一种耐烧蚀丁羟包覆层的研究

研究了空隙率、固体填料组分级配对包覆层料浆黏度的影响。采用正交试验,考察了多种填料对丁羟包覆层烧蚀性能的影响,确定了填料的最佳配比。通过验证试验,考察了包覆层应用于某推进剂时的烧蚀性能。     

冷冻法硝酸磷肥两段中和料浆黏度变化规律研究

为满足硝酸磷肥生产设备对料浆流动性的要求,从而寻求较佳的工艺条件,对冷冻法硝酸磷肥脱钙母液氨中和时料浆的黏度进行测定,以确定硝酸磷肥两段中和不同条件对料浆黏度的影响。结果表明,磷矿中的镁和钙与料浆黏度成正比,镁的影响大于钙的影响;控制一段中和料浆pH为1.5~2.0、n(N)/n(P)为1~2时料浆黏度≤100 mPa·s,当温度在100~140℃时料浆黏度≤50 mPa·s,满足要求。     

以聚硅氧烷乳液/聚丙烯酸铵为复合分散剂制备高性能氮化硅料浆

以聚硅氧烷乳液(S-17)/聚丙烯酸铵[poly(acrylic acid)ammonium,PAA-NH4]为复合分散剂制备了高浓度且稳定的Si3N4凝胶注模料浆,用电泳仪分析了料浆中颗粒表面zeta电位,用转子黏度计测量了料浆的黏度,用沉降法表征了Si3N4粉体的分散稳定性,用黏度法获得颗粒对聚硅氧烷分子的吸附等温线.研究了PAA-NH4分散剂和聚硅氧烷表面活性剂对高固相含量、低黏度料浆的稳定性影响机制.结果表明:单独使用PAA-NH4不能达到较好的稳定效果,采用聚硅氧烷乳液/PAA-NH4复合分散剂,聚硅氧烷乳液用量为0.4%(质量分数,下同),PAA-NH4为0.8%时,可制备固相体积含量为50%,黏度低于1.0 Pa·s,稳定性较高的料浆.该料浆适于凝胶注模操作.根据静电作用原理,结合颗粒对聚硅氧烷分子的吸附特性,提出通过降低液相表面张力来降低料浆黏度及提高稳定性,探讨了高固相含量料浆分散的理论机理.     

工艺参数对凝胶注模成型ZrO_2料浆性能的影响

以亚微米级ZrO2粉体为原料,采用丙烯酰胺(AM)/N,N-亚甲基双丙烯酰胺(MBAM)凝胶体系,通过凝胶注模成型工艺制备低粘度、高固相含量的ZrO2料浆。探讨了分散剂用量、料浆pH值、固相含量及研磨时间等工艺参数对ZrO2料浆性能的影响。用Zeta电位仪、粘度计和流变仪分别对料浆的Zeta电位、粘度值和流变学特性曲线进行测定。结果表明,A型分散剂(聚丙烯酸盐)用量为ZrO2体积的2%~2.5%时,对超细ZrO2粉体分散效果最佳,其料浆pH值以10~11为宜,研磨时间控制在12~15h,料浆固相体积分数可达50%~54%。     

浓缩酸性料浆制磷酸铵的研究

对以金河磷矿为原料制得的磷酸铵酸性料浆,进行了料浆中和度与pH值、料浆沸点与其w(H2O)、料浆中w(H2O)与黏度、料浆温度与黏度、料浆中w(H2O)与密度等的实验研究.结果表明:当中和度为0.52时,料浆中w(H2O)≤10%时,浓缩操作可以顺利进行,此时在130 ℃时料浆黏度为285 mPa·s.利用此酸性料浆浓缩得到的MAP产品中w(P2O5)有效≥42%,P2O5有效率[w(P2O5)有效/w(P2O5)全]≥98%,此实验数据可为进一步工业性试验提供参考依据.     

包覆型铝粉颜料在水性涂料中的应用

以正硅酸乙酯(TEOS)和乙烯基三乙氧基硅烷(VTES)为前驱物,通过溶胶-凝胶反应在铝颜料表面形成了一层致密的包覆层,再通过甲基丙烯酸甲酯(MMA)和丙烯酸(AA)的自由基聚合反应对铝颜料进行第二层包覆,制备了含亲水基团的包覆型铝粉颜料,以此包覆的铝颜料配制了水性铝粉涂料.研究了铝粉及交联剂的用量、涂料黏度和烘烤温度...     

复合溶剂NMP/CaCl2热稳定性对PPTA树脂黏度的影响

研究了影响PPTA树脂比浓对数黏度的NMP/CaCl_2复合溶剂,NMP/CaCl_2复合溶剂的热稳定性直接影响PPTA树脂比浓对数黏度及相对分子质量分布,一般PPTA树脂黏度较高可以提高纺丝强度,PPTA树脂黏度平均提高一个单位对位芳纶纤维强度提高3～4 g/D,PPTA树脂相对分子质量分布较窄有利于纺丝的稳定。重点研究了复合溶剂的热稳定性对PPTA树脂黏度及相对分子质量分布的影响。     

纳米TiO2料浆分散性的研究

在分析纳米TiO2粉体团聚现象成因的基础上,研究了HN分散剂对料浆分散性的影响。通过料浆沉降体积、黏度、电位、比表面积等表征了料浆性能的变化;同时研究了稀土离子、PH值、超声处理工艺等对料浆分散性的影响。结果表明,加入HN分散剂后,料浆分散性有很大提高,且不同固相含量的料浆使用的HN分散剂有一最佳值,其中30%质量分数的料浆中分散剂最佳量为0.25%;加入分散剂后,料浆黏度减小,电位提高,比表面积增大;稀土离子(CeO2,Ce(NO3)3)的加入、超声的使用也能提高料浆的分散性,料浆分散性的最佳PH值范围为碱性。     

PPTA浆液的配置及其纺丝性能探讨

以低黏度聚对苯二甲酰对苯二胺(PPTA)为原料,工业浓硫酸为溶剂,采用干喷湿纺法制备对位芳纶,探讨了PPTA浆液的配制及其纺丝性能。结果表明:选择PPTA树脂比浓对数黏度(ηinh)为6.0 d L/g,浆液中PPTA质量分数为19.3%,对纺丝性能非常重要;控制PPTA树脂灰分含量小于100μg/g,浓硫酸中的杂质含量小于100μg/g,可以提高PPTA浆液的可纺性和纤维的强度;配浆螺杆温度分8区,设置温度前低后高,可以减少浆液的降解,浆液粘稠度均匀;配制的PPTA浆液在8 h内纺丝,所得纤维都有较高的断裂强度,大于18.3 c N/dtex。     

聚合工艺参数对PPTA树脂黏度的影响

研究了对芳纶(PPTA)树脂在聚合过程中影响黏度的因素,采用Ca Cl2/NMP复合溶剂,通过单因素实验得到PPTA树脂黏度最大时的工艺条件为:PPD∶TPC物质的量比1∶1. 003,复合溶剂中水分130×10-6,盐含量8.4%,双螺杆聚合反应器转速70 r/min;采用两次投料方式可有效减少PPTA树脂黏度值的波动。     

Viscosity measurement of gelcasting slurry during in-situ gelation by a micro X-ray CT scan system

This paper reports the use of a micro X-ray CT scan system to measure the viscosity increase during in-situ gelation of a gelcasting slurry. Three small steel balls were dropped in the slurry at a desired time interval after the addition of the gelling agent, while being monitored by the CT scan system. It was determined that the plot of the logarithm of the calculated viscosities based on the settling velocity of the falling ball versus the gelation time can be classified into three regions with increasing slopes. The first region is designated as the idle time during which the gelcasting slurry can be further processed and cast into a mold. The second region is the onset of gelation during which the polymer networks start to form with a gradual increase in the viscosity, whereas the third region is attributed to the increased concentration of the polymerized networks as typified by the significant increase in the slurry viscosity. Moreover, the falling ball method was found to be more sensitive to detecting the onset of gel formation in the gelcasting slurry than stress-controlled rheometric analyses.     

苯乙烯对植物纤维渗透性及UP复合材料成型质量影响

为提高真空辅助树脂注射成型工艺制备植物纤维增强复合材料的生产效率和成型质量,以苯乙烯为稀释剂,以不同黏度不饱和聚酯树脂(UP)和苎麻织物制备苎麻织物增强UP复合材料.基于达西定律研究UP黏度对苎麻增强体渗透率的影响,结合复合材料纤维体积分数、力学性能以及内部缺陷对复合材料成型质量进行分析.结果表明,随着UP黏度降低,增...     

Curing of unsaturated polyester resins: Viscosity studies and simulations in pre-gel state

The curing of styrene-unsaturated polyester (UP) resins was studied until gelation. The viscosity and gel points were measured during curing and were correlated with curing temperature, initiator concentration, and accelerator concentration. A gelation model concerning the formation of intra-crosslinked polymer coils, called microgels, was proposed. The model describes the gelation mechanism in four stages: induction, microgel formation, transition, and macro-gelation. The kinetic and gelation parameters of the model were experimentally obtained. The gel points and viscosities in the pre-gel state were simulated by the gelation model for isothermal and nonisothermal curings. Comparisons of the simulation results with experimental data showed good agreement.     

有机累托石改性不饱和聚酯的研究

采用有机累托石改性不饱和聚酯。研究了有机累托石用量对不饱和聚酯粘度、凝胶时间等的影响；利用透射电镜(TEM)分析了不饱和聚酯的微观结构。研究结果表明，有机累托石的加入对不饱和聚酯的粘度、凝胶时间均有影响；但有机累托石的加入，不会改变不饱和聚酯的固化机理；且提高不饱和聚酯的弯曲强度及耐水煮性。     

SiC浆料的流变性能研究

为制备结构均匀的多孔SiC陶瓷的料浆,本文比较了不同质量分数(40%~60%)的SiC浆料的剪切应力和黏度随剪切速率的变化.结果表明:浆料的等电点在3.6左右,Zeta电位值随着pH值的增加而减小,碱性环境下分散效果更好;用Casson方程拟合浆料的剪切应力,相关系数在0.98以上,随着固相含量的增加,拟合的极限粘度和屈服应力增加;当剪切速率达到100 s-1时,固相含量为40%~55%浆料的粘度都在1 Pa·s以下,固相含量为60% 的浆料粘度大概是2.1 Pa·s.     

Regime transition in viscous and pseudo viscous systems: A comparative study

A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µ_L ≤ 1149 mPa‐s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X‐ray tomography. The internal dynamic flow structure and the bubble size distribution shows a dual role of the liquid viscosity on the hydrodynamics. Further, the effect of solid concentration (C_s = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo slurry viscosities similar to the liquid viscosities of the gas–liquid systems. The effects of liquid and pseudo slurry viscosities on flow structure, bubble size distribution, and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition from homogeneous bubbly to slug flow regime occurs is initiated by the addition of particles as compared to the particle free system for apparently same viscosity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3079–3090, 2014     

石墨凝胶注模工艺研究

采用凝胶注模成型工艺制备了石墨浆料,研究了石墨粉体类型、pH值、分散剂加入量和固相含量对浆料粘度的影响,浆料温度对凝胶固化时间的影响,以及乙酰丙酮对素坯强度的影响.实验结果表明:当采用等静压石墨粉,pH值为7,分散剂加入量为4wt%,固相含量为50vol%时,可制备流动性良好的石墨浆料;浆料温度为3 ℃时,凝胶固化时间为5.6 min;当乙酰丙酮加入量为0.6wt%时,素坯强度达到15.8 MPa.     

Viscosities of unsaturated polyester resins: Combining effects of prepolymer structure,resin composition,and temperature

The effects of temperatures, styrene concentration, and molecular composition of unsat-urated polyester (UP) prepolymers on the viscosity of UP-styrene systems are studied. The viscosity of UP resins follows the Arrhenius-type expression with resin temperature as well as with the styrene molar fraction of the resin. The two Arrhenius correlations can be combined into a simple dual-Arrhenius equation by combination rule. This dual-Arrhenius equation comprises pseudo viscosity parameters of styrene monomer and UP prepolymer, respectively. The pseudo viscosity parameters of styrene monomer are experimentally found constant; while those of UP prepolymer seem to be number-average molecular weight correlated rather than weight-average molecular weight correlated. The UP prepolymers having different molecular structures show different pseudo viscosity parameters due to their own molecular interaction parameters. The pseudo viscosity parameters of UP'prepolymers should be determined experimentally for the time being. © 1996 John Wiley & Sons, Inc.     

Effects of PVB on the gelation behavior of BaTiO3-based dielectric particles and glass suspension

The effect of polyvinyl butyral (PVB) resins on the gelation behavior of the BaTiO₃-based dielectric particles and borosilicate glass particulate suspensions was investigated in a system where organic solvents, dispersant, binder and gelation modifier were used as processing additives in a low temperature cofired ceramic fabrication processes. The strong flocculation, gels of the suspension without a modifier was attributed to the reaction and strong linkage between the boron in the borosilicate glass and the functional hydroxyl group of PVB resins, which was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. When the butyral content of PVB employed in each slurry formulation diminish by approximately 8%, it caused the concentrated suspension to gel. The butyral content of PVB had a much greater impact on gelation than did the molecular weight of PVB. As the molecular weight of PVB was increased, the apparent viscosities of the slurries increased due to the broader chain length of higher molecular weight of PVB. According to the relative viscosity measurement results, both suspensions with high and low PVB molecules had similar viscosity values and it might be regarded as the more viscous feature of PVB polymer solution.     

Si3N4—MgAl2O4—ZrO2系陶瓷凝胶注模成型的研究

本文对Si_3N_4-MgAl_2O_4-ZrO_2系陶瓷料浆注凝成型工艺进行了较系统的研究,着重分析了复合分散剂、PH值及固相含量对粘度的影响,最终获得了固相含量为47vol％,粘度为455mPa·s,注模性能良好的注凝料浆,使用该料浆已制备了多种复杂形状的氮化硅基陶瓷制品。