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Ammonium nitrate (AN)-based composite propellants have gained popularity because of the clean burning nature of AN as an oxidizer. However, such propellants have several disadvantages such as poor ignition and low burning rate. The burning characteristics of the AN propellant were improved when a portion of this propellant was replaced by an energetic material and the addition of a catalyst. In this study, RDX (1,3,5-trinitroperhydro-1,3,5-triazine) was used as the energetic material, and Fe2O3and MnO2were used as catalysts. The burning characteristics of the AN/RDX propellants supplemented with catalysts were investigated, and the effects of the replacement of AN by RDX and the catalyst addition were evaluated. [ABSTRACT FROM PUBLISHER]

Ammonium nitrate (AN) has attracted much attention due to its clean burning nature as an oxidizer. However, an AN-based composite propellant has the disadvantages of low burning rate and poor ignitability. In this study, we added nitramine of cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX) as a high-energy material to AN propellants to overcome these disadvantages. The thermal decomposition and burning rate characteristics of the prepared propellants were examined as the ratio of AN and nitramine was varied. In the thermal decomposition process, AN/RDX propellants showed unique mass loss peaks in the lower temperature range that were not observed for AN or RDX propellants alone. AN and RDX decomposed continuously as an almost single oxidizer in the AN/RDX propellant. In contrast, AN/HMX propellants exhibited thermal decomposition characteristics similar to those of AN and HMX, which decomposed almost separately in the thermal decomposition of the AN/HMX propellant. The ignitability was improved and the burning rate increased by the addition of nitramine for both AN/RDX and AN/HMX propellants. The increased burning rates of AN/RDX propellants were greater than those of AN/HMX. The difference in the thermal decomposition and burning characteristics was caused by the interaction between AN and RDX. [ABSTRACT FROM PUBLISHER]

Ammonium nitrate (AN)-based composite propellants have attracted a considerable amount of attention because of the clean burning nature of AN as an oxidizer. However, such propellants have several disadvantages such as poor ignition and a low burning rate. In this study, the burning characteristics of AN-based propellants supplemented with Fe2O3 as a burning catalyst were investigated. The addition of Fe2O3 is known to improve the ignitability at low pressure. Fe2O3 addition also increases the burning rate, while the pressure exponent generally decreases. The increasing ratio ( R) of the burning rate of the AN/Fe2O3 propellant to that of the corresponding AN propellant vs. the amount of Fe2O3 added ( ξ) depends on the burning pressure and AN content. R decreases at threshold value of ξ. The most effective value of ξ for increasing the burning rate was found to be 4 % for the propellant at 80 % AN, and the value generally decreased with decreasing AN content. According to thermal decomposition kinetics, Fe2O3 accelerates the reactions of AN and binder decomposition gases in the condensed- and/or gas-phase reaction zones. The burning characteristics of the AN-based propellant were improved by combining catalysts with differing catalytic mechanisms instead of supplementing the propellant with a single catalyst owing to the multiplicative effect of the former. [ABSTRACT FROM AUTHOR]

Polytetrahydrofuran (PTHF) is an effective binder ingredient for improving propellant performance, even though it is not an energetic material. PTHF becomes sufficiently rubbery for use as a binder when a triol material such as glycerin is added as a crosslinking modifier. The cured PTHF/glycerin binder had unsatisfactory mechanical characteristics for use as a propellant binder, so a more appropriate crosslinking modifier than glycerin needs to be found. In this study, glycerol propoxylate (GPO), with a molecular weight of 260, was used as a crosslinking modifier, and the curing behavior, tensile properties, and thermal decomposition behaviors of the PTHF binder using GPO were investigated. The PTHF/GPO blend did not solidify when the PTHF/GPO mole ratio ( ξ) was greater than a certain value. The PTHF ( Mn=650)/GPO blend with ξ≤5 and the PTHF ( Mn=1400)/GPO blend with ξ≤3 were used as propellant binders. From the curing behaviors and tensile properties, it was found that the PTHF/GPO binders ensured optimal mixing of the propellant ingredients and casting of the uncured propellant into the rocket motor case, and the tensile properties of the binders changed more drastically with the variation in ξ than did those of the PTHF/glycerin binders. The thermal decomposition behaviors of the PTHF/GPO binders were hardly dependent on ξ and were almost identical to those of the PTHF/glycerin binders. [ABSTRACT FROM AUTHOR]

Polytetrahydrofuran (PTHF) is an effective binder ingredient used for improving the performance of propellants. PTHF becomes sufficiently rubbery for use as a binder with the addition of an adequate crosslinking modifier. This study investigated the viscoelastic and thermal decomposition behaviors of the PTHF binder prepared using glycerin as a crosslinking modifier, as well as the influence of the molecular weight of PTHF on the characteristics of the PTHF binder. The curing behavior of the PTHF binder was suitable for the manufacture of propellants, and the superior tensile properties of the PTHF binder made it suitable for use as a propellant binder. The degree of crosslinking of the samples decreased as the molecular weight of the PTHF increased. The PTHF binder has unique dynamic mechanical properties owing to its melting and chemical structure, and these properties were dependent on the molecular weight of PTHF. The glass transition temperature ( Tg) and the loss tangent at Tg decreased as the molecular weight of the PTHF increased. The temperature and frequency dependence of the PTHF binder were influenced by the melting point of PTHF. The viscoelastic properties of the binder prepared using PTHF with a molecular weight of 650 followed the time-temperature superposition principle. The activation energy for the relaxation of this binder varied remarkably at the melting point of PTHF. The thermal decomposition behavior indicated that at low temperatures, the consumption rate of the binder with low-molecular-weight PTHF was slightly larger than that of the binder with high-molecular-weight PTHF. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Ammonium nitrate (AN)-based composite propellants have several major problems, namely, a low burning rate, poor ignitability, low energy, and high hygroscopicity. The addition of a burning catalyst proved to be effective in improving the burning characteristics of AN-based propellants. In this study, the burning characteristics of AN-based propellants supplemented with MnO2 as a burning catalyst were investigated. The addition of MnO2 is known to improve the ignitability at low pressure. The most effective amount of MnO2 added ( ξ) for increasing the burning rate is found to be 4 %. The increasing ratio with ξ is virtually independent of the burning pressure and the AN content. However, the pressure exponent unfortunately increased by addition of MnO2. The apparent activation energy of the thermal decomposition for AN and the propellant is decreased by addition of MnO2. From thermal decomposition kinetics it was found that MnO2 could accelerate the thermal decomposition reaction of AN in the condensed phase, and therefore, the burning characteristics of the AN-based propellant are improved. [ABSTRACT FROM AUTHOR]