Characterization of die drool sample produced by HDPE melt extrusion

Musil, Jan; Zatloukal, Martin

doi:10.1063/1.4802602

Cited by 2 publications

(2 citation statements)

References 15 publications

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“…Besides, our works focused on flow induced molecular weight fractionation and die drool during HDPE melt extrusion 28,[38][39][40][41]45,57,84,[148][149][150][151]171 presented in more detail in other parts of the text, in a recently published contribution 40 two linear unfilled HDPEs differing in a small amount of high molecular weight species only were investigated. With the aid of the GPC technique, it was found that first, the content of long chains in the drool sample produced by more elastic HDPE containing high molecular weight species is smaller in comparison with the drool sample produced by less elastic HDPE free of high molecular weight species.…”

Section: Flow-induced Molecular Weight Fractionation Theorymentioning

confidence: 99%

Historical Review of Die Drool Phenomenon in Plastics Extrusion

Musil

Zatloukal

2014

Polymer Reviews

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Die drool phenomenon is defined as unwanted spontaneous accumulation of extruded plastics on die exit face(s) of extrusion die during plastics extrusion process. Such accumulated material builds up on die exit face(s) and frequently or continually sticks onto the extruded product and by this way reduces the quality of the product. When the die drool appears, the extrusion process must be shut down and the die exit face(s) must be manually cleaned, which is time consuming as well as money consuming.Die drool has been observed from the beginning of plastics extrusion and the first published remark about it was made in 1946. For a long time it was considered as only an engineering problem and even if a wide range of suppressing ideas based on modification of extrusion dies, plastics materials, and processing conditions have already been patented, its source remained unclear. During the last few years, a number of experimental as well as theoretical research papers focusing on its fundamental nature have been published. Nowadays, die drool is considered as a fundamental rheological phenomenon.The force which drives the building up of extruded plastics on die exit face(s) is negative pressure (suction) occurring in the die exit edge(s) region where the free surface of the extruded plastics is created. Moreover, two different die drool types (external and internal) exist. The formation mechanisms of external/internal die drool are based on negative pressure occurring in the die exit region together with deformation of free extrudate surface/material separation wherever inside the extrusion equipment, respectively. From the processing point of view, the internal die drool is much more problematic than the external one, primarily due to a higher build up rate and compact shapes of the accumulated drool mass. Two theories of internal die drool formation mechanism based on wall slip theories (flow-induced molecular weight fractionation and stress-induced cohesive chain disentanglement) have been recently proposed and tested.In this historically ordered review, breakthrough works in the field of die drool research are presented, many ways to suppress it are shown, techniques for its quantitative evaluation and experimental methods for its analytical investigation are introduced, external and internal die drool types are explained, and theories of external as well as internal die drool formation mechanism are presented and discussed in depth, which

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Section: Flow-induced Molecular Weight Fractionation Theorymentioning

confidence: 99%

Historical Review of Die Drool Phenomenon in Plastics Extrusion

Musil

Zatloukal

2014

Polymer Reviews

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“…For the pure shear flow, the function f ( I |D| , II D , III D ) becomes equal to 1 and thus, the viscosity becomes a function of second invariant of deformation rate tensor D (IID=sans-serifγ˙2) only. In the pure uniaxial extensional flow, where I|D|= 2trueε˙, IID=3sans-serifε˙2, and IIID=sans-serifε˙3/4, the function f ( I |D| , II D , III D ) becomes nonzero and model becomes capable of representing steady-state extensional flows for different polymer melts [69,70,71,72,73,74].…”

Section: Theoreticalmentioning

confidence: 99%

Evaluation of Thermally Induced Degradation of Branched Polypropylene by Using Rheology and Different Constitutive Equations

Drábek

Zatloukal

2016

Polymers

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Abstract:In this work, virgin as well as thermally degraded branched polypropylenes were investigated by using rotational and Sentmanat extensional rheometers, gel permeation chromatography and different constitutive equations. Based on the obtained experimental data and theoretical analysis, it has been found that even if both chain scission and branching takes place during thermal degradation of the tested polypropylene, the melt strength (quantified via the level of extensional strain hardening) can increase at short degradation times. It was found that constitutive equations such as Generalized Newtonian law, modified White-Metzner model, Yao and Extended Yao models have the capability to describe and interpret the measured steady-state rheological data of the virgin as well as thermally degraded branched polypropylenes. Specific attention has been paid to understanding molecular changes during thermal degradation of branched polypropylene by using physical parameters of utilized constitutive equations.

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Characterization of die drool sample produced by HDPE melt extrusion

Cited by 2 publications

References 15 publications

Historical Review of Die Drool Phenomenon in Plastics Extrusion

Historical Review of Die Drool Phenomenon in Plastics Extrusion

Evaluation of Thermally Induced Degradation of Branched Polypropylene by Using Rheology and Different Constitutive Equations

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