高剪切速率下硼与HTPB、PBT和GAP端羟基的反应活性

含硼富燃料推进剂具有较高的质量热值和体积热值,是固体火箭冲压发动机较理想的燃料之一,而无定形硼与黏合剂中的羟基可发生反应,导致推进剂药浆表观黏度增大快、药浆适用期缩短等问题。计算了分别以端羟基聚丁二烯(HTPB)、3,3?二叠氮甲基氧丁环?四氢呋喃共聚醚(PBT)和聚叠氮缩水甘油醚(GAP)为粘合剂的含硼推进剂的理论体积热值,并采用双螺杆转矩流变仪和红外光谱研究了B/HTPB、B/PBT和B/GAP体系在高剪切速率混合过程中的流变和红外特性,分析了硼粉表面酸性杂质与粘合剂端羟基的反应活性。结果表明,经过合理配方设计,B/PBT/AP和B/GAP/AP的质量比为50∶20∶30时的体积热值均超过64.00 MJ·~(-3),大于B/HTPB/AP体系的体积热值(61.08 MJ·dm~(-3))。在剪切速率为355.56 s~(-1)、55℃条件下,含25%硼的B/HTPB体系表观黏度快速增加到260 Pa·s,混合110 min发生凝胶现象;含40%硼的B/PBT体系混合7 h黏度仅从3.63 Pa·s上升到10 Pa·s;含55%硼的B/GAP体系混合7 h黏度由5.96 Pa·s下降到0.33 Pa·s。B/HTPB混合体系红外光谱B—O振动吸收峰随着混合时间的增加而逐渐增强,C—O(伯醇)振动吸收峰随着混合时间的增加而逐渐减弱,而B/PBT和B/GAP体系混合420 min后红外光谱B—O振动吸收峰和C—O(伯醇、仲醇)振动吸收峰几乎没有变化。PBT和GAP端羟基与硼粉酸性杂质的反应活性比HTPB的端羟基的活性低很多,这有利于改善含硼推进剂药浆的工艺性能。     

Azidated Ether-Butadiene-Ether Block Copolymers as Binders for Solid Propellants

Polymeric binders for solid propellants are usually based on hydroxyl-terminated polybutadiene (HTPB), which does not contribute to the overall energy output. Azidic polyethers represent an interesting alternative but may have poorer mechanical properties. Polybutadiene–polyether copolymers may combine the advantages of both. Four different ether-butadiene-ether triblock copolymers were prepared and azidated starting from halogenated and/or tosylated monomers using HTPB as initiator. The presence of the butadiene block complicates the azidation step and reduces the storage stability of the azidic polymer. Nevertheless, the procedure allows modifying the binder properties by varying the type and lengths of the energetic blocks.     

HTPB/液化改性MDI聚合反应的动力学

用红外分光光度计研究了端羟基聚丁二烯(HTPB)与液化改性4,4’-二苯基甲烷二异氰酸酯(LMDI)的反应动力学,计算了相应体系的反应活化能。通过红外光谱研究了60℃时HTPB与LMDI本体聚合反应形成聚氯酯的浓度-时间依赖行为,研究发现,随时间的增加,反应物的浓度呈指数下降,而浓度的倒数-时间则呈直线的关系。结果表明,NCO与OH的反应遵循二级反应动力学,反应活化能Ea=54．3kJ／mol。     

端异氰酸酯基聚丁二烯液体橡胶的制备

以相对分子质量3500的端羟基聚丁二烯液体橡胶（简称丁羟,HTPB）为软段,甲苯二异氰酸酯（TDI）为硬段,制备端异氰酸酯基聚丁二烯液体橡胶（ITPB）,探讨了反应机理和合成条件,并利用红外光谱对原料和产品结构进行表征和对比分析。结果表明,随着反应体系中R值增大,ITPB中-NCO含量逐渐增多;反应时间为3．5h、反应温度85℃时,其力学性能最佳。     

宽温域宽应变率下丁羟四组元HTPB推进剂单轴压缩力学行为

为研究丁羟四组元端羟基聚丁二烯（HTPB）推进剂在宽温域宽应变率下的单轴压缩力学行为,基于万能材料试验机、高速液压伺服试验机、分离式霍普金森压杆,结合可程式恒温恒湿试验机等温控手段,开展了宽温域宽应变率下的推进剂单轴压缩力学性能实验,获取了-40,-25,-10,20,50 ℃ 5个温度下10^-4~10³ s^-1应变率的丁羟四组元HTPB推进剂的应力应变曲线,并建立了HTPB推进剂的分段式单轴压缩率温本构关系。结果表明,HTPB推进剂的力学响应存在显著的率温相关性,在任意应变率下其力学响应都呈阶段性变化,即线弹性阶段-非线性屈服阶段-应变软化阶段或应变硬化阶段;且在高应变率下,非线性屈服行为后的应变软化现象明显弱于低、中应变率。此外,高应变率时,随着温度的降低,应力应变曲线的变化速率逐渐减缓;而低、中应变率却恰恰相反,随着温度的降低,应力应变曲线的变化速率逐渐加快。HTPB推进剂的力学强度随着温度的降低显著增大,温度从50 ℃降低至-40 ℃时,HTPB推进剂试件在宽应变率作用下的最大应力从2.2~8.8 MPa增长至约11~22 MPa。同时基于实验数据构建了分段式率温本构关系,发现其在温度较高时拟合效果更好,能够较好地预测HTPB推进剂的力学行为。     

建筑用聚烯烃聚氨酯胶粘剂研制

以端羟基聚丁二烯 (HTPB)、甲苯二异氰酸酯 (TDI)以及有关配合剂为原料 ,制备了无溶剂单组分的聚烯烃聚氨酯胶粘剂 ,对扩链剂种类以及含量、胶粘剂中NCO和白碳黑的含量作了试验 ,测试了胶粘剂的外观、粘度、粘接强度和力学性能。测试结果表明 ,以 1,4丁二醇作为扩链剂 ,与HTPB的羟基含量摩尔比例是 3,控制胶粘剂中NCO含量在 4 .87%左右 ,白碳黑的含量为 10g ,可以获得粘接性能比较优越的聚烯烃型聚氨酯胶粘剂。     

Cast aluminized explosives (review)

This paper reviews the current status and future trends of aluminized explosives. The major focus is on cast compositions, which encompass both the melt-cast trinitrotoluene (TNT) based and the slurry cast polymer-based compositions. Widely reported RDX and HMX based aluminized compositions with TNT used as a binder are discussed in detail. Various researchers have suggested a 15–20% Al content as an optimum from the viewpoint of velocity of detonation. A higher Al content, however, is incorporated in most of the compositions for a sustained blast effect, due to the potential of secondary reactions of Al with detonation products. The effect of the aluminum particle size on performance parameters (velocity of detonation, etc.) is included. There are some recent works on nanometric Al based compositions, and the results obtained by various researchers suggest mixed trends for RDX-TNT compositions. Studies on nitrotriazol and TNT based compositions bring out their low vulnerability. Some of the interesting findings on ammonium dinitramide and bis(2,2,2-trinitro-ethyl)nitramine (BTNEN) based compositions are also included. The review brings out superiority of polymer based aluminized explosives, as compared to conventional TNT based compositions, particularly, with respect to low vulnerability. In general, aluminized plastic bonded explosives find numerous underwater applications. Ammonium perchlorate (AP) is also incorporated, particularly, for enhancing underwater shock wave and bubble energy. Hydroxyl terminated polybutadiene appears to be the binder of choice. However, nitrocellulose, polyethylene glycol, and polycaprolactone polymer based compositions with energetic plasticizers, like bis-dinitropropyl acetal/formal (BDNPA/F, 1/1 mix), trimethylol ethane trinitrate, and triethylene glycol dinitrate are also investigated. Polyethylene glycol and polycaprolactone polymer based compositions are found to be low vulnerable, particularly, in terms of shock sensitivity. Highly insensitive polymer bonded nitrotriazol based compositions are being pursued all over the globe. The highly insensitive CL-20/AP combination meets the demands of high density and high velocity of detonation. Glycidyl azide polymer and poly nitratomethyl methyl oxetane appear to be binders of interest for plastic bonded explosives in view of their superior energetics. The vulnerability aspects of these compositions, however, need to be studied in detail. Brief information on plastic bonded and gelled thermobaric explosives is also included. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 98–115, July–August, 2008.     

Synthesis and Application of Borate Ester Bonding Agents for a Four‐Component Hydroxy‐Terminated Polybutadiene Propellant

Low molecular weight interconnection monomers including polyepichlorohydrin, poly(propylene oxide), poly(ethylene glycol adipate), and poly(butylene adipate) were synthesized to evaluate the effects of the molecular structure of interconnection monomers on the bonding efficiency of borate ester bonding agents (BEBA) applied in four‐component hydroxy‐terminated polybutadiene (HTPB) propellants. The monomers were characterized by IR spectroscopy, elemental analysis, and gel permeation chromatography. A series of new borate ester bonding agents were synthesized using the as‐synthesized interconnection monomers as well as poly(ethylene glycol) and applied in the preparation of four‐component HTPB propellants. The application results showed that BEBA‐4 prepared from poly(butylene adipate) could significantly improve the mechanical properties of the four‐component HTPB propellant, reduce the slurry viscosity leading to improvement of processing properties and aging resistant performance, while no significant effect on the burning characteristics of the propellant was observed.     

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.     

HTPB热固PBX老化过程中的体积收缩

采用加速老化试验研究了HTPB热固PBX样品在老化过程中的体积收缩情况,从后固化反应和相对交联密度变化两个方面分析了体积收缩的原因。结果表明,在老化初期,PBX体积收缩率随老化温度的升高和老化时间的延长而增大。70℃老化90d后,体积收缩率接近定值;HTPB弹性体在老化过程中的后固化反应是引起体系体积收缩的根本原因。