Rheology of polymer melts in high shear rate

Takahashi, Hideroh; Matsuoka, Takaaki; Kurauchi, Toshio

doi:10.1002/app.1985.070301214

Cited by 37 publications

(17 citation statements)

References 1 publication

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“…(9). Takahashi et al72 have carried out experiments to measure the viscosity of pure PS melt at very high shear rates (up to 10 8 s −1 ) using a specially designed high‐shear‐rate rheometer. They observed that the second Newtonian region was not observed for PS melts, instead a transition region was observed over which dual values of the apparent viscosity were obtained at one shear rate.…”

Section: Modeling Of Thermophysical Propertiesmentioning

confidence: 99%

Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling

Shukla

Koelling

2007

J of Applied Polymer Sci

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In this work, a new methodology is developed that describes the viscoelastic scaling of a polymerphysical foaming agent (PFA) solution in a detailed and internally consistent manner. The approach is new in that while previous researchers have largely focused on scaling down experimentally obtained high pressure polymer-PFA solution viscosity data onto a master curve for the viscosity of the undiluted polymer melt at a reference temperature and atmospheric pressure, we have generated the shear viscosity data required for our simulations by systematically scaling up the viscosity values obtained from measurements on a pure polymer melt to the desired temperature, pressure, and concentration values characterizing the flow. Simulations have been run for the flow of a polymer-PFA solution through an extrusion foaming die with an abrupt axisymmetric contraction and good qualitative agreement is obtained with experimental pressure drop measurements obtained previously in our laboratory. The pressure drop rates and temperature rise rates have been estimated at the surface of incipient nucleation. Because of the short residence times in the die for the microcellular foaming process, approximating the flow through the die as a single phase flow in our simulations still gives useful insights into the dynamics of the flow.

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Section: Modeling Of Thermophysical Propertiesmentioning

confidence: 99%

Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling

Shukla

Koelling

2007

J of Applied Polymer Sci

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“…A second Newtonian plateau for the PP and HDPE melts was also observed by Rides et al at the shear rates of above 2 × 10 6 s −1 . Takahashi et al observed not only a second Newtonian plateau at the shear rate of above 3 × 10 6 s −1 but also a second shear thinning region at the shear rate of above 7 × 10 6 s −1 for the HDPE melt. For the polystyrene (PS) melt, Kelly et al and Rides et al found the shear thickening behavior at the shear rates of above 5.0 × 10 5 and 3.6 × 10 5 s −1 , respectively.…”

Section: Introductionmentioning

confidence: 98%

“…The polymer melts are subjected to complicated rheological history featuring higher shear rates (over 10 6 s 21 ) during injection molding, especially micro-injection molding [1][2][3][4]. However, there is still a lack of knowledge of high-shear-rate rheology of polymer melts [5][6][7][8][9][10][11][12], especially its comparison for different polymers under high shear rates [8][9][10][11][12]. Haddout et al [8,9] found that the polypropylene (PP) and high-density polyethylene (HDPE) melts follow pseudoplastic shear thinning behavior at the shear rates of up to 10 6 s 21 , above which their shear viscosity curves reach a quasi-Newtonian plateau.…”

Section: Introductionmentioning

confidence: 99%

Comparison of superimposed effects in high-shear-rate capillary rheology of polystyrene, polypropylene, and linear low-density polyethylene melts

2014

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Polymer melts exhibit unique rheological behaviors at high shear rate up to 106 s−1, which is a common phenomenon in micro‐injection molding. Both online and commercial capillary rheometers, which were modified to allow regulation of back pressure, were used for measuring the melt shear viscosities of polystyrene (PS), polypropylene (PP), and linear low‐density polyethylene (LLDPE) under high shear rates. The rheological characteristics of the three melts were compared through the systematical analyses for three significant effects, namely the end pressure loss, pressure dependence, and dissipative heating in capillary flow. Pronounced end effect begins to appear at the shear rates of 1.6 × 105, 8.0 × 105, and 2.8 × 106 s−1 for the PS, PP, and LLDPE melts, respectively. The significance of the end effect can be ordered as PS > PP > LLDPE. It seems that the polymers with more complex molecular structures exhibit a higher degree of divergence between the comprehensively corrected and uncorrected melt viscosity curves. Moreover, the dissipation effect begins to predominate over the pressure effect under the lowest shear rate of 105 s−1 for the PS melt among the three melts. POLYM. ENG. SCI., 55:506–512, 2015. © 2014 Society of Plastics Engineers

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“…For the purpose of further extending the measuring range to a much higher level (e.g. 10 5 –10 7 s −1 ), the online capillary rheometers have been developed based on the injection‐molding machine [2–4]. It is worthy to note that under high shear rates or high pressures, the increasing influences of the end pressure loss, pressure dependence of the melt viscosity, dissipative heating, and melt compressibility on the capillary flow may evidently affect the reliability of the rheological measurement [5, 6], provided that no proper treatments are applied.…”

Section: Introductionmentioning

confidence: 99%

“…A few of works have been carried out to characterize the high‐shear‐rate rheological behavior of polymer melt [2–4, 18]. Under the shear rates of about 10 6 s −1 , the degradation of polymer [2], the second Newton plateau [2–4], and shear thickening behavior [4] were observed. Nevertheless, to the best knowledge of the authors, there is a lack of reports on the systematical analyses for the aforementioned four effects in capillary rheology under high shear rates, which may be responsible for the unique rheological behaviors.…”

Section: Introductionmentioning

confidence: 99%

Superimposed effects in high‐shear‐rate capillary rheology of polystyrene melt

Guan

Huang

2012

Polymer Engineering & Sci

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During micro‐injection molding, the polymer melt may undergo a shear rate up to 106 s−1, at which the rheological behaviors are obviously different from those in conventional molding process. Using both online and commercial rheometers, high‐shear‐rate capillary rheology of polystyrene (PS) melt is analyzed systematically in this work. The accurate end pressure drop and pressure coefficient of viscosity are determined via the enhanced exit pressure technique. Experimental and theoretical investigations are conducted on four significant effects, that is, the dissipative heating, end pressure loss, pressure dependence, and melt compressibility in capillary flow. For the PS melt, which exhibits distinct temperature and pressure dependence of viscosity, both dissipation and end effects become pronounced as the shear rate exceeds 2 × 105 s−1. From lower to higher shear rates (103–106 s−1), the competition between dissipation and pressure effects results in the overestimation to underestimation of Bagley‐corrected pressure drop, and finally the comprehensively corrected viscosity becomes about half of the uncorrected one owing to the enhanced superimposed effects. Moreover, the compressibility shows a minor influence on the shear viscosity. Under the shear rate range investigated, the power‐law relationship is sufficient for describing the corrected viscosity curve of PS melt used. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

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Rheology of polymer melts in high shear rate

Cited by 37 publications

References 1 publication

Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling

Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling

Comparison of superimposed effects in high-shear-rate capillary rheology of polystyrene, polypropylene, and linear low-density polyethylene melts

Superimposed effects in high‐shear‐rate capillary rheology of polystyrene melt

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