旋转流变仪及其技术在聚乙烯中的表征应用研究

通过使用旋转流变仪,对HDPE(高密度聚乙烯)、LDPE(低密度聚乙烯)聚合物进行一系列的流变试验,从得到的流变曲线、粘度曲线,着重分析了剪切速率、粘度、模量、分子量分布、弹性效应等因素对材料流变行为的影响,从而获得聚合物在相应加工过程中的流变数据,为产品评定、工艺调试等提供理论和技术方面的指导。     

国外合成树脂及塑料文摘

ＮＲ和ＥＰＤＭ对ＨＤＰＥ／ＰＰ共混物流动行为的影响／Ｈｅｒｎａｎｄｅｚ Ｓａｎｃｈｅｚ,Ｆ．（墨西哥）／Ｐｏｌｙｍ．Ｂｕｌｌ．（Ｂｅｒｌｉｎ） 1999,42（4）：481～ 488（英）。在不同共混比和剪切速率下,作者研究了聚丙烯（ＰＰ）和高密度聚乙烯（ＨＤＰＥ）与一种弹性体（天然的或乙烯—丙烯—二烯共聚物）的三元共混物的熔体流变性能。给出了流变仪测量结果,并讨论了共混物组成对流变性能的影响。根据非牛顿流体指数定律讨论了剪切速率对粘流曲线的影响。聚烯烃共混物中加入弹性体使粘度—组成曲线发生了变化。根据共混物可…     

HDPE树脂流变参数与分子量分布的关系研究

测定了4种高密度聚乙烯(HDPE)树脂的分子量及其分布,研究了其毛细管流变行为和动态流变行为,并分析了得到的流变参数和分子量分布的关系。结果表明:仅在较低挤出速度或较高温度条件下,用毛细管流变测得的非牛顿指数才能用作分子量分布的量度;用动态流变测得的剪切变稀指数、流变多分散指数、幂率指数均可在一定程度上反映了HDPE树脂分子量分布的大小,其中幂率指数与分子量分布的相关性最好(相关系数r2=0.994)。     

用熔体的零切粘度和熔融指数研究聚丙烯的分子量分布

本文采用自制落球粘度计测定了用高效催化剂和化学降解两种方法生产的常用纤维级聚丙烯的零切粘度η_0,并与熔融指数仪测得的熔融指数MI值相结合求得聚丙烯分子量分布指数α值。研究表明,本法测得的η_0与熔体流变仪测得的η_0基本相符。本文还探讨了影响η_0测试的诸因素,在正确操作情况下,测试误差可小于5%。本仪器简单、价廉,在聚丙烯生产厂可推广使用作为指导生产工艺的依据。     

高分子分子量、分子量分布与熔体指数（MI）关系的研究（Ⅰ）──熔体指数（MI）与分子量、分子量分布关系的理论模型及关联式

本文考察了有关零剪切速率下高聚物熔体粘度与分子量、分子量分布及星形支化结构之间关系，用应力张量，高分子链间缠结数目及分子量变化率之间的自相似变化模型理论，推导了一个普适方程，用来关联熔体指数（ＭＩ）与分子量（Ｍｗ），分子量分布（）及Ｍａｒｋ－Ｈｏｕｗｉｎｋ常数之间关系，为进一步研究和验证提供了理论依据。     

PP/Mg(OH)_2阻燃复合材料流变行为的研究

用日本岛津ＡＧ－２０００型毛细管流变仪，在几个温度下，研究了ＰＰ和ＰＰ／Ｍｇ（ＯＨ）２阻燃复合材料的流变行为。研究结果表明：ＰＰ／Ｍｇ（ＯＨ）２阻燃复合材料熔体流变行为同ＰＰ一样，仍属于非牛顿型假塑性行为；在２００℃温度，相同剪切速率下，ＰＰ和ＰＰ／Ｍｇ（ＯＨ）２阻燃复合材料的粘流活化能十分接近，１０３Ｓ－１剪切速率下，ＰＰ／Ｍｇ（ＯＨ）２阻燃复合材料熔体粘流活化能为３．７１４Ｋｃａｌ／ｍｏｌ，与ＰＰ相差只有０．０３７Ｋｋｃａ／ｍｏｌ，挤出胀大比为１．２９，低于ＰＰ。     

国产Z30S聚丙烯纺制细旦丙纶复丝的研究

研究了国产Ｚ３０Ｓ聚丙烯及其改性切片的分子量（ＭＷ）和分子量分布（ＭＷＤ）以及纺丝工艺对纺制细旦丙纶复丝可纺性和卷绕丝结构性质的影响。研究表明，采用Ｚ３０Ｓ切片即使纺丝温度高达２８０℃时，卷绕丝仍是α晶型结构，若添加少量降温母粒共纺或经改性后纺丝，卷绕丝可获得准晶型或混晶型结构，有较好的可纺性和后拉伸性；纺丝工艺条件，诸如纺丝温度、冷却条件、泵供量和纺丝速度等对卷绕丝的结构和性质虽起重要的影响，但ＰＰ的ＭＷ和ＭＷＤ则起首要的影响。     

二维平板制件注塑充模流动计算机分析

用Ｃ－Ｍｏｌｄ软件对二维平板制件（海尔洗碗机盖）注塑充模过程进行计算机流动模拟分析，应用动态应力流变仪测试所用材料ＰＰ１３００和ＨＩＰＳ４９２动态流变性能，由Ｃｏｘ－Ｍｅｒｚ规则得到宽剪切速率范围的粘度，用改进Ｃｒｏｓ模型拟合得到ｎ、Ｂ、τ、β、Ｔｂ等参数。研究了注射温度、注射时间、浇口位置、材料性质对充模过程的影响；利用优化螺杆速率分布考察了浇口位置、注射温度、注射时间、保压压力等对锁模力、熔体入口压力的影响，结果表明，对ＰＰ１３００而言较佳工艺为注射时间４ｓ，注射温度２３０℃，保压时间２５～３０ｓ，最大注射压力４０ＭＰａ，并将原浇口向左偏离３０ｍｍ。     

BA氯化接枝改性CPVC流变行为的研究

采用氯化原位接枝法制备改性CPVC，在氯化的同时加入丙烯酸丁酯（BA）得到CPVC-g-PBA，利用毛细管流变仪研究了CPVC和CPVC-g-PBA的流变行为，讨论了两者的剪切应力和剪切速率以及温度对熔体流变行为、熔体粘度的的的影响，并测定了其非牛顿指数。     

氨纶纺丝熔体的流变行为

笔者应用毛细管流变仪研究了自制熔纺氨纶切片的流变行为，探讨了熔体表现粘度、非牛顿指数、结构粘度指数、表观粘流活化能等流变特性与温度及剪切速率的关系。结果发现，氨纶熔体为切力变稀流体，其非牛顿指数随温度的升高而增大，在210℃时达到最大值。结构粘度指数随温度升高而下降，在210℃时达到最小值，说明在此温度下熔体的可纺性最好。溶体表观粘度与温度的相关性显著，并且随着剪切速率的增大，聚氨酯熔体的粘流活化能减小。     

Comments on the accuracy of zero shear intrinsic viscosity of high molecular weight polyacrylamide

The intrinsic viscosity of a polymer is traditionally measured with a capillary tube viscometer where the shear rate range is moderately high. Such method is valid when the polymers are non-ionic and have low to moderate molecular weight. The viscosity-shear rate curves obtained for dilute aqueous solutions of two high molecular weight polyacrylamides using two rotational viscometers indicate a strong shear-dependent viscosity in the medium to high shear rate regions. The zero shear intrinsic viscosity of the polymers determined by extrapolation from the high shear rate region to the zero shear condition may result in large errors. Its implication in predicting the molecular weight of polymers using the Mark-Houwink-Sakurada equation is discussed. A rheological equation for intrinsic viscosity as a function of shear rate is proposed.     

相对分子质量及其分布对烯烃共聚物动态流变性能的影响

通过对一系列具有不同相对分子质量和相对分子质量分布的乙烯/α-烯烃（丁烯和己烯）共聚物的动态流变行为测试,研究了相对分子质量及其分布（即多分散性）对储能模量与频率、损耗模量与频率以及储能模量与损耗模量在低频区的关系曲线斜率的影响规律。结果表明：储能模量、损耗模量与频率以及储能模量与损耗模量的关系曲线的斜率不仅均低于理想的单分散体系,而且均随着相对分子质量或相对分子质量分布的增加而降低。     

Influence of pH and protei thermal treatment on the rheology of pea protein-stabilized oil-in-water emulsions

The influence of emulsion pH and previous thermal treatment of the protein on the rheological behavior of pea protein-stabilized emulsions has been studied. Oil-in-water emulsions with 65% weight oil and 6% weight pea protein isolate were prepared. Emulsion pH was varied between 3.5 and 7.0. In addition to this, the protein aqueous phase was submitted to different previous thermal treatments by modifying temperature from 25 to 90°C and heating time from 20 to 60 min. To study the influence of the above-mentioned variables, droplet size distribution and steady-state flow curves were determined, and linear viscoelastic measurements were carried out. An increase in the pH of the emulsion initially leads to an increase in emulsion viscosity and viscoelastic functions, as well as to a decrease in the mean droplet size, up to an emulsion pH close to the protein isoelectric point, where a singular rheological behavior is found. An increase in temperature or heating time on the protein aqueous phase yields higher values of steady-state viscosity and linear viscoelasticity functions, up to a complete denaturation of the protein.     

树脂类型对PVC溶胶流变性能的影响

研究了不同生产方法糊树脂制备的聚氯乙烯（PVC）溶胶,在旋转流变仪程序升温模式下的流变性能。通过扫描电子显微镜、激光粒度仪和凝胶渗透色谱仪研究了PVC糊树脂的颗粒形貌、粒度及分布以及相对分子质量及相对分子质量分布特征,从而建立了PVC溶胶流变性能参数与糊树脂特性参数间的关系。结果表明,随着温度的升高,PVC溶胶的储能模量、损耗模量和复数黏度等流变参数呈非正态分布变化趋势,可分为4个阶段：前三阶段,流变参数先降低,后由缓慢升高至急速升高,形成一个肩峰并达到一个最大值,黏度变化趋势与树脂颗粒形态有关;第四阶段,流变参数逐步变小,黏度主要受树脂相对分子质量及相对分子质量分布的影响。     

High pressure polymerization of ethylene and rheological behavior of polyethylene product

A mathematical model of the high pressure polymerization of ethylene in tubular reactors was tested with experimental data obtained from an industrial size tubular reactor. Series of experiments involving changes in operating conditions were carried out, and process data and polyethylene samples were collected. The collected samples were characterized for their molecular weight distributions and various rheological material functions involving shear and extensional flows. The findings of the model were compared against the generated process data and the molecular weight distributions of the samples. The determined rheological behavior exhibited strong dependence on the primary characteristics of the resins. Overall, this study should introduce a better understanding of the interactions between high pressure reaction conditions and the primary properties of polyethylene, including moments of molecular weight distribution and extent of branching on one hand and the interrelationships between primary properties and the rheological behavior of the high pressure polyethylene product on the other hand.     

超高相对分子质量聚乙烯冻胶的流变行为研究

研究了超高相对分子质量聚乙烯(UHMWPE)冻胶的流变特性,以及温度、相对分子质量对冻胶 的lgη_a-lgγ流动曲线、非牛顿指数和结构粘度指数的影响。结果表明:UHMWPE冻胶属于宾汉流体,具 有明显的非牛顿性,结构粘度指数随UHMWPE相对分子质量的增大而增大,随冻胶温度的升高而降低。     

Effect of chain structure on the melt rheology of modified polypropylene

The effect of molecular structure of polypropylene (PP) on the melt rheological properties were investigated for electron irradiated polymer and di-2-ethylhexyl peroxy dicarbonate (EHPC)-treated polymer. The modifications were examined in terms of the rheological behaviors, molecular weight distribution, and the degree of branching. The high melt strength PP was obtained by irradiating with 50 and 80 kGy and adding EHPC. The modified PPs showed the strain hardening in the uniaxial elongational viscosity, though the linear elongational viscosity was lower than that of the unmodified PP. Low angle laser light-scattering measurements of the modified PPs showed the interesting results; high irradiation doses such as 50 and 80 kGy caused higher molecular weight chains branching. Nevertheless, the long branching chains were not detected for the EHPC modified PP, which also showed the strain hardening in uniaxial elongational flow. In this article, the relation between chain structure and rheological properties is discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1493–1500, 1999     

多分散聚合物稀溶液体系的Rouse模型

本文将Rouse提出的均一分布球簧链式分子模型加以推广.得到了多分散体系的本构方程.对几种最常见的分子量分布,在稳态剪切流中,分别计算了它们的物质函数以及特性粘数与重均聚合度的关系.结果表明,这一线性模型的流变性质与聚合物的分子量分布有密切的关系;若通过物质函数的监测,则还能预示聚合反应的动态过程.     

Study of mechanical and rheological behaviors of linear and branched polycarbonates blends

A study of the mechanical and rheological properties of linear and branched polycarbonates blends is presented. Phase separations of the blends were checked through DSC and SEM, and, subsequently, mechanical and rheological properties were investigated. Phase separations were not observed in the blends. The mechanical properties were examined through tensile, flexural, and impact tests. All the mechanical properties of the blends were relatively independent of the compositions. For study of the rheological properties, melt viscosity, storage and loss moduli, and melt tension of the blends with various compositions were examined at various temperatures. The dependence of the viscosity on the molecular weight was also studied. As the content of branched polycarbonate increases, the dependence of the viscosity on the molecular weight and the shear thinning behavior became more marked. Melt tensions were also increased as the branched polycarbonate content increased in the blends for all tested temperatures. In this study, the blend systems which have same mechanical properties but different rheological properties can be obtained through blending of linear and branched polycarbonates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1814–1824, 2001     

A unifying approach for melt rheology of linear polystyrene

Several studies of melt rheological properties of polystyrene have been conducted over the past 50 years. Several approaches, including empirical models, have been developed to understand the behavior of materials using simple equations. The existing melt rheology models are best suited for high‐molecular‐weight polymers whose T_g does not vary. In this work, a semiempirical viscosity equation has been derived, including the effect of T_g dependence on molecular weight, to describe the melt rheology of low‐molecular‐weight polymers. The equation is derived based on a combination of well‐known concepts, such as the effects of free volume and molecular dynamics on polymer rheology. This provides a better understanding of the rheological behavior in the low‐molecular‐weight regime with respect to temperature and molecular weight. Because of the industrial trend towards lower molecular weight materials for applications such as high solids coatings, this unifying approach, based on the free volume theory with a simple expression, is of extreme practical significance. This equation can predict the zero shear viscosity behavior for different molecular weights, including low‐molecular‐weight regions, and temperatures. Viscosity calculations using the empirical equation agree with published experimental data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2597–2607, 2007