Entry flow of polyethylene melts in tapered dies

Ansari, M; Alabbas, A; Hatzikiriakos, SG; Mitsoulis, E

dc.contributor.author	Ansari, M	en
dc.contributor.author	Alabbas, A	en
dc.contributor.author	Hatzikiriakos, SG	en
dc.contributor.author	Mitsoulis, E	en
dc.date.accessioned	2014-03-01T01:33:22Z
dc.date.available	2014-03-01T01:33:22Z
dc.date.issued	2010	en
dc.identifier.issn	0930-777X	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20398
dc.subject	Polyethylene	en
dc.subject.classification	Engineering, Chemical	en
dc.subject.classification	Polymer Science	en
dc.subject.other	Contraction angles	en
dc.subject.other	Contraction flow	en
dc.subject.other	Cross model	en
dc.subject.other	End effects	en
dc.subject.other	Excess pressure	en
dc.subject.other	Extensional viscosity	en
dc.subject.other	Fluoropolymer	en
dc.subject.other	Local minimums	en
dc.subject.other	Multimodes	en
dc.subject.other	No-slip boundary conditions	en
dc.subject.other	No-slip condition	en
dc.subject.other	Numerical simulation	en
dc.subject.other	Order of magnitude	en
dc.subject.other	Polyethylene melt	en
dc.subject.other	Shear rates	en
dc.subject.other	Slip condition	en
dc.subject.other	Viscoelastic models	en
dc.subject.other	Viscoelastic spectra	en
dc.subject.other	Viscous models	en
dc.subject.other	Birefringence	en
dc.subject.other	Fluorine containing polymers	en
dc.subject.other	Optimization	en
dc.subject.other	Polyethylenes	en
dc.subject.other	Pressure drop	en
dc.subject.other	Shear deformation	en
dc.subject.other	Thermoplastics	en
dc.subject.other	Vehicular tunnels	en
dc.subject.other	Viscosity	en
dc.subject.other	Computer simulation	en
dc.title	Entry flow of polyethylene melts in tapered dies	en
heal.type	journalArticle	en
heal.identifier.primary	10.3139/217.2360	en
heal.identifier.secondary	http://dx.doi.org/10.3139/217.2360	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	The excess pressure losses due to end effects (mainly entrance) in the capillary flow of several types of polyethylenes were studied both experimentally and numerically under slip and no-slip conditions. These losses were first measured as a function of the contraction angle ranging from 15° to 90°. It was found that the excess pressure loss attains a local minimum at a contraction angle of about 30° for all types of polyethylenes examined. This was found to be independent of the apparent shear rate. This minimum becomes more dominant under slip conditions that were imposed by adding a significant amount of fluoropolymer into the polymer. Numerical simulations using a multimode K-BKZ viscoelastic model have shown that the entrance pressure drops can be predicted fairly well for all cases either under slip or no-slip boundary conditions. The clear experimental minimum at about 30° can only slightly be seen in numerical simulations, and at this point its origin is unknown. Further simulations with a viscous (Cross) model have shown that they severely under-predict the entrance pressure by an order of magnitude for the more elastic melts. Thus, the viscoelastic spectrum together with the extensional viscosity play a significant role in predicting the pressure drop in contraction flows, as no viscous model could. The larger the average relaxation time and the extensional viscosity are, the higher the differences in the predictions between the K-KBZ and Cross models are. © Carl Hanser Verlag, Munich.	en
heal.publisher	CARL HANSER VERLAG	en
heal.journalName	International Polymer Processing	en
dc.identifier.doi	10.3139/217.2360	en
dc.identifier.isi	ISI:000280878000004	en
dc.identifier.volume	25	en
dc.identifier.issue	4	en
dc.identifier.spage	287	en
dc.identifier.epage	296	en