Wall slip and melt-fracture of polystyrene melts in capillary flow

Komuro, Ryohei; Kobayashi, Kōji; Taniguchi, Takashi; Sugimoto, Masataka; Koyama, Kiyohito

doi:10.1016/j.polymer.2010.03.014

Cited by 13 publications

(10 citation statements)

References 24 publications

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“…However, various studies have indicated that the flow behavior of polymeric melt through a microscopic scale channel is different from the flow behavior on the macroscopic scale . The fact that rheological properties in micro‐channels are significantly affected by many factors which could be micro‐scale‐dependent has been widely documented . The flow profile in micro‐scale channels, for example, was found to be different from that on the macron scale for polyethylenes …”

Section: Introductionmentioning

confidence: 99%

“…Behavior of wall slip and geometrical dependence of shear viscosity of polymer melts on the flow channel present complex variations. Komuro et al investigated the wall slip and flow instability of a short branching polystyrene (PS). Based on a modified Mooney method, the slip velocity appeared to increase with increasing melt temperature and the critical slip stress above which a slip occurred decreased.…”

Section: Introductionmentioning

confidence: 99%

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Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow

Lin

Kelly

Ren

et al. 2013

J of Applied Polymer Sci

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The shear viscosity of polymethylmethacrylate (PMMA) melt is particularly investigated by using a twin-bore capillary rheometer at four temperatures of 210, 225, 240, and 255 C with different capillary dies. Experimental results show that the geometrical dependence of shear viscosity is significantly dependent on melt pressure as well as melt temperature. The measured shear viscosity increases with the decrease of die diameter at lower temperatures (210 and 225 C) but decreases with the decrease of die diameter at higher temperatures (240 and 255 C). Based on the deviation of shear viscosity curves and Mooney method, negative slip velocity is obtained at low temperatures and positive slip velocity is obtained at high temperatures, respectively. Geometrical dependence and pressure sensitivity of shear viscosity as well as temperature effect are emphasized for this viscosity deviation. Moreover, shear viscosity curve at 210 C deviates from the power law model above a critical pressure and then becomes less thinning. Mechanisms of the negative slip velocity at low temperatures are explored through Doolittle viscosity model and Barus equation, in which the pressure drop is used to obtain the pressure coefficient by curve fitting. Dependence of pressure coefficient on melt temperature suggests that the pressure sensitivity of shear viscosity is significantly affected by temperature. Geometrical dependence of shear viscosity can be somewhat weakened by increasing melt temperature.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow

Lin

Kelly

Ren

et al. 2013

J of Applied Polymer Sci

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“…The advantage of the modified Mooney method is that it can used to determine the interfacial slip velocity in core-sheath systems even when polymers with different shear rate-dependent viscosities are coextruded. Further, the slip at the PP/PS interface occurs at shear stress values that are significantly lower than the shear stress necessary for the onset of wall slip (≈ 10 5 Pa) (Hatzikiriakos and Dealy 1992;Mitsoulis et al 2005;Komuro et al 2010). If both wall slip and interfacial slip interfacial slip are present, it is not possible to determine the individual contributions to the total slip velocity using only the modified Mooney method.…”

Section: Resultsmentioning

confidence: 99%

Slip at the interface between immiscible polymer melts I: method to measure slip

et al. 2013

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Slip at the interface between immiscible polymer melts remains poorly understood. A method that relies solely on rheological measurements to obtain the interfacial slip velocity uses the slip-induced deviation in the flow variables. To use the method, accurate estimates of the flow variables under the assumption of no-slip are necessary. Although such estimates can be easily derived under some cases, in general, this is not straightforward. Therefore, methods to determine the interfacial slip velocity without using estimates for the flow variables under no-slip conditions are desirable. In this work, we focus on investigations of slip at the interface between two immiscible polymer melts undergoing two-phase coaxial flow. To enable such investigations, we have adapted the Mooney method, usually used to investigate wall slip, to investigate polymer/polymer interfacial slip. Using this method, we have measured the slip velocity at the interface between polypropylene and polystyrene as a function of the interfacial stress. To determine the validity of the modified Mooney method, we also determine the slip velocity using the slip-induced deviation in the flow variables. To enable this determination, we use polypropylene and polystyrene with almost identical shear rate-dependent viscosities over a range of shear rates. The slip velocity obtained from the modified Mooney method displayed excellent agreement with that determined using the deviation from no-slip. In agreement with prior work, the dependence of the slip velocity on the interfacial stress is a power-law. Our investigation spans a sufficiently wide range of interfacial stress R. Komuro · S. K. Sukumaran ( ) · M. Sugimoto · K. Koyama Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata, 992-8510, Japan e-mail: sa.k.sukumaran@gmail.com to enable the direct observation of two power-law regimes and also the transition between the two regimes. We also find that the power-law exponent of approximately 3 at low stresses decreases to approximately 2 at high stresses.

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“…High flow ability of melt is helpful to ease the flow resistance, especially for the flows in micron channel. Many scholars found that the flow behavior of polymer melts on the microscopic scale could be significantly different from that on the macroscopic scale . The micro‐shear viscosity, which was defined as the shear viscosity of polymeric melt flowing in micron channel, was found to deviate from the conventional shear viscosity measured on the macroscopic scale.…”

Section: Introductionmentioning

confidence: 99%

“…Shear viscosity of polymers changed with the die scale in capillary flow was previously defined as geometrical dependence . This geometrical dependence was mainly attributed to the wall‐slip behavior in many literatures . For example, Zhao et al suggested that the wall slip between polymer bulk and wall surface was largely contributed to the geometrical dependence of shear viscosity based on the entanglement‐disentanglement slip mechanism for polymethylmethacrylate (PMMA) and adsorption‐desorption slip mechanism for high density polyethylene (HDPE).…”

Section: Introductionmentioning

confidence: 99%

Capillary study on geometrical dependence of shear viscosity of polymer melts

Lin

Kelly

Woodhead

et al. 2013

J of Applied Polymer Sci

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Geometrical dependence of viscosity of polymethylmethacrylate (PMMA) and high density polyethylene (HDPE) are studied by means of a twin-bore capillary rheometer based on power-law model. Contrary geometrical dependences of shear viscosity are observed for PMMA between 210 and 255 C, but similar geometrical dependences are revealed for HDPE between 190 and 260 C. The fact that wall slip can not successfully explain the irregular geometrical dependence of PMMA viscosity is found in this work. Then, pressure effect and dependence of fraction of free volume (FFV) on both pressure and temperature are proposed to be responsible for the geometrical dependence of capillary viscosity of polymers. The dependence of shear viscosity on applied pressure is first investigated based on the Barus equation. By introducing a shift factor, shear viscosity curves of PMMA measured under different pressures can be shifted onto a set of parallel plots by correcting the pressure effect and the less shear-thinning then disappears, especially at high pressure. Meanwhile, the FFV and combining strength among molecular chains are evaluated for both samples based on molecular dynamics simulation, which implies that the irregular geometrical dependence of PMMA viscosity can not be attributed to the wall slip behavior.

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Wall slip and melt-fracture of polystyrene melts in capillary flow

Cited by 13 publications

References 24 publications

Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow

Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow

Slip at the interface between immiscible polymer melts I: method to measure slip

Capillary study on geometrical dependence of shear viscosity of polymer melts

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