Ends pressure losses in extrusion of polymer melts through dies

White, James L.; Kondo, Akio

doi:10.1002/app.1977.070210826

Cited by 20 publications

(7 citation statements)

References 23 publications

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“…For extrusion operation conditions, there are temperature, extrusion rate, or shear rate, and so on. It was found in experiments that the exit effect during extrusion flow of polymer melts weakened with increasing shear rate [27] , leading to smaller fluctuation of DP ex , and higher measure precision. In this case, the deviation among the above calculations will be reduced.…”

Section: Discussion and Analysismentioning

confidence: 99%

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Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Liang

2006

Polymer-Plastics Technology and Engineering

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The viscoelastic behavior, such as end pressure losses, die swell, and normal stress difference, is a very important rheological phenomenon of viscoelastic fluids in channel flow. Therefore, understanding the elastic behavior and the mechanisms is quite necessary and meaningful for polymer rheology. Extrusion is a usual processing way in polymer industry. The viscoelastic behavior and the factors affecting it during die extrusion flow of polymeric melts are discussed, and the relationships among these viscoelastic properties, such as entry pressure drop (DP en ), exit pressure drop (DP ex ), die-swell ratio (B), and the first normal stress difference (N 1 ), are analyzed in this article. The results showed that there are some simple and available expressions for describing the relationships among these viscoelastic property parameters and the values of these parameters can be evaluated. Furthermore, the recent progresses in the quantitative expressions for prediction of these viscoelastic property parameters and their correlations are briefly reviewed.

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Section: Discussion and Analysismentioning

confidence: 99%

“…(24) is suitable to describe the relationship between N 1 and DP ex . White et al [27] studied the correlation between N 1 and DP end during capillary extrusion of low-density polyethylene (LDPE) melt and noted. According to the research results of Pena et al [11] , the ratio of DP ex to DP end is about 0.17.…”

Section: Discussion and Analysismentioning

confidence: 99%

Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Liang

2006

Polymer-Plastics Technology and Engineering

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“…According to the results above and the conclusions proposed by Carreau et al [7], it is clear that Equation (6) describes suitably the correlation of the first normal stress difference with exit-pressure drop. White and Kondo [18] discussed the relationship between N 1 and end-pressure drop (ÁP ends ) based on the results from capillary extrusion of low-density polyethylene (LDPE) made by Han [17], and noted that ÁP ends % 2N 1 . The research results of Pena et al [5] showed that the ratio of ÁP ex -ÁP ends is about 0.17.…”

Section: Discussionmentioning

confidence: 99%

Estimation of Melt Shear Modulus from Extrudate Swell Ratio and Exit-pressure Drop Data

Liang

2004

Journal of Thermoplastic Composite Materials

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Obvious viscoelastic phenomena, such as die-swell and exit-pressure losses, appear when a viscoelastic fluid leaves a die. It is generally believed that the die-swell ratio (B), the melt shear modulus (G), and the exit-pressure drop (ÁP ex ) are important parameters for the characterization of the elastic behavior of viscoelastic fluids during die flow. There may be, therefore, some interrelations between them. In the present article, relationships among G, B, and ÁP ex are discussed. On the basis of previous work, some expressions for describing relationships between B and G, ÁP ex , and B, as well as ÁP ex and G during flow of viscoelastic fluids in a long circular die are proposed. The values of G are estimated from the measured B during extrusion of a carbon black and calcium carbonate-filled rubber compound, and predictions of G by using the measured data of ÁP ex are compared with its calculations from the B data during capillary extrusion of a high-density polyethylene (HDPE) melt. The results showed that G increases linearly with increasing shear stress. Furthermore, a good agreement was obtained among these theoretical calculations of G at high shear stress level, also being consistent with predictions by using the Bagley-Duffey equation.

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“…White and Kondo, [21] have proposed that the primary normal stress difference, N 1 , is proportional to the entrance pressure losses (assuming negligible exit pressure losses), N1 ¼ a Pe, where a $ 0.5 for low density polyethylene. We submit that the numerical value of the calculated extensional stress according to Cogswell analysis, s e is equal to N 1 , therefore according to White and Kondo the value of the coefficient 3(n þ 1)/ 8 should be around 0.5, which indeed is the case as seen in Table 1 Tang and Kalyon [22] have studied the effect of slip at the wall in these flows.…”

Section: Abrupt Contraction Flow Analysismentioning

confidence: 99%

A Note on the Elasticity of Polymer Melts Described by Primary Normal Stress Difference (N₁)

García-Franco

2013

Macromolecular Symposia

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A method is proposed to characterize the elastic behavior of polyolefin melts, by calculating the first normal stress difference, N1 as a function of shear rate. The method is predicated on Cogswell's abrupt contraction flow analysis.1 These results are compared with experimental measurements and calculated values with a variety of methods, such as: i) Laun's rule2 for obtaining viscometric functions from linear viscoelastic data, ii) methods proposed by A. Khalik, et. al.3,4 and Wagner,5 for calculating N1 from viscosity data, and iii) N1 values calculated with the Johnson & Segalman constitutive equation.6 These comparisons yield acceptable agreement.

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Ends pressure losses in extrusion of polymer melts through dies

Cited by 20 publications

References 23 publications

Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Estimation of Melt Shear Modulus from Extrudate Swell Ratio and Exit-pressure Drop Data

A Note on the Elasticity of Polymer Melts Described by Primary Normal Stress Difference (N₁)

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Ends pressure losses in extrusion of polymer melts through dies

Cited by 20 publications

References 23 publications

Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Quantitative Characterization of Viscoelastic Properties and their Relationship During Extrusion Flow of Polymer Melts

Estimation of Melt Shear Modulus from Extrudate Swell Ratio and Exit-pressure Drop Data

A Note on the Elasticity of Polymer Melts Described by Primary Normal Stress Difference (N1)

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A Note on the Elasticity of Polymer Melts Described by Primary Normal Stress Difference (N₁)