固相缩聚半芳香透明聚酰胺的流变性能

采用毛细管流变仪对固相缩聚半芳香透明聚酰胺(Semi-AromaticTransparent Polyamide,简称SATPA)的流变性能进行了研究。研究结果表明:固相缩聚SATPA熔体属假塑性流体,非牛顿指数随剪切速率的增大而减小;表观黏度随温度、剪切速率和剪切应力的升高而降低。随着剪切速率的增大,黏流活化能减小,表观黏度对于温度的敏感性减弱。     

Study of rheological property of nylon‐1212 with Haake Rheometer

Rheological properties of nylon‐1212 have been studied by means of Haake Rheometer. The effect of shear rate and temperature on the apparent vicosity of nylon‐1212 was discussed. A correlation of non‐Newtonian index with the temperature was obtained. The results showed that the apparent viscosity decreases with the increase of the temperature. With increasing shear rate, shear thinning of nylon‐1212 was observed clearly. From the relation of the temperature dependence of the polymer, we obtained the viscous flow activation energy. We conclude that the apparent viscosity is sensitive to temperature at lower shear stress because of higher viscous flow activation energy, and the temperature affect on the apparent viscosity becomes weaker at higher shear stress because of lower viscous flow activation energy. We have investigated the creep and elastic recovery of nylon‐1212. A creep test was carried out to define the linear viscoelastic range as 1.0 and 5.0 Pa for 195 and 190°C nylon‐1212 melts, respectively. A time‐dependent response was found for the creep and recovery phases at a lower applied shear stress. However, at higher shear stress, the creep and recovery phases were time‐independent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 379–385, 2003     

Melt shear viscosity of PP/Al(OH)3/Mg(OH)2 flame retardant composites at high extrusion rates

The melt apparent shear viscosity (η_a) of polypropylene (PP) composites filled with aluminum hydroxide [Al(OH)₃] and magnesium hydroxide [Mg(OH)₂] was measured by means of a capillary rheometer under experimental conditions of temperature ranging from 180 to 200°C and apparent shear rate varying from 10 to 2 × 10³ s⁻¹, to identify the effects of the filler particle content and size on the melt viscosity. The results showed that the melt shear flow of the composites obeyed the power law and presented pseudoplastic behavior. The dependence of η_a on temperature was consistent with the Arrhenius equation. The sensitivity of η_a for the composite melts to temperature was greater than that of the unfilled PP, and weakened with increasing apparent shear rate. The η_a increased linearly with an increase of the weigh fraction of the flame retardant, especially in the low apparent shear rate region. The η_a of the composites decreased slightly with an increase of particle size of flame retardant. Moreover, the variation for the η_a with particle size of flame retardant was much less than with apparent shear rate under these test conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

醚型阳离子染料可染共聚酯流变性能的研究

研究了醚型阳离子染料可染改性共聚酯(ECDP)的流变性能,与阳离子染料可染共聚酯(CDP)及聚对苯二甲酸乙二醇酯(PET)进行了比较。结果表明:ECDP属于切力变稀流体。在相同温度和剪切速率的条件下,与PET相比,CDP熔体的表观粘度(ηa)增加,ECDP的ηa下降;随着第四单体聚乙二醇含量的增加,ECDP的ηa、粘流活化能及结构粘度指数均下降,而非牛顿指数增加,流动性增强,可纺性得到改善。     

高黏度聚酯流变行为的研究

采用毛细管流变仪研究了高黏度聚酯(PET)的表观黏度及黏流活化能随温度(280～300℃)及剪切速率(20～104s-1)的变化。结果表明:高黏度PET熔体随着剪切速率的增加出现切力变稀现象,随着熔体温度升高,剪切速率对熔体的表观黏度的影响降低;高黏度PET的黏流活化能随着剪切速率的提高而降低;在温度为300℃,剪切速率为3 000 s-1时,高黏度PET熔体具有较好的流动性。     

进口聚苯硫醚树脂流变性能的研究

采用毛细管流变仪研究了日本聚苯硫醚(PPS)树脂的流变性能。结果表明:随着剪切速率的增加,PPS的表观粘度降低;当温度升高时,PPS的表观粘度也降低;剪切速率越高,温度对剪切速率的影响越小;随着温度的增加,非牛顿指数增加且趋近于1,PPS熔体为假塑性流体;PPS的粘流活化能随着温度的增加而减小;此外,随着温度的增加,结构粘度指数减小。     

Compatibility,steady and dynamic rheological behaviors of polylactide/poly(ethylene glycol) blends

Understanding the rheological behavior of plasticized polylactide (PLA) contributed to the optimization of processing conditions and revealed the microstructure–property relationships. In this study, the morphological, thermal, steady and dynamic rheological properties of the PLA/poly(ethylene glycol) (PEG) blends were investigated by scanning electron microscope, differential scanning calorimeter, and capillary and dynamic rheometers, respectively. The results illuminated that the melt shear flow basically fitted the power law, whereas the temperature dependence of the apparent shear viscosity (η_a) or complex viscosity (η*) followed the Arrhenius equation. Both the neat PLA and PLA/PEG blends exhibited shear‐thinning behavior. Because the incorporation of PEG reduced the intermolecular forces and improved the mobility of the PLA chains, the η_a, η*, and storage and loss moduli of the PLA/PEG blends decreased. The PEG content (W_PEG) ranged from 0 to 10 wt %, both η_a and η* decreased significantly. However, the decrements of η_a and η* became unremarkable when W_PEG exceeded 10 wt %. The reason was attributed to the occurrence of phase separation, which resulted in the decrease in the plasticization and lubrication efficiencies. This study demonstrated that the addition of the right amount of PEG obviously improved the flow properties of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42919.     

Explaining the abnormally high flow activation energy of thermoplastic polyurethanes

The rheological properties of a thermoplastic polyurethane (TPU) were studied at small and large deformation via three different types of rheometry: dynamic shear, capillary, and torque (an instrumented batch mixer). The effect of degradation during TPU processing on the melt viscosity was investigated and several factors, such as temperature, time, shear stress, and flow type that may affect the degradation were studied. Apparent activation energy of flow (E_a) was determined to be 328 kJ/mol, much larger than expected. A simple model was derived to describe the relationship of molecular weight and thermal dissociation of urethane linkages. Contributions of flow and the degradation reaction of TPU to overall activation energy were found to be additive: E_a=E_η+1.7ΔH_deg. True activation energy of flow (E_η) was estimated to be 144 kJ/mol. While the high apparent flow activation energies in dynamic shear and capillary rheometry can be explained by simple thermal degradation, melt viscosities interpreted from the instrumented batch mixer showed a much lower apparent activation energy (186 kJ/mol). This low value may be due to a combination of effects: errors in the relation between viscosity and mixer torque for TPU, side reactions resulting from air exposure, high stress level during the melting, and extensional stresses.     

On-Line Rheological Measurements and Mechanical Properties of Acrylonitrile-Butadiene-styrene/Corn Starch Composite

In this work, rheological and mechanical properties of acrylonitrile–butadiene–styrene/corn starch composites (ABS/starch) were studied. The composites were prepared using a laboratory-scale, single-screw extruder. Rheological properties were determined using the single-screw extruder, apparent shear rate (γ _a ), apparent shear stress (τ _a ), apparent viscosity (η _a ), non-Newtonian index (n), and flow activation energy at a constant shear rate (E _γ) and constant shear stress (E _τ). Mechanical properties in terms of tensile tests were performed using Testometric M350-10KN, stress at break, strain at break, and Young's modulus were determined. Rheological results showed that the composites are pseudo plastic in behavior, and the apparent viscosity of the composites increases with increasing starch content above the additive rule, which indicates a partial compatibility in the composite. It was also found that the flow activation energy of the composite increases with increasing starch content. The mechanical results showed that the strain at break of the composite decreases sharply by the presence of starch, whereas the Young's modulus increases with increasing starch content.     

Physical Characterization of a Commercial Suspoemulsion as a Reference for the Development of Suspoemulsions

Viscoelasticity, low shear flow, microstructure, and physical stability of a commercial suspoemulsion pesticide are studied to serve as a point of reference for the development of new suspoemulsions. Creep compliance tests allow the zero‐shear rate viscosity, η₀, to be calculated. As expected, the values of η₀ decrease with temperature. The storage modulus is higher than the loss modulus until a crossover frequency, ω*, which is located at the lower frequencies studied. The dynamic parameters decrease with higher temperature and ω* increases in agreement with a faster relaxation mechanism. Multiple light scattering predicts the occurrence of a creaming destabilization process, whose kinetics depends on temperature. Rheological measurements are demonstrated to be a powerful tool to assist in the prediction of destabilization processes together with the multiple light scattering technique.     

Comparative studies of rheological properties of polyacrylamide and partially hydrolyzed polyacrylamide solutions

The present work is concerned with experimental results of rheological characteristics of polyacrylamide (PAM) and of partially hydrolyzed polyacrylamide (HPAM) (degree of hydrolysis up to 80%) in aqueous and aqueous/sodium chloride solutions with changing experimental conditions such as polymer concentration, temperature, solvent quality, and shear rate applied. It has been observed that the all‐aqueous and aqueous/NaCl solution of PAM and of HPAM exhibited the non‐Newtonian behavior with shear‐thinning and shear‐thickening areas. The onset of shear‐thickening at depends mainly on the degree of HPAM hydrolysis, as well as on solution concentration, temperature, solvent quality, and polymer molecular weight. Rheological parameters from power law (Ostwald de Waele model) and activation energy of viscous flow (E_a) are determined and discussed. The changes in apparent shear viscosity during aging of solutions of PAM and HPAM are also described. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2235–2241, 2007     

纺丝用可熔性聚四氟乙烯的流变性能研究

采用毛细管流变仪,对PFA熔体的流变性能进行研究。讨论了温度、剪切速率对纺丝用PFA熔体的非牛顿指数、表观粘度、结构粘度指数等方面的影响。结果表明,PFA熔体非牛顿指数随温度上升而升高。在不同温度下,PFA熔体的粘度均随着剪切速率的增大而减小,表观粘流活化能随剪切速率增加而减小。PFA熔体的结构粘度指数Δη随熔体温度的增高而逐渐减小。     

Dynamic rheological behavior of poly(ether ketone ketone) from solid state to melt state

High performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η₀) and thermal activation energy E_a. Master curves were built and the shift factor a_T was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, E_a and η₀ were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46456.     

Rheological study of eucalyptus tar pitches

The development of advanced carbonaceous materials (ACMs) from biopitches is important to increase the revenue of the charcoal making industry and to stimulate the use of biomass, thereby attending to the appeals for environmental preservation. A pioneer study on the rheological behavior of eucalyptus tar pitches was carried out in this work. This behavior plays an important part in obtaining ACMs from pitch, particularly in the spinning step of carbon fiber production. Our results showed that biopitches have a strong dependence on the viscosity and temperature/softening point ratio. An Arrhenius‐type law gave the activation energies for viscous flow. Different from conventional polymers, this energy was higher for more polymerized pitches because of their higher molecular stiffness. The results obtained by the Williams–Landel–Ferry equation showed that the viscosity can be associated with the free volume. Lower viscosities correspond to larger free volume. The plot of the apparent viscosity versus the shear time at constant temperature and shear rate showed that the pitches have a purely viscous flow. Experiments that changed the shear rate showed that biopitches behave as Newtonian fluids. Purely viscous and Newtonian behaviors are desirable for more stable spinning. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 900–908, 2002; DOI 10.1002/app.10096     

Rheological properties of the blends of polychloroprene with poly[ethylene(vinyl acetate)]

Blends of poly[ethylene(vinylacetate)] (EVAc-45; 45% VAc content) and polychloroprene (CR) have been studied with respect to capillary and dynamic flow. It is found that EVAc-45, CR, and their blends are shear thinning (pseudoplastic) in nature. Though shear viscosity (η_a) and dynamic out-of-phase viscosity (η′_E) obeys power law, dynamic elongational viscosity (η′_E) does not follow it due to the synchronization of molecular vibration with the applied frequency at around 11 Hz. Both η_a and η′_E of the blends show positive deviation with respect to their additive values. The relative positive deviation (RPD) in shear flow increases with increasing temperature and shear rate. In the case of dynamic flow, RPD increases with increasing temperature but exhibits a decreasing trend with increasing frequency. RPD can be fitted well into a fifth-order equation with a weight fraction of CR (W_CR) in EVAc-45—CR blends. From rheological point of view, this relative positive deviation indicates blend compatibility between EVAc-45 and CR. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1759–1765, 1997     

Study on hyperbranched polyesters as rheological modifier for Spandex spinning solution

The rheological behavior of polyurethane (PU)/N,N‐dimethylformamide (DMF) spinning solutions with various contents of hyperbranched polyesters was studied using a RS150L‐controlled stress rotational rheometer. The results showed that the viscosity of the spinning solutions could be greatly reduced by adding hyperbranched polyesters even at 0.5 wt% loading. The zero‐shear viscosity of solutions with hyperbranched polyesters was much lower than that of pure PU/DMF solution, which indicated a lower degree of entanglement when solutions were in a static state. The apparent activation energy of viscous flow and the critical shear rate for shear thinning of solutions with hyperbranched polyesters were much lower than that for pure PU/DMF solution, which indicated a weaker entanglement structure formed. In addition, the effect of hyperbranched polyesters on the mechanical properties of Spandex fiber was discussed. Copyright © 2006 Society of Chemical Industry     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

聚苯硫醚流变行为研究

采用高压毛细管流变仪研究了进口聚苯硫醚(PPS)树脂的流变性能,分析了剪切速率、温度对PPS树脂流变行为的影响。结果表明,PPS树脂的非牛顿指数均小于1;在低剪切速率下,PPS树脂的表观黏度对温度的依赖程度高于高剪切速率下的依赖程度;PPS树脂的黏流活化能随剪切速率的增加呈减小趋势,其结构黏度指数随温度升高而减小。     

Rheological properties of glass bead-filled low-density polyethylene composite melts in capillary extrusion

The melt flow of glass bead-filled low-density polyethylene composites in extrusion have been observed by using a capillary rheometer to investigate the effects of temperature, shear rate, and filler content on the rheological properties of the melts. The results show that the melt shear flow obeys a power law, and the dependence of the apparent shear viscosity, η_app, on temperature is in accord with an Arrhenius equation. At the same temperature and shear rate, η_app increases slightly with increasing the volume fraction of glass beads, but the flow behavior index decreases with increasing filler content. In addition, the first normal stress difference of the melts linearly increases with increasing wall shear stress. Good agreement is shown with the N₁ calculated with the equation presented in this article and the pressured data from the sample melts. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1451–1456, 1999     

Preparation and properties of nano‐montmorillonite paper–plastic laminating adhesive

Emulsion paper–plastic nanometer laminating adhesive of 1.5% organic montmorillonite (OMMT) was prepared by OMMT intercalating polyacrylate‐system materials. In this article, it was discovered that nanometer‐laminating adhesive has better adhesion, smaller latex particles size, lower surface tension, and higher drying speed than general laminating adhesive. The rheologic behavior of the emulsion was discussed and it was shown that the value of n (the flow index of emulsion) was reduced and viscous flow activation energy (E_a) was increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 872–877, 2005