Rheology of thermo-gelling capillary suspensions
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ORIGINAL CONTRIBUTION
Rheology of thermo-gelling capillary suspensions Amit Ahuja1
· Chaiwut Gamonpilas2
Received: 30 July 2020 / Accepted: 15 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Rheological measurements were performed to examine the behavior of thermally responsive capillary suspensions. These capillary suspensions were prepared by dispersing laponite nanoparticles in a continuous oil phase and an immiscible secondary fluid consisting of an aqueous solution of a thermogelling polymer, Pluronic F127 (PF127). The addition of PF127 (which undergoes sol-gel transition at elevated temperatures) into the secondary phase resulted in a capillary-networked suspension whose rheology can be tailored by increasing the temperature above the gelling temperature of PF127. We investigated the yielding behavior of this system using dynamic oscillatory measurements at different temperatures. These suspensions yield via a two-step process which was observed as two distinct plateaus for storage modulus in a typical plot of storage modulus versus oscillation strain. This yielding behavior is attributed to the rupturing of the bicontinuous network structure at lower strains which is followed by the breakup of particle aggregates at larger strains. Keywords Capillary suspension · Laponite · Pluronic F127 · Thermo-responsive · Two-step yielding
Introduction The capillary suspensions are obtained by dispersing a small quantity of an immiscible liquid to a particle suspension which triggers particle aggregation as a consequence of capillary bridging between the particles leading to orders of magnitude changes in the rheological properties [1–6]. Recently, the role and functionality of capillary interactions in controlling the complex flow behavior of solid particle suspensions have gained increased attention in the literature [2–4, 7, 8]. The capillary forces have been demonstrated
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00396-020-04772-8) contains supplementary material, which is available to authorized users. Amit Ahuja
[email protected] Chaiwut Gamonpilas [email protected] 1
TA Instruments–Waters LLC, 159 Lukens Drive, New Castle, DE 19720, USA
2
Advanced Polymer Technology Research Group, National Metal and Materials Technology Center (MTEC), 114 Thailand Science Park, Pahonyothin Road, Khlong 1, Khlong Luang, Pathum Thani 12120, Thailand
to successfully tailor the rheological properties, textural or sensory attributes, stability against sedimentation, flocculation, and heat to fulfill the requirements of formulation and processing [9, 10]. Understanding the functional role of capillary bridges in tuning the flow properties of fluid-fluid-solid system is of great industrial importance. Apart from their usage in the formulation and processing of consumer products [6, 9–11], Li-ion battery applications [12], new routes for the production of ceramic materials [13], and capillary inks for 3D printing [14], capillary f
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