挤出机螺杆转速对HDPE／MPA共沸物结构和阻透性能的影响

从理论上分析了挤出机螺杆转速与聚合物中分散相颗粒数的关系以及螺杆转速对共混物阻透性能的影响,实验测定了在不同转速下制得的共混物的阻透性能。并根据阻透性能与结构参数之间的对应关系,从渗透实验数据推算出不同转速下共混物内不可透薄片的形状参数。实验表明,一般情况下溶剂透过共混物的渗稼率随着转速的增加,有一个先锋后升的变化过程。渗透率最低点对应的转速为最佳转速。分散相体积分数不同,其最佳共混转速不同。当共混转速超过临界转速后,溶剂渗透率的对数值随转速线性增加。     

混沌螺杆混沌混合性能模拟与实验

针对混沌螺杆的混沌单元,对其加工高分子材料的混合性能进行模拟并与螺杆单元比较,采用PP/ABS共混物进行力学性能与微观形态实验。结果表明:混沌单元的停留时间概率密度曲线峰宽,拉伸长度对数曲线斜率增大,对物料拉伸折叠作用强,有利于提高共混物的混合性能;随着混沌螺杆转速的增加,PP/ABS共混物的冲击强度和拉伸强度先下降后上升;混沌单元的周期性间断多副螺棱具有很好的混沌混合特征,物料开始进入混沌单元时分散相被迅速分离,分散相粒径减小有一个相对缓慢期,随后分散相又被迅速分离,使得分散相粒径不断减小,提高了PP/ABS共混物的混合效果。     

PE-HD／PA6／EVOH阻透容器成型工艺与性能研究

将高密度聚乙烯（阻HD）、聚酰胺6（PA6）与乙烯-乙烯醇共聚物（EVOH）的复配体和相容剂初混合后，通过挤出机熔融共混、中空吹塑制得阻透容器。考察了树脂及共混物的流变性能，研究了相容剂用量、阻透树脂用量和成型工艺条件对容器阻透性能的影响。利用扫描电镜（SEM）观察了瓶壁的层状结构。实验结果表明，PA6／EVOH复配体增加了阻透树脂的熔体黏度，提高了层状共混工艺的稳定性。与PE-HD／PA6二元共混容器相比。PE-HD／PA6／EVOH三元共混容器所需相容剂更少。当阻透树脂用量为15～18份、相容剂用量为2～3份、加工温度在225～230℃之间、螺杆转速控制在30r／min左右、停留时间在3min时，PE-HD／PA6／EVOH共混容器的阻透性能得到明显提高。     

PE-HD/EVOH共混阻透管材的研制

将高密度聚乙烯(PE-HD)、乙烯一乙烯醇共聚物(EVOH)和相容剂混合后,加人塑料管材挤出成型机中,经熔融共混、冷却定型、辅机牵引制得层状共混阻透管材。研究了相容剂用量、阻透树脂用量和成型工艺参数对管材阻透性能的影响,考察了树脂的流变性能及共混阻透管材的力学性能,并与PE-HD)/聚酞胺6(PA-6)共混管材性能进行比较。利用扫描电镜观察阻透管材壁面的层状结构。实验结果表明,与PE-HD/PA6共混管材相比,PE-HD/EVOH共混管材所需相容剂少,成型工艺参数易于控制,其阻透性能及力学性能更好。当阻透树脂用量为16~18份,相容剂用量为1-3份,加工温度在225℃左右,螺杆转速控制在20 r/min左右,牵伸速度为1. 5一1. 6 m/min时,PE-HD/EVOH共混管材的阻透性能得到明显提高     

溶剂分子透过HDPE/MPA层状共混物的扩散模型

建立了溶剂分子透过聚合物层状共混物的扩散模型 ,给出了溶剂分子相对有效扩散系数D₀ /D与分散相体积分数、不可透薄片形状参数α以及薄片接头缺口参数δ之间的关系式 .经采用不同值及α值共混物得到的实验数据证明 ,该模型与实验结果吻合良好.     

主要工艺参数对三螺杆挤出机流动混合性能的影响

采用Polyflow软件模拟了聚合物熔体PP在三螺杆挤出机计量段内的流动混合过程。借助统计学方法,将累积最大剪切应力分布、累积停留时间分布和混合指数作为评价指标,分析了主要工艺参数(喂料量和转速)对三螺杆挤出机流动混合性能的影响。同时进行PP/EPDM体系共混物制备实验,通过探究工艺参数对分散相粒径及其分布和力学性能的影响以验证数值计算结果。研究结果表明:喂料量和转速增大时,三螺杆挤出机的流动混合性能提高,但当喂料量和转速太大时却不利于三螺杆挤出机的流动混合。     

螺杆转速对PP/POE共混物形态及冲击性能的影响

通过双螺杆挤出机熔融共混制备了聚丙烯/(乙烯/辛烯)共聚物(PP/POE)共混物,研究了螺杆转速对PP/POE共混物形态及力学性能的影响。结果表明,随着螺杆转速的提高,共混物中POE粒子的尺寸先减小后增大,这可以通过Tokita公式来解释。缺口冲击实验表明,PP/POE共混物的缺口冲击强度随着螺杆转速的增加呈先升高后降低的趋势,当螺杆转速为110r/min时,共混物的缺口冲击强度最高,其相形态与冲击性能有很好的相关性;共混物的缺口冲击强度随POE粒径的增大而降低,达到一定程度时出现脆韧转变特征,这点与S.Wu理论相符合。     

HDPE／PA共混吹塑容器阻渗性能的研究进展

综述了HDPE／PA共混吹塑容器阻渗性能的研究,阐明了分散相PA表态与共混物阻渗性能之间的关系,HDPE／PA共混物的相容性,共混物中组分之间的相对粘度比以及加工条件对阻渗性能的影响,建议今后研究工作应着重探讨流动场对HDE/PA混吹塑容器阻渗性能的影响机理。     

纳米纤维用PP/CAB共混母粒中分散相尺寸的影响因素研究

利用相分离的方法制备热塑性聚丙烯(PP)纳米纤维,将不相容的PP和醋酸丁酸纤维素(CAB)两种聚合物在双螺杆挤出机中共混,制备出合适的母粒用于熔融静电纺丝。通过不同条件下的实验,研究了影响PP分散相粒子尺寸大小的因素,利用扫描电子显微镜观察了共混物的形态,并通过旋转流变仪测量了共混物在不同温度和不同剪切速率下的流变行为。结果表明,PP含量和熔融温度对分散相粒子尺寸的影响最为显著,其次为共混时间,螺杆转速的影响最小;当PP质量分数为20%,熔融温度为210℃,螺杆转速为25 r/min,共混时间为4 min时,可得到尺寸较小的PP分散相粒子。将上述条件下制备的母粒通过熔融静电纺丝技术制备PP/CAB纤维,经丙酮处理除去CAB,得到的PP纳米纤维的平均直径为320 nm左右,与直接熔融静电纺丝制备的PP纤维(平均直径为3.5μm左右)相比,纤维的直径降低了一个数量级,使得纤维细化。     

聚丙烯的官能化及其与尼龙66相容性研究

对聚丙烯（PP）进行官能化，并研究了接枝单体含量，引发剂含量，螺杆转速对接枝率和熔体流动速率的影响。再将不同接枝率的PP与尼龙66共混，研究了接枝率对共混物力学性能及相容性的影响；用扫描电子显微镜观察了共混物的形态，与未增容共混体系相比，增容后共混体系分散相尺寸明显减小，增容共混物的形态依赖于增容剂在共混物中的含量，增容剂的分子量及官能化基团的含量。     

Analysis of agglomerate dispersion mechanisms of multiwalled carbon nanotubes during melt mixing in polycarbonate

Dispersion of primary nanotube agglomerates in polymer melts is one of the difficult tasks when applying melt mixing for nanocomposite preparation. Hence, there is a need for a better understanding of the ongoing processes. Filler agglomerates generally undergo dispersion by rupture and erosion mechanisms, which usually occur simultaneously. To analyse these mechanisms and their corresponding dispersion kinetics 1 wt% multiwalled carbon nanotubes (MWNT) were incorporated into polycarbonate using a microcompounder. Different mixing speeds at constant melt temperature were applied thereby changing the applied stress. The states of MWNT agglomerate dispersion at different mixing times were assessed by quantifying the agglomerate area ratio and particle size distribution using image analysis of optical transmission micrographs. A model is proposed to estimate the fractions of rupture and erosion mechanisms during agglomerate dispersion. At low mixing speeds, the dispersion was found to be governed by both mechanisms, whereas rupture dominance increases with increasing mixing speed. Further, the relationship between electrical resistivity and dispersion was studied indicating a critical behaviour. A dependency on the amount of dispersed nanotubes was found only in a certain range of state of dispersion.     

Investigation of axial segregation in a rotating drum

A binary mixture of particles is used to investigate axial segregation in a rotating drum. The effects of the rotational speed, the fill level, the particle size ratio and the resilience of particles on the segregated band widths are evaluated. When rigid glass particles 0.35 mm or 0.70 mm as the key components are mixed particles with a size ratio of 2, 3, or 4, the dimensionless band width is less affected by the rotational speed, except at fill levels 10% and 20% with 0.35 mm particles as the key components. The dimensionless band width decreases with the increase of the level of fill. Experimental results show that there exists a size ratio where the dimensionless band width has a minimum value using rigid particles. The value is approximately 3. The existence of this value was attributed to the diffusion and inertia mechanisms of the motion of a single particle.A comparison was made on the influence of the fill level and the speed of rotation on the dimensionless band width using rigid glass beads and non-rigid rubber particles. The dimensionless band width increases with the increase of the level of fill using 1 mm rubber particles as the key components with a size ratio 2 at all rotational speeds studied. Whereas the dimensionless band width decreases with increasing level of fill when 1 mm glass particles as the key components with a size ratio 2 are mixed at all rotational speeds studied. When particles of different elastic properties are mixed, segregated bands are formed but are less pure compared to the bands formed due to size segregation. The interfaces between the rubber-rich bands and the glass-rich bands are curved. A remarkable convective motion at the surface of the particle bed is observed.     

HOLDUP MEASUREMENT IN A SCHEIBEL EXTRACTION COLUMN

ABSTRACT The total holdup of a dispersed organic phase in a rotary-agitated Scheibel liquid-liquid extraction column of the first type is studied experimentally. The column is 2 inches in diameter and contains 11 stages with a 4-inch height packed section and a 1-inch height mixing section. The packed section is made of stainless steel wire mesh packing with a 93.74% free area and acts as a settler for the coalescence of droplets. Three systems are studied: benzene/water, methyl isobutyl ketone (MIBK)/water and 20% TBP-80% kerosene/1?M nitric acid. The effects of different phase flow rates and rotation speeds (300-670?rpm) on the dispersed phase holdup are investigated. The results show that the holdup increases with increasing dispersed phase flow rate but does not vary with continuous phase flow rate. For benzene, the holdup is large at low rotation speeds and decreases with increasing rotation speed until a minimum holdup is reached, after this transition point, the holdup increases with increasing rotation speed. This phenomena is analogous to that found in a pulse column. For MIBK and 20% TBP-kerosene, the holdup always increases with rotation speed in our experimental range and the transition point is not observed as M in benzene. This is attributed to the much larger interfacial tension of benzene-water as compared with the other 2 systems.     

反渗透过程溶质脱除率方程

<正>溶解扩散理论、摩擦模型和表面力-孔流模型假设稳态时膜中溶质通量恒定“-”。本文分 析了该假设存在的理论依据,并基于膜的吸附-扩散模型’‘’建立了反渗透过程溶质脱除率方 程。     

熔融纺丝成形条件对PET初生丝超分子结构及其力学性能的影响——第1报 不同纺速下PET初生丝超分子结构及其力学性能的研究

本文借助于沸水收缩率、自然拉伸比以及用X射线衍射法测定的结晶度,表观晶粒尺寸和晶区取向因子等指标来描述熔融纺丝时不同纺速下PET初生丝的超分子结构。纺丝速度在1500～4800m/min范围内变化。测得的数据表明在较低的纺速下卷取的PET初生丝是不结晶的,而在较高纺速下纺制的PET初生丝结晶度要高得多。在实验的纺速范围内,PET初生丝的结晶度在纺速增加的过程中有突变现象,这主要是分子取向诱导所致,也即存在一个诱导结晶的临界取向度。最后,就不同纺速下PET初生丝的力学性能特征值进行了讨论。     

生物胶乳对纸张施胶性能的影响

合成胶乳表面施胶剂是常用的表面施胶剂,但是近年来合成胶乳的价格不断上升,给企业的成本带来巨大的压力。而生物胶乳作为环保型胶乳,又具备合成胶乳的功能,研究生物胶乳代替部分合成胶乳,有良好的前景。以丁苯胶乳、生物胶乳为原料,从胶乳配比、纳米粒子含量、分散速度、分散转速等方面着手,以抗张强度、平滑度、施胶度、白度为指标,得出了表面施胶液的最佳方案,即丁苯胶乳/生物胶乳为80∶20,纳米碳酸钙含量为8%,分散时间为80 min,分散转速为3 000 r/min。在适宜条件下进行表面施胶,纸张的施胶度可以提高10.74,并且抗张指数可以提高32.2%,平滑度等指标都有明显的改善。     

Experimental study on the laminar flame speed of hydrogen/natural gas/air mixtures

Laminar flame speeds of hydrogen/natural gas/air mixtures have been measured over a full range of fuel compositions (0–100% volumetric fraction of H₂) and a wide range of equivalence ratio using Bunsen burner. High sensitivity scientific CCD camera is use to capture the image of laminar flame. The reaction zone area is employed to calculate the laminar flame speed. The initial temperature and pressure of fuel air mixtures are 293 K and 1 atm. The laminar flame speeds of hydrogen/air mixture and natural gas/air mixture reach their maximum values 2.933 and 0.374 m/s when equivalence ratios equal to 1.7 and 1.1, respectively. The laminar flame speeds of hydrogen/natural gas/air mixtures rise with the increase of volumetric fraction of hydrogen. Moreover, the increase in laminar flame speed as the volumetric fraction of hydrogen increases presents an exponential increasing trend versus volumetric fraction of hydrogen. Empirical formulas to calculate the laminar flame speeds of hydrogen, natural gas, and hydrogen/natural gas mixtures are also given. Using these formulas, the laminar flame speed at different hydrogen fractions and equivalence ratios can be calculated.     

PVC膜专用料力学性能影响因素的探究

采用转矩流变仪、扫描电子显微镜、差示扫描量热仪和傅立叶变换红外光谱仪研究了聚氯乙烯(PVC)在不同加工温度和转速下的流变性能、塑化行为和结晶性能,探究了塑化效果、微纳层叠器数量对PVC力学性能的影响和PVC专用料吹塑成膜后的力学性能。结果表明,随着加工温度升高、转速增加,塑化时间缩短、凝胶化度增加,塑化行为进行越充分,而平衡扭矩随着加工温度升高而减小,随转速提高而增大;PVC结晶度随加工温度提高而增大,随转速增加而下降。在加工温度为185℃下,随着转速的提高,试样的断裂伸长率不断增大,而纵向、横向拉伸强度先增大后减小,且在转速为40 r/min时均达到最大值,分别为24.8 MPa和23.3 MPa,;在转速为40 r/min下,随着加工温度的提高,试样的断裂伸长率不断增大,而纵向、横向拉伸强度均先增大后减小,且在加工温度为185℃时均达到最大值,分别为24.6 MPa和22.6 MPa。PVC片材的密度和纵向拉伸强度与微纳层叠器数量成正比;与未加微纳层叠器相比,经过6节微纳层叠器后吹塑成膜的轴向拉伸强度提高13.5%,轴向断裂伸长率提高12.4%,轴向直角撕裂强度相应提高34.7%。     

老龄垃圾渗滤液特性分析及其MAP预处理实验研究

分析了垃圾填埋场渗滤液的特点及水质影响因素,叙述了磷酸铵镁沉淀法（MAP法）去除垃圾渗滤液中氨氮的基本原理,探讨了MAP法在不同搅拌时间、不同Mg∶N∶P和不同搅拌速度下对氨氮的去除效果,确定MAP法的最优操作条件为：反应时间45 min,搅拌速度160 r/min,Mg∶N∶P（物质的量比）为1.8∶1∶0.8。     

CFD Prediction of the Critical Agitation Speed for Complete Dispersion in Liquid‐Liquid Stirred Reactors

A computational fluid dynamics (CFD) model is adopted to simulate the turbulent immiscible liquid‐liquid flow in a stirred vessel based on a two‐fluid model with a k‐ϵ‐A_P turbulence model. An improved inner‐outer iterative procedure is adopted to deal with the impeller rotation in a fully baffled stirred tank. Different drag formulations are examined, and the effect of the droplet size on both the dispersed phase holdup distribution and the velocity field is analyzed. Two different numerical criteria are tested for determining the critical impeller speed for complete dispersion. The simulated critical impeller speeds are generally in good agreement with the correlations in the literature when the fixed droplet size is properly selected. This demonstrates that the modeling approach and the numerical criteria proposed in this work are promising for predicting the dispersion characteristics in liquid‐liquid stirred tanks.