Geometrical solution to the sharkskin instability

TitleGeometrical solution to the sharkskin instability
Publication TypeJournal Article
Year of Publication2007
AuthorsPol, HV, Joshi, YM, Tapadia, PS, Lele, AK, Mashelkar, RAnant
JournalIndustrial & Engineering Chemistry Research
Volume46
Issue10
Pagination3048-3056
Date PublishedMAY
Type of ArticleArticle
ISSN0888-5885
Abstract

We study the effect of die exit divergence on the sharkskin behavior, both experimentally as well as through the use of computational fluid dynamics (CFD) simulations. Sharkskin or surface fracture is known to occur immediately after the die exit, because of the large elongational deformation that a polymer melt experiences as it exits the die. We show that the diverging taper at the die exit postpones or completely removes the occurrence of sharkskin. The corresponding CFD simulations of an equivalent K-BKZ fluid show that the taper at the die exit significantly reduces the severity of the elongational flow, thereby reducing the normal stresses as the polymer melt leaves the die. We believe that, in an extrusion operation, the provision of a diverging taper at the die exit is one of the potential measures by which sharkskin instability can be eliminated on an industrial scale.

DOI10.1021/ie0610391
Type of Journal (Indian or Foreign)Foreign
Impact Factor (IF)2.567
Divison category: 
Chemical Engineering & Process Development
Polymer Science & Engineering