Determination of viscosities for alumina–polyethylene blends

The rheology of different proportions of low-density polyethylene (LDPE) and low-density polyethylene wax (LDWAX) without and with alumina was studied and correlated to a model. The viscosities of the polymer blend (LDPE + LDWAX) were studied for various compositions of LDWAX at different temperatures. The Arrhenius plot of logarithmic viscosity and reciprocal temperature for the polymer blends is linear. The enthalpy of viscous flow, determined from the slope of the Arrhenius Plot, varies linearly as a function of the average molecular weight. It is thus possible to predict the viscosity of any intermediate composition of the polymer blend. The viscosities of alumina-polymer blends (AP blend) with 50 vol% of alumina, prepared by solvent method, were also studied as a function of temperature, at a shear rate of 1333.33 s^–1. The AP blends show a lower enthalpy of viscous flow compared to pure polymer blend because of the presence of stearic acid used as surfactant for alumina. The model developed in this study enables the prediction of viscosities of AP blends at any weight average molecular weight (M _w) of the main binder and temperature.     

Thermoviscoelastic Properties of Phenolic Resin/Polymeric Isocyanate Binder Systems

Thermoviscoelastic properties of phenolic resin/polymeric isocyanate binder systems (i.e., ISOCURE Parts I and II) are reported. The effects of blend composition and the reaction between the binders on these properties of the systems are also considered. The viscous properties of binders and their blends were measured using computer-controlled rotational viscometers (Brookfield HBDV-II+ viscometer and HAAKE Rotovisco 12 rheometer in the cone-and-plate mode). The elastic properties of the phenolic urethane polymer (the blend composition) were measured by means of a modified jet thrust technique based on measuring the thrust of a liquid jet. Although both binders are Newtonian liquids, their blends exhibit viscoelastic non-Newtonian fluid flow behavior. The viscosity of the blends increases both with time and with an increasing Part I content and may reach comparatively high values at high values of either parameter. This behavior is explained as a result of the rubbery nature of the phenolic urethane polymer, which was produced as a product of reaction between Part I and Part II. The use of the jet thrust method allowed determination of the relaxation time of various blends at different shear rates.     

Correlation Between Miscibility and Rheological Characteristics of the Polystyrene (PS) and Poly(styrene-co-acrylonitrile) (PSAN) Blends

Rheological measurement has been an effective technique to characterize the miscibility of polymer blends. This article investigates the viscoelastic behavior of poly(styrene) (PS) and poly(styrene-co-acrylonitrile) (PSAN) binary solutions in tetrahydrofuran (THF) relative to PS/PSAN/THF ternary solutions mainly reporting the findings of the authors involving the correlation between the miscibility and rheological behavior. Rheological properties, such as shear viscosity, and shear stress as a function of shear rate were investigated for different blend compositions. Moreover, complex viscosity, loss and storage moduli were also investigated as functions of both the frequency and blend composition. The criterion of miscibility based on the rule of mixture has been discussed. The present study revealed very small window of miscibility as only composition, 50/50 showed values close to the additivity rule or intermediate to those of the neat polymers, thereby indicating very weak interactions between the blend components. On the basis of various findings during the rheological investigation, the blend under study is classified almost immiscible. Moreover, the obtained results also suggested that the miscibility depends on the blend composition and frequency.     

Thermal stability and melt rheology of poly(<Emphasis Type="Italic">p</Emphasis>-dioxanone)

Melt viscosities of poly(p-dioxanone) (PPDO) samples having different molecular weights were studied using a controlled-strain rotational rheometer under a nitrogen atmosphere. First, PPDO’s thermal stability was evaluated by recording changes in its viscosity with time. The result, that samples’ viscosities decreased with time when heated, demonstrated that PPDO is thermally unstable: its degradation activation energy, obtained by using a modified MacCallum equation, was a relatively low 71.8 kJ/mol K. Next, viscoelastic information was acquired through dynamic frequency measurements, which showed a shear thinning behavior among high molecular weight PPDOs, but a Newtonian flow behavior in a low molecular weight polymer (M _w = 18 kDa). Dynamic viscosity values were transferred to steady shear viscosities according to the Cox–Merz rule, and zero shear viscosities were derived according to the Cross model with a shear thinning index of 0.80. Then flow activation energy (48 kJ/mol K) was extrapolated for PPDO melts using an Arrhenius type equation. This activation energy is independent of polymer molecular weight. A linear relationship between zero shear viscosity and molecular weight was obtained using a double-logarithmic plot with a slope of 4.0, which is near the usually observed value of 3.4 for entangled linear polymers. Finally, the rheological behaviors of PPDO polymer blends having bimodal molecular weight distributions were investigated, with the results indicating that the relationship between zero shear viscosity and low molecular weight composition fraction can be described with a Christov model.     

Microstructural,thermal and rheological correlations to mechanical response of polyamide-6(glass filled)/polyetherimide blend: effect of ethylene-octene copolymer on toughening of blend

Melt mixed glass-filled polyamide 6(PA6)/polyetherimide (PEI) blends were prepared in a co-rotating twin screw extruder over the entire composition range of 0–100 wt% of polyamide 6. These blends were characterized by structural, rheological, mechanical and thermal properties. Crystallization behavior and phase morphology of the blends were also investigated. The blend with the composition PA6/PEI 75/25 showed overall improved mechanical properties along with low resultant viscosity which can be processed on standard equipment. Shear viscosity along with shear stress of the blends were analyzed using shear rheometer which concluded that the blends can be processed on standard equipment due to resultant low viscosity. Scanning electron microscope micrographs revealed that the morphology of the blends showed a two phase structure in which the minor phase was dispersed as domains in the continuous phase. Polyolefin elastomer (POE) as impact modifier was added to the above composition in the range of 0–15 phr to study its effect. The thermal characteristics of PA6, PEI, and PA6/PEI blends with and without POE were investigated using DSC and TGA which revealed that the melting temperature and crystallization temperature of the blend remained unchanged while XRD results showed percent crystallinity was increased slightly. Furthermore, it can be said that the blend with composition PA6/PEI 75/25 with 10 phr impact modifier loading was suitable for high end applications because it combines the high mechanical properties of glass-filled PA6 with inherent flame-retardant property of PEI while POE overcomes the physical weakness of moisture absorption.     

振动共混对聚丙烯/聚碳酸酯流变性能的影响

在传统转矩流变仪上叠加机械振动制成了振动共混流变仪。实验证明，振动共混降低了70／30聚碳酸酯／聚丙烯共混物的粘度和储存模量，随着制备时的振动振幅和频率的提高，这种效果更加突出。但过大振幅振动中，低剪切与高剪切间的频繁更换，特别是明显的低剪切下相翻转转慢，导致形成了部分不稳定“双连续”相态，这时共混物粘度和模量反而比小振幅振动下制备的共混物的高。一个描述该体系表面张力／液滴半径之比与剪切速率关系的经验表达式较好地分析了流变参数与微观相形态之间的关系，说明了振动促使分散相粒子的破碎和两相的分散，确实影响共混物的相形态。振动共混对聚丙烯／聚碳酸酯流变性能的影响上海交通大学化学化工学院高分子材料研究所，上海　200240振动共混　聚丙烯　聚碳酸酯　流变性能　影响　转矩共混流变仪　相形态在传统转矩流变仪上叠加机械振动制成了振动共混流变仪。实验证明，振动共混降低了70／30聚碳酸酯／聚丙烯共混物的粘度和储存模量，随着制备时的振动振幅和频率的提高，这种效果更加突出。但过大振幅振动中，低剪切与高剪切间的频繁更换，特别是明显的低剪切下相翻转转慢，导致形成了部分不稳定“双连续”相态，这时共混物粘度和模量反而比小振幅振动下制备的共混物的高。一个描述该体系表面张力／液滴半径之比与剪切速率关系的经验表达式较好地分析了流变参数与微观相形态之间的关系，说明了振动促使分散相粒子的破碎和两相的分散，确实影响共混物的相形态。     

V-POSS/MPE共混熔体的流变行为与力学性能

为研究笼型倍半硅氧烷(POSS)对茂金属聚乙烯(MPE)的改性作用,用毛细管流变仪研究了MPE与乙烯基笼型倍半硅氧烷(V-POSS)共混物熔体的流变行为;讨论了共混物组成、剪切应力、切变速率及温度对熔体流变性、非牛顿指数和挤出膨胀比及力学性能的影响。结果表明,加入V-POSS熔体的流动性随切应力增大而变好,假塑性增强,挤出膨胀比降低。在V-POSS的含量>2%后,非牛顿指数n值在0.50～0.55之间波动。V-POSS在共混体系中有增塑和交联剂两种作用,V-POSS含量为2%时共混物力学性能最佳。     

聚丙烯及其碳酸钙填充体系在外力场下的流变特性

以不同配比的CaCO3/PP共混物为研究对象,利用实验室自主研制的多功能全电动聚合物流变特性测试仪,研究了数据提取与处理方法、不同CaCO3填充量及加工工艺参数(剪切速率、振幅和振动频率)对体系流变特性的影响,以及数据提取与处理方法和振动参数对体系流变特性影响的差异性。试验结果表明:不同的数据提取与处理方法会影响聚合物的表观剪切黏度测试结果,在稳态条件下有显著差异,在振动力场作用下这种效应明显减弱;在低剪切速率区,共混体系的表观剪切黏度随着CaCO3填充量的增加而升高,在高剪切速率区,CaCO3填充量的影响程度大大减弱;共混体系的表观剪切黏度随着振动振幅的增加迅速下降,而随着振动频率的增加表现出类正弦周期性变化的特征。     

High-shear effects on the nano-dispersed structure of the PVDF/PA11 blends

The fabrication of miscible or nanostructured polymer blends or alloys raises much hope, but poses significant scientific and industrial challenges over the past several decades. Here, we propose a novel strategy using high-shear processing and demonstrate the high-shear effects on the nanodispersed structure formed in the poly(vinylidene fluoride) (PVDF)/polyamide 11 (PAll) blends, in which PA11 domains with a size of several tens of nanometers are dispersed in the PVDF phase. For the blend of PVDF/PA11 = 65/35, the TEM image shows that many nanometer-sized PAl1 particles are dispersed in the PVDF domain to form a special type of domain-in-domain morphology. In contrast, no PVDF nano-dispersion was observed in the PA11 phase. The effects of both the screw rotation speed and the mixing time on the blend structure were systematically studied. It shows that the extruder screw rotation speed and the mixing time are two critical factors to prepare the nanostructured blends. In addition, the investigations on the thermal behavior of the obtained blends indicate the improved miscibility between PVDF and PAl1 by the high shear processing.     

熔体的粘性和弹性对LDPE／PS共混物形态的影响

研究了粘性和弹性对低密度聚乙烯／聚苯乙烯共混物形态的影响。结果表明，不相容聚合物在均匀剪切流动中的分散程度以及分散相的形状与组分的粘度比、相对弹性和体积分数有关。当分散相的粘性和弹性较基相大得多时，随分散相的体积分数增加，球状的液滴形成葡萄串状。若两组分的粘性和弹性相当，在适中的混合比下，分散相产生高度变形。不管组分的粘反比和弹性比大小，若分散相的体积分数非常低，共混物的主要形态皆为分散相的球状液滴分散在基体中。     

Melt rheology and extrudate morphology studies of polystyrene/polybutadiene blends in the presence and absence of compatibilisers

Melt rheology and extrudate morphology of polystyrene (PS)/polybutadiene (PB) blends were studied with special reference to the effect of blend ratio and two different types of compatibilisers, the random copolymers and block copolymers. Uncompatibilized blends had viscosities approximately intermediate between those of the component polymers. In the case of uncompatibilized blends both positive and negative deviation was observed in the viscosity-composition curve at different shear rate range studied. The viscosity of the compatibilized blend was found to increase when a few percent of block copolymer was added. However, at high concentrations of the compatibiliser, the viscosity values leveled off. This is due to interfacial saturation. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the block copolymer was added followed by a clear leveling off at higher concentration. However, the random copolymer was not an effective interface modifier in agreement with microscopy study. These experimental results supports the earlier investigations of solid state NMR studies on these blends (Polymer (2005) 46(22):9385).     

Processing conditions, morphology and properties of a polycarbonate + a thermotropic polymer liquid crystal blend

We have investigated phase structure – properties relationships of polycarbonate (PC) + a polymer liquid crystal (PLC) blends processed in a twin-screw extruder at several conditions. The PLC is PET/0.82 PHB – a copolyester of poly(ethylene terephtalate) and p -hydroxybenzoic acid. For comparison the blend was additionally extruded in a wide range of shear rates in a capillary rheometer at two different spinning rates and compression-molded. The blend processed in the rheometer exhibits lower values of modulus and tensile strength than the blend extruded due to destruction of the initial orientation and dispersion level gained during extrusion. The orientation of PLC-rich islands increases up to the shear rate of 50–100 s^–1, whereas deformation at higher shear rates exhibits a droplet–breakup phenomenon, confirmed by SEM micrographs. The rheological measurements (oscillation mode) evidence a high shear thinning of the PLC. By contrast, the influence of the deformation rate on the viscosity for PC and the blend is negligible, suggesting also a low interaction level in the interfacial area. This conclusion was confirmed by dynamic mechanical measurements. As expected, our experiments prove that structure and properties of the blend are affected by processing (shear and elongation) conditions. Increasing shear rate leads to elongation of dispersed domains but exceeding critical values can lead to droplet breakup and destruction of created structure. The unique morphology created during extrusion can be destroyed during additional processing (in rheometer). Formation of fibrils is also dependent on additional treatment – spinning speed. Optimized spinning speed can lead to 50% increase in stiffness of the blend. Electronic Publication     

PTFE/PA6和PTFE/PA66共混物的吸水性及流变行为

通过浸水实验、缺口冲击断裂实验和动态流变测试,考察了PTFE含量对PTFE/PA6和PTFE/PA66共混物的吸水率、冲击断裂强度及熔体黏度的影响以及熔体黏度随温度和频率的变化规律。结果表明,PTFE/PA6和PTFE/PA66共混物的吸水率均随着PTFE含量的增加而减小,即PTFE的加入抑制了共混物的吸水性。两种共混物的冲击强度比纯PA明显降低,但是吸收水对两种共混物冲击强度的影响不显著。随着PTFE含量的增加,共混物熔体的黏度先减小后增加,说明适量的PTFE可以改善共混物的成型加工特性。共混物熔体的黏度随加载频率的增大而降低,符合假塑性流体流动规律。有趣的是,对于PTFE/PA6共混物的黏度随着温度的升高而减小,而PTFE/PA66共混物黏度随着温度升高近似成指数规律增大。     

稀溶液黏度法研究醋酸纤维素/聚乙烯吡咯烷酮共混物的相容性

以冰醋酸为共溶剂,利用乌氏黏度计在25℃研究了醋酸纤维素(CA)、聚乙烯吡咯烷酮(PVP)以及不同组成的CA/PVP共混物(CA的质量分数分别为0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9)的粘性行为。基于稀溶液黏度法确定的4种相容性判据(Δb,Δb’、Δ[η]m和α)探讨CA/PVP共混体系的相容性。实验结果表明,当醋酸纤维素在CA/PVP共混体系中的质量分数低于0.12或者在0.8～0.91范围内时,CA与PVP是相容的,其余的组成体系都是不相容的。因此,CA/PVP共混体系是部分相容体系。     

Characterization of Gamma Irradiated Plasticized Carboxymethyl Cellulose (CMC)/Gum Arabic (GA) Polymer Blends as Absorbents for Dyestuffs

Polymer blends based on carboxymethylcellulose (CMC) and gum arabic (GA) were prepared by solution casting method. Glycerol was added to the polymer blend solution as a plasticizer with different ratios (2·5, 5, 10 and 20%). Then, the plasticized blends were exposed to gamma irradiation at different doses (5, 10 and 20 kGy). The physical properties of the plasticized polymer blends were investigated in terms of gel fraction (%) and swelling percent (%). Thermal properties were investigated by TGA. Also, the structure of the plasticized polymer blends was characterized by Fourier transform infrared spectroscopy. Scanning electron microscope was investigated in order to examine the compatibility between two polymers in the blend and also between polymer blend and plasticizer. The prepared plasticized polymer blends were used as an adsorbent for different dyestuffs. The sorption of dyestuffs by the plasticized polymer blend was determined by a method based on spectroscopic analysis. The results showed that the plasticized polymer blend has a high affinity for basic, acid, reactive and direct dyes. The obtained results showed that using glycerol as plasticizer improved the swellability of polymer blend and also the dye uptake (%).     

基于分子模型的支化聚合物流变性能模拟

通过布朗(Brown)动力学方法模拟了有限伸展非线性弹性(FENE)珠-簧链支化聚合物分子模型在稳态和瞬态剪切流场中的运动,得到分子构象信息,同时对支化聚合物分子力场进行计算分析,模拟支化聚合物流变性质,研究支链长度、弹簧模型参数和剪切速率等对该模型定常与非定常流变性质的影响。结果表明,珠簧链模型能够较好地描述支化聚合物分子结构,随支链长度的增加,支化聚合物黏度升高,随剪切速率的升高,伴随有假塑性剪切变稀现象发生,并且弹簧拉伸常数不同,支化聚合物黏度稳态值也不同。     

Biodegradable aliphatic polyester-poly (epichlorohydrin) blend/organoclay nanocomposites; synthesis and rheological characterization

Polymer/organoclay nanocomposite systems were prepared from biodegradable aliphatic polyester (BAP)-poly(epichlorohydrin) (PECH) blends via the solvent casting method. From X-ray diffraction analysis, it was confirmed that the increased interlayer distance of the clay was solely affected by the BAP, implying that the BAP has better affinity to clay than PECH in a competitive intercalation mechanism. To clarify the sole effect of clay on polymer blend nanocomposite systems, we fixed the clay content at 3 wt%. The mechanical properties and rheological characteristics in steady and oscillatory shear modes of BAP-PECH/clay nanocomposites were investigated and compared with those of BAP-PECH blends without clay.     

PVDF、LCP及其共混物的流变行为

研究了ＰＶＤＦ、ＬＣＰ的表观粘度随温度,剪切速率的变化规律,并对液晶含量对共混物熔体度的影响进行了讨论。     

Phase Diagram for Predicting In Situ Fibrillation of LCP During Molding

The present work represents an important attempt at constructing a phase diagram for predicting the type and extent of fibrillation of the liquid crystalline polymer (LCP) phase in LCP-based polymer blends. A polycarbonate (PC)/LCP polymer blend was utilized in the current study. The combined effects of three factors, namely, the shear rate, the LCP content in the blend, and interfacial adhesion between the LCP phase and the matrix polymer (PC) were considered. In contrast, work in reported literature has usually considered the individual effect of only one or at most two of these three factors. A thermotropic liquid crystalline polymer, LC5000, consisting of 80/20 of hydroxybenzoic acid and poly(terephthalate) was employed. The effect of interfacial adhesion between the LCP and the PC matrix on fibrillation was considered by using a compatibilizer for the PC/LCP blend. It was demonstrated that the constructed phase diagram could successfully be used to predict and illustrate the conditions under which in situ fibrillation of the LCP phase would occur in the LCP-based blend.     

Mechanical, morphological and thermal properties of in situ ternary composites based on poly(ether imide), silicone rubber and liquid crystalline polymer

A compatibilization method for improving the mechanical and thermal properties of thermoplastic/thermotropic liquid crystalline polymer (LCP) blends has been tested in blends of poly(ether imide), PEI, with a thermotropic copolyester (Vectra B-950). It is based on the addition of a third component, a functionalized elastomer (hydroxy terminated silicone rubber), to the blend that interacts with the matrix polymer and the thermotropic liquid crystalline polymer, facilitates the structural development of the thermotropic liquid crystalline polymers (TLCP) phase by acting as a compatibilizer at the interface. The main properties of blends required are flexibility of material in presence of compatibilizer. The viscosity of the compatibilized in situ composite was increased by the silicone rubber owing to the strong interaction. The coefficient of thermal expansion (CTE) of PEI/TLCP blend becomes lowered when the content of silicone rubber is increased. Morphological observation showed that the addition of compatibilizer significantly reduced the size of the dispersed LCP phase and improved their dispersion within the matrix. Measurement of the tensile properties shows increased strength as well as enhanced modulus and elongation when PEI/TLCP blend is properly compatibilized. This is attributed to fine fibril generation induced by the addition of compatibilizer.