Al2O3/PVDF杂化膜的制备及凝胶相变过程的研究

利用乙烯基三甲氧基硅烷为偶联剂,异丙醇铝（AIP）为无机前驱体,与KOH甲醇溶液改性的聚偏氟乙烯（PVDF）混合形成铸膜液,通i封目转化法制备具有化学键相结合的Al2O3/PVDF杂化膜。研究了杂化制膜液体系相行为及凝胺沉淀过程动力学过程,探讨了AIP对杂化膜结构和性能影响的机理。结果表明：加入AIP后,铸膜液的粘度增加,且AIP含量的增加会改变铸膜液体系的相平衡关系,使其成为热力学不稳定体系,降低其对非溶剂的容纳能力,从而加速铸膜液的凝胶化过程。凝胶化初期成膜过程胶凝速度最快,之后随时问的延长而逐渐减慢。不同的铸膜液体系的胶凝速度不同。随着AIP含量的增多,凝胶速度增加,体系发生相分离的速度变快,但当AIP含量达到20％时,凝胶速率反而下降。     

蒙脱土改性环氧树脂及其复合材料性能研究

以蒙脱土(MMT)作为EP(环氧树脂)的改性剂制备EP/MMT纳米复合材料。考察了MMT含量对EP/MMT体系的凝胶时间、黏度和力学性能等影响。结果表明:MMT的加入明显缩短了EP体系的凝胶时间,并显著缩短了EP体系达到高黏度的时间;当w(MMT)=4%时,EP/MMT纳米复合材料的力学性能相对最好,其浇铸体的拉伸强度、弯曲强度和冲击强度分别为85 MPa、140 MPa和35 kJ/m2,其复合材料的拉伸强度和弯曲强度分别为160 MPa和200 MPa。     

斩拌时间和凝胶化时间对微波熟制鱼饼品质的影响

以冷冻鱼糜为原料,采用微波加热工艺制作鱼饼,研究斩拌时间和凝胶化处理时间对微波熟制鱼饼品质的影响。结果表明：斩拌时间对鱼饼的凝胶特性、质构、持水性、白度和感官品质均有极显著影响（P＜0.01）;随着斩拌时间的延长,鱼饼的破断力、凹陷深度、凝胶强度、弹性、内聚性、咀嚼性和感官评分呈现先增大后减小趋势,白度呈上升趋势,持水性呈先下降后上升再下降趋势;凝胶化处理时间对鱼饼弹性影响不显著（P＞0.05）,但对鱼饼的凝胶特性、硬度、咀嚼性、内聚性、持水性、白度和感官评分有极显著影响（P＜0.01）;凝胶化处理20 min显著改善了鱼饼品质,此时鱼饼的破断力、凹陷深度、硬度、弹性、咀嚼性、白度和感官评分均达到最大值,相比未进行凝胶化处理时分别增加86.92%、38.67%、37.05%、6.94%、43.07%、3.41%和14.65%;正交试验结果表明,鱼饼的最佳斩拌和凝胶化处理工艺为斩拌6 min,凝胶化处理20 min,此条件下鱼饼的凝胶强度为2 157.53 g·mm,白度为79.72,感官评分为8.66 分。     

高温延缓型有机硼OB-200交联压裂液的性能与应用

报道了实验考察高温延缓型有机硼交联剂OB 200在5g/L羟丙基瓜尔胶水基压裂液中的各项性能及其影响因素的结果,简述了在7口井上应用该压裂液的情况。OB 200/HPG压裂液在pH=11.5、温度5～35(40)℃时交联时间长达4.7～5.6min;不加破胶剂的压裂液在温度115～135℃时,8h内可完全破胶液化,讨论了OB 200体系的自动破胶机制;在135℃、170s-1条件下剪切2h,压裂液粘度>120mPa·s;高速(500s-1)剪切后,在低速下(80s-1)粘度可恢复到初始值的94.5%(95℃下)或70.0%(135℃下);在95～135℃滤失小,滤失系数为6.93×10-4～9.81×10-4m/(min)1/2;残渣含量低,135℃下破胶20h后为319mg/L,而对比硼酸盐压裂液(90℃)和有机钛压裂液(135℃)分别为364和457mg/L;在人造岩心上测得渗透率伤害率在5.74%～9.66%,平均7.32%,而对比有机钛压裂液为24.07%～29.98%,平均27.09%。在中原油田桥口和户部寨地区7口井2706～3769m井段用该压裂液压裂,施工成功率100%,获得了油、气增产效果。图5表4参3。     

Electrospray modeling of highly viscous and non‐Newtonian liquids

The electrohydrodynamic spraying of highly viscous and non‐Newtonian aqueous solutions of sodium alginate were experimentally modeled with high direct‐current electric fields. A prototype electrospray setup comprising a nozzle connected to a high‐voltage counter electrode connected to earth and a curing facility to solidify the droplets was used. The main aim was initially set to extend the knowledge of the electrospray to highly viscous liquids, where shear thinning was the main rheological feature of fluid flow through the nozzle of the spray system. To model the process, the effects on the size of beads of the electric field strength, nozzle diameter, flow rate, and the material properties of density, viscosity, surface tension, and electrical conductivity were characterized. The size distribution of the beads was obtained after the droplets were cured in a calcium chloride solution with an image analyzer system. The rheological study, carried out on different concentrations of alginate solution (i.e., 1–3 w/v %), showed a significant reduction in the viscosity as a function of the shear rate. Considering the shear‐thinning behavior of the solutions, in the modeling we applied the viscosity at the operational shear rate in the nozzle. Four dimensionless groups were introduced to obtain the relationship between the dimensionless group representing diameter and the other groups in the dripping and jet modes with statistical analysis of the experimental data. The proposed equations correlated the size of beads within ±10% deviations as compared to the experimental results. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of beta-lactoglobulin A and B whey protein variants on the rennet-induced gelation of skim milk gels in a model reconstituted skim milk system

The effect of fortifying reconstituted skim milk with increasing levels of the β-lactoglobulin (β-LG) genetic variants A, B, and an A-B mixture on rennet-induced gelation was studied by small deformation-sensitive rheology. Free-zone capillary electrophoresis and high-sensitivity oscillatory rheology were used to elucidate the role of potential heterotypic associative interactions between whey proteins and casein in a mixed colloidal system, subjected to moderate heating (65°C for 30 min) prior to renneting, on the gelling properties of the system. Increasing levels of added whey protein, in the concentration range of 0.225 to 1.35% of added protein, led to a concomitant progressive increase in the equilibrium shear storage modulus, G′ (recorded after ∼10,800 s), in the order β-LG B > β-LG A and β-LG A-B, as the general expected consequence of the setup of denser casein gel networks. The preferential effect of β-LG B over β-LG A on the mechanical strength of the gels may be due to the formation of cross-links and aggregates involving whey proteins and rennet hydrolysis products or an increase in the size of the casein micelle caused by the grafting of β-LG B to its surface, or both. The results of free-zone capillary electrophoresis were consistent with the notion that β-LG B (and not β-LG A) binds to the casein micelle under an optimal stoichiometry of 1:0.045 (mg/mg), even in the absence of heat treatment. The liquid-like character of the gel networks formed, tan δ, was a parameter sensitive to the level of addition of β-LG A in particular. At low concentrations (up to 0.45%) of β-LG A, tan δ increased by almost twice as much, which was interpreted as a result of the increase in the loss modulus, G″, of the sol fraction because of the presence of unbound β-LG A. At greater incremental concentrations of β-LG (>0.45%), the formation of smaller whey protein aggregates confined to the sol fraction may have led to a progressive decrease in tan δ. The critical gel time, t_gel, was also affected by the concentration of added whey protein and described 3 zones of behavior, irrespective of the type of whey protein variant. The critical gel time was slightly shorter for β-LG B than for β-LG A at 0.45% of added whey protein, but this difference became larger at 0.67%. Even when only β-LG B was found to associate with casein prior to renneting, both β-LG A and β-LG B, either alone or mixed, had a profound influence on the mechanical strength and coagulation kinetics of the rennet-induced casein gels. This knowledge is expected to be useful to exert better control and optimize processing conditions during the manufacturing of cheese and cheese analogs.     

稠油油藏有机铬交联聚合物调驱实验研究

从海上油田开发实际需求出发,针对南堡35-2油田储层非均质特征、储层物性和流体性质特点,利用室内实验方法,对以有机铬为交联剂的交联聚合物溶液的成胶性能、流动能力、粘弹性进行了测定,对交联聚合物溶液的封堵和驱油效果进行了评价。结果表明,有机铬交联聚合物溶液能够在南堡35-2油田地质条件下形成"分子内"交联体系,注入油藏后可达到增大孔隙流动阻力、增加注入压力的作用;注入时机、交联聚合物注入量、聚合物浓度、原油粘度和物理模型等参数将影响封堵和驱油效果。     

A study of function mechanism of hemxamethyl tetra-amine in gelation process of uranium

The UO2 ceramic microspheres are the most important materials in the spherical fuel elements for high temperature reactor (HTR). A process for preparation of UO2 kernels known as total gelation process of uranium (TGU) was developed as the production process of 10 mW HTR at Tsinghua University. The TGU process is based on the traditional sol-gel process, external gelation process and internal gelation process of uranium (EGU and IGU), which implies that the gelation action is initiated both by ammonia out of the gel particles and hemxamethyl tetra-amine (HMTA) inside the gel particles. The gelation behavior and the properties of uranium microspheres were investigated of the solution with and without HMTA. It is observed that good spherical particles can be obtained without HMTA in the sol, which indicates a more controllable and industrialized route will be set up. Contrasts between this route and the traditional EGU were also listed .     

Gelation Kinetics of Agars from Pterocladia capillacea Examined by Dynamic Rheometry

ABSTRACT: The changes in storage modulus (G') during isothermal gelation of agar fractions from Pterocladia capillacea were kinetically investigated with respect to the curing condition, agar concentration, and the molecular property of agar. Generally, the reciprocal of gelling time, the maximal increasing rate of G', and the rate constants of Avramipseudo-1st-order kinetics correlated with the curing conditions more significantly than with the molecular properties examined. This tendency was opposite to the result based on simple 2nd-order rate constant. And, the effects of molecular size on rheological and kinetic parameters were greater than those of the 3,6-anhydro-galac-tose content examined. After verification of the kinetic data obtained, potentially molecular changes during gelation process are illustrated.     

超声波湿法混炼炭黑/天然橡胶复合材料的性能研究

利用超声波的乳化均质作用,将经水湿润的炭黑与稀释的天然胶乳混合均匀,然后采用蒸发成膜法和胶凝成膜法制备胶膜(炭黑/天然橡胶复合材料),探究制膜方法及超声波处理时间和功率对胶膜性能的影响。结果表明:蒸发成膜法成膜时间过长,打开的炭黑二次结构重新团聚,胶膜中炭黑分散性差,胶膜的拉伸强度较小,而胶凝成膜法稳定性更高,胶膜中炭黑分散性好;超声波处理时间为90 s、功率为840~960 W时,超声波的乳化均质效果最好,炭黑二次结构打开程度更高,此时采用胶凝成膜法制备胶膜,成膜速度快,炭黑来不及团聚,胶膜中炭黑分散性较好和结合橡胶较多,胶膜的拉伸强度较大。