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.     

二甲氨基乙氧基氧杂硼烷对环氧树脂的潜伏固化活性

以3种含分子内N→B配位键的环状结构的二甲氨基乙氧基氧杂硼烷:β,β'-二甲氨基乙氧基-4,4,5,5-四甲基-1,3,2-二氧杂戊硼烷(PDB)、β,β'-二甲氨基乙氧基-5,5-二甲基-1,3,2-二氧杂己硼烷(NDB)和β,β'-二甲氨基乙氧基-1,3,2-苯并二氧硼烷(CDB)为研究对象,采用敞口观察法测定其水解稳定性,通过差示扫描量热法(DSC)、烘箱固化实验、恒温潜伏性实验及红外光谱(FTIR)分析,研究3种氧杂硼烷对环氧树脂的固化活性和潜伏性能,采用Ozawa-Avrami法估算固化反应的表观活化能(E a).结果表明,苯环π电子共轭效应、烷氧基给电子效应以及氧杂硼烷空间结构差异等因素影响了3种二甲氨基乙氧基氧杂硼烷上硼原子电子云密度及N→B配位络合强度,导致其水解稳定性及对环氧树脂的固化活性顺序为NDBPDBCDB,潜伏性能则正好相反.E51与PDB组成的单组分环氧树脂在常温放置3个月后,环氧基的转化率为0.22.     

The Curing Process and Elastic Modulus of HTPB-Containing Polyurethanes

By means of the functionality distribution deduced and weight averaged functionality a and molecular size vb2, the sol-gel distribution equations of HTPB(Hydroxyl terminated polybutadiene) + TDI (Toluene-2, 4-diisocyanate) expressed by the model of Aai-B2 type polycondensation were solved and the elastic modulus were calculated. The experimental results of HTPB+TDI curing process indicate that a, vb2 and functionality distribution function are available basically.     

Investigation of ultraviolet curable waterborne polyurethane acrylate dispersion based on hydroxyl-terminated polybutadiene

A new kind of ultraviolet (UV) curable waterborne polyurethane acrylate dispersion was synthesized based on hydroxyl-terminated polybutadiene (HTPB), poly-(propylene glycol) (PPG), isophorene diisocyanate (IPDI), 2-hydroxy ethyl acrylate (HEA) and dimethylol propionic acid (DMPA) after neutralizing by triethylamine (TEA). 2-Hydroxy-1-[4-2-hydroxyethoxy) phenyl]-2-methyl-1-propanone (Irgacure 2959) was used as a photoinitiator and deionized water as a diluent. Fourier transform infrared (FTIR) analysis was used to identify the chain structure of the UV-curable polyurethane prepolymer based on HTPB and the curing process. Effects of relative content of HTPB and PPG on emulsion stability, resistance to water and ethanol, thermal stability, compatibility of soft and hard segment, as well as the mechanical property of the cured film were investigated. Translated from Polymer Materials Science and Engineering, 2006, 22(3): 199–203 (in Chinese)     

热动力学方法测定端羟基聚丁二烯固化反应动力学参数

用热动力学方法对高分子固化反应动力学进行研究,在RD-Ⅰ型热导式自动量热计的基础上,设计了反应器,测定了端羟基聚丁二烯(HTPB)与甲苯二异氰酸酯(TDI)固化反应的动力学参数(表观活化能和反应速率常数),结果与文献值、粘度法和红外光谱法的结果相符。     

Synthesis and characterization of poly(vinyl ferrocene) grafted hydroxyl-terminated poly(butadiene): A propellant binder with a built-in burn-rate catalyst

The graft copolymer hydroxyl-terminated polybutadiene-g-polyvinyl ferrocene (HTPB-g-PVF) was synthesized free radically from HTPB and vinyl ferrocene (VF) in benzene, using azobisisobutyronitrile as the radical initiator at 75°. The graft copolymer was analysed for its structural and thermal characteristics. The chemically bound ferrocene in HTPB-g-PVF, catalysis the oxygen up-take and oxidative degradation reactions of HTPB, and the mechanisms of the catalysis are discussed. The most probable grafting sites on HTPB and the mechanism of grafting also are discussed. The extent of the grafting, which was a function of VF concentration, was low. The graft copolymer also was tried as a propellant-binder-cum-burn-rate (BR) catalyst in a composite solid propellant, using toluene diisocyanate and trimethylol propane as curatives with dibutyl tin dilaurate as the curing catalyst, and the BRs of the propellants were evaluated at 3.9 MPa. The BRs increased with the extent of VF grafting but not proportionally. The BRs also were compared with those of reference HTPB propellants containing VF, Fe₂O₃, copper chromite, and so forth as BR catalysts. Chemically linked ferrocene in the binder augmented the propellant BR, probably because of the presence of catalytically active sites in the binder for its degradation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4090–4099, 1999     

端羟基聚丁二烯与2,6-甲苯二异氰酸酯固化网络 弹性力学性质的分子模拟

采用最大熵模型, 构建了HTPB预聚物的最可几结构. 考察了HTPB (nC＝9)与TDI全混合以及半混合的两种固化建模方式. 分子动力学模拟得到的HTPB (nC＝9)-TDI固化网络的N—N径向分布函数显示半混模式比全混模式的结构更均匀. 采用分子动力学动态模拟与静态拉伸方法对HTPB (nC＝9)-TDI固化网络进行弹性力学性质的模拟计算. 比较了半混和全混模式对拉伸模量计算的影响, 表明半混模式得到的固化网络能得到合理的模拟结果. 初步表明最大熵模型在研究HTPB固化问题上静态或动态模拟结果都具有唯象可行性.     

利用扭辫分析法对液体丁羟胶固化的研究(Ⅰ)

本工作用扭辫分析(TBA)技术研究了端羟基聚丁二烯(HTPB)-甲苯二异氰酸酯(TDI)体系的固化反应表现动力学,得到了该反应的表观活化能,并用粘度和红外光谱测定作了验证,认为TBA技术用于研究液体橡胶固化问题是一种有意义的方法。     

Curing of liquid polydimethylsiloxanediols with trialkoxytitanium borates

Curing of SKTN liquid siloxane rubbers (polydimethylsiloxanediols) with trialkoxytitanium borates, leading to incorporation of titanium and boron atoms into vulcanized polysiloxane molecules and to formation of the corresponding network polyelementoorganosiloxanes, was studied. The kinetics of curing of liquid polydimethylsiloxanediols with trialkoxytitanium borates was examined. The effective rate constants of curing and the activation energy of the reaction were calculated.     

羟基封端聚丁二烯的临界点色谱定量方法研究

为建立混合物中羟基封端聚丁二烯（HTPB）的临界点色谱定量方法，以C18为固定相，考察了HTPB在四氢呋喃-乙腈和四氢呋喃-水两种流动相体系下的临界点色谱条件。结果表明，四氢呋喃-乙腈体积比为70.7：29.3以及四氢呋喃-水体积比为92：8时，HTPB的保留值与其相对分子质量无关。将该临界点色谱方法用于胶黏剂混合组分中HTPB的测定，结果表明，HTPB在46.7~216.4 mg/L范围内呈良好线性关系，相关系数（r）>0.99，检出限为4.2 mg/L。自配HTPB和矿物油双组分样品的加标回收率为89.2%~101.1%，相对标准偏差小于0.66%（n=6）。应用该方法对市售聚氨酯胶黏剂进行检测，测定结果为HTPB成分占26.6%。该方法快速、准确，能满足聚合物混合产品的生产质量控制和失效分析的要求。     

Effect of ammonium oxalate/strontium carbonate on the burning rate characteristics of composite propellants

AP/HTPB based composite propellants with additives such as ammonium oxalate (AO), mixture of ammonium oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG and FTIR experiments. The results show that the burning rates of these propellants are decreased significantly. TG-DTG experiments indicate that decomposition temperatures of AP with these additives are increased. Furthermore, the activation energy of the decomposition reaction of AP is also increased in the presence of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition of AP. The burning rates of these propellants are decreased. The burning rate temperature sensitivity of AP/HTPB based propellants is reduced significantly by the addition of AO or AO/SC. But the effect of AO is less than that of AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the same time, to reduce pressure exponent. The reduced heat release at the burning surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity. Synergetic action is probably produced between AO and SC within AP/HTPB based propellants in the pressure range tested. This synergetic effect causes the heat release to reduce and the burning surface temperature to increase. Moreover, it makes the net exothermal reaction of condensed phase become little dependent on T ₀. Thus, the burning rate temperature sensitivity is reduced.     

端羟基聚丁二烯/增塑剂共混物相容性的分子动力学模拟

固体推进剂和炸药的力学性能在很大程度上依赖于配方中高分子粘结剂与增塑剂的相容性. 本文对相容和非相容两种体系进行了分子动力学(MD)模拟, 以考察分子模拟方法的实用性. 为预测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, 采用MD模拟方法在COMPASS力场下, 对HTPB、DOS、NG和共混物HTPB/DOS、HTPB/NG的密度、内聚能密度及溶度参数等进行了模拟计算. 通过比较溶度参数差值(△δ)的大小、分子间径向分布函数和模拟前后体系密度变化情况均可以预测HTPB/DOS属于相容体系,而HTPB/NG属于不相容体系, 与实验结果一致. 径向分布函数分析同时揭示了HTPB/增塑剂组分之间的相互作用及本质. 本文的模拟方法可以作为预测聚合物与增塑剂相容性的有利工具, 也可以为固体推进剂和炸药的配方设计提供理论指导.     

The effect of organic modifiers with different chain lengths on the dispersion of clay layers in HTPB (hydroxyl terminated polybutadiene)

The series of HTPB (hydroxyl terminated polybutadiene)/organoclay nanocomposite was formed by melt blending with rotationary and revolutionary mixer which generated high shear stress. Organoclays were formed by modifying the pristine clays with organic modifiers which had different hydrophobic chain lengths. As the length of organic modifier increased, the gap size between layers of organoclay became broader. The clays modified with octadecylamine (C18) and dodecyl amine (C12) showed wider gap sizes than that modified with octyl amine (C8). This gap size affected the dispersion state of clays, exfoliation/intercalation in HTPB polymer medium. The mixtures of HTPB with C18 and C12 were transparent without sedimentation and showed almost exfoliated structure. HTPB/C18 mixture showed the higher viscosity and yield strength than HTPB/C12 due to exfoliation. HTPB/C12 showed more elastic behavior than HTPB/C18 mixture because the organoclay C12 had less content of organic modifier.     

A novel form-stable paraffin-based hydroxyl-terminated polybutadiene binder containing microencapsulated paraffin wax

Leakage and incompatibility of paraffin wax (PW) in hydroxyl-terminated polybutadiene (HTPB) binders is a major obstacle to its application in polymer-bonded explosives (PBX). In order to solve this issue, we designed a microencapsulated PW (MePW)/PW/HTPB composite in this paper. Melamine–formaldehyde-shelled MePW (MF MePW)/PW/HTPB composites with different contents of MePW and PW were prepared by cast molding method. The chemical composition, crystallinity and microstructure of MePW/PW/HTPB composites were analyzed with Fourier transformed infrared spectroscopy, X-ray diffraction and scanning electron microscope, respectively. The results showed that PW and MF MePW have been uniformly dispersed in HTPB without any chemical interaction. Moreover, differential scanning calorimeter analysis, thermal gravimetric analyzer, thermal cycling test, leaking test, tensile and compressive test were used to investigate the thermal and mechanical properties of these composites. The composites have high latent heat and good thermal reliability. The thermal stability, tensile and compressive strength of MePW/PW/HTPB composites were dramatically increased with the increasing mass fraction of MePW. The introduction of MePW can obviously prevent the leakage of PW in both HTPB binders and PBX. Consequently, it is anticipated that MePW can be used in the next-generation of paraffin-based high-temperature PBX systems.

     

New poly(ether‐ester) thermosets obtained by cationic curing of DGEBA and 7,7‐dimethyl‐6,8‐dioxaspiro[3.5] nonane‐5,9‐dione with several Lewis acids as initiators

Scandium, ytterbium, and lanthanum triflates and boron trifluoride monoethylamine were used as cationic initiators to cure a mixture 2:1 (mol/mol) of diglycidylether of bisphenol A (DGEBA) and 7,7‐dimethyl‐6,8‐dioxaspiro[3.5]nonane‐5,9‐dione (MCB). The evolution of the epoxy and lactone during curing and the linear ester groups in the final materials were evaluated by Fourier Transform Infrared in the attenuated‐total‐reflection mode. The kinetic parameters of the curing process were calculated from DSC analysis applying isoconversional procedures. The shrinkage on curing and the thermal degradability of the materials on varying the initiator used were evaluated. The expandable character of MCB was confirmed. The materials obtained were more degradable than conventional epoxy resins due to the tertiary ester groups incorporated in the network by copolymerization. © 2008 Wiley Periodicals, Inc J Polym Sci Part A: Polym Chem 46: 1229–1239, 2008     

Synthesis of polyurethane acrylate oligomers based on polybutadiene polyol

Polyurethane acrylate oligomers (PUA) were prepared by a competitive reaction of 4,4′-dicyclohexyl methane diisocyanate (H₁₂MDI) with hydroxy terminated polybutadiene (HTPB) and hydroxyethylacrylate (HEA). Kinetic models were established for noncatalytic and catalytic systems, and the reaction constants were calculated using a numerical method. The evolution of the noncatalyzed and catalyzed reactions were analyzed, respectively, by SEC and FTIR. Comparing the reactivities of HTPB and HEA, as well as other small molar mass model alcohols, the HTPB showed the higher reactivity. HTPB is 700 times more reactive than HEA at 80°C. This high reactivity was analyzed as a result of lower concentration of hydrogen bonds in bulk HTPB. The activation energy of the noncatalyzed and catalyzed reactions were found to be, respectively, 56.98 and 45.16 KJ/mol. The structures of the PUA synthetized in one-step or two-step process were analyzed and discussed using a gelation model and the kinetic data obtained. © 1996 John Wiley & Sons, Inc.     

端羟基聚丁二烯型聚氨酯/聚苯乙烯(或聚甲基丙烯酸甲酯)互穿网络的形态和玻璃化转变

互穿聚合物网络(IPN'S)已经成为高聚物共混改性,高聚物间相容性的一个重要研究领域,IPN材料的宏观性能与其微观形态有着密切的关系,如能通过改变结构、组成、交联密度及合成条件等因素来控制IPN的形态,则就可以入为地制备各种性能优良的材料。本文用透射电镜和差示扫描量热仪对同步法合成的端羟基聚丁二烯型聚氨     

Curing kinetics of boron‐containing phenol–formaldehyde resin formed from paraformaldehyde

A boron‐containing phenol–formaldehyde resin (BPFR) was synthesized from boric acid, phenol, and paraformaldehyde. The curing reaction of BPFR was studied by Fourier‐transform infrared spectrometry and differential scanning calorimetry. According to the heat evolution behavior during the curing process, several influencing factors on isothermal curing reaction were evaluated. The results show that the isothermal kinetic reaction of BPFR follows autocatalytic kinetics mechanism, and kinetic parameters m, n, k₁, and k₂, were derived, respectively. In the latter reaction stage, the curing reaction becomes controlled mainly by diffusion. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 638–644, 2002     

端羟基聚丁二烯型聚氨酯/聚苯乙烯(或聚甲基丙烯酸甲酯)互穿网络的形态和玻璃化转变

The morphology structure and glass transition behavior of polybutadiene-based polyuretha-ne/polystyrene (or polymethyl methacrylate) interpenetrating polymer network (PU(HTPB)/ PSt-IPN, PU(HTPB)/PMMA-IPN) were investigated by TEM and DSC. TEM showed that the phase inversion of PU(HTPB)/PSt-IPN occurred in the concentration of 25% PU(HTPB), and the size of dispersed phase domains of the IPN formed was smaller in the concentration about 50% PU(HTPB). Increasing DVB content or proportion of NCO to OH enhanced in-terpenetration of two components. All of IPN samples exhibited special cellular structure. According to the fact that PU(HTPB) was formed first,a formation mechanism of the struc-ture was proposed.     

丁羟胶型聚氨酯弹性体的水解稳定性

丁羟胶型聚氨酯弹性体的水解稳定性;弹性体;扩链剂