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Extensional rheometry of cellulose ether solutions: flow instability

Vadodaria, Saumil Sudhir; English, Robert John

Authors

Saumil Sudhir Vadodaria

Robert John English



Abstract

Capillary breakup extensional rheometry
of semi-dilute hydroxyethyl cellulose (HEC) solutions
was performed under several step-stretch conditions.
The resulting parameters, i.e. terminal steady state
extensional viscosity (gE) and the timescale for
viscoelastic stress growth, commonly referred to as
the extensional relaxation time (kE) were found to be
sensitive to the step-stretch conditions. The kE
decreased with increasing step-strain as opposed to
the gE. Prior to the filament break-up, a ‘bead-onstring’
instability was observed close to the mid-plane.
It is believed that this instability originated from the
accumulation of viscoelastic stresses near the filament
neck leading to the ‘elastic recoil’ of the extended
polymer chains. The reasons for this belief are
discussed in detail with the perspective of the past
literature. Such type of flow instability has been
reported for the first time for a cellulosic system.
Various dimensionless numbers were plotted for the
HEC solutions and compared with those obtained from
past studies for various biopolymers as well as
synthetic polymers.

Journal Article Type Article
Acceptance Date Dec 7, 2015
Online Publication Date Dec 22, 2015
Publication Date Dec 22, 2015
Deposit Date Jan 8, 2016
Publicly Available Date Jan 8, 2016
Print ISSN 0969-0239
Electronic ISSN 1572-882X
Publisher BMC
Peer Reviewed Peer Reviewed
Volume 23
Issue 1
Pages 339-355
DOI https://doi.org/10.1007/s10570-015-0838-1
Keywords Extensional rheology; CaBER; Cellulose ether; Hydroxyethyl cellulose; Bead-on-string; Flow instability;
Public URL http://researchrepository.napier.ac.uk/id/eprint/9422
Publisher URL http://dx.doi.org/10.1007/s10570-015-0838-1
Contract Date Jan 8, 2016

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