Measurement of the coefficient of dynamic friction at extrusion processing conditions

Gamache, E.; Lafleur, Pierre G.; Peiti, Christian; Vergnes, Bruno

doi:10.1002/pen.11554

Cited by 18 publications

(16 citation statements)

References 9 publications

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“…This contradicts Gamache et al who observed no significant correlation between the ECOF and the pellet shape when doing experiments with polypropylene cylinders and flattened cylinders. 22 Yet, the ECOF presented in their work is between 0.2 and 0.6, which is comparable to this study.…”

Section: Discussionsupporting

confidence: 87%

Experimental study of the influences of the pellet shape on the bulk density and the frictional behavior of polypropylene

Längauer

Kneidinger

Liu

et al. 2015

J of Applied Polymer Sci

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Bulk solids are the raw material for almost every polymeric thermoplastic product. Their properties determine the quality of solids conveying and also influence the melting behavior of the material in processing units. This study investigates the influence of pressure and temperature on the bulk density of two thermoplastic polypropylene pellets of different shapes. Furthermore, the external friction dependent on temperature and pressure of those materials is examined at conditions usually occurring in the solids conveying zone of smooth barrel plasticating units. The experiments are carried out using a tribometer for polymer pellets which was adapted for these tests by making the sample chamber, the piston, and the cylindrical roll heatable. The tests show that long cylindrical pellets exhibit low bulk densities at low pressure and temperature, which can be increased dramatically-even above the values of spheroidal pellets-as those parameters increase. Moreover, the external coefficient of friction is always higher for the long cylinders and strongly dependent on the temperature. Those facts add up and can cause a higher output of single-screw extruders.

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Section: Discussionsupporting

confidence: 87%

Experimental study of the influences of the pellet shape on the bulk density and the frictional behavior of polypropylene

Längauer

Kneidinger

Liu

et al. 2015

J of Applied Polymer Sci

View full text Add to dashboard Cite

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“…Gamache et al . investigated the dynamic coefficient of friction of two polypropylene pellet shapes . They also found a dependence of the coefficient of friction on the pellet shape.…”

Section: Discussionmentioning

confidence: 99%

“…It is well known from extrusion experience that the shape and the dimensions of the pellets influence the conveying behavior and the mass flow rate of single screw extruders. In literature, only few studies investigate friction of polymer pellets . Gamache investigated the frictional behavior of bulk materials in a shearing cell with an annular gap .…”

Section: Introductionmentioning

confidence: 99%

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Experimental analysis of the influence of pellet shape on single screw extrusion

Längauer

Liu

Kneidinger

et al. 2014

J of Applied Polymer Sci

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Extrusion technology is one of the most prominent methods for processing polymers. The shape of polymer pellets plays an important role in conveying solid material through the extruder and thus directly influences the mass flow rate. In the course of this article, the influence of the pellet shape of a polypropylene homopolymer on the processing conditions using a smooth barrel single‐screw extruder is evaluated. Especially the mass flow rate, the melt temperature, and the pressure build up in the barrel are investigated. It can be shown that processing long cylindrical pellets leads to a higher mass flow rate than comparable experiments with virgin pellets or short cylinders. Additionally, screw cool and pull‐out tests, measurements of the external coefficient of friction as well as the bulk density of the different pellet geometries are performed. The interaction of the screw geometry and the pellet shape is found to have the biggest influence. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41716.

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“…6A;ano utcome anticipated duetothe much greatert emperatureriseseen in the batchcell simulations.It should benoted herethatthe temperaturesin thesestudieswere still farbelowthe melting range of HDPE in ordertomaintain friction-driven conveying withn egligible cohesivep article interactionsgenerated. Negligible pressurewasbuilt-upi nthese simulations(open discharge flow)sothatt he contactarea evolved between collidingparticleswasneversignificantlydifferentfrom the batchtrials,and sothatfrictionalheating in the solidsconveying zone wasminor (Gamache etal.,1999).…”

Section: 2solidsconveying Zone Of Asingle-screwextrudermentioning

confidence: 99%

Studying the Effective Thermal Properties of Solids in Extrusion Machinery using a Discrete Particle Simulation Approach

Moysey

Cloet

Thompson

2008

International Polymer Processing

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Inthispaper,b othe xperimentaltrialsand numericalsimulationsarep resented toi mproveo ur understanding of the heat transferw ithin granularpolymerbedsfors ystemsw ithand without shear.Bothamorphous polymer,polystyrene (PS), and asemi-crystalline polymer,high-density polyethylene (HDPE)ofvarying particle sizefrom 6mm to25mmwereexamined. The estimated effectivethermalconductivity datafrom the experimentaltrialswasfound byfittotwosimple semi-empiricalm odelsallowing readers toreadilyapproximatethe property based on porosity of the bed and solid thermalproperties.Discretep article simulations,i. e. DEM, wereused to recognizethe importanceo fh eatt ransport through the stagnantinterstitialg asphasei ncomparison top article-particle conduction. The results underscorethe importanceo fi ncluding aneffectivethermalconductivity forgranularsolidsin an extruderwhen using continuummodels. 1IntroductionManyoperationsin the field of polymerprocessing involvethe plastication of polymerparticulate. Fort hosep rocesses,production ratesand process stability arelargelydictated byhow effectiveheatcanbetransferred through the solids.Ironically, granularheattransferisrarelyacknowledged in the field,a nd asaresult,ispoorlyunderstood. Most modelsconsidering heat transferw ithin polymerprocessing technology,forexample extrusion and injection molding,treatthe granularmediumas acontinuum(aseitheranelasticplugorfluid) and usethe thermophysicalpropertiesof the solid polymerwithout thoughtfor the interstitialfluid present (Tadmorand Broyer,1972;Lindt, 1976). Indoing so,researchers canoverestimatethe heattransferratebyalmost anorderof magnitude. Experimentaland numericalstudiesin otherfieldsof engineering whichconsider granularmedia(metal,glass,c eramics,etc.) haveshownthat neglecting the interstitialf luid often leadst osignificantinaccuraciesin the predicted heattransferof the bulk systems (Yagi and Kunii,1957; Molerus,1997; Argentoand Bouvard,1996); onlyu nderextensivecompaction wherethe interstitialvoids become vanishinglysmall,canthe contribution of the intersti-tialf luid beconsidered insignificant.Whethert he interstitial fluid experiencessignificantmotion suchasthe caseofafluidized bed (Wirth,1995;Yusufe tal.,2005),orr emainsr elativelys tagnant (Vargasand McCarthy,2002)will alsoh avea dramaticinfluenceo nthe heatt ransferforagranulars ystem. Within continuummodeling,aneffectivethermalconductivity (Gonzo,2002; Kunii and Smith,1960;Kunii and Levenspiel, 1991;Bauer,1993)will improvethe accuracyof heattransfer problemsand generallycanbep rovided ass imple semi-empiricale xpressionsbased on the solid thermalp ropertiesand the porosity of the granularassembly.Severalsuche mpirical expressionswill bediscussed in thispaper.However,selecting among thesem odelst oreasonablyapproximatethe thermalcharacterof the granularmediarequires apriori knowledge of the system and considering the complex and dynamicstateofthe particle bed in anextruderduring densification and sintering,itmaybeunreasonable toe xpectt hat anys uche xpression will besuitable ov...

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Measurement of the coefficient of dynamic friction at extrusion processing conditions

Cited by 18 publications

References 9 publications

Experimental study of the influences of the pellet shape on the bulk density and the frictional behavior of polypropylene

Experimental study of the influences of the pellet shape on the bulk density and the frictional behavior of polypropylene

Experimental analysis of the influence of pellet shape on single screw extrusion

Studying the Effective Thermal Properties of Solids in Extrusion Machinery using a Discrete Particle Simulation Approach

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