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The rheological behavior of ultrahigh molecular weight polyethylene (UHMWPE) semidilute solutions with different solvents has been studied. In a temperature range of 150–185°C, the viscosity of a UHMWPE semidilute solution with paraffin oil as solvent (soln 1) is more temperature-independent and viscosity-stable than that with decalin as solvent (soln 2). Usually the reduction of the molecular entanglement density in solution causes a rapid reduction in viscosity. Apparently soln 1 has a different entanglement density compared with soln 2. The activation energy of UHMWPE semidilute solutions changes with both shear stress and shear rate. The regressive equations for both solutions in between Eσ and σ or E? and $ {\dot \gamma } $ have been obtained from a least-squares method. Finally, there is a discontinuity in the non-Newtonian flow region of η vs. $ \dot \gamma ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $ curve, no matter which temperature or solvent was used. The discontinuity occurs at a shear rate of about 70 s?1, where a transformation from a qualitative change in entanglement in the solution takes place. 相似文献
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The effect of aluminium stearate on the rheological behavior of ultra-high molecular weight polyethylene (UHMWPE) semidilute solutions with paraffin oil as the solvent has been investigated. Adding aluminium stearate to paraffin oil can prevent the spinning solution from adhering to the pipe or screw, greatly improving the flow behavior of UHMWPE solutions. The geometric sizes of spinnerette hole, such as length–diameter ratio L/D and entrance angle of a capillary, also affect the flow behavior of the spinning solution. The calculated first normal stress difference σ11 ? σ22 and the Bagley-end correction e from experimental data show that the elastic effect on spinning solutions in flow is quite large, although the shear rate is below 20 s?1. 相似文献
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Rheological behaviors of ultrahigh-molecular-weight polyethylene (PE)/high-density PE/SiO2 blends are investigated using parallel-plate rheometer and capillary rheometer. The molecular chain conformational change mechanism is used to explain flow instabilities during extrusion. The viewpoints are proposed: (1) critical shear rate depends on the relative strength of irreversible viscous loss and reversible elastic orientation for molecular chains in transverse velocity gradient field inside the die and (2) critical shear stress depends on the extent of molecular chain conformational change inside the die, and the ease of conformational recovery after leaving the die. Modified nano-SiO2 particles are detected a certain interfacial adhesion in PE matrix. The interfacial interaction limits viscous flow inside the die and conformational recovery after leaving the die, thus causing not only the flow instabilities to occur prematurely on shear rate and delaying sharkskin on shear stress, but also an alternate “sharkskin-melt fracture” appearance after global extrusion fracture. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47713. 相似文献
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通过添加质量分数为0~2.0%的金属离子配位剂(M)、质量分数为7.5%~12.0%的亲水性环保型增塑剂(A)和质量分数为0~2.0%的聚醚类增塑剂(B),制备了用于熔融纺丝的改性PVA;采用毛细管流变仪研究了改性PVA体系在120~135℃的流变行为。结果表明:改性PVA流体是一种对剪切作用敏感的假塑性流体;在相同温度和剪切速率下,随M含量的增加,改性PVA熔体的表观黏度、剪切敏感性、温度敏感性、非牛顿性上升,可纺性下降;随A含量的增加,改性PVA熔体的表观黏度、温度敏感性、非牛顿性下降,剪切敏感性、可纺性上升;随B含量的增加,改性PVA熔体表观黏度、剪切敏感性、温度敏感性、非牛顿性呈先下降后上升的趋势,而可纺性呈先上升后下降的趋势。改性PVA在135℃和少量M存在的条件下,A质量分数为12.0%、B质量分数为0.5%~1.0%时,适合熔融纺丝。 相似文献
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Rodrigo Alvarenga Rezende Paulo Jorge Bártolo Ausenda Mendes Rubens Maciel Filho 《应用聚合物科学杂志》2009,113(6):3866-3871
The rheological behavior of alginate solutions were investigated for the optimal design of a biomanufacturing system to produce alginate structures for tissue engineering. Its rheological properties were determined by a rheometer through rotational and oscillatory tests. Experimental results were used to model the alginate solutions characteristics. The findings suggest that alginate solutions undergo shear‐thinning effects with increasing shear rates. It is also possible to observe that its loss modulus is higher than the storage modulus ones being both modulus dependent upon the frequency, which is a typical characteristic of dilute solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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Jong‐Hwan Park Ho‐gyum Kim Dong‐Hee Han Jeong‐Cheol Lim Dae‐Hee Oh Kyung‐Eun Min 《应用聚合物科学杂志》2007,103(4):2481-2486
The rheological properties of hydrophilic fumed silica dispersed in polyethylene glycol (PEG) were investigated. The dispersion was prepared by dispersing the fumed silica in PEG with various concentrations. The reversible sol–gel transition was observed over 5 wt % of silica concentration as a function of temperature. The gelation temperature was found to depend on the applied shear stress and silica concentration, and the high shear stress was found to lead to the decrease of sol–gel transition temperature of the dispersion with the same silica concentration. As the silica concentration increases, the sol–gel transition shifts to the lower temperature. © 2006 Wiley Periodicals, Inc. J Apple Polly Sci 103: 2481–2486, 2007 相似文献
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Three types of high-strength polyethylene (PE) fiber-reinforced composite sheets were made by compression molding at the vicinity of melting point of the fiber. Sheet I was molded from only PE fibers. Sheets II and III were prepared by the compression molding of PE fiber with conventional high- and low-density polyethylene films, respectively. The mechanical properties, thermal behavior, and morphologies of the sheets have been investigated and compared with each other. The tensile strength and elastic modulus of sheet III are 660 MPa and 14 GPa, respectively, which were 60 and 30 times higher than those of typical low-density PE film. Although the elastic modulus of sheet III is 6 GPa less than that of sheet II, the tensile strength of 660 MPa is highest in the three types of sheets prepared in this study. The mechanical properties of sheets II and III were about half of predicted theoretical ones. It was concluded that the interfacial adhesion between PE fiber and PE matrix was an important factor to improve the mechanical properties of this PE sheet. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1431–1439, 1998 相似文献
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The pore structure of filled films of ultrahigh-molecular-weight polyethylene fabricated by gel technology was investigated
by IR spectroscopy and optical microscopy. The sorption capacity of films containing nanoparticles of zeolite and montmorillonite
with respect to alkali and alkaline-earth metals was determined as a function of the degree of filling.
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Translated from Khimicheskie Volokna, No. 2, pp. 33–37, March–April, 2007. 相似文献
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Understanding the rheological behavior of collagen/chitosan blends is fundamental to design the optimized collagen/chitosan composite materials. Steady shear, dynamic frequency sweep, thixotropy and creep-recovery tests were investigated to characterize the rheological behavior of collagen/chitosan blends as a function of chitosan content (0%–90% [wt/wt]). All the samples showed pseudoplasticity with shear-thinning behavior. With the increase of chitosan, the viscosity significantly decreased from 862.54 to 0.60 Pa s at 0.05 s−1. The storage modulus and loss modulus also decreased while the dynamic denaturation temperature increased from 39.79 to 45.18°C. Besides, the thixotropy weakened and when the chitosan content reached 70%, the final recovery percentage was only 4.6%. The entanglements between collagen fibers observed by atomic force microscopy became weaker. Finally, the corresponding mathematical models were used to simulate the experimental data, and the obtained parameters might provide some useful theoretical guidance for the processing of the collagen/chitosan blended solutions. 相似文献
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We have characterized the melt rheological behavior and the solid tensile properties of sawdust/polyethylene composites prepared in an internal mixer. Various concentrations (from 0 to 60 wt %) and three particle sizes have been tested, in presence of a coupling agent (maleic anhydride grafted polyethylene). In the molten state, for each particle size, a mastercurve of the complex viscosity as function of frequency can be plotted, using a shift factor depending on weight fraction. We show that the shift factors can be described by a Krieger‐Dougherty law, leading to a “universal” viscosity law of the Carreau‐Yasuda type. In the solid state, the presence of sawdust increases Young modulus in uniaxial elongation, mainly for small size particles, but reduces dramatically deformation at break and tensile strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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The overall performance of coated products is determined by the intrinsic material properties in solution and processing conditions. To characterize the behavior of these materials, the viscosity of polymers in solution at various concentrations was measured and the experimental data were fitted with the Carreau model. The results describe the rheological behavior of coating materials, and provide a basis for the modeling of polymer flow during the coating process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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T. A. Anan’eva A. Yu. Kuznetsov E. P. Shirshova S. D. Khizhnyak P. M. Pakhomov 《Fibre Chemistry》2008,40(3):173-178
The effect of the thermodynamic quality of the solvent on the properties of polymer solutions was determined. Thermal annealing
affects formation of the structure and the mechanical properties of UHMPE. Fourier transform IR spectroscopy revealed the
effect of the filler on the structure of the polymer matrix. The morphology of filled UHMPE fibres was characterized by optical
microscopy; the fibres have a longitudinally oriented structure and the filler aggregates in particles up to 50 μm in size,
which does not allow classifying the materials obtained as nanocomposites.
Translated from Khimicheskie Volokna, No. 3, pp. 4–8, May–June, 2008. 相似文献
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We report on a comparative study of the rheological properties of guar [GG], methyl guar [MG], hydroxypropyl guar [HPG] and hydroxypropyl-methyl guar [MHPG] polymers aqueous solutions in semidilute (both unentangled and entangled) and concentrated regimes, using oscillatory and steady-shear techniques. In the dilute regime, molecular weights and radii of gyration have been investigated by means of light scattering measurements.Data obtained from steady-shear rheology were satisfactorily analyzed according to Cross model and the effects of polymer concentration and temperature on the rheological behaviour of guar and guar derivatives have been investigated and discussed in terms of rheological parameters, such as the zero-shear viscosity η0, the characteristic time τ and critical coil-overlap concentration C∗.The storage and loss moduli of guar and guar derivatives aqueous solutions have been measured using angular frequencies in the range between 10−3 and 10 rad/s. The data have been analyzed using the “blob” model for semidilute solutions and the scaling approach proposed by Rubinstein, Dobrynin and Colby for concentrated solutions. These rheological parameters obey a time-concentration superposition principle, so that master curves can be constructed over a wide frequency range. Moreover, we show that, at lower temperatures, these systems behave as thermo-rheological simple systems, in that the oscillatory shear response at different temperatures can be superimposed according to the empirical time-temperature superposition principle. Although these systems can be conveniently described within a unifying scaling model, the behaviour of guar derivatives are somewhat different. At higher temperatures, relatively small deviations from the scaling behaviour of the storage modulus of MG and MHPG polymers were observed. These findings can be justified by a structural re-organization of the macromolecular network, due to the hydrophobic interactions. 相似文献
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Ammonium acrylate was first used as a comonomer to copolymerize with acrylonitrile. The viscosity behavior of dimethyl formamide solutions of acrylonitrile/ammonium acrylate copolymer was studied, and the rheological kinetics of the solutions were studied for comparison. It was shown that the solutions behaved the same as a Newtonian flow as the rotor speed increased beyond 12 rpm. With an increase in temperature, the apparent viscosity of acrylonitrile/ammonium acrylate copolymer solutions showed a trend of decreasing. The changes in the apparent flow‐activation energy of solutions (Eη) calculated by the Arrhenius equation became less prominent along with the changes in the molecular weight of the acrylonitrile/ammonium acrylate copolymers. Eη increased continuously with an increase in copolymer concentration. The viscosity of copolymer solutions decreased continuously as the concentrations of KCl and NaCl increased up to 0.015 mol/L, and then it increased. The Eη showed an obvious trend of decreasing with the addition of alkali salts, and the changes in the Eη containing NaCl were more prominent than those of solutions containing KCl. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2320–2324, 2007 相似文献
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Thermosets obtained by reacting highly functionalized maleic anhydride-grafted polyethylene and a polyetherdiamine at several NH2/MA molar ratios were characterized for their gel content, thermal, mechanical, and thermo-mechanical behavior. Gel content varied with composition and a maximum (57%) observed when NH2/MA molar ratio was 1.5. Two melting transitions were observed for thermosets, representing the semicrystalline polyethylene fraction in the gel and sol part of the material in contrast to a single transition for the starting polyethylene. Overall crosslinking suppressed the crystallinity of the polyethylene in the thermoset. A single Tg observed in the DMA analysis suggested phase mixing between the polyethylene and polyether chains. A shift in the Tg observed was related to the degree of crosslinking in the thermosets. Tensile properties of the thermosets were observed to be a strong function of composition and the degree of crosslinking and the optimum mechanical performance was shown by thermosets when NH2/MA molar ratio was 1.5 and 2.0. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献