linearly as the void fraction increases. The effect of the void fraction on the burning rate for a propellant containing PoAP is not identical with that for a propellant containing HoAP. It was found that the effect of the void fraction on the burning rate could be estimated by the void fraction when the bubble contamination is uniform in size and shape.

Fine porous and hollow ammonium perchlorate (AP) particles were prepared by the spray‐drying method. Propellants prepared with porous or hollow AP were found to have bubble contamination. The bubble in the propellant appeared inside the porous and hollow AP particles because the voids in porous and hollow AP cannot be completely filled with HTPB. The relationship between the burning rate and the weight mean diameter, Dw, and the specific surface area, Sw, is divided into two regions. The burning rate was almost constant above the critical Dwand increased with decreasing Dwbelow that. The burning rate was almost constant below the critical Swand increased with increasing Swabove that. These critical points did not depend on the voids in the AP particles. The burning rate of the propellant prepared with spherical AP was dependent on Dwand Sw.The burning rates of the propellants prepared with porous or hollow AP were not associated with Dwor Swalone and were greater than that of the propellant prepared with spherical AP at a constant Dwor Sw.The voids in porous and hollow AP particles thus had a positive effect on the burning rate.

Due to the requirements for the preparation of an ammonium perchlorate (AP)/hydroxy-terminated polybutadiene (HTPB) based composite propellant, an upper limit content of AP applicable in the propellant, ϕmax (wt%), exists. The rheology of concentrated AP/HTPB suspensions prepared at ϕmax is investigated in this study. The relative viscosity, ηrϕ(-), of the suspensions prepared at ϕmax is almost constant at approximately 200. For the suspensions prepared at ϕmax, the HTPB layer thickness, Hϕp (µm), on the AP particle, calculated from the specific surface area measured by the air-permeability method, is closely related to the void fraction, ɛmax(-), for the loose packing of the AP powder. Hϕp decreases with increasing ɛmax. By reversal conclusion it was found that the relative viscosity of the suspension, of which the HTPB layer thickness is Hϕp, will accordingly be ηrϕ.

Due to the requirements for the preparation of an ammonium perchlorate (AP)/hydroxy-terminated polybutadiene (HTPB) based composite propellant, an upper limit content of AP applicable in the propellant, ϕmax (wt%), exists. The rheology of concentrated AP/HTPB suspensions prepared at ϕmax is investigated in this study. The relative viscosity, ηrϕ(-), of the suspensions prepared at ϕmax is almost constant at approximately 200. For the suspensions prepared at ϕmax, the HTPB layer thickness, Hϕp (µm), on the AP particle, calculated from the specific surface area measured by the air-permeability method, is closely related to the void fraction, ɛmax(-), for the loose packing of the AP powder. Hϕp decreases with increasing ɛmax. By reversal conclusion it was found that the relative viscosity of the suspension, of which the HTPB layer thickness is Hϕp, will accordingly be ηrϕ.

Due to the requirements for the preparation of an ammonium perchlorate (AP)/hydroxy‐terminated polybutadiene (HTPB) based composite propellant, an upper limit content of AP applicable in the propellant, φmax(wt%), exists. The rheology of concentrated AP/HTPB suspensions prepared at φmaxis investigated in this study. The relative viscosity, ηrφ(‐), of the suspensions prepared at φmaxis almost constant at approximately 200. For the suspensions prepared at φmax, the HTPB layer thickness, Hφp(µm), on the AP particle, calculated from the specific surface area measured by the air‐permeability method, is closely related to the void fraction, εmax(‐), for the loose packing of the AP powder. Hφpdecreases with increasing εmax. By reversal conclusion it was found that the relative viscosity of the suspension, of which the HTPB layer thickness is Hφp, will accordingly be ηrφ.

A fine porous ammonium perchlorate (FPAP) was prepared by the spray-drying method. The burning behavior of a propellant containing FPAP was investigated and compared with that of a propellant containing a fine ammonium perchlorate without porosity (FAP), of which the mean diameter was almost the same as that of FPAP. The results are as follows: (1) The burning rate of the propellant containing FPAP increases with increasing FPAP content. (2) When the propellants containing FPAP or FAP have the same composition, the burning rate of the propellant containing FPAP is larger than that of the propellant containing FAP at various pressures. (3) The temperature sensitivity of a propellant containing FAP is relatively constant at various pressures. However the temperature sensitivity of the propellant containing FPAP decreases with increasing pressure. (4) It was found that the differences in the burning behavior of the propellant containing FPAP and the propellant containing FAP are caused by the porosity of FPAP.

A fine porous ammonium perchlorate (FPAP) was prepared by the spray-drying method. The burning behavior of a propellant containing FPAP was investigated and compared with that of a propellant containing a fine ammonium perchlorate without porosity (FAP), of which the mean diameter was almost the same as that of FPAP. The results are as follows: (1) The burning rate of the propellant containing FPAP increases with increasing FPAP content. (2) When the propellants containing FPAP or FAP have the same composition, the burning rate of the propellant containing FPAP is larger than that of the propellant containing FAP at various pressures. (3) The temperature sensitivity of a propellant containing FAP is relatively constant at various pressures. However the temperature sensitivity of the propellant containing FPAP decreases with increasing pressure. (4) It was found that the differences in the burning behavior of the propellant containing FPAP and the propellant containing FAP are caused by the porosity of FPAP.

A fine porous ammonium perchlorate (FPAP) was prepared by the spray‐drying method. The burning behavior of a propellant containing FPAP was investigated and compared with that of a propellant containing a fine ammonium perchlorate without porosity (FAP), of which the mean diameter was almost the same as that of FPAP. The results are as follows: (1) The burning rate of the propellant containing FPAP increases with increasing FPAP content. (2) When the propellants containing FPAP or FAP have the same composition, the burning rate of the propellant containing FPAP is larger than that of the propellant containing FAP at various pressures. (3) The temperature sensitivity of a propellant containing FAP is relatively constant at various pressures. However the temperature sensitivity of the propellant containing FPAP decreases with increasing pressure. (4) It was found that the differences in the burning behavior of the propellant containing FPAP and the propellant containing FAP are caused by the porosity of FPAP.