HTPB/增塑剂玻璃化转变温度及力学性能的分子动力学模拟

为了预测高分子粘结剂端羟基聚丁二烯(HTPB)与增塑剂癸二酸二辛酯(DOS)、硝化甘油(NG)的相容性及HTPB/增塑剂共混物的玻璃化转变温度(Tg)和力学性能,在COMPASS力场条件下采用分子动力学(MD)模拟方法对相容体系(HTPB-DOS)和不相容体系(HTPB-NG)进行了研究.结果表明,通过比较溶度参数差值(Δδ)的大小可以预测HTPB与增塑剂的相容性,即HTPB与DOS属于相容体系,而HTPB与NG不相容.通过温度-比容曲线可以得到HTPB、HTPB/DOS与HTPB/NG的Tg分别为197.54,176.30和200.03K.力学性能分析结果表明,添加DOS增塑剂后使HTPB的弹性模量(E),体积模量(K)和剪切模量(G)下降,材料刚性减弱,柔性增强,力学性能得到改善.本模拟方法可以作为预测聚合物/增塑剂共混物性能的有利工具,也可以为固体推进剂和高聚物粘结炸药的配方设计提供理论指导.     

端羟基聚丁二烯/增塑剂共混物相容性的分子动力学模拟和介观模拟

应用分子动力学(MD)和介观动力学(MesoDyn)模拟方法对固体推进剂中端羟基聚丁二烯(HTPB)与增塑剂癸二酸二辛酯(DOS)、硝化甘油(NG)的相容性进行了研究. 采用MD模拟方法在COMPASS力场下, 对纯物质、HTPB/增塑剂共混物的密度、内聚能密度、溶度参数和共混物分子间的Flory-Huggins作用参数及结合能等进行了模拟计算, 通过比较溶度参数差值(Δδ)的大小、模拟前后体系密度变化情况均可以预测HTPB与增塑剂的相容性, 结合能的分析揭示了HTPB/增塑剂共混物组分间的相互作用及本质. 将Flory-Huggins作用参数转化为MesoDyn模拟的输入参数, 采用MesoDyn模拟方法对HTPB/增塑剂共混体系的介观形貌与动力学演变过程进行了研究, 通过模拟得到的等密度图、自由能密度和有序度参数等可以判断共混体系的相容性. MD和MesoDyn模拟结果均表明: HTPB/DOS属于相容体系, 而HTPB/NG属于不相容体系, 其结论与实验结果一致.     

HTPB固体推进剂增塑剂选取分子模拟研究

固体推进剂中增塑剂要求同粘合剂体系相容性良好,并提高体系的低温性能.本文采用分子动力学(MD)方法,首先计算了端羟基聚丁二烯(HTPB)粘合剂及增塑剂癸二酸二辛酯(DOS)、己二酸二辛酯(DOA)、壬酸异癸酯(TOA)、邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二辛酯(DOP)的溶度参数,以此从相容性角度选取推进剂增塑剂;计算数值基本吻合实验值,表明常用的增塑剂从相容性都能满足要求.其次模拟获取了HTPB及HTPB/增塑剂混合体系的比体积-温度关系得到了体系的玻璃化转变温度(Tg),揭示增塑剂对HTPB体系低温性能的影响.结果显示:(1)HTPB的Tg模拟值为202K,基本吻合实验值196K.(2)HTPB/DOS混合体系中,当增塑剂DOS的质量含量从12%、22%、29%到36%(摩尔含量分别为50%、66%、75%和90%)增加时,体系的Tg线性降低;TOA和DOP增塑的粘合剂体系(摩尔含量为75%)Tg也降低,而增塑剂DOA和DBP对体系的Tg影响不大.因此,基于相容性及提高粘合剂低温性能考虑,DOS、DOA和DOP作为HTPB的增塑剂优于TOA和DBP.     

硝酸酯增塑剂力学性能和界面相互作用的分子动力学模拟

运用分子动力学(MD)方法, 模拟研究了硝化甘油(NG)及其与硝化三乙二醇(TEGDN)组成的硝酸酯增塑剂的低温力学性能. 结果表明, NG/TEGDN混合体系较NG单组分体系的刚性减弱, 延展性和各向同性增强. 结合能计算和径向分布函数分析揭示了混合型硝酸酯增塑剂组分之间的相互作用及其本质.     

CL-20/HMX共晶及其为基PBX界面作用和力学性能的MD模拟研究

为提高共晶炸药的实际使用价值, 改善其安全性和力学性能, 以CL-20/HMX共晶炸药为基, 分别添加2种高聚物粘结剂Estane 5703(聚氨基甲酸乙酯)和HTPB(端羟基聚丁二烯), 共构建两种共晶基高聚物粘结炸药(PBX)模型, 进行细致的295 K NPT分子动力学(MD)模拟研究. 通过两种PBX模型及其与该共晶炸药的MD模拟结果比较表明, 与基炸药之间的结合能Estane 5703大于HTPB, 预示含少量Estane 5703的PBX稳定性和相容性更佳; 对相关函数g(r)揭示粘结剂与基炸药界面相互作用的方式, 以基炸药中H分别与Estane 5703中羰基O和HTPB中端羟基O之间的氢键较强. 与CL-20/HMX共晶炸药相比, 少量粘结剂Estane 5703或HTPB的加入, 使弹性系数C_ij下降, 拉伸模量(E)、体积模量(K)和剪切模量(G)均显著减小, 而泊松比(ν), 柯西压(C₁₂－C₄₄)和K/G值明显增大, 表明PBXs体系刚性减小, 延展性增强, 力学性能大为改善. 少量粘结剂包覆使PBXs致钝, 主要归因于其隔热、吸热并使体系变“软”的缓冲作用, 而界面作用造成的分子结构引发键键长变化变为次要因素.     

分子动力学模拟研究聚乳酸/聚酰胺11共混物的相容性

采用分子动力学(MD)模拟方法在COMPASS力场下,研究了不同质量比(10/90,30/70,50/50,70/30和90/10)聚乳酸(PLA)/聚酰胺11(PA11)共混物的相容性.研究结果表明:不同比例下PLA/PA11共混物的Gibbs自由能变化均大于零,其共混物很难形成均相体系;共混体系结合能的计算以及不同组分分子间C—C原子对径向分布函数的分析揭示了PLA和PA11的相互作用主要源自其分子间的范德华力;此外,模拟得到的所有比例下共混物的Flory-Huggins相互作用参数(χ)均大于临界Flory-Huggins相互作用参数(χcritical),进一步证明PLA与PA11不能形成相容体系。     

ε-CL-20基PBX结构和性能的分子动力学模拟——HEDM理论配方设计初探

以高能量密度化合物ε-CL-20(六硝基六氮杂异伍兹烷)为主体,分别添加5种高聚物黏结剂(Estane5703、GAP、HTPB、PEG和F2314)构成高聚物黏结炸药(PBXs).用分子动力学(MD)方法模拟研究各PBX的结合能、相容性、安全性、力学性能和能量性质,通过比较和分析,为优选黏结剂、指导HEDMs配方设计提供信息和规律.由结合能预测各PBX的相容性和稳定性排序为:ε-CL-20/PEG>ε-CL-20/Estane5703≈ε-CL-20/GAP>ε-CL-20/HTPB>ε-CL-20/F2314.以对相关函数g(r)描述了组分之间相互作用的方式.5种黏结剂的少量加入均能显著改善ε-CL-20的弹性力学性能,增强各向同性.各黏结剂并非通过改变ε-CL-20的分子结构影响PBX的感度.它们主要通过自身的热容(C°p)和密度(ρ)影响PBX的安全性和能量性质.     

HTPB与Al不同晶面结合能和力学性能的分子动力学模拟

采用分子力学(MM)和分子动力学(MD)方法, 在250、300、350、400、450 K, 对固体推进剂端羟基聚丁二烯(HTPB)和铝晶胞不同晶面结构所组成的层模型在COMPASS力场下, 进行模拟计算, 求得结合能和静态力学性能(弹性系数、模量和泊松比). 模拟结果表明, 在400 K时HTPB与Al(011)面的结合能最大, 从综合力学性能优劣上看, 各个面从优到劣的排序为(011)>(221)>(001), HTPB与Al的结合能与力学性能具有对应关系, 结合能大的力学性能优异, 结合能小的力学性能较差.     

聚乳酸/聚氨酯共混体系相容性研究

采用热塑性聚氨酯弹性体(TPU)作为改性剂来增韧聚乳酸(PLA),通过溶度参数法、聚合物混合焓变法预测了TPU和PLA的相容性,并且通过稀溶液粘度法、动态热机械分析(DMA)及扫描电镜(SEM)对两者相容性进行表征,结果显示PLA和TPU为部分相容体系.共混溶液的粘度与组成含量的变化呈非线性关系;PLA/TPU共混膜的...     

结合分子动力学验证PBS基共聚物和淀粉复合材料之间的相互作用

将聚乙二醇200(PEG200)或聚乙二醇400(PEG400)作为第四种单体分别和丁二酸(SA)、丁二醇(BDO)、乙二醇(EG)熔融共聚得到不同醚链长度的PEG200-PBES、PEG400-PBES共聚酯,再与改性的热塑性淀粉(TPS)共混,采用溶液混合方法,制备出固体复合材料,并且研究了引入不同醚链长度对复合材料各种性能的影响;结合分子动力学(MD)模拟分析了不同醚链长度(PEG-PBES)/TPS复合体系分子之间的相互作用.研究结果表明,随着醚链的增长,复合材料的相容性显著增加,(PEG400-PBES)/TPS复合体系的χ参数和Emix值更接近于0,内聚能密度及溶度参数值大于(PEG200-PBES)/TPS和PBS/TPS复合体系的相应值,说明PEG400-PBES与TPS有更好的相容性.同时,随着醚链的增长,复合材料拉伸强度由原来的1.86 MPa提高到8.84 MPa,断裂伸长率由25.54%提高到74.75%,热失重50%时的温度由281.68℃提高到310.53℃.     

RDX基PBX的模型、结构、能量及其与感度关系的分子动力学研究

以RDX（环三亚甲基三硝胺）为基、PS（聚苯乙烯）为粘结剂构成PBX（高聚物粘结炸药）的MD（分子动力学）模拟初始模型.比较分别以1根46链节和2根23链节PS置于RDX（001）晶面上的两种（PBX1和PBX2）模型下的MD模拟结果,发现二者的结构、相互作用能和力学性能均很接近.取PBX2进行5种温度（195,245,295,345和395 K）下的NPT系综、MD模拟系统研究,发现随温度依次升高,各体系中RDX引发键N NO2键的最大键长（Lmax）递增,N–N键连的N与N之间的双原子作用能（EN-N）和内聚能密度（CED）递减,与感度随温度升高而增大的实验事实相一致.综合已有工作,对高能复合材料（如PBX和固体推进剂等）的感度理论研究,建议关注其中易爆燃组分在外界刺激下的结构和能量变化,其引发键Lmax和作为引发键强度度量的双原子作用能（如EN-N）,可作为热和撞击感度相对大小的理论判据.     

Molecular dynamics study on the relationships of modeling, structural and energy properties with sensitivity for RDX-based PBXs

In this paper,a primary model is established for MD(molecular dynamics) simulation for the PBXs(polymer-bonded explosives) with RDX(cyclotrimethylene trinitramine) as base explosive and PS as polymer binder.A series of results from the MD simulation are compared between two PBX models,which are represented by PBX1 and PBX2,respectively,including one PS molecular chain having 46 repeating units and two PS molecular chains with each having 23 repeating units.It has been found that their structural,interaction energy and mechanical properties are basically consistent between the two models.A systematic MD study for the PBX2 is performed under NPT conditions at five different temperatures,i.e.,195 K,245 K,295 K,345 K,and 395 K.We have found that with the temperature increase,the maximum bond length(L max) of RDX N N trigger bond increases,and the interaction energy(E N-N) between two N atoms of the N-N trigger bond and the cohesive energy density(CED) decrease.These phenomena agree with the experimental fact that the PBX becomes more sensitive as the temperature increases.Therefore,we propose to use the maximum bond length L max of the trigger bond of the easily decomposed and exploded component and the interaction energy E N-N of the two relevant atoms as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites such as PBXs and solid propellants.     

Studies on the properties of EPDM–CSE blend containing HTPB for case‐bonded solid rocket motor insulation

Elastomeric blends based on ethylene propylene diene (EPDM) rubber as a primary polymer have been investigated for the thermal insulation of case‐bonded solid rocket motors (SRMs) cast with composite propellant containing hydroxy terminated polybutadiene (HTPB) as a polymeric binder. EPDM rubber found as an attractive candidate for the thermal insulation of case‐bonded SRM due to the advantages such as low specific gravity, improved ageing properties, and longer shelf life. In spite of these advantages, EPDM, a non‐polar rubber, lacks sufficient bonding with the propellant matrix. Bonding properties are found to improve when EPDM is blended with other polar rubbers like polychloroprene, chlorosulphonated polyethylene (CSE), etc. This type of polar polymer when blended with EPDM rubber enhances the insulator‐to‐propellant interface bonding. In the present work, an attempt has been made to study the properties of EPDM–CSE based insulator by incorporating HTPB, a polar polymer as well as a polymeric binder, as an additive to the EPDM–CSE blend by varying the HTPB concentration. Blends prepared were cured and characterized for rheological, mechanical, interface, and thermal properties to study the effect of HTPB addition. This paper reports the preliminary investigation of the properties of EPDM–CSE blend containing HTPB, as a novel and futuristic elastomeric insulation for case‐bonded SRM containing HTPB as propellant binder. Copyright © 2007 John Wiley & Sons, Ltd.     

HMX和HMX/HTPB PBX的晶体缺陷理论研究

建立空位和掺杂点缺陷模型, 用分子动力学(MD)方法, 研究晶体缺陷对β-环四亚甲基硝胺(HMX)和β-HMX/HTPB(端羟基聚丁二烯)高聚物粘结炸药(PBX)的力学性能和爆炸性能的影响. 结果表明, 相对于HMX“完美”晶体(1)考察缺陷晶体(2和3), 以及相对于HMX完美晶体基PBX(1)考察缺陷PBX 2和PBX 3, 均发现弹性系数和(拉伸、体积、剪切)模量下降, 导致体系刚性减弱, 延展性和韧性增强. 这与在基炸药HMX晶体(1, 2和3)中分别加入HTPB高聚物粘结剂形成PBX 1, PBX 2和PBX 3呈现类似的相应的变化趋势和效果. 此外, 研究表明, 爆炸性质也依赖于体系的组成和结构. 因加入的是低能高聚物, 故PBX(1), PBX(2)和PBX(3)的爆热、爆速和爆压均比相应的基炸药(1, 2和3)低, 即晶体(1)＞PBX(1), 晶体(2)＞PBX(2), 晶体(3)＞PBX(3). PBX(1), PBX(2), PBX(3)与对应基炸药(1, 2, 3)的爆速和爆压取相同变化次序, 亦即PBX(1)＞PBX(2)＞PBX(3)对应于晶体(1)＞晶体(2)＞晶体(3). 这些计算结果和规律对PBX配方设计显然具有指导作用.     

Improving the Mechanical Properties of Glycidyl Azide Polymeric Matrix Used in Composite Solid Rocket Propellant by Adding Advanced Cross‐Linker

Glycidyl azide polymer (GAP) based binders have poor mechanical characteristics in comparison with hydroxyl terminated polybutadiene (HTPB) binders. In this study, advanced cross‐linker was used to improve the mechanical properties of GAP binder. GAP was prepared and characterized in comparison with HTPB prepolymer. Density, characteristics groups, nitrogen content, humidity, viscosity, and milligram equivalent of (OH) per binders were determined. A cross‐linker consists of trimethylol propane (TMP) and curing catalyst, dibutyltin dilaurate (DBTDL), was used as an additive to GAP polymeric matrix to enhance its functionality. Polymeric matrices based on GAP and HTPB were prepared with different curing ratio (NCO/OH) ranging from 0.7 to 1.5. Different weight percentages of cross‐linker were added to study its effect on the mechanical properties of GAP matrix. Five samples based on HTPB polymer and twenty samples based on GAP polymer were prepared. A LLOYD testing machine was used to determine the stress‐strain curves of all the studied samples. It was concluded that the cross‐linker used has significant influence on the characteristics of GAP polymeric matrix. Also the addition of 5 wt % of cross‐linker to GAP matrix at curing ratio = 1 produced optimum mechanical characteristics very close to that of HTPB matrix used in composite solid rocket propellants (CSRP). The optimum GAP polymeric matrix is candidate to replace the traditional HTPB binder in advanced CSRP.     

Comparative ballistic efficiency of solid composite propellants: which plasticizer/polymer combination is the energetically preferred binder?

The relative efficacy of real energetic plasticizers and polymers for model solid composite propellants comprising 25% aluminum hydride, 50% dinitramide ammonium salt and 25% binder (20% a plasticizer and 5% a polymer) has been estimated. The quantitative dependence of the efficiency of plasticizers on the value of their enthalpy of formation ΔH_t⁰, the oxygen coefficient α, percentage of hydrogen %H and density d has been revealed. 3,4-Dinitrofurazan tested as a plasticizer for the binder provides effective impulse values at the 3^rd stage up to ～2 s higher than those for other plasticizers.     

Compatibility study of 1,3,3-trinitroazetidinewith some energetic components and inert materials

The compatibility of 1,3,3-trinitroazetidine (TNAZ) with some energetic components and inert materials of solid propellants was studied by using the pressure DSC method. Where, cyclotetramethylenetetranitroamine (HMX), cyclotrimethylenetrinitramine (RDX), nitrocellulose (NC), nitroglycerine (NG), 1.25/1-NC/NG mixture, lead 3-nitro-1,2,4-triazol-5-onate (NTO-Pb), aluminum powder (Al powder) and N-nitrodihydroxyethylaminedinitrate (DINA) were used as energetic components and hydroxyl terminated polybutadiene (HTPB), carboxyl terminated polybutadiene (CTPB), polyethylene glycol (PEG), polyoxytetramethylene- co-oxyethylene (PET), addition product of hexamethylene diisocyanate and water (N-100), 2-nitrodianiline (2-NDPA), 1,3-dimethyl-1,3-diphenyl urea (C₂), carbon black (C.B.), aluminum oxide (Al₂O₃), cupric 2,4-dihydroxybenzoate (β-Cu), cupric adipate (AD-Cu) and lead phthalate (φ-Pb) were used as inert materials. The results showed that the binary systems of TNAZ with HMX, NC, NG, NC+NG and DINA are compatible, with RDX and Al powder are slightly sensitive, with NTO-Pb, β-Cu, AD-Cu, C.B. and Al2O3 are sensitive, and with HTPB, CTPB, PEG, PET, N-100, 2-NDPA, C₂ and φ-Pb are incompatible.