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Title: Surface mobility and slip of polybutadiene melts in shear flow

Abstract

Surface mobility and wall slip of entangled polybutadiene melts were studied with attenuated-total-reflectance infrared spectroscopy at stresses characteristic of the sharkskin, spurt, and melt-fracture regimes. Small-scale slip, accompanied by an apparent decrease in transverse mobility, occurs in the sharkskin regime, but at a stress above the visual onset of sharkskin in capillary viscometry. Simulations cannot distinguish between a cohesive mechanism and a lubrication mechanism that might follow from a stress-induced phase transition, but an adhesive failure seems to be excluded. The near-surface length scale is of the order of four to six times the equilibrium root-mean-square end-to-end distance, and the estimated slip velocity is insensitive to molecular weight. Strong slip occurs in the spurt regime, either at the wall or within one radius of gyration. Substantial apparent slip occurs with a fluorocarbon surface, but the mechanism does not appear to be an adhesive failure; there seems to be a substantial decrease in the friction coefficient of chains over a distance of order 300 nm or more from the fluorocarbon surface, and the transverse chain mobility in this region appears to be enhanced rather than retarded. Overall, the results of this study indicate that the influence of the wall extends farthermore » into the sheared melt than would be expected from the chain dimensions, except in the case of strong slip. (c) 2000 Society of Rheology.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [2]
  1. Materials Sciences Division, Lawrence Berkeley National Laboratory, and Department of Chemical Engineering, University of California, Berkeley, California 94720-1462 (United States)
  2. Department of Chemistry, University of Alabama, Birmingham, Alabama 35294 (United States)
Publication Date:
OSTI Identifier:
20216309
Resource Type:
Journal Article
Journal Name:
Journal of Rheology
Additional Journal Information:
Journal Volume: 44; Journal Issue: 3; Other Information: PBD: May 2000; Journal ID: ISSN 0148-6055
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BUTADIENE; POLYMERS; MELTING; INFRARED SPECTRA; REFLECTION; SLIP FLOW; FRACTURES; SHEAR; INSTABILITY; EXPERIMENTAL DATA

Citation Formats

Wise, Geoffrey M., Denn, Morton M., Bell, Alexis T., Mays, Jimmy W., Hong, Kunlun, and Iatrou, Hermis. Surface mobility and slip of polybutadiene melts in shear flow. United States: N. p., 2000. Web. doi:10.1122/1.551100.
Wise, Geoffrey M., Denn, Morton M., Bell, Alexis T., Mays, Jimmy W., Hong, Kunlun, & Iatrou, Hermis. Surface mobility and slip of polybutadiene melts in shear flow. United States. doi:10.1122/1.551100.
Wise, Geoffrey M., Denn, Morton M., Bell, Alexis T., Mays, Jimmy W., Hong, Kunlun, and Iatrou, Hermis. Mon . "Surface mobility and slip of polybutadiene melts in shear flow". United States. doi:10.1122/1.551100.
@article{osti_20216309,
title = {Surface mobility and slip of polybutadiene melts in shear flow},
author = {Wise, Geoffrey M. and Denn, Morton M. and Bell, Alexis T. and Mays, Jimmy W. and Hong, Kunlun and Iatrou, Hermis},
abstractNote = {Surface mobility and wall slip of entangled polybutadiene melts were studied with attenuated-total-reflectance infrared spectroscopy at stresses characteristic of the sharkskin, spurt, and melt-fracture regimes. Small-scale slip, accompanied by an apparent decrease in transverse mobility, occurs in the sharkskin regime, but at a stress above the visual onset of sharkskin in capillary viscometry. Simulations cannot distinguish between a cohesive mechanism and a lubrication mechanism that might follow from a stress-induced phase transition, but an adhesive failure seems to be excluded. The near-surface length scale is of the order of four to six times the equilibrium root-mean-square end-to-end distance, and the estimated slip velocity is insensitive to molecular weight. Strong slip occurs in the spurt regime, either at the wall or within one radius of gyration. Substantial apparent slip occurs with a fluorocarbon surface, but the mechanism does not appear to be an adhesive failure; there seems to be a substantial decrease in the friction coefficient of chains over a distance of order 300 nm or more from the fluorocarbon surface, and the transverse chain mobility in this region appears to be enhanced rather than retarded. Overall, the results of this study indicate that the influence of the wall extends farther into the sheared melt than would be expected from the chain dimensions, except in the case of strong slip. (c) 2000 Society of Rheology.},
doi = {10.1122/1.551100},
journal = {Journal of Rheology},
issn = {0148-6055},
number = 3,
volume = 44,
place = {United States},
year = {2000},
month = {5}
}