Shear flow analyses for polymer melt extruding under superimposed vibration

The introduction of a vibration force field has a profound influence on the polymer formation process.However, its formation mechanism has not been explored until now, With the application of experimental equipment designed by the authors named “Constant Velocity Type Dynamic Rheometer of Capillary” or (CVDRC) ,we were able to analyze in detail the whole extrusion process of a polymer melt. We did this after superimposing a sine vibration of small amplitude parallel to the extruding direction of the polymer melt, Then, we created a calculation model to determine the shear stress at the wall of the capillary using a superimposed vibration, We also determined the calculation steps needed to establish the afore-mentioned shear stress. Through measurement and analysis, the instantaneous entry pressure of the capillary, the pressure gradient, and the shear stress of the polymer melt within the capillary under vibration force field can be calculated.     

纺丝聚合物熔体流变性的实验研究

采用西德布拉本达公司挤出流变仪测试纺丝聚合物熔体流变性能,该仪器用螺杆挤出机作为熔融器,为狭缝式毛细口模提供一定压力的熔体;由于熔融历程与熔融纺丝生产过程类似,因而测试所得数据更接近熔融纺丝的实际情况,实测特性粘度[η]为0.67～1.03dL/g的几种纤维级聚酯(PET)的流动特性以及若干国产及进口纤维级聚丙烯的流变特性,得到了一系列数据,这些数据将为纺丝机械设计和纺丝工艺参数设计提供依据。     

用Cox-Merz关系式确定适于某些中等浓度聚合物溶液的滑动函数 Ⅰ非仿射变形假定和滑动函数的理论计算

对某些中等浓度聚合物溶液,在它们的不同流变函数之间,存在一条重要的经验定律,即Cox—Merz关系式。另一方面,对该类溶液,已知其动态流变性能(G′、G″),可通过Rouse谱加以解释。在Rouse模型理论中,如果在溶液的两种速度场之间——微观分子链附近的溶剂速度场和宏观可测量的溶液平均速度场之间引入一种与宏观速度梯度▽■相关的滑动函数,则理论的预言能力大为改善,而这种滑动函数可通过Cox-Merz关系式加以确定。本工作介绍了非仿射变形假定和滑动函数的基本概念,为一类浓度适中的聚合物溶液确定滑动函数的形式,作为推论,进一步确定了剪切流场中的物质函数——ψ_1、ψ_2、η~+、η~-。一些公开发表的实验数据被引证,与理论结果吻合良好。     

添加剂对热塑性聚氨酯熔体加工与流变性能的影响

基于哈克流变仪测试,研究了不同添加剂对热塑性聚氨酯(TPU)加工性能的影响。试验结果表明,增塑剂和偶联剂与TPU之间的物理化学作用和偶联剂处理的纳米二氧化硅微粒的增强作用均使共混体系的粘度上升、非牛顿行为加剧。乙烯-乙烯醇(EVOH)共聚物与TPU发生增塑混容作用和化学降解反应,使共混体系平衡转矩取决于EVOH用量。     

注射成形中聚合物熔体黏度的在线测量装置

设计并制造在线测量注射成形过程中聚合物熔体黏度变化的装置. 在测量装置中,非等温高剪切流变模具的型腔结构设计成厚度为1 mm或2 mm的狭缝,底部不封口,维持熔体的持续流动;在流动中心线上沿流动方向布置一组压力传感器实时检测聚合物熔体在模具型腔中的压力变化情况,并使用模温机控制模具温度. 使用PXIe采集系统采集、显示、记录实验数据. 实验通过压力传感器测量得到不同位置熔体压力,根据修正的牛顿黏性定律计算熔体黏度,并与Cross-WLF模型的理论值进行对比. 实验结果表明：所设计的模具安全可靠,可获得低密度聚乙烯(LDPE)熔体在注射成形过程中熔体压力的变化情况,从而可以计算出材料在成形过程中的表观黏度演化情况. 实验测量结果与理论值在剪切速率大于500 s^?1的高剪切速度范围内较吻合,误差均在18%以内,最小为4%. 该装置能满足真实成形条件下聚合物熔体信息的在线检测要求.     

双单体固相接枝聚丙烯的流变性能

以过氧化苯甲酰为引发剂制备了苯乙烯、乙酸乙烯酯对马来酸酐和聚丙烯（PP）的二元固相接枝共聚物，并对其结构与性能进行了研究，探讨了剪切应力、剪切速率和温度对固相接枝改性PP熔体流动行为、熔体粘度的影响．结果表明：固相接枝改性PP的熔点和热焓比纯PP的相应值均有所下降；其非牛顿指数n值比纯PP的n值有所增加，说明改性后PP的熔体流动比纯PP偏离非牛顿型流体；其粘流活化能（Eη）比纯PP的Eη有大幅度提高，说明接枝改性后PP的表观粘度对温度的变化非常敏感．     

Dynamic analysis and simulation of four-axis forced synchronizing banana vibrating screen of variable linear trajectory

A new concept of banana vibrating screen which has the same effect as traditional banana vibrating screen in a new way was put forward.The dynamic model of vibrating screen was established and its working principle was analyzed when the action line of the exciting force did not act through the centroid of screen box.Moreover,the dynamic differential equations of centroid and screen surface were obtained.The motions of centroid and screen surface were simulated with actual parameters of the design example in Matlab/Simulink.The results show that not only the amplitude has a significant decrease from 9.38 to 4.10 mm,but also the throwing index and vibrating direction angle have a significant decrease from 10.49 to 4.59,and from 58.10° to 33.29°,respectively,along the screen surface,which indicates that motion characteristics of vibrating screen are consistent with those of traditional banana vibrating screen only by means of a single angle of screen surface.What’s more,such banana vibrating screen of variable linear trajectory with greater processing capacity could be obtained by adjusting the relative position of force center and the centroid of screen box properly.     

Rheological behavior and process prediction of low viscosity epoxy resin for RTM

The rheological behavior of a low epoxy resin system-SR8100/SD8734 for RTM in aviation industry was studied with viscosity experiments. The dual-Arrhenius rheological model and the improved engineering viscosity model were introduced and compared with the experimental data. The results indicated that the viscosity in the earlier stage calculated by dual-Arrhenius model matched the experimental data. As rising to 400 m·Pas, the viscosity calculated by the improved engineering model was closer to the experimental data. The processing windows of the resin system for RTM were determined by combining the two models, which could predict the rheological behavior of the resin system in a more credible way. 30-45 ℃ was the optimum processing temperature.     

EVA改性丙纶的流变性能

报道了用EVA对丙纶物理改性的实验研究,论述了这种改性丙纶的流变性能。由于引入极性基团,破坏了丙纶的高规整性导致的高度结晶,并且通过部分溶出改性剂生成微孔,从而大大改善了丙纶纤维的吸湿性能和导电性能。共混体系的粘度对温度和压力都有明显的依赖性,改性剂EVA的加入量不同影响了共混体系的粘度,在纺丝过程中值得注意。     

共振阶段带隔振台振动筛基础的动负荷

计算了带隔振台大型直线振动筛对地基的动负荷,研究了二次隔振与一次隔振两种情况下对于基础的动负荷,并进行了对比,重点研究了发生共振情况下阻尼对基础动负荷的影响,本文的工作对振动筛对基础的动负荷分析具有重要意义,为进一步研究振动筛和地基基础的藕合振动奠定了基础。     

P(PEGA-HAM)/PEG与PP共混蓄热调温纤维的制备及其性能

以P(PEGA-HAM)/PEG固-固相变粒子为相变材料(PCM)、以PP-g-PEGA为增容剂与成纤聚合物(PP)按不同比例混合,通过熔融纺丝工艺制备不同相变材料含量的蓄热调温纤维。IR测试分析确定了固-固型相变粒子的化学结构以及三元共混体系的化学组成;通过DSC、纤维强力仪以及SEM表征了蓄热纤维的热性能、力学性能以及外观形态;利用XRD和毛细管流变仪表征了三元共混体系的结晶性能和流变性能。结果表明,当PCM为12%、PP-g-PEGA为3%时,调温纤维的相变焓为12.17J/g,断裂强度为4.86cN/dtex,纤维表面光滑完整;P(PEGA-HAM)/PEG含量的增多破坏了PP基体中α晶的形成,使得PP的结晶度降低,三元共混体系的剪切黏度随着PCM的增多呈现先减小后增大的流变行为,剪切黏度随着温度的升高而降低。     

LDPE含量对LLDPE/LDPE共混物性能的影响

以线性低密度聚乙烯（LLDPE）与低密度聚乙烯（LDPE）为原料,经Brabender挤出机熔融吹膜制备出LLDPE/LDPE共混膜,并借助差示扫描量热仪（DSC）、偏光显微镜（POM）、电子万能试验机和毛细管流变仪研究了LLDPE/LDPE共混物的结晶行为、结晶形态、力学性能以及熔体流变性能.结果表明：加入适量LDPE后,共混膜仍然具有较好的综合力学性能.随着LDPE质量分数的增加,共混物的结晶度下降,晶粒尺寸减小;共混物的熔体流变性能提高.     

PROMOTER FLOW ACTION OF SOLID-STATE LOW MELT POINT METAL ON THE POLYPROPYLENE

With the aid of a slip-disentanglement theo-ry,a reological equation has been deduced about the compos-ite system of solid-state low melting point metal and poly-mer. By measuring some rheological properties of the compos-ite system composed of low melt point metal and polypropy-lene (LMPM/PP),the results show that LMPM has a pro-moter flow action upon PP when using a small amount ofLMPM and , if some coupled agents are added,the promoterflow action will be remarkable. Moreover, while LMPM beingadded into the composite,the temperature sensitivity of systemwill go up. This indicates that the system’s viscosity will dropfurther if its temperature is increased.     

聚合物多轴拉伸的网格模型

在聚合物加工成型中．薄膜双轴拉伸成型就是平面拉伸成型．随着聚合物在固相状态下加工的日愈发展，建立这种成型加工方式下的本构模型显得很迫切，国内尚无相关报道．本文介绍了聚合物多轴拉伸网格模型的研究进展，然后建立起聚合物多轴拉伸网格模型，并在此基础上阐述了Ball模型参数的确定以及模型的实验验证，为聚合物多轴拉伸的研究提供了有益的指导．     

基于功率平衡的振动筛横梁动态分析

以直线振动模型机的承重梁为研究对象,基于功率平衡的基本原理,利用Ritz级数法建立了承重梁的动力学模型,分析了承重梁附加物(筛体质量、激振器及减振弹簧等)所引起的附加力作用,并对承重梁进行了固有频率、振型及动态响应等动力学参数的理论计算.经过对设计的振动筛模型机进行的试验研究,理论计算与试验结果相吻合,表明利用功率平衡和Ritz级数法建立的动力学模型具有阶数低、计算稳定性好、精度较高等优点,计算所得的振动筛承重梁各种动力学特性参数能满足工程需要,能够为大型直线振动筛横梁结构的动态设计提供简便的动力学分析和计算方法.     

粘弹性流体流变特性的研究

以粘弹性流体聚丙烯酰胺水溶液为研究对象，用ＲＰＸ—７０５型高级流变仪，对不同配比（重量浓度小于８％）的聚丙烯酰胺水溶液体系进行了流变行为的测定，实验结果表明：当聚丙烯酰胺的含量在５００ｐｐｍ左右时，流体已有明显的弹性，但流体的粘度恒定，即为典型的Ｂｏｇｅｒ流体。当浓度超过１％时，已为典型的粘弹性流体。浓度为２％～８％范围内，聚丙烯酰胺溶液的粘度及第一法向应力差系数与剪切速率之间的关系均服从幂律关系。     

高含沙水流流变参数的试验研究

用极限浓度综合反映诸因素对高含沙水流流变参数——刚性系数和宾汉极限切应力的影响,提出了确定极限浓度的新方法,并根据流变试验资料,建立了精度较高、适用范围较广的流变参数表达式。     

The rheological property and foam morphology of linear polypropylene and long chain branching polypropylene

The rheological behavior, thermal properties and foam morphology of linear polypropylene and long chain branching polypropylene prepared through UV irradiation reactive extrusion were studied by rheological test, melt index test, DSC and supercritical carbon dioxide foaming technology. Rheological test and melt index test confirmed that under UV irradiation and extrusion, adding photo-initiator and crosslinking agent could achieve the purpose of branching, thus improved the melt strength of polypropylene effectively. The DSC results revealed that with the introducing of long chain branching, the melting range of the polypropylene broadened and the crystallization temperature increased. Owing to the introduction of long chain branches, polypropylene exhibited higher melt strength and strain hardening behavior. Compared with linear polypropylene, the foam morphologies of long chain branching polypropylene were more uniform.     

聚苯乙烯注塑成型制品双折射行为模拟分析

建立了模拟聚合物注塑成型过程中流动应力的数学模型.利用Leonov黏弹性模型对聚苯乙烯熔体在非等温幂率稳态剪切流下的流动行为进行模拟分析.并研究了聚苯乙烯在注塑成型填充过程中,由于流动而产生的剪切和拉伸作用以及模腔内聚合物熔体的温度变化对制品双折射行为的影响,得到了与实验相符的结果,证明了本研究中模拟方法的可行性.     

PET/纳米SiO2复合物的流变性及纺丝性能

聚合物纳米复合材料是现代材料学的重点研究内容之一,对于开发高性能、多功能性材料具有重要意义.本研究采用在合成聚对苯二甲酸乙二醇酯(PET)时直接添加纳米SiO2,制备了可用于纺丝的PET/纳米SiO2复合物.对复合物的流变性、可纺性及纤维力学性能的研究表明:PET/纳米SiO2复合物的熔体流变性属切力变稀流体,随剪切速率的增加,SiO2的增稠作用缓解,熔体粘度下降较大;升高温度也可使熔体粘度有较大下降.因此,可通过提高剪切速率或提高温度改善熔体的流动性能;在SiO2添加量小于2%时,可制得分子量较低、熔体粘度适宜于纺丝的聚酯复合物,该复合物可纺性良好,可用于制备抗起球聚酯纤维.