Special Issue "Rheology of Gels"

A special issue of Gels (ISSN 2310-2861).

Deadline for manuscript submissions: closed (30 June 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Osvaldo H. Campanella

Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA
Website | E-Mail
Interests: food science; rheology; self-assembled nanoparticles; polymer behavior

Special Issue Information

Dear Colleagues,

The increasing importance of gels in a large number of technological fields has promoted considerable attention in the study of these materials.  In particular, the rheological properties of gels are largely affected by their physicochemical and microstructural properties and they influence potential applications in many technological areas, including medical, biotechnological, and many products such as fuels, ceramics, and foods among others. Gels are generally classified as chemical and physical and the type of gel mainly depends on the major components forming it. Rheological properties of physical and chemical gels are very different and mainly depend on the gel microstructure and strength. Although rheological properties are considered bulk and macroscopic properties, they are strongly affected by the gel chemical composition and microstructure, which depends on both covalent and physical bindings. Therefore, a comprehensive rheological study of gels would involve their characterization at different sizes scales that go from molecular (studied with the aid of molecular modeling) to nano, micro, meso and macro scales.

This Special Issue will provide an international forum of researchers discussing the most recent studies concerning the rheology of gels and how it relates to the gel classification, its composition, microstructure and application. Through this Special Issue, rheological methods used to characterize the rheology of different types of gels at different scales will be discussed, as well as how to use the rheological information to elucidate novel materials and applications within the areas listed above.

Prof. Osvaldo H. Campanella
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • rheology
  • gel fluid
  • plastic flow
  • non-Newtonian fluid
  • shear stress
  • extensibility
  • viscoelastic behavior

Published Papers (5 papers)

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Research

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Open AccessArticle Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels
Received: 10 October 2017 / Revised: 7 November 2017 / Accepted: 16 November 2017 / Published: 20 November 2017
Cited by 1 | PDF Full-text (3289 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7%) and a hydrophobic solvent (Hydrocarbon fuel, JP-8). Viscosity measurements as a function of [...] Read more.
This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7%) and a hydrophobic solvent (Hydrocarbon fuel, JP-8). Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s−1), and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM) were obtained to show how the structure of the gel is affected upon application of shear. Full article
(This article belongs to the Special Issue Rheology of Gels)
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Graphical abstract

Open AccessArticle Fumed and Precipitated Hydrophilic Silica Suspension Gels in Mineral Oil: Stability and Rheological Properties
Received: 26 June 2017 / Revised: 3 August 2017 / Accepted: 7 August 2017 / Published: 9 August 2017
Cited by 3 | PDF Full-text (2695 KB) | HTML Full-text | XML Full-text
Abstract
Hydrophilic fumed silica (FS) and precipitated silica (PS) powders were suspended in mineral oil; increasing the silica volume fraction (φ in the suspension led to the formation of sol, pre-gel, and gel states. Gelation took place at lower φ values in the FS [...] Read more.
Hydrophilic fumed silica (FS) and precipitated silica (PS) powders were suspended in mineral oil; increasing the silica volume fraction (φ in the suspension led to the formation of sol, pre-gel, and gel states. Gelation took place at lower φ values in the FS than the PS suspension because of the lower silanol density on the FS surface. The shear stresses and dynamic moduli of the FS and PS suspensions were measured as a function of φ. Plots of the apparent shear viscosity against shear rate depended on φ and the silica powder. The FS suspensions in the gel state exhibited shear thinning, followed by a weak shear thickening or by constant viscosity with an increasing shear rate. In contrast, the PS suspensions in the gel state showed shear thinning, irrespective of φ. The dynamic moduli of the pre-gel and gel states were dependent on the surface silanol density: at a fixed φ, the storage modulus G′ in the linear viscoelasticity region was larger for the FS than for the PS suspension. Beyond the linear region, the G′ of the PS suspensions showed strain hardening and the loss modulus G″ of the FS and PS suspensions exhibited weak strain overshoot. Full article
(This article belongs to the Special Issue Rheology of Gels)
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Open AccessArticle Mechanical, Swelling, and Structural Properties of Mechanically Tough Clay-Sodium Polyacrylate Blend Hydrogels
Received: 4 November 2016 / Revised: 13 February 2017 / Accepted: 20 February 2017 / Published: 25 February 2017
Cited by 6 | PDF Full-text (1637 KB) | HTML Full-text | XML Full-text
Abstract
We investigated the mechanical, swelling, and structural properties of mechanically tough clay/sodium polyacrylate (PAAS) hydrogels prepared by simple mixing. The gels had large swelling ratios, reflecting the characteristics of the constituent polymer. The swelling ratios initially increased with the increase of the swelling [...] Read more.
We investigated the mechanical, swelling, and structural properties of mechanically tough clay/sodium polyacrylate (PAAS) hydrogels prepared by simple mixing. The gels had large swelling ratios, reflecting the characteristics of the constituent polymer. The swelling ratios initially increased with the increase of the swelling time, and then attained maximum values. Afterwards, they decreased with an increase of the swelling time and finally became constant. An increase in the clay concentration lead to a decrease in the swelling ratios, whereas an increase in the PAAS concentration lead to an increase in the swelling ratios. Tensile measurements indicated that the toughness for clay/PAAS (Mw = 3.50 × 106) gels was several hundred times larger than that of clay/PAAS (Mw = 5.07 × 105) gels, i.e., the use of ultra-high molecular weight PAAS is essential for fabricating mechanically tough clay/PAAS blend hydrogels. Synchrotron small-angle X-ray scattering (SAXS) results showed that the SAXS intensity measured at small scattering angles decreased with an increase in the clay concentration, indicating that the interparticle interactions were more repulsive at higher concentrations. The decrease of the scattering intensity at high clay concentrations was larger for the clay/PAAS (Mw = 5.07 × 105) gel system than for the clay/PAAS (Mw = 3.50 × 106) gel system. Full article
(This article belongs to the Special Issue Rheology of Gels)
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Open AccessArticle Effect of Xanthan Gum on the Rheological Behavior and Microstructure of Sodium Caseinate Acid Gels
Received: 28 March 2016 / Revised: 31 August 2016 / Accepted: 31 August 2016 / Published: 10 September 2016
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Abstract
The aim of this work was to study the effect of xanthan gum (XG) on the gelation process of bovine sodium caseinate (NaCAS) induced by acidification with glucono-δ-lactone (GDL) and on the mixed acid gel microstructure. Before GDL addition, segregative phase separation was [...] Read more.
The aim of this work was to study the effect of xanthan gum (XG) on the gelation process of bovine sodium caseinate (NaCAS) induced by acidification with glucono-δ-lactone (GDL) and on the mixed acid gel microstructure. Before GDL addition, segregative phase separation was observed in all the NaCAS-XG mixtures evaluated. The gelation process was analyzed by using a fractional factorial experimental design. The images of the microstructure of the mixed acid gels were obtained by conventional optical microscopy and the mean diameter of the interstices was determined. Both the elastic character and the microstructure of the gels depended on the concentrations of XG added. As XG concentration increased, the kinetics of the gelation process was modified and the degree of compactness and elasticity component of the gel network increased. The microstructure of gels depends on the balance among thermodynamic incompatibility, protein gelation and NaCAS-XG interactions. Full article
(This article belongs to the Special Issue Rheology of Gels)
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Review

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Open AccessReview Rheology of Emulsion-Filled Gels Applied to the Development of Food Materials
Received: 4 April 2016 / Revised: 25 June 2016 / Accepted: 4 August 2016 / Published: 16 August 2016
Cited by 2 | PDF Full-text (1272 KB) | HTML Full-text | XML Full-text
Abstract
Emulsion-filled gels are classified as soft solid materials and are complex colloids formed by matrices of polymeric gels into which emulsion droplets are incorporated. Several structural aspects of these gels have been studied in the past few years, including their applications in food, [...] Read more.
Emulsion-filled gels are classified as soft solid materials and are complex colloids formed by matrices of polymeric gels into which emulsion droplets are incorporated. Several structural aspects of these gels have been studied in the past few years, including their applications in food, which is the focus of this review. Knowledge of the rheological behavior of emulsion-filled gels is extremely important because it can measure interferences promoted by droplets or particle inclusion on the textural properties of the gelled systems. Dynamic oscillatory tests, more specifically, small amplitude oscillatory shear, creep-recovery tests, and large deformation experiments, are discussed in this review as techniques present in the literature to characterize rheological behavior of emulsion-filled gels. Moreover, the correlation of mechanical properties with sensory aspects of emulsion-filled gels appearing in recent studies is discussed, demonstrating the applicability of these parameters in understanding mastication processes. Full article
(This article belongs to the Special Issue Rheology of Gels)
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