【作者】 张艳丽；

【导师】 龚自正；

【作者基本信息】 西南交通大学 ， 固体力学， 2010， 博士

【摘要】 1,3,5-三氨基2,4,6-三硝基苯(1,3,5-triamino-2,4,6-trinitrobenzene, TATB)是著名的高能钝感炸药,以其为基的高聚物粘结炸药(Polymer-Bonded Explosive, PBX)应用十分广泛。但在以TATB为基的PBX中TATB与高聚物粘结剂间的粘结性不好,容易产生界面“脱粘”,较大程度地影响了它的综合性能,限制了它的应用范围。偶联技术是改变界面“脱粘”现象的一个有效的方法,但是目前,人们对偶联剂的偶联机理认识还不足,实验上选取偶联剂的方式还处在以实验探索为主的状态,亟待理论指导。基于此,本论文首先运用量子化学计算中的密度泛函理论方法在微观尺度上研究了目前被公认的TATB基PBX的较理想的偶联剂——γ-氨丙基三乙氧基硅烷(y-Aminopropyltriethoxysilane, KH550)的水解产物与TATB基PBX中各组分分子间的相互作用,并根据混合体系的几何构型、自然键轨道分析及分子间相互作用能等,预测了KH500的水解产物在TATB基PBX中可能存在的偶联机理。为了证实这种预测和更清楚直观的观察到KH550的水解产物在TATB基PBX中的作用行为,本论文采用了一种目前广泛使用的介观模拟技术——耗散粒子动力学方法在介观尺度上研究了在添加偶联剂和未添加时TATB基PBX的介观结构形貌、粒子数密度分布及一些宏观性质等,结果不仅形象展现了TATB与氟聚物粘结剂间的粘结机制,而且还为偶联剂在TATB基PBX中的作用行为给出了直观形象的描述。另外,氟聚物粘结剂对TATB的包覆性和粘结性还与在TATB基PBX造型粉的制备过程中氟聚物粘结剂在不同溶剂、不同浓度下分子链的伸展状况密切相关,故本文采用耗散粒子动力学方法研究了表征氟聚物粘结剂在不同溶剂、不同浓度下分子链伸展状况的两个重要参数——均方根末端距和回旋半径,从而预测了氟聚物在何种溶剂、何种浓度下能够对TATB产生较好的润湿效果。关于本论文的具体研究成果和结论概述如下：在DFT/B3LYP/6-31G水平下,本论文研究了硅烷偶联剂与TATB分子间的相互作用,求得硅烷偶联剂与TATB混合体系的三种优化构型、电子结构等；经自然键轨道分析可知,硅烷偶联剂与TATB间的较大电荷转移主要是通过TATB硝基上O的孤对电子与硅烷偶联剂羟基上O和H的反键轨道间的相互作用而发生的：TATB硝基上的O原子与硅烷偶联剂羟基上的H原子间可形成相对较强的氢键作用,与实验结果相吻合；另外,经零点振动能和基组叠加误差校正后精确求得混合体系的最大结合能为-17.969kJ/mol.同样地在B3LYP/6-31G水平上,本论文运用密度泛函理论研究了高聚物粘结剂与硅烷偶联剂分子间的相互作用,求得高聚物粘结剂与硅烷偶联剂混合体系的四种优化构型,经零点振动能和基组叠加误差校正后精确求得混合体系的最大结合能为24.514kJ/mol,大于硅烷偶联剂与TATB分子间的最大结合能。又经原子净电荷和自然键轨道分析表明二者之间存在较强电荷转移,分子间存在H……O和F……H等氢键作用。由分子间的最大结合能和分子间的氢键作用可以预测,若在TATB、高聚物粘结剂和硅烷偶联剂的混合体系中,硅烷偶联剂有可能处在高聚物粘结剂的聚集体中,而非同于一般的偶联剂,处在填料与粘结剂间起到“分子桥”的连接作用。为了验证采用量化计算对硅烷偶联剂在TATB基PBX中偶联机制的预测,本论文利用耗散粒子动力学对四种TATB基PBX的介观结构形貌及其演变过程进行了研究。结果表明：氟聚物粘结剂在TATB中形成线形网状结构,但不能完全包覆TATB;随着三氟氯乙烯重复单元在氟聚物粘结剂中含量比例的增加,氟聚物粘结剂在TATB中的扩散变得越来越容易；升高温度促进了氟聚物粘结剂在TATB中的扩散以及对TATB的包覆作用；研究结果表明,温度在400K时,氟聚物形成蜂窝状结构,能很好地包覆TATB。为了研究硅烷偶联剂在TATB基PBX中的偶联机制,本论文利用耗散粒子动力学方法研究了在添加硅烷偶联剂时TATB基PBX的介观结构形貌、氟聚物的聚集状态、粒子数密度分布；并以未添加硅烷偶联剂时TATB基PBX的介观结构形貌为参考,分别从粘结剂与炸药间的粘结机理——吸附理论、润湿理论和扩散理论的角度分析了添加硅烷偶联剂对氟聚物与TATB间粘结性的促进作用,得到了氟聚物与TATB间的粘结机理和硅烷偶联剂的偶联机制。结果表明,硅烷偶联剂在TATB基PBX中具有独特的偶联机制,硅烷偶联剂将与TATB亲和性差的三氟氯乙烯结构单元拽拉在它的周围,一起聚集在氟聚物团的内部,而将与TATB亲和性好的偏氟乙烯结构单元排挤在氟聚物团的表面上,即使得与TATB亲和性好的偏氟乙烯结构单元更多地聚集在TATB和氟聚物粘结剂间的界面上,从而提高了TATB与氟聚物粘结剂间的粘结作用。本论文的还利用耗散粒子动力学方法研究了F2311和F2314分别在乙酸乙酯和乙酸丁酯溶剂中在多种浓度下的链的伸展状况,为氟聚物选择何种溶剂何种浓度能够对TATB产生最佳的润湿效果提供了理论数据。结果发现乙酸乙酯是F2311的良溶剂,在浓度小于10%时,能够对TATB颗粒产生较好的润湿效果。乙酸丁酯是F2314的良溶剂,浓度为6%时,能够对TATB颗粒产生最好的润湿效果。总之,本文以改善氟聚物粘结剂与TATB间的粘结性和包覆性为目的,运用先进的量子化学计算方法和介观尺度上的耗散粒子动力学计算方法,深入研究了硅烷偶联剂与TATB基PBX内各组分分子间的相互作用和TATB基PBX的介观结构形貌及其宏观性质,丰富了高聚物粘结炸药配方设计和改善高聚物粘结炸药综合性能的研究,属于量子炸药化学和大尺度混合炸药化学研究领域的最新研究成果。更多还原

【Abstract】 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is the famous insensitive high explosive, and its based polymer-bonded explosives (PBX) are widely used. But the bindings between TATB and its polymeric binders are weak, which deduces the interfacial "bebonding" Therefore, the combination properties of TATB-based PBX are influenced and the applications of TATB-based PBX are limited. The coupling technique is a valid method to restrain the interfacial "bebonding". However, the understandings of the coupling mechanism of the coupling agent are insufficient. The selecting of the coupling agents in experiments is mainly based on explorations, so the theoretical guidance is urgently needed. Based on above, the intermolecular interactions between the recognized perfect TATB’s coupling agent-the hydrolysate of y-Aminopropyltriethoxysilane (KH550) and the components of the TATB-based PBX are investigated at the microscopic level using the density functional theory (DFT) method. According to the optimized geometries of the mixing systems, natural bond orbital analysis and the intermolecular interaction energies, the coupling mechanism of the silane coupling agent in TATB-based PBX is predicated. In order to prove above prediction and observe the behavior of the hydrolysate of KH550 in TATB-based PBX visually, the dissipative particle dynamics method was used to investigate the mesoscopic morphologies, the distribution of the particle numerical density and some macroscopic properties of the TATB-based PBX with the addition of the coupling agent or not at the mesoscopic level. The results not only show the bonding mechanism between TATB and fluoropolymer, but also the behaviors of the coupling agent in TATB-based PBX. In addition, there is a close relationship between the warp of the fluoropolymers to TATB and the extension of the fluoropolymer in the different solvents and at different concentrations. So the dissipative particle dynamics method was used to investigate the two important parameters which can illuminate the extension of fluoropolymers-root mean square end-to-end distance and radius of gyration. Therefore, in which solvent and at which concentrations, the fluoropolymer being of the excellent warp properties to TATB is predicted. Our achievements and conclusions are as follows:At DFT-B3LYP-6-31G level, the intermolecular interactions between silane coupling agent and TATB are investigated, the three fully optimized geometries of the mixture and the electronic structures are obtained. Based on the natural bond orbital analysis, the great intermolecular charge transfer between silane coupling agent and TATB is mainly caused by the interactions between the lone pair electrons of oxygen atom in nitro group of TATB and antibonding orbital between O and H in the hydroxyl group of silane coupling agent; a strong hydrogen bond between the O of TATB and the H of the hydroxyl group of silane coupling agent is found. In addition, the accurate intermolecular interaction energies are calculated with zero point energy correction and basis set superposition error correction. The largest corrected intermolecular interaction of the mixtures is -17.969kJ/mol.Likewise, the intermolecular interactions between silane coupling agent and polymeric binder are investigated at the B3LYP/6-31G level by means of the density functional theory. Four fully optimized geometries of the mixture are obtained. The accurate intermolecular interaction energies are calculated with zero point energy correction and basis set superposition error correction. The largest corrected intermolecular interaction of the mixture is 24.514kJ/mol, which is larger than that of the silane coupling agent and TATB. Atomic net charges and nature bond orbital analysis is performed. Charge transfer between two molecules is great. The hydrogen bonds are formed in H...O and F...H. Based on the the largest corrected intermolecular interaction and the hydrogen bonds, it is predicted that the silane coupling agent will be in the aggregation of the polymeric binder in the mixture of the polymeric binder, silane coupling agent and TATB, rather than playing a molecular brigde role between filler and binder.In order to prove the prediction of the coupling mechanism of the silane coupling agent in the TATB-based PBX, which is predicted by means of the quantum calculations, the mesoscopic structures of TATB-based PBXs and their time evolutions were investigated using the dissipative particle dynamics (DPD) method. The results indicate that most of the polymers are condensed to spheres and only several polymer chains extend into TATB, the polymers form reseau structure in TATB; TATB is fixed in the polymers, but can not be wrapped perfectly by the polymers. At the same time, with the increasing of the temperature and the content of the polychlorotrifluoroethylene (PCTFE) monomers in the polymer, more polymers are dispersed in TATB. When the temperature is up to 400K, the polymers form the alveolate structure, and wrap TATB perfectly. In order to investigate the coupling mechanism of the silane coupling agent in TATB-based PBX, the mesoscopic morphologies of TATB-based PBXs, the assembly of the fluoropolymers and the distributions of the particle’numerical density were studied using the dissipative particle dynamics method. The TATB-based PBXs without the addition of the silane coupling agent are made as the references, the improvement of the bindings between TATB and fluoropolymers are analyzed according to the binding mechanism between explosive and polymeric binders-adsorption theory, wetting theory and diffusion theory, therefore, the interaction mechanism between TATB and fluoropolymer as well as the coupling mechanism of the silane coupling agent are obtained. The simulation results show the silane coupling agent being of an extraordinary coupling mechanism. The silane coupling agents pull the TATB’unaffinity group-chlorotrifluoroethylene structural unit together assembling inside of the fluoropolymers ball, while push the TATB’affinity group-vinylidene fluoride structural unit outside of the fluoropolymer ball. Because of the assembling of the TATB’ affinity groups at the interface, the bindings between TATB and fluoropolymers are enhanced.The extension of F2311 and F2314 in ethyl acetate and butyl acetate solvents at different concentrations was also studied using the dissipative particle dynamics. It provides the theoretical date for selecting which solvent and which concentration for fluoropolymers being of the excellent warp properties to TATB. The results show that ethyl acetate is the good solvent for F2311, when the concentrations are below 10%, F2311 is of the excellent wetting effect to TATB. Butyl acetate is the good solvent for F2314, when the concentration is at 6%, F2314 is of the excellent wetting effect to TATB.In summary, the advanced quantum chemistry calculation method was used to investigate the intermolecular interactions between the coupling agent and the components of TATB-based PBX, and the dissipative particle dynamics was used to investigate the mesoscopic morphologies and some macroscopic properties of the TATB-based PBX. Our studies have enriched the studies of the formulation designs of polymer-bonded explosive and the improvement of the combination properties of polymer-bonded explosive, which are belong to the newest achievements of the quantum explosive chemistry and the large scale composite explosive chemistry.更多还原