New Propellant Component,Part I. Study of 4,6‐Dinitroamino‐1,3,5‐Triazine‐2(1 H)‐One (DNAM)

This paper reports a study of the synthesis and characterization of 4,6‐dinitroamino‐1,3,5‐triazine‐2(1 H)‐one (DNAM) carried out under the perspective of looking for new ingredients in propellant formulations. Emphasis is given to the characterization of DNAM. The following attributes were identified: low sensitivity to impact and friction, thermal stability over a wide temperature range, energetic nature, high density, and interesting particle size distribution. In Part 2 a preliminary evaluation of DNAM capabilities in a propellant formulation will be presented.     

Development of Composite Solid Propellant Based on Nitro Functionalized Hydroxyl‐Terminated Polybutadiene

This paper presents an overview of a modified composite propellant formulation to meet future requirements. The composite propellant mixtures were prepared using nitro functionalized Hydroxyl‐Terminated Polybutadiene (Nitro‐HTPB) as a novel energetic binder and addition of energetic plasticizer. The new propellant formulation was characterized and tested. It was found that the Nitro‐HTPB propellant with and without energetic plasticizer exhibited high solid loading, high density, and reasonable mechanical properties over a wide range of temperatures. It was shown that the burning rate of Nitro‐HTPB propellant is up to 40% faster than that of the HTPB propellant. These results are encouraging and suggest that it should be possible to improve the ballistic performance of popular HTPB propellants through use of the studied Nitro‐HTPB binder.     

含相稳定硝酸铵CMDB推进剂的机械感度和燃烧性能

通过测试撞击感度、摩擦感度和燃速,研究了含相稳定硝酸铵(PSAN)的改性双基(CMDB)推进剂的燃烧性能和机械感度。结果表明,PSAN可改善CMDB推进剂的机械感度;用PSAN作氧化剂,其推进剂的燃速低于RDX作氧化剂的燃速,压强指数高于后者的压强指数;1～5MPa压力范围内随PSAN在配方中含量的增加,推进剂的燃速降低,压强指数升高。     

含3,5-二硝氨基-1,2,4-三唑肼盐推进剂的能量特性计算

为评价新型高氮化合物3,5-二硝氨基-1,2,4-三唑肼盐(HDNAT)作为固体推进剂组分的应用潜力,采用NASA-CEA软件,在标准条件下(pc∶p0=70∶1),计算了含HDNAT的丁羟推进剂(HTPB)、聚叠氮缩水甘油醚(GAP)推进剂和改性双基推进剂(CMDB)的能量特性。绘制了HTPB/Al/AP/HDNAT推进剂(金属Al的最大质量分数为20%)的标准理论比冲Isp、特征速度C*、燃烧温度Tc、燃气平均相对分子质量Mw的等性能三角图。结果表明,HDNAT单元推进剂的比冲为2 533.0N·s/kg;在HTPB推进剂中,当HDNAT质量分数为50%时,Isp最大为2 658.0N·s/kg,较基础配方提高了326.6N·s/kg;在GAP推进剂中,当HDNAT质量分数为30%时,Isp最大为2 529.0N·s/kg,较基础配方提高了252.7N·s/kg;在CMDB推进剂中,当HDNAT质量分数为27%时,Isp最大为2 593.1N·s/kg,较基础配方提高了57.3N·s/kg。     

储氢合金/AP/HTPB推进剂的热分解性能

采用TG-DTG、DSC以及动力学分析方法研究了储氢合金/AP/HTPB推进剂的热分解性能。结果表明,相对于Al/AP/HTPB推进剂,储氢合金/AP/HTPB推进剂的热分解温度降低,放热量提高;A20/AP/HTPB推进剂的凝聚相反应程度提高2.44%,第二、三温区的热分解活化能(Kissinger法)分别降低4.06%和22.63%;A30/AP/HTPB推进剂的凝聚相反应程度提高10.61%,第二、三温区的热分解活化能(Kissinger法)分别降低30.89%和38.87%。储氢合金对AP/HTPB推进剂的热分解有催化作用,并且该催化作用随着储氢合金中Mg0.45Ni0.05B0.5Hx含量的增加而增强。     

AP/Al/SMX/HTPB四组元推进剂能量特性的理论研究

采用推进剂性能评估软件(PEP),计算和比较了2,3-二羟甲基-2,3-二硝基-1,4-丁二醇四硝酸酯(SMX)和HMX取代高氯酸铵/铝粉/丁羟黏合剂(AP/Al/HTPB)推进剂中AP对配方能量性能的影响。用高温化学平衡计算代码模拟计算了AP/Al/SMX/HTPB和AP/Al/HMX/HTPB复合固体推进剂的能量和标准发动机工作过程。结果表明,与HMX相比,SMX能在更大的配比范围内提高HTPB推进剂的能量水平。在质量分数14%HTPB、18%Al的配方中,SMX能有效将推进剂的平衡流比冲提高到2 622.5N·s/kg,比HTPB三组元能量优化配方高27.5N·s/kg。在质量分数14%HTPB、15%Al的配方中,SMX取代AP后,比冲最高可达2 634.2N·s/kg,比HTPB三组元能量优化配方高39.2N·s/kg。在质量分数15%Al、HTPB质量分数为12%和10%的配方中,SMX质量分数可分别达到45%和65%;最高比冲可分别达到2 652.9和2 679.3N·s/kg,比HTPB三组元能量优化配方分别高57.9和84.3N·s/kg。在不含Al或Al含量很低的配方中,SMX可取代全部AP。     

Viscoelastic behavior of hydroxyl terminated polybutadiene containing glycerin

Hydroxyl terminated polybutadiene (HTPB) is widely used as a propellant binder. A plasticizer is usually added to improve the processing properties, the mechanical properties, and the burning characteristics of the propellant. Glycerin was found to be an effective additive to improve these properties. The glycerin/HTPB blend was hard enough to act as a binder for the composite propellant when the glycerin/HTPB mole ratio was less than 10. Only a small quantity of glycerin was incorporated into the network structure of the cured HTPB. Most of the added glycerin physically entered the voids in the network of the cured HTPB. Addition of a small quantity of glycerin (mole ratio less than 0.1) significantly altered the network density and the viscoelastic properties of the blends. The properties were only slightly dependent on the amount of the added glycerin in the mole ratio range of 0.1–10. The dangling ends were formed in the HTPB network by the addition of glycerin and the network structure was loosened, thereby enhancing the mobility of the chain segment. The viscoelastic properties of the blends followed the time‐temperature superposition principle, and the properties were estimated accurately by the Williams‐Landel‐Ferry approach. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of GAP-PB-GAP Triblock Copolymer and Application as Modifier in AP/HTPB Composite Propellant

A new triblock copolymer polyglycidylazide-block-polybutadiene-block-polyglycidylazide (GAP-PB-GAP) has been synthesized. The synthesis was done by cationic ring opening polymerization of epichlorohydrin (ECH) with HTPB as the alcohol and boron trifluoride etherate as the catalyst followed by the conversion of the -CH₂Cl group into -CH₂N₃ group. The presence of the azido groups in the GAP polymer chain makes it more energetic and the triblock copolymer can be used as an energetic binder/additive for propellant energy modification. Since the triblock copolymer has polybutadiene (PB) as the central block, which is from HTPB itself, it can be used as an additive in HTPB based polymeric formulations to improve their properties. In the present work, a part of HTPB, the propellant binder in ammonium perchlorate (AP)/HTPB propellant was removed and replaced with the GAP-PB-GAP copolymer. Burn rate, mechanical properties, and heat of combustion properties of these propellants were measured and compared with the unmodified HTPB/AP propellant. The results show that the burn rate of the HTPB/AP solid propellant could be enhanced by the addition of the triblock copolymer.     

Influence of Particle Size on the Combustion of CL‐20/HTPB Propellants

The effect of nitramine particle size on the combustion behavior of inert binder based propellants has been extensively studied for RDX and HMX, but not CL‐20. Although materials such as RDX and HMX are useful for particular combustion applications, CL‐20 has a greater potential to improve the oxygen balance and energy density of a propellant. The current work investigates the effect of CL‐20 particle size on the combustion of CL‐20/HTPB propellants down to submicrometer sizes. An influence of particle size on the burning rate and combustion mechanism is reported. The 30 micrometer formulation burning rate data showed evidence of convective burning specifically at higher pressures, but the pressure dependence was comparable to neat CL‐20 at pressures below 8 MPa. A change in the combustion mechanism of the submicrometer formulation as a function of pressure was determined to be a result of the interaction of the propellant flame and the combustion residue. Data suggested that at low pressures diffusion in terms of active cooling was dominant for the submicrometer formulation. Higher pressure data for both the submicrometer and 3 micrometer formulations suggest the degree of active cooling is decreased as the burning rate pressure exponent is near 0.5 for both propellants. The indirect evidence for the presence of a melt layer for CL‐20 propellants is discussed.     

Effects of Temperature and Strain Rate on the Dynamic Fracture Properties of HTPB Propellant

In order to study the influence of temperature and strain‐rate on HTPB propellant fracture capability under impact loading conditions, a dynamic fracture experiment at different temperatures was carried out by using the cracked straight‐through Brazilian disc (CSTBD) specimen on the split Hopkinson pressure bar (SHPB), and the dynamic initiation fracture toughness of the HTPB propellant was obtained. Experimental results indicate that the proposed dynamic fracture testing for the HTPB propellant is effective. The dynamic initiation fracture toughness is obviously sensitive to temperature and strain‐rate, and its value increases with decreasing temperature and increasing strain rate, and a linearity relationship exists between the fracture toughness and the logarithm of the strain rate, and the linearity also increases with increasing loading rate. A master curve of quadratic function for the fracture toughness was obtained.     

Preliminary Characterization of Propellants Based on p(GA/BAMO) and pAMMO Binders

In previous papers, the synthesis and characterization of OH‐terminated glycidyl azide‐r‐(3,3‐bis(azidomethyl)oxetane) copolymers (GA/BAMO) and poly‐3‐azidomethyl‐3‐methyl oxetane (pAMMO) by azidation of their respective polymeric substrates were described. The main objective was the preparation of amorphous azido‐polymers, as substitutes of hydroxy‐terminated polybutadiene (HTPB) in new formulations of energetic propellants. Here, the subsequent characterization of both the binders is presented. First of all, several isocyanates were checked in order to optimize the curing reaction, and then two small‐scale formulations of a propellant, based on aluminium and ammonium perchlorate, were prepared and characterized. Finally, the mechanical properties and burning rate were compared to those of a similar propellant based on HTPB as binder.     

铝/有机氟化物复合物对含铝HTPB推进剂燃烧性能的影响

为研究有机氟化物(OF)对含铝HTPB固体推进剂燃烧性能的影响,采用球磨法制备了纳米和微米铝/有机氟化物复合物(nmAl/OF和μmAl/OF),将其作为复合添加剂替代微米铝粉加入HTPB推进剂中,并考察其对推进剂燃烧性能的影响。采用SEM、TEM、粒度分析等对nmAl/OF和μmAl/OF复合物及推进剂凝聚相燃烧产物进行了表征。结果表明,nmAl/OF和μmAl/OF复合物有不同的结合状态;添加OF、nmAl/OF和μmAl/OF后,推进剂的爆热值下降约2%;添加nmAl/OF的推进剂配方燃速最低,在3MPa时仅为6.28mm/s,添加OF和μmAl/OF体系的推进剂燃速压强指数相比于原配方降低约20%;添加nmAl/OF的推进剂配方凝聚相燃烧产物粒度(D_(50))比原配方降低约47%。     

From Cross‐linking to Plasticization – Characterization of Glycerin/HTPB Blends

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.     

Prediction and Comparison of Shelf Life of Solid Rocket Propellants Using Arrhenius and Berthelot Equations

The Arrhenius equation and the Berthelot equation for the prediction of shelf life of composite propellant formulations are compared. The elongation has a measurable variation with time and is taken as the fastest degrading parameter for HTPB/AP/Al based composite solid rocket propellants. An HTPB based aluminized composite propellant with 85 % solid loading and an initial elongation of 63.24 % is prepared. It is kept at an elevated temperature of 60 °C to achieve a higher rate of degradation for a prolonged time period (1 year). The elongation is monitored at regular intervals using JANNAF class C dog bone specimen in uni‐axial tensile mode. A reduction of the elongation to less than 50 % is taken as the end‐of‐shelf life of the propellant. The shelf life of the propellant is calculated to be 1.2 years at 60 °C. For the extrapolation of the shelf life at 60 °C to the shelf life at 27 °C, the results of both the Arrhenius equation and the Berthelot equation are compared. The activation energy (E) in the Arrhenius equation is obtained as 72.8 kJ mol⁻¹ and the 10 °C reaction rate rise factor (γ₁₀) is found to be 2.4. This comparison is independent of the propellant formulation and other researchers have reported a similar range of values for these parameters. The shelf life of this propellant formulation at 27 °C is conservatively predicted to be 20 years using both equations. In addition to estimation of shelf life by both equations using elongation as control parameter, this paper gives scaling curves, which are valid universally for predicting shelf life at 27 °C from data of shelf life at 60 °C. The use of scaling curves is independent of properties, propellant formulation and degradation mechanism considered for analysis.     

低铝粉含量的HMX/HTPB推进剂研究

对低铝粉含量的HMX/HTPB推进剂进行了配方研究。为获得少烟、高密度、高模量、高燃速、低压强指数的优良的综合性能,配方调试以铝粉质量分数<10%,用HMX替代部分AP来达到少烟目的;以HTPB/TDI/MAPO/STR黏合剂体系来获取高模量;通过AP级配调节,燃速催化剂的选择等方法,使推进剂具有不挥发物质量分数≥88.5%、20℃下密度≥1.78 g/cm3、σm≥3.1 MPa,燃速≥40 mm/s的良好性能,并具有药浆初始黏度低,流动、流平性好的优点。HTPB/AP/Al/HMX四组元推进剂经BSFΦ127标准发动机地面试车,内弹道p–t曲线在压强30 MPa以下,燃烧稳定;推进剂燃烧未急升导致压强异常现象。研制成的药柱经发动机地面试验可知混合比冲高达2 456.7 N·s/kg。     

Structure-property relationship of HTPB-based propellants. I. Effect of hydroxyl value of HTPB resin

Composite propellants based on hydroxyl-terminated polybutadience (HTPB) resin are the most common contemporary solid propellants for launch vehicle and missile applications. A series of HTPB resins, manufactured by free-radical polymerisation using a peroxide initiator, with varying molecular weights and hydroxyl values, was used in propellant formulation experiments with a view to studying the resin production variables and their influence on the resultant propellant properties. It is seen that HTPB resins with a wide range of hydroxyl values could be effectively utilized in propellant formulations. Also, propellants with higher strain capability and chain flexibility could be produced from lower hydroxyl value resins. © 1993 John Wiley & Sons, Inc.     

B/Fe_2O_3/NC复合物的制备及其对HTPB/AP推进剂性能的影响

为改善硼粉(B)的性能和纳米氧化铁(Fe_2O_3)在固体推进剂中的分散性,用静电喷雾法制备了B/Fe_2O_3/NC复合物,采用扫描电镜(SEM)表征了复合物的表面形貌,用TG-DSC分析了复合物的热性能及其对HTPB/AP推进剂热性能的影响,并用燃速测试和密闭爆发器实验研究了该复合物对HTPB/AP推进剂燃烧性能的影响。结果表明,所制备的B/Fe_2O_3/NC复合物均以团聚体的形式存在,复合物中B的活性提高,其氧化反应温度提前;团聚硼粉对HTPB/AP推进剂燃烧性能的改善效果明显优于原料硼粉;加入Fe_2O_3后,会进一步改善含硼推进剂的燃烧性能,而且随Fe_2O_3含量的增加,在密闭爆发器中HTPB/AP推进剂达到最高压力所需的时间逐渐减小。当Fe_2O_3的质量分数为8%时,推进剂在常压空气中的燃速最大,为不添加B/Fe_2O_3/NC复合物的HTPB/AP推进剂的2.77倍。B/Fe_2O_3/NC复合物对推进剂的热分解具有一定催化作用,且随Fe_2O_3含量的增加催化作用增强。     

Burning‐rate enhancement of a high‐energy rocket composite solid propellant based on ferrocene‐grafted hydroxyl‐terminated polybutadiene binder

Four different samples of ferrocene‐grafted hydroxyl‐terminated polybutadiene (Fc‐HTPB), containing 0.20, 0.52, 0.90, and 1.50 wt % iron, were synthesized by the Friedel–Crafts alkylation of ferrocene with hydroxyl‐terminated polybutadiene (HTPB) in the presence of AlCl₃ as a (Lewis acid) catalyst. The effects of the reaction conditions on the extent of ferrocene substitution were investigated. The Fc‐HTPBs were characterized by IR, ultraviolet–visible, ¹H‐NMR, and ¹³C‐NMR spectra. The iron content and number of hydroxyl groups were estimated, and the properties, including thermal degradation, viscosity, and propellant burning rates (BRs), were also studied. The thermogravimetric data indicated two major weight loss stages around 395 and 500°C. These two weight losses were due to the depolymerization and decomposition of the cyclized product, respectively, with increasing temperature. The Fc‐HTPB was cured with toluene diisocyanate and isophorone diisocyanate separately with butanediol–trimethylolpropane crosslinker to study their mechanical properties. Better mechanical properties were obtained for the gumstock of Fc‐HTPB polyurethanes with higher NCO/OH ratios. The BRs of the ammonium perchlorate (AP)‐based propellant compositions having these Fc‐HTPBs (without dilution) as a binder were much higher (8.66 mm/s) than those achieved with the HTPB/AP propellant (5.4 mm/s). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure–property relationship of HTPB-based propellants. III. Optimization trials with varying levels of diol–triol contents

A systematic study has been conducted on a composite solid propellant formulation using hydroxyl-terminated polybutadiene (HTPB) prepolymer with varying molecular weights and hydroxyl values. Fairly extensive regions of resin parameters have been studied. Contours of important propellant properties have been laid down. In this set of experiments, varying levels of diol and triol contents were used at two different NCO/OH ratios to arrive at the optimum level needed for different grades of HTPB resin. It is seen that different grades of HTPB resin require varying levels of diol–triol contents to give similar properties for the end product. Also, for the best performance, varying the diol–triol ratio at the optimum level of the diol–triol content is necessary. © 1994 John Wiley & Sons, Inc.     

HTPB/AP复合推进剂冲击波点火实验研究

根据增效射孔器的实际作用,以AP-丁羟（HTPB/AP）复合推进剂为研究对象,利用隔板试验研究了冲击波对AP-丁羟复合推进剂的点火性能,结果表明,合理控制冲击波强度能够使AP-丁羟复合推进剂可靠点燃,并为其它推进剂的点火提供了一种新方法.