温度对RDX/PET/NPBA推进剂药浆流变特性的影响

为获得温度对RDX/PET/NPBA推进剂药浆流变特性的影响,采用稳态和动态流变学方法测试了不同温度下RDX在硝酸酯增塑的PET黏合剂药浆中的黏度,研究了其流变特性随温度的变化规律。结果表明,当实验温度低于53℃时,RDX/PET/NPBA药浆黏度随温度的升高快速降低;高于53℃时,降幅变缓;当温度为57~60℃时,药浆黏度处于相对平稳状态。温度升高引起RDX/PET/NPBA药浆黏度的变化与黏合剂基体、RDX溶解度及RDX与键合剂作用三者之间均有关联。同时从RDX/PET/NPBA胶片实验结果得出,温度升高后胶片的力学性能提高,表明温度对键合剂的作用影响较大。     

固体推进剂用含能黏合剂体系研究进展

黏合剂含能化是近年来推进剂研究的热点之一,对叠氮基黏合剂和硝酸酯增塑聚醚黏合剂体系的制备、燃烧性能和能量性能进行了简要总结,并对今后黏合剂的发展做了展望。     

聚乳酸/田菁胶共混体系的加工流变性能研究

为了提高聚乳酸的黏度并降低其加工成本,采用田菁胶对聚乳酸进行共混改性。利用转矩流变仪对聚乳酸/田菁胶共混体系的加工流变性能进行研究,讨论了7种增塑剂(甘油、聚乙二醇4000、聚乙二醇6000、聚乙二醇10000、聚乙二醇20000、柠檬酸三丁酯和磷酸三苯酯)及其用量对共混体系加工流变性能的影响。结果表明,甘油的增塑效果不好,扭矩–时间曲线上并没有出现明显的塑化峰。当增塑剂用量为10~15份时,其它6种增塑剂均具有较好的增塑效果。以聚乙二醇6000增塑体系为例讨论了加工条件(加工温度和转速)对体系加工流变性能的影响。发现提高加工温度和转矩流变仪转速可以在一定程度上加快聚乳酸/田菁胶共混体系的塑化。需根据所用加工设备和工艺合理地选择增塑剂种类及其用量和加工条件。     

IPN技术在推进剂黏合剂体系中的应用研究进展

系统介绍了互穿聚合物网络(IPN)技术在复合固体推进剂、硝酸酯增塑聚醚(NEPE)推进剂及改性双基推进剂黏合剂体系中的应用研究进展,特别综述了环氧乙烷-四氢呋喃共聚醚(PET)类、聚乙二醇(PEG)类和聚叠氮缩水甘油醚(GAP)类NEPE推进剂用黏合剂的IPN技术改性进展。最后总结了IPN技术在固体推进剂黏合剂体系中的应用,并对其未来的发展前景进行了展望。     

聚乳酸/聚丙二醇增塑体系热性能和流变性能

聚乳酸是一种可完全生物降解的环保材料.研究了聚乳酸/聚丙二醇增塑体系的热性能和流变性能.差示扫描量热仪测试结果表明:随聚丙二醇含量的增加,增塑体系的玻璃化转变温度、结晶温度和熔点均逐渐降低.通过毛细管流变仪测试,发现增塑体系随聚丙二醇含量的增加,熔体指数逐渐增加,表现黏度逐渐降低.聚丙二醇在增塑体系中起到增塑作用,并改善了聚乳酸的加工性能.     

PET黏合剂及其弹性体热解与推进剂热解相关性研究

采用差示扫描量热/热重(DSC/TG)和裂解气相色谱质谱联用(Py-GC/MS)分析技术研究了PET黏合剂体系、PET/TDI弹性体以及含PET黏合剂体系的简单组分推进剂的热分解特性和热裂解产物状况,探索了PET弹性体的热分解与含PET黏合剂体系的推进剂热解性能之间的相关性.研究结果表明,混合硝酸酯增塑的PET黏合剂体...     

复合固体推进剂老化特征研究进展

对复合固体推进剂老化特征及其影响因素以及在老化研究中常用试验方法和寿命预估方法进行了概述,详细阐述了国内外HTPB(端羟基聚丁二烯)、NEPE(硝酸酯增塑聚醚)、叠氮聚醚3种不同黏合剂体系推进剂老化性能的研究进展和相关结论。     

AlH_3固体推进剂能量性能的理论研究

根据最小自由能原理,利用ramj能量计算软件研究了AlH_3对Al相对含量、CL–20(六硝基六氮杂异伍兹烷)对AP(高氯酸铵)相对含量和黏合剂体系增塑比等因素对AlH_3固体推进剂能量性能的影响规律。结果表明:当推进剂其他组分含量一定时,随AlH_3对Al相对含量的提高,推进剂的氧系数、理论比冲升高,但密度、燃温和燃气平均相对分子质量降低;随CL–20对AP相对含量的增加,推进剂的密度和理论比冲升高,但氧系数和燃气平均相对分子质量降低,燃温先升高后降低;随黏合剂体系增塑比的提高,推进剂的氧系数、密度、理论比冲、燃温和燃气平均相对分子质量均增加。在上述影响规律的基础上,通过系统计算,发现当推进剂配方的w(含能固体)为72%,黏合剂体系增塑比为2.8,推进剂理论比冲≥2 744 N·s/kg时,推进剂的密度随w(Al+AlH_3)的增加先增加后降低,并在w(Al+AlH_3)为19%时达到最大值1.759 g/cm~3。此外,提高配方含能固体含量或提高黏合剂体系增塑比可进一步提高推进剂的最大密度。     

团聚硼颗粒在HTPB富燃料推进剂中的流变特性

为了探索球形团聚硼颗粒的制备效果,对端羟基聚丁二烯(HTPB)黏合剂、不同类型的团聚硼颗粒与HTPB黏合剂以一定质量配比形成的悬浮液,以及含团聚硼颗粒HTPB富燃料推进剂流变特性进行了对比研究。结果表明,HTPB黏合剂的表观黏度随温度的升高而降低,最终趋于某一定值;在一定温度下,无定形硼粉经团聚改性后,团聚硼颗粒与HTPB形成悬浮液的表观黏度和屈服值较团聚前降低,且两者均随时间的增加而增加;采用含团聚硼颗粒的富燃料推进剂药浆的流变特性大大改善,有利于含硼富燃料推进剂能量的提高和燃烧性能的改善。     

NEPE推进剂应力松弛试验研究

针对NEPE(硝酸酯增塑聚醚)推进剂,开展了温度、应变、加载速率等因素对应力松弛试验影响规律的研究。利用推导的应力松弛方程,指出了各因素影响程度大小。结果表明:随测试温度的升高,NEPE推进剂的松弛模量逐步降低;随初始应变的增加,其松弛模量逐步增加,且初始应变的影响与推进剂的拉伸曲线形状密切相关;加载速率对NEPE推进剂的松弛特性影响不大。     

中国神木煤灰渣在高温下的流变特性

利用高温流变仪测定了中国神木煤灰渣在不同温度下的流变特性,并利用光学显微镜观察了煤灰渣在高温下冷激后的微观形貌,同时利用热力学软件FactSage预测了煤灰渣在不同温度下结晶粒子的相对含量与其均相熔体组成随温度的变化。实验结果表明:当实验温度为煤灰渣的全液相温度时,其流型表现为牛顿性流体;当温度低于其全液相温度时,随着温度的降低,其流型依次变为Bingham流型与Casson流型。同时随着温度的降低,由于煤灰渣中的固含量在不断增加,使得煤灰渣表现出明显剪切变稀的流变现象。最后利用Urbain模型与改进后的Einstein-Roscoe模型分别对煤灰渣中均相熔体黏度与实际黏度进行了模拟,其模拟值与实验值有良好的相关性。     

DNP/HMX熔铸炸药的流变性能

为了解3,4-二硝基吡唑(DNP)/HMX悬浮液在不同影响因素下的流变行为,采用Brookfield R/S Plus流变仪对其流变性能进行测试,分析了HMX含量、粒度、颗粒级配、体系温度以及不同添加剂对悬浮液流变性能的影响。结果表明,DNP单质为牛顿流体,表观黏度约为16.4mPa·s,比TNT高82%,比DNAN高140%;同一剪切速率下,DNP/HMX悬浮液表观黏度随固含量的增加而增加,当HMX质量分数为30%时,悬浮液近似牛顿流体;HMX质量分数高于30%时,表观黏度随剪切速率的增加呈指数型下降的趋势愈发明显;悬浮液表观黏度随颗粒粒径的增大和温度的增加而降低,当温度从95℃升到105℃时,黏流活化能(E)从29211J/mol增至38458J/mol;固含量为60%时,平均粒径(d50)分别为16.6μm和575.6μm的HMX颗粒的最佳质量比为1∶5,此时悬浮液表观黏度最小。N-甲基-4-硝基苯胺(MNA)降低了悬浮液的表观黏度,乙酸丁酸纤维素(CAB)和微晶蜡-80(MV80)增加了悬浮液的表观黏度。     

Rheology evolution of a geopolymer precursor aqueous suspension during aging

Geopolymer-based glass-ceramic matrix composites can be processed at room temperature and a heat treatment below 100°C leads to matrix hardening thanks to the geopolymerization mechanisms. The stabilization of the matrix into glass-ceramics is achieved via a post-curing at high temperature. This paves the way of the utilization of cost-effective liquid composite molding processes, for which all the necessary equipment is already available for processing temperature ranges related to polymer matrix composites, provided that the rheological behavior of the precursor is suitable to conveniently permeate the fibrous preform. The paper describes the thixotropic rheological behavior of a reference suspension at processing temperature (10°C-20°C) and its evolution along aging at −18°C. The changes are interpreted in terms of geopolymerization mechanisms (dissolution and polycondensation) and suspension rheology (predominance of hydrodynamic effects at high shear rate). On this basis, a phenomenological modeling framework, combining two Krieger-Dougherty equations, is proposed to build a relationship between the effective viscosity of the suspension and the phenomena involved during aging (dissolution of aluminosilicate particles) and shearing (microstructure scalar variable).     

Elucidation of Viscosity Reduction Mechanism of Nano Alumina Suspensions with Fructose Addition by DSC

Control of the rheological properties of the nanoparticle suspensions is challenging. In this study influence of the solids content and the fructose addition on the viscosity of nano alumina suspensions have been investigated by low temperature differential scanning calorimetry (LT‐DSC), rheometry, and zeta potential measurements. Analysis of the water melting events in LT‐DSC revealed useful information for explaining the rheological behavior of the nanoparticle suspensions. It was shown that the bound water layer has a negligible effect on the viscosity of micrometer‐size particle suspension while it increases the effective solid content of alumina nanoparticle suspensions significantly leading to high viscosities. The presence of fructose modifies the bound water layer, decreases the effective solids content, hence resulting in viscosity reduction. Fructose addition lowers the pH of the suspension, but has a negligible effect on the zeta potential. The origin of the bound water, and electrostatic and steric effects of the fructose addition on the viscosity are discussed.     

A review on the rheological behavior and formulations of ceramic suspensions for vat photopolymerization

Vat photopolymerization is an additive manufacturing process that produces high-performance ceramic parts. A critical step in the process is the preparation of a suspension that meets the requirements of high ceramic loading and proper rheological behavior, since an increase in solid loading might compromise the suspension rheology, resulting in non-uniform layer recoating. This review examines the rheological behavior of ceramic suspensions for vat photopolymerization, discussing the influence of the suspension formulation (solid loading, ceramic particle size and size distribution, monomers, diluents, and dispersants) on rheological aspects such as viscosity, shear-thinning/thickening behavior, critical shear rate, yield stress, and thixotropy. It provides a summary of the best formulations, which achieved low viscosity (<3 Pa.s) and high solid loading (>40 vol%), and reports the main trends and challenges of ceramic vat photopolymerization, suggesting general guidelines for the preparation of highly loaded photocurable ceramic suspensions with low viscosity.     

圆管中中性悬浮液流动阻力和流变性的实验测定

对高浓度的液固悬浮液在圆管中的流变特性进行了实验研究,实验体系为聚苯乙烯颗粒在NaCl水溶液中的中性悬浮液。测定了在层流状态下,固体颗粒的体积分数变化（20%～50%）、悬浮液流速变化（0.031～0.22 m&#8226;s^-1）以及颗粒粒度变化对悬浮液压降的影响规律。实验结果表明,固体颗粒的浓度会影响悬浮液的流变性质,颗粒粒径对悬浮液流变性影响微弱。悬浮液的压降随颗粒体积分数和流速的增大而增大,悬浮液的流动特性在较高颗粒浓度范围内符合幂率流体模型。     

Investigation of Crystal Morphology and Shock Sensitivity of Cyclotrimethylenetrinitramine Suspension by Rheology

Crystal morphology and shock sensitivity of a series of cyclotrimethylenetrinitramine (RDX) particles suspended from ethylene glycol were investigated. Flow rheology was employed to measure the rheological properties of the suspensions at constant temperature; it was observed that the stress‐shear rate and viscosity behavior of the suspensions were controlled by the particle morphology. The viscosity of the RDX suspensions changed with the roundness/smoothness of RDX crystals at all applied shear rates. The suspensions containing crystals with smoother morphology showed reduced viscosity. When the viscosity data was compared to the shock sensitivity results from the RS‐RDX Round Robin study, a good correlation was obtained. This study has validated the use of flow rheology to indicate the morphology and shock sensitivity of crystalline particles.     

Influence of Powder Agglomerates on the Structure and Rheological Behavior of Injection-Molded Zirconia–Wax Suspensions

Surface-modified zirconia powders with 20% to 100% of the particle surface area covered with stearic acid was blended with 50 vol% of an organic wax vehicle for rheological study. These fractions of surface coverage gave rise to different degrees of powder agglomeration. A further adsorption of the wax on partially modified particle surfaces was examined, which was likely to exhibit different degrees of solid surface-wax affinity depending upon whether the particle surfaces were "bare" or "premodified." The rheological behavior of the suspensions revealed that the shear viscosity as well as the yield stress increased appreciably with decreased fractions (or surface coverage) of the pre-adsorption. The observed suspension rheology due to incomplete surface modification can be accounted for by the formation of agglomerates which suppress suspension flowability to a significant extent. The formation of the agglomerates alters the suspension structure by reduction of the maximum solid concentration (φ_max) that is attainable for a given powder. This change in suspension structure (decrease in φ_max) leads to a restriction of particle mobility, reflected as a linear function of the yield stress of the suspensions.     

Assessment of aged biodegradable polymer‐coated nano‐zero‐valent iron for degradation of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX)

BACKGROUND: This study reports on the effects of aging on suspension behavior of biodegradable polymer‐coated nano‐zero‐valent iron (nZVI) and its degradation rates of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) under reductive conditions. The polymers investigated included guar gum, potato starch, alginic acid (AA), and carboxymethyl cellulose (CMC). Polymer coating was used to mitigate nZVI delivery hindrance for in situ treatment of RDX‐contaminated groundwater. RESULTS: The RDX degradation rates by bare nZVI and starch‐coated nZVI suspensions were least affected by aging although these suspensions exhibited the least favorable dispersion behavior. CMC, AA, and guar gum coating improved nZVI rates of degradation of RDX but these rates decreased upon aging. The best suspension stability upon aging was achieved by CMC and AA. Guar gum with loadings rates one order of magnitude lower than that of CMC and AA achieved good iron stabilization but significantly higher RDX degradation rates. CONCLUSION: It is demonstrated that both migration and reactivity of polymer‐stabilized nZVI should be explicitly evaluated over a long period before application in the field. Guar gum coated nZVI appeared best suited for in situ application because it maintained good suspension stability, with RDX degradation rates least affected by aging compared with the other polymers tested. © 2012 Society of Chemical Industry     

影响氧化铝水基料浆流变学特性的关键因素

用流变学的方法在RV-20型流变仪上研究不同条件,如:固含量、分散剂加入量、烧结助剂、增塑剂等对碱性氧化铝悬浮体的流变性的影响.结果表明:氧化铝陶瓷碱性料浆(pH＞7)在低的剪切速率(＜100 s-1)时,表现为剪切变稀.在水基料浆中添加MgO时,会发生强烈的水合反应,导致料浆失去流动性.增塑剂甘油的加入导致料浆粘度升高的幅度是有限的,不会对料浆固含量和浇铸工艺造成显著不利的影响.加入水溶性丙烯酸乳液后,在低的剪切速率下,料浆仍然呈现剪切变稀行为,随着乳液含量的增加,料浆的静态粘度逐渐增大.分散剂聚丙烯酸氨的加入量对料浆的稳定性具有显著的影响.在分散剂的加入量为固相质量的0.8%左右时,分散剂在陶瓷颗粒表面形成饱和吸附,此时料浆的稳定性达到了最佳状态.