Burning Rate Modifier Research Articles

Hydroxyl‐terminated polybutadiene(HTPB) propellants cross‐linked by dimer acid diisocyanate (DDI): Cross‐linking network and properties

AbstractConsidering the high toxicity of toluene diisocyanate (TDI) and the low reactivity of isophorone diisocyanate (IPDI), a low‐toxicity curing agent, dimer acid diisocyanate (DDI), was used to cross‐link HTPB elastomers and propellants. The unique long‐chain structure of DDI not only ensures the elastic modulus and tensile strength of the elastomer, but also improves the flexibility to some extent. The long flexible chains promote the segment movement, which is very important for the formation of hydrogen bonds between segments. The chemical cross‐linking network and hydrogen bonding association play a significant role in the mechanical properties of the HTPB/DDI system. The relationship between the mole ratio of ‐NCO to ‐OH (R‐value) and the mechanical properties of HTPB/DDI elastomers were also investigated. In the range of R‐value from 0.85 to 1.2, the elastic modulus and tensile strength first increase and then decrease, and the elongation at break first decreases and then increases. Under the same curing conditions, the elastic modulus and tensile strength of the HTPB/DDI propellant are similar to the HTPB/TDI propellant. For the HTPB/AP/Al propellants and HTPB/AP/RDX/Al propellants, the HTPB/DDI system has lower burning rates in the range of 5–19 MPa than the HTPB/TDI system and HTPB/IPDI system. The application of DDI can reduce the burning rates of the propellant without adding any burning rate modifiers. It is considered that DDI can replace TDI and IPDI as a new curing agent with low toxicity and moderate reactivity for HTPB systems.

Ferrocene-fullerene dyad as a novel burn rate modifier for propellants

The burn rate of composite rocket propellants serves as a critical ballistic parameter in the construction of a rocket engine. Due to their large surface areas, carbon-based materials such as carbon nanotubes, graphene, and fullerene have demonstrated promising results as burn rate modifiers (BRMs) for propellants. Unlike their inorganic counterparts, these materials, being combustible, contribute to energy output besides enhancing the burn rate. This study reported a ferrocene-fullerene dyad as a BRM prepared through the thermal decomposition of ammonium perchlorate (AP) in composite solid propellants. By incorporating 0.6 wt% of the dyad, the burn rate of the prepared propellants increased by 70%, accompanied by a rise in their calorific value.

Pb(II)-MOFs assembled with tetrazole-based carboxylic acids as a burn rate modifier

Three tetrazole-based carboxylic acids, 3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4L1), 2-(5-pyridin-4-yl-tetrazol-2-yl)propionic anion (HL2), and 5-(2-pyridyl)tetrazole-2-acetic acid (HL3), were selected as ligands to synthesize three new Pb(II)-coordination polymers, [Pb2(L1)] · H2O (1), [Pb(L2)(NO3 −)] (2), and [Pb(L3)2(H2O)] · H2O (3). These metal-organic frameworks have been characterized by elemental analysis, FT-IR, and single crystal X-ray diffraction. The results demonstrated that 1 displayed a 3-D network, while 2 and 3 show 2-D framework and 1-D chain, respectively. The differential scanning calorimetry and thermogravimetric analyses gave thermodynamic parameters (ΔH, ΔS, and ΔG). The results showed that 1–3 may be promising high-energy materials.

A Metal Inorganic Framework Designed as a Propellant Burn Rate Modifier

A Metal Inorganic Framework Designed as a Propellant Burn Rate Modifier

The Effect of Different Morphologies of Polyaniline on Its Catalytic Activity for the Thermal Decomposition of Ammonium Perchlorate

AbstractIn this study, a novel strong green catalyst as a promising replacement for conventional transition metal oxides (TMOs) based burning rate modifiers was introduced. For this aim, the morphology of the nano‐porous polyaniline (NP‐PANi) was manipulated by changing its synthesis method, and the effect of that on the activity of the catalyst on the thermal decomposition of ammonium perchlorate (AP) was investigated. To achieve this goal, NP‐PANi was synthesized by three different methods comprising: chemical, sonochemical, and electrochemical routes. The synthesized polymers were deeply characterized using FTIR, N2 adsorption‐desorption, FESEM, and EDAX analysis. From BET results, electro‐PANi has the highest surface area, highest pore volume, and the smallest pore size among others and, as expected revealed the best catalytic activity. It merged two peaks of AP decomposition into a drastically solo sharp peak revealed at low temperature (approximately 90 °C lower than) and increased the enthalpy of the reaction significantly by about 140 %. The obtained results can open a new window in the world of practical green burning rate modifiers for the energetic material industry.

A Metal Inorganic Framework Designed as a Propellant Burn Rate Modifier

The kinetics of a strategically synthesized burn rate enhancer (BRE) are investigated in its reaction with ammonium perchlorate (AP). The BRE is designed for multifunctionality by 1) producing reactive gases that couple with AP gas production; 2) trapping reactive gases with high surface area; and 3) exposing metal cations to incite exothermic reactions at a temperature coincident with AP decomposition. This study advances inorganic synthesis by introducing a metal inorganic framework (MIF) composed of an aluminum cation (Al+3) surrounded by inorganic “linker” molecules of oxidizing species. To increase surface area, a porous, amorphous MIF (a‐MIF) is synthesized by controlling solution properties of an acid–base precipitation reaction. Upon gas generation, high surface area and aluminum‐rich surface of a‐MIF accelerate AP decomposition and induce an exothermic reaction that is otherwise endothermic in thermal equilibrium analysis. AP decomposition rate is advanced by reducing peak onset temperature and increasing decomposition rate with addition of a‐MIF (i.e., from 17% min−1 at 401 °C to 18% min−1 at 365 °C). Enthalpy of AP decomposition increases from +240 J g−1 to −1040 J g−1. Results introduce an approach for increasing the decomposition rate of solid oxidizers by demonstrating a recipe for designing and synthesizing an MIF.

Precise Regulation of Combustion Characteristics of High-Energy Composite Propellants by Incorporation of CL-20 Crystals Intercalated with Energetic Burn Rate Modifiers.

In this study, a 2D structured triaminoguanidine-glyoxal polymer with a high nitrogen content has been coordinated with metal ions to produce energetic metal complexes (TAGP-Ms) employed as energetic burn rate inhibitors. The metal ions (Ba2+, K+, and Ca2+) are elaborately selected based on their ability of suppressing the burn rate of composite propellants. The CL-20 crystals were intercalated with prepared TAGP-Ms materials via a solvent-antisolvent method for realization of the precise control on burning behaviors of studied propellants. The influence of TAGP-Ms inhibitors on thermal decomposition and combustion characteristics of high-energy composite propellants was evaluated using thermal analysis and a combustion diagnostic method. Results of TGA/DSC-FTIR measurements suggest that the thermal decomposition of CL-20-containing composite propellants was found to be constrained by varied degrees as a result of TAGP-Ms additions, in which the TAGP-K displays a stronger effect on suppressing the thermal decomposition of CL-20 compared with that of other TAGP-Ms. The FTIR spectra indicate that the primary gaseous phase products are composed of N2O, H2O, and CO2 in CL-20 decomposition, as well as by HCl, H2O, NO2, and N2O in the decomposition of AP for all studied composite propellants. The combustion characterizations show that the TAGP-K-containing composite propellant exhibits a significantly reduced rate of heat release but is associated with a higher flame radiation intensity increased by 4.2% compared with that of the reference propellant, which clearly implies that the TAGP-K is capable of suppressing the energy release rate while ensuring the high energetic features of propellants to be well maintained. Moreover, the burn rate pressure exponents are considerably decreased by ∼10% for the TAGP-K-containing propellants in comparison with those of propellants with the typical formulation, which strongly suggests that TGAP-Ms are promising candidates for tuning the combustion behaviors of composite propellants by influencing the decomposition processes of CL-20 and AP collectively.

The Influence of Potassium Salts Phase Stabilizers and Binder Matrix on the Properties of Novel Composite Rocket Propellants Based on Ammonium Nitrate.

The environmental impact and availability of ingredients are vital for the new generation of rocket propellants. In this context, several novel composite propellants were prepared based on the "greener" oxidizer phase-stabilized ammonium nitrate (PSAN), a micronized aluminum-magnesium alloy fuel, iron oxide powder burn rate modifier, triethylene glycol dinitrate (TEGDN) energetic plasticizer and a polyurethane (PU) binder. The novelty of this study is brought by the innovative procedure of synthesizing and combining the constituents of these heterogeneous compositions to obtain high-performance "eco-friendly" rocket propellants. The polymorphism shortcomings brought by ammonium nitrate in these energetic formulations have been solved by its co-crystallization with potassium salts (potassium nitrate, potassium chromate, potassium dichromate, potassium sulphate, potassium chlorate and potassium perchlorate). Polyester-polyol blends, resulting from recycled post-consumer polyethylene terephthalate (PET) glycolysis, were utilized for the synthesis of the polyurethane binder, especially designed for this type of application. To adjust the energetic output and tailor the mechanical properties of the propellant, the energetic plasticizer TEGDN was also involved. The performance and safety characteristics of the novel composites were evaluated through various analytical techniques (TGA, DTA, XRD) and specific tests (rate of combustion, heat of combustion, specific volume, chemical stability, sensitivity to thermal, impact and friction stimuli), according to NATO standards, providing promising preliminary results for further ballistics investigations.

Tunning Combustion Behaviors of Composite Modified Double-Based Propellants with a Novel Energetic Burn Rate Modifier

ABSTRACT The flexible control in burning rate and stable combustion of solid propellants over a broad range of pressures essentially determine the performance of solid rocket motors. The nanoscale metals and their oxides are usually utilized as the traditional burn rate modifiers in adjusting the combustion behaviors of solid propellants, but the energy characteristics of propellants are greatly compromised owing to the inert nature of additives used. In this paper, a series of metal complexes of triaminoguanidine-glyoxal polymer (TAGP-Ms) with high nitrogen content were synthesized and employed as energetic burn rate inhibitors in tunning the combustion properties of composite modified double-based (CMDB) propellants. The influences of prepared TAGP-Ms on the thermal decomposition and combustion of CMDB propellants were comprehensively investigated based on thermal analysis technique and combustion characterization methods. It was found that the peak temperatures of the second exotherm displayed for the propellants containing TAGP-Ms inhibitors were significantly increased by more than 30°C (except for TAGP-Cu), indicating the TAGP-Ms is capable of suppressing the thermal decomposition of CMDB propellants. More importantly, the heat releases of CMDB propellants were substantially enhanced by 16%~34% determined by DSC analysis. In comparison to the blank reference, the energetic TAGP-Ms inhibitors could promote the heat of combustion for the involved CMDB propellants by 5%~9%. The burning rates of CMDB propellants were notably reduced over a wide range of pressures by adding TAGP-Ms, whereas the calculated pressure exponents at pressures ranging from 10 to ~ 22 MPa appear to be relatively high due to the accelerated HMX decomposition. The measured combustion wave temperatures suggest that the CMDB propellants with TAGP-Ms undergo a three-stage combustion process with the highest temperatures in the range of 2160 ~ 2230°C.

Design and Development of Composite Propellant Using CuFe2O4 Spinel Decorated Graphene Oxide Nanocomposite as Novel Burn Rate Modifier

AbstractThe burning rate of composite rocket propellant is a principal ballistic property that is considered while designing the rocket motor. Carbon bonded materials such as CNT(carbon nanotubes), fullerene, graphene, etc. due to their high surface area have exhibited promising results as burn rate modifiers in a propellant. Apart from enhancing the burn rate, unlike their inorganic counterparts, they are combustible and contribute towards energy output. Herein, we report a spinel structure CuFe2O4 decorated Graphene Oxide nanocomposite as novel burn rate modifier (BRM) in propellant composition. By incorporating 0.6 % of this burn rate modifier to the propellant remarkable improvement in burn rate by 61 % was observed.

Macrocycle as a "Container" for Dinitramide Salts.

Dinitramic acid salts are promising components as oxidizers and burning-rate modifiers of high-energy compositions. However, most of these salts are not free of drawbacks such as hygroscopicity. Therefore, their application under special conditions of use and storage is limited. The synthesis and storage of stable dinitramic acid salts is a topical issue. Here, we synthesized an adduct starting from the nickel salt of dinitramic acid with carbohydrazide and glyoxal to settle the problem of stability and storage of that salt. The chemical composition of the adduct was confirmed by infrared spectroscopy and elemental analysis. The Ni content was determined by atomic emission spectroscopy. Thermogravimetric DSC and TGA analyses showed the adduct to have three decomposition stages. The adduct exhibits a good thermal stability and a low sensitivity to mechanical stimuli. Here, the adduct is demonstrated to be a promising burning-rate inhibitor of pyrotechnic compositions.

Are All Solid Propellant Burning Rate Modifiers Catalysts?

AbstractSolid rocket motors are used for both national defense and launch vehicles. The internal ballistics of the motor depend on the propellant burning rate, which is often modified by burning rate enhancers. Despite the common use, there is not a complete mechanistic understanding of how these modifiers influence the combustion process. In this comment, it is argued that these additives can influence propellant combustion as a catalyst, via thermodynamic means, or a combination. An approach is suggested on how to classify traditional and novel burning rate modifiers as a first step to improving the scientific community‘s knowledge on the matter.

Facile Synthesis and Catalytic Activity Assessment of Copper Chromite Nanoparticles for Ammonium Perchlorate Decomposition

The universal burning rate modifier used in composite solid propellants is copper chromite. The fabrication of copper chromite nanoparticles (CCNs) is highly appreciated; as superior performance could be accomplished. This research looks at how copper chromite nanoparticles can be made in a sustainable way using hydrothermal processing. Mono-dispersed particles with a medium particle size of 12 nm were seen in TEM micrographs. The XRD diffractogram revealed a crystalline structure. The co-precipitation approach was used to incorporate CCNs into ammonium perchlorate (AP). Differential scanning calorimetry (DSC) and thermal gravimetric analysis were used to analyze the activity of catalysis in CCNs on AP breakdown (TGA). The enthalpy of AP breakdown was enhanced from 742 J/g to 1391 J/g. CCNs caused the Peak of high-temperature decomposition shift toward lower temperatures, resulting in the overlapping of the two peaks into a single peak. At 244 °C, CCNs showed a decrease in AP endothermic phase transition. These characteristics could ensure high-burning-rate catalyzed decomposition processes.

-Ferrocenedicarboxylic Acid Salts as Burning Rate Modifiers of Double-Base Propellant

To expand the possibilities of using solid propellants in gas generators or civil- purpose rockets, the properties of new compounds proposed as burning rate modifiers were considered. -ferrocenedicarboxylic acid and its insolubility in water copper, iron, and lead salts were synthesized. The effect of the salts on the burning rate of a double-base propellant was studied. It was shown that individually 3% of copper salt (CFDA) has the most considerable effect on the burning rate, increasing by times at the pressure interval of 1–10 MPa. It is possible to lower the n value in the burning law from 0.71 to 0.21 in a pressure range of 6–15 MPa with use of lead salt. Carbon nanotubes significantly increase the efficiency of FDA salts. An interesting phenomenon was discovered: Iron salt (IFDA) affects the burning rate only at pressure up to 2 MPa, and at higher pressures, but only in combination with a carbon nanotube. IFDA also reduces the efficiency of CFDA. An explanation of that fact was suggested.

NiZnFe2O4: a potential catalyst for the thermal decomposition of AP and burn rate modifier for AP/HTPB based propellants

NiZnFe2O4: a potential catalyst for the thermal decomposition of AP and burn rate modifier for AP/HTPB based propellants

Enhancing the Regression Rate of Hydroxyl-Terminated-Polybutadiene-Based Mixed Hybrid Rockets

This study has identified potential hydroxyl-terminated-polybutadiene (HTPB) based fuel compositions that provide a high-density specific impulse but do not burn like a solid propellant. Due to low solid loading in these fuel compositions, precuring the HTPB and isophorone diisocyanate mixture is necessary to get uniform density and composition across the length of the grain. Nearly 7 h of precuring gave the best results in terms of uniformity of the propellant composition. This study also discusses the effect of available burn rate modifiers for ammonium perchlorate and a type of aluminium on the enhancement of regression rate in mixed hybrid rockets. Finally, the hybrid propellants developed had an oxidizer mass flux index close to 0.5, which is desirable.

Cobalt copper ferrite: burning rate modifier for composite solid propellants and its catalytic activity on the thermal decomposition of ammonium perchlorate

Cobalt copper ferrite: burning rate modifier for composite solid propellants and its catalytic activity on the thermal decomposition of ammonium perchlorate

Studies of burning rate and pressure exponent of a new combustion catalyst derived from p-phenylene

ABSTRACT This contribution describes the determination of the internal ballistic properties of tubular into the use of homobimetallic iron compound derived from p-phenylene ([{Cp*Fe}2-p-Ph’]) as a burning rate modifier in solid heterogeneous rocket propellant. The solid heterogeneous rocket propellants based on hydroxyl-terminated polybutadiene (HTPB) and ammonium perchlorate (AP) with 0.3%wt Fe2O3 (named Propellant 1) and 0.3%wt [{Cp*Fe}2-p-Ph’] (named Propellant 2) content in the propellant composition were prepared and investigated. The ballistic parameters of the examined propellants were determined by combustion in a laboratory rocket motor. The ballistic properties were evaluated in the pressure range 7–30 MPa. It was found that the linear burning rate was increased for propellants 1 and 2 in comparison to propellant without the modifier. Determinations of the tensile and decomposition temperature of the propellants 1 and 2 were also investigated. Comparatively lower n-value was observed for composition containing propellant 2 than for propellant 1 and HTPB-based propellant without the modifier.

Investigation of kinetic parameters for ammonium perchlorate thermal decomposition in presence of gCN/CuO by TG-MS analysis and kinetic compensation correction

The desire to develop a benign burn rate modifier for propellants has accentuated polymeric carbon nitride (gCN) as a potential candidate for the thermal decomposition of ammonium perchlorate (AP). Here, we have synthesized composites of leaf-shaped CuO and gCN via a facile sonochemical approach. From DSC analysis, the addition of gCNCuO1 reduced the decomposition temperature of AP by 59°C and increased the heat release by ~ 1.4 times that of pure AP. The kinetics of AP decomposition was well investigated via in-situ TG-MS technique. From evolved gas analysis evolution of NO, Cl, HCl, N2O/CO2, NO2 and Cl2 fragments were detected. The quantitative interpretation of kinetic parameters for AP decomposition was done using Coats-Redfern method and the normalization of E values were carried out by applying Kinetic Compensation Correction (KCC). After normalization, E values were decreased by 17 ​kJ/mol and 18 ​kJ/mol for the first and second stages respectively.

Nanodiamonds characterization and application as a burning rate modifier for solid propellants

A nanodiamond powder (n-D) synthesized by detonation method was characterized in detail, and the combustion of solid propellants contained 10 wt. % of n-D as a burning rate modifier was investigated. n-D characterization was implemented by XRD, SEM, DSC, and size distribution analyses. Specific surface area analysis was performed using BET-method. The size of primary nanodiamond particles has not changed after acid treatment and drying, but the particles' agglomeration decreased the value of a specific surface area. The effect of n-D modification on the burning rate of solid propellants with an active and inert binder was investigated. The addition of the n-D to propellants formulation instead of carbon black powder has significantly increased their burning rate (by at least 50 %) in the studied pressure range. The observed trend was associated with the high chemical reactivity of n-D and its extremely high value of specific surface area.