不同工艺条件下PS/ScCO2均相体流变特性研究

通过建立含有类似锥板流变仪结构的实验平台对不同的温度、压力、剪切速率以及CO2质量分数等工艺条件下聚苯乙烯(PS)/超临界CO2(ScCO2)均相体的流变性能展开研究。结果表明:压力的升高会增加均相体的黏度,压力由7.5 MPa升高到10.5 MPa时,CO2质量分数为0.5%的均相体黏度增加了140 Pa s,约为原来的4.6%;增加温度则会降低均相体黏度,而且随着温度的升高,黏度的下降趋势在逐渐减小,温度从443.15 K逐渐增加到473.15 K时,CO2质量分数为0.5%的均相体黏度的减少值分别为778,482,327 Pa s;当均相体中CO2质量分数逐渐增加时,其黏度变化呈线性下降,CO2质量分数每升高0.1%,均相体黏度下降约为52 Pa s;加大剪切速率可以大幅度降低均相体的黏度,当CO2质量分数为0.5%的均相体在剪切速率从(120/π)/s增加到(240/π)/s时其黏度下降趋势最大,值为40%。     

无规共聚聚丙烯的流变性能研究

采用毛细管流变仪对无规共聚聚丙烯(PP-R)的流变行为进行了具体分析。结果表明:PP-R的黏度随温度变化的敏感性不大;随着剪切速率的提高,PP-R的黏度明显降低(剪切变稀);入口压力降(P0)与温度和剪切速率均有关温,度升高P,0减小剪,切速率增大P,0升高。     

ABS熔体在微尺度通道中粘性耗散效应的研究

针对微尺度通道中粘性耗散效应对非牛顿聚合物熔体流动特性的影响,采用毛细管流变仪、高精度温度传感器和微尺度口模等组成的粘性耗散测量装置,对非结晶型ABS(Acrylonitrile Butadiene Styrene,ABS)聚合物材料,在不同入口温度和剪切速率下,流经直径分别为350μm和500μm,长径比不同的微通道时的粘性耗散效应,进行了实验测量和数值模拟。结果表明,微通道入口熔体温度一定时,粘性耗散效应引起的出口熔体温升,均随剪切速率的增大而近似线性增加;而剪切速率一定时,微通道的出口熔体温升则随其长径比的增大和入口熔体温度的降低而明显升高。     

微孔塑料连续挤出成型快速降压口模的数值模拟

利用Polyflow有限元软件对聚苯乙烯(PS)/CO2均相体系在连续挤出成型圆形快速降压口模中的流动进行数值模拟,考察快速降压口模入口角、长径比及口模温度对PS微孔塑料熔体沿轴线方向的压力降速率和剪切速率的影响。结果表明,当入口角大于30°时,改变入口角对压力降速率和剪切速率无明显影响,即对微孔塑料的气泡成核影响微小,但当入口角为0°时,与其它各入口角相比,其熔体压力降速率最大,气泡成核时间最早;在毛细管段口模直径不变的情况下,改变其长径比对熔体气泡成核亦无明显影响,但压力降随口模长度缩短而变小;口模温度对剪切速率影响不大,但降低口模温度,压力降速率明显提高,从而有利于微孔塑料的气泡成核。     

温度和剪切协同作用对十六烷基三甲基氯化铵溶液表观黏度的 影响

深入研究表面活性剂的流变特性，对于理解湍流减阻机理和改进制药、化工等领域的产品质量具有重要意义。本文研究了相同升温速率、不同剪切速率以及相同剪切速率、不同升温速率对阳离子表面活性剂十六烷基三甲基氯化铵（CTAC）溶液表观黏度的影响。研究表明：当温度较低时，剪切速率对表面活性剂溶液表观黏度的影响起主导作用；随着温度的升高，高温对胶束的影响增强导致溶液在高温处出现剪切稀化现象。当浓度为0.3125mmol/L时，溶液临界温度随剪切速率的升高保持恒定；但当浓度升高至0.6250～1.2500mmol/L时，在高温和高剪切的作用下，黏度曲线出现“平台”和短暂的增稠现象。对于中等浓度表面活性剂溶液，浓度升高导致蠕虫状胶束出现分支并抑制了“平台”的产生；随着升温速率的增大，胶束结构的响应时间滞后于升温速率，但当γ=150s^?1时，滞后效应减弱，高剪切对胶束结构的破坏占主导作用。     

发泡机头流道内PS/CO2均相体系压力场的模拟

利用有限元软件包Polyflow模拟不同条件下发泡机头流道内PS/CO2熔体的流动,获得了压力,计算出压降速率,并分析熔体温度、CO2含量、机头模口流道直径和质量流率对流道内压力和压降速率的影响。结果表明,在加工条件允许的范围内,降低熔体温度,可以显著提高机头流道中的压力和机头模口流道中的压降速率;当熔体温度一定时,机头流道中的压力和机头模口流道中的压降速率随着CO2含量的增加而降低。尤其当熔体温度为150℃,CO2质量含量由1%增加到2%时,机头模口流道中的压降速率急剧降低;减小机头模口流道直径可有效地提高机头流道内的压力和压降速率。熔体温度175℃,CO2质量含量5%、质量流率1kg/h时,模口直径由1mm减小到0.5mm,机头入口段压力由5.9MPa增大到近30MPa。     

内胎胶挤出流动中出口压力降的估算

应用前文中提出的出口压力降△exit与挤出胀大比的关系式,估算了挤出条件下内胎胶的出口压力损失。结果表明,当温度一定时,△exit随着剪切速率的增加而增大;而在固定的剪切速率下,△exit则随着温度的升高而下降。     

EPDM/PP热塑性弹性体的制备及其流变特性

以聚丙烯(PP)和三元乙丙橡胶(EPDM)等为原料,采用完全动态硫化共混技术制备EPDM/PP热塑性弹性体(TPV),使用毛细管流变仪对TPV熔体的流变特性进行测试。分别研究了剪切速率、挤出温度对黏度、剪切应力和挤出胀大比的影响,以及不同条件下熔体流过毛细管口模时流速对压力降的影响。结果表明,TPV熔体是假塑性流体,其剪切应力随剪切速率增大而增大,随挤出温度的升高而降低;黏度随剪切速率和挤出温度的增大而降低;挤出胀大比则随剪切速率和挤出温度的增大而增大;毛细管口模的压力降也随流速和毛细管口模长度的增大而增大。     

MWCNTs/rGO纳米杂化材料改性氨纶的流变性能

采用一步水热还原法制备了多壁碳纳米管(MWCNTs)/还原氧化石墨烯(r GO)纳米杂化材料,进一步通过溶液混合方法将纳米杂化材料与氨纶混合制备了氨纶/MWCNTs/r GO(NCs)溶液,使用旋转流变仪研究了NCs溶液浓度和温度对其静、动态流变行为的影响。结果表明,高浓度的NCs溶液黏度对剪切速率较为敏感,产生明显的剪切变稀现象,但在低剪切速率下其黏度仍有较宽的稳定平台;随温度降低,浓度为10%的NCs溶液黏度升高,剪切变稀现象更为明显,当温度低于60℃时,黏度的稳定平台变窄;NCs溶液在角频率较低时具有较好的纺丝性能,角频率大于200 rad/s时,储能模量高于损耗模量,纺丝时容易造成出口胀大堵塞纺丝孔,对于纺丝不利;NCs溶液的非牛顿指数随着温度升高而升高,与剪切变稀随温度升高而减弱的现象一致。由静、动态流变测试结果综合分析,浓度为10%的NCs溶液适宜纺丝的温度应该大于60℃,剪切速率应低于20 s-1。     

含CO_2采油井油管腐蚀影响因素及防治措施研究

西部S油田含CO_2采油井油管腐蚀问题严重,通过室内模拟试验,采用高温高压动态腐蚀反应釜模拟井筒动态腐蚀环境,考察了采出液含水率、温度、CO_2分压、矿化度和流体流速对油管钢材腐蚀速率的影响,并优选出了一种性能优良的抗CO_2缓蚀剂RYH-301,评价了其对目标油田采油井油管钢的防腐蚀效果。结果表明:随着采出液含水率、温度、CO_2分压、矿化度以及流速的增大,油管钢材的腐蚀速率均呈现出逐渐增大的趋势;抗CO_2缓蚀剂RYH-301能够对目标油田采油井油管钢材起到较好的防护作用,当其质量浓度为150 mg/L时,缓蚀率可达98%以上。     

微孔塑料挤出快速降压口模的数值模拟

应用FLUENT软件对微孔塑料连续挤出成型过程中的快速降压口模内的熔体流动进行数值模拟,经过简化及边界处理,分别研究了微孔塑料在不同CO2浓度、不同流量和不同温度条件下微孔塑料连续挤出过程中快速降压口模中的压力和速度分布情况。结果表明:压力降随熔体温度和CO2浓度的升高而降低,随熔体流量的升高而增大。导管中的速度也几乎均匀分布,在毛细管人口处中心线速度突然增大。熔体流量和CO2浓度的变化对口模压降和口模速度的影响比较大,而温度的变化对其影响要小得多。     

Effect of the entry cone angle of the spinneret hole on the flow characteristics of the polymer melt

Conclusions The effect of the entry cone angle of a spinneret hole on the flow characteristics of the polymer melt has been investigated. This dependence has a complex character, which is expressed in the fact that initially the pressure drop in the spinneret hole decreases with increase in the angle, then rises, and again decreases.The local minimum and maximum points on the curve which characterizes the dependence of pressure drop on entry cone angle depend on the viscosity anomaly of the polymer melt and on increase in the latter they are displaced in the direction of smaller angles.Translated from Khimicheskie Volokna, No. 3, pp. 39–41, May–June, 1986.     

直接精馏法提取纤维素乙醇

采用直接精馏法研究了高固含量(质量分数)、高黏度的玉米秸秆发酵醪液的精馏工艺,设计了带搅拌桨的不锈钢筛板-填料精馏塔,确定了固含量为11.56%的发酵醪液的幂律模型本构方程,进而得到塔釜中发酵醪液的黏度和搅拌桨转速的关系。在进料量为2.7 L/h、进料体积分数为10%左右、进料温度为30℃、操作压力为常压的条件下,考察了进料位置、回流比、搅拌桨转速等操作条件对纤维素乙醇精馏的影响。实验结果表明:第27块塔板进料、操作回流比5.0、搅拌桨转速36 r/min为最佳操作条件,塔顶乙醇收率可达到99%以上。     

雷松藻消化的工艺条件

将F藻(Lessonia trabeculata)的茎部浸泡后粉碎至1~3 mm进行消化反应,考察了Na2CO3浓度、料液质量比、搅拌转速、消化温度和消化时间对褐藻胶消化得率和褐藻胶溶液粘度的影响,通过正交实验对消化工艺条件进行优化,并对褐藻胶进行红外光谱定性分析. 结果表明,最佳消化条件为：温度70℃, Na2CO3浓度1.67%,搅拌转速400 r/min,料液质量比1:15,时间8 h. 该条件下褐藻酸钠产品得率为34.80%,粘度为2261.67 mPa×s,远高于市售产品的173.30 mPa×s. 褐藻酸钠基本理化指标均符合国家标准、粘均分子量为11.85 kDa.     

不同工艺参数时快速降压口模的数值模拟

在微孔塑料连续挤出成型中,运用Ployflow软件对快速降压口模内熔体流动进行模拟分析,研究了不同CO2浓度、不同熔体体积流量对口模内熔体压力、速度分布及挤出胀大影响。结果表明,口模内熔体压力降在一定的范围内随着熔体体积流量的增大而增大,随着CO2浓度的升高而降低;一定范围内,CO2浓度对口模出口处熔体平均速度的影响不明显,而熔体体积流量对口模出口处熔体平均速度的影响很明显;对于挤出胀大的影响,CO2浓度不宜过高或者过低,2 %（质量分数,下同）时表现最佳;在一定熔体体积流量的范围内,熔体体积流量越高,挤出胀大表现得越不明显。     

Influence of the melt viscosity and operating conditions on the degree of filling,pressure, temperature,and residence time in a co‐kneader

The effect of the melt viscosity and operating conditions on processing parameters in a co‐kneader with a discharge die was experimentally investigated. Filling ratio, pressure, temperature, and residence time distribution were measured. Experiments were performed with polypropylene resins. The viscosity of the melt was varied either by changing the regulation temperature of the kneader or the molecular weight of the polymer. The filling pattern in the co‐kneader shows the conveying capability of the various elements without any effect of the melt viscosity. Experimental residence time distributions remain the same at a given feed rate and screw speed, regardless of the viscosity of the material. The global degree of filling in a zone combining conveying elements, kneading elements, and restriction ring was found to be nearly constant in the conditions of this study and therefore a simple relation exists between the mean residence time and the feed rate. Beside expected variations of the die pressure and melt temperature when the viscosity, screw speed or feed rates change, a model based on heat equation and experimental data demonstrate the high capability of the co‐kneader for heat exchange and for the control of self‐heating during mixing. POLYM. ENG. SCI., 58:133–141, 2018. © 2017 Society of Plastics Engineers     

数值模拟静态混合器结构对PS/CO_2熔体温度的影响

利用专用CFD软件Polyflow对SMX型和Kenics型静态混合器中PS/CO_2发泡溶液进行数值模拟计算,分析比较不同板厚在不同元件个数条件下两种静态混合器消耗的压力损失,以及不同CO_2浓度对静态混合器压力损失的影响;并引入"离散系数"分析比较两种静态混合器出口温度均匀性的变化.数值模拟的结果表明:SMX型静态混合器冷却效果优于Kenics型静态混合器,并且SMX型静态混合器出口温度均匀性高于Kenics型静态混合器.     

The effect of a new type of pin mixing section on the performance of a single-screw extruder

The effect of a holed-pin mixing section on the performance of a single screw extruder was investigated and compared with a free flight and a normal pin mixing section, using a practical single-screw extruder. The effect of axial distance between two pins in a holed-pin mixing section on performance was also studied. Mixing ability was quantified using the statistical approach of carbon black concentration distribution in the extruded film mixed with a carbon black masterbatch. The results indicate that a free flight gives the lowest melt temperature rise, pressure drop, and driver power, but the worst mixing; a holed-pin mixing section has better mixing ability, lower melt temperature rise, and lower driver power than a normal pin mixing section does; the value of the pressure drop of the two types of pin mixing sections is approximately identical. A longer axial distance between the two pins in a holed-pin mixing section gives better mixing and lower melt temperature rise than a shorter one; however, when the distance is longer than a critical value, the improvement of mixing is not so outstanding; for different axial distances between two pins, no great change in pressure drop was found and the extrusion throughput has almost no great relation to the axial distance.     

Properties of mixtures of zinc chloride and N-methylpyridinium chloride in the molten state—II. Specific mass, electrical conductivity and viscosity

The concentration and temperature dependences of the specific mass and of the transport properties of molten mixtures of zinc chloride of N-methylpyridinium chloride have been investigated. The specific mass linearly decreases with the temperature at all compositions of the mixture. In the limited temperature range available in this study (423–473 K), the temperature dependence of the transport properties is adequately described by the Arrhenius law. The specific mass regularly increases from pure N-methylpyridinium chloride to pure zinc chloride. The equivalent conductance generally decreases with the concentration of zinc chloride in the melt but remains practically constant from X_ZnCl2 = 0.33 to X_ZnCl2 = 0.50. The viscosity isotherms show a maximum value at X_ZnCl2 = 0.33 and a minimum for X_ZnCl2 = 0.45. The discussion of the results is founded upon the structural properties of the melts and takes into account the Walden's relation between the viscosity and the equivalent conductance.