Developing conductive immiscible polystyrene/polypropylene blends with a percolated conducting polyaniline/polyamide filler by tuning its specific interactions with the styrene-based triblock compatibilizer grafted with maleic anhydride

An approach to induce conductivity in immiscible polystyrene/polypropylene (PS/PP) blends is described using a percolated conducting polyaniline/polyamide (PANI/PA) filler combined with a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride compatibilizer. The approach is based on the ability of the compatibilizer to concomitantly stabilize the cocontinuous morphology and to improve the state of dispersion of the PANI/PA filler. Selective localization of PANI/PA in the PS phase with improved filler dispersion is achieved with the optimal master batch (MB) preparation technique followed by its optimized sequence addition to the blend components. This results in an increase in the dc conductivity by six decades as compared with that of the neat compatibilized blend at an effective 4.8-wt % PANI concentration. An investigation of the effect of functionality and concentration of the filler and the compatibilizer on the filler connectivity in the blend is performed. The prevailing specific interactions are analyzed by Fourier transform infrared spectroscopy and thermogravimetric analysis of the MBs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48433.     

Review on morphology development of immiscible blends in confined shear flow

The bulk dynamics of immiscible polymer blends during flow is relatively well understood, especially when the system contains Newtonian components. Recently, a number of studies have focused on flow of immiscible blends in confined geometries. In that case, the morphology development is not only affected by the material characteristics and the type of flow, but also by the degree of confinement. Here, we present an overview on the morphology development in immiscible two-phase blends in confined shear flow. Firstly, we focus on the typical microstructures that are observed in confined dilute blends. Secondly, in order to understand those peculiar morphologies, the systematic studies on single droplets in confined shear flow are reviewed. In addition to the experimental work, theoretical, phenomenological, and numerical models that include the effects of confinement are discussed.     

Enhancing the Rheological Performance of Wheat Flour Dough with Glucose Oxidase,Transglutaminase or Supplementary Gluten

The enzymes glucose oxidase and transglutaminase are frequently used to improve the breadmaking performance of wheat flours, as they have the ability to considerably alter the viscoelastic nature of the gluten network. To evaluate a flour’s breadmaking performance, rheological tests offer an attractive framework. In this study, the rheological impact of adding glucose oxidase or transglutaminase to wheat flour dough is investigated by means of linear oscillatory shear tests, creep-recovery shear tests and startup extensional tests. The former tests reveal that the enzymes render the dough stiffer and enhance its elastic character, until saturation is reached. In the breadmaking process, the use of excessive amounts of enzyme is known to be counterproductive. The strain-hardening index clearly reveals this overcross-linking effect. Besides enzymes, the gluten network can also be reinforced by adding supplementary gluten, which was indeed found to enhance the extent of strain-hardening.     

The Effects of Process-Induced Pectin Changes on the Viscosity of Carrot and Tomato Sera

The influence of process-induced pectin changes on the kinematic viscosity of the serum phases of carrot and tomato purées was investigated in this study. Variations in the amount of pectin present in the serum phase and pectin’s fine structure were induced by subjecting carrot and tomato to different thermal treatments, i.e. a mild and a strong heat treatment, followed by blending and high-pressure homogenisation at different pressure levels (0, 20 and 100 MPa). Changes in pectin structure were monitored by determination of the degree of methoxylation, analysing the molar mass distribution and immuno-dot blotting using anti-pectin antibodies. Characterisation of serum pectins revealed that a strong thermal treatment caused pectin thermosolubilisation and depolymerisation, especially in carrot sera, and high-pressure homogenisation provoked predominantly mechanical pectin solubilisation in carrot sera and pectin depolymerisation in tomato sera. It was observed that the kinematic viscosity of carrot sera was mainly affected by the amount of solubilised pectin, whereas in tomato sera, the kinematic viscosity could mainly be explained in terms of polysaccharide chain length. The degree of methoxylation of pectin, which has a broader distribution in tomato sera than in carrot sera, seemed to have a less pronounced role in determining the kinematic viscosity. In general, it could be concluded that serum viscosity is mainly determined by the amount and size of the solubilised pectin. The influence of serum viscosity on the rheology of the studied purées was limited as the rheology of this type of system is largely determined by the particle properties of the dispersed phase.     

Electrochemical oxidation of terbium(III) in aqueous media: influence of supporting electrolyte on oxidation potential and stability

Journal of Applied Electrochemistry - Apart from the generally dominant trivalent oxidation state, several lanthanides can occur in divalent or tetravalent states as well. Changing the valence...     

A Review on the Relationships between Processing,Food Structure,and Rheological Properties of Plant‐Tissue‐Based Food Suspensions

Nowadays, there is much interest in controlling the functional properties of processed fruit‐ and vegetable‐derived products, which has stimulated renewed research interest in process–structure–function relations. In this review, we focus on rheology as a functional property because of its importance during the entire production chain up to the moment of consumption and digestion. This review covers the literature of the past decade with respect to process–structure–rheology relations in plant‐tissue‐based food suspensions. It became clear that the structure of plant‐tissue‐based food suspensions, consisting of plant‐tissue‐based particles in an aqueous serum phase, is affected by many unit operations (for example, heat treatment) and that also the sequence of unit operations can have an effect on the final structural properties. Furthermore, particle concentration, particle size, and particle morphology were found to be key structural elements determining the rheological properties of these suspensions comprising low amounts of starch and serum pectin. Since the structure of plant‐tissue‐based products was shown to be changed during processing, rheological parameters of these products were simultaneously altered. Therefore, this review also comprises a discussion of the effect on rheological properties of the most relevant processing steps in the production of plant‐tissue‐based products. Linking changes in rheology due to processing with process‐induced alterations in structural characteristics turned out to be quite intricate. The current knowledge on process–structure–function relations can form the basis for future improved and novel food process and product design.     

Structure–mechanical property relationships in acrylate networks

The objective of this work is to investigate the effect of the molecular mobility and resin formulation of UV-curable acrylate systems on conversion and ultimate mechanical properties. Thin single-layer films are produced from a series of nine mixtures of bisphenol A ethoxylate diacrylate, having different molecular weights (BisDA_{n = 2}, BisDA_{n = 4}, and a 50/50 mixture), with different amounts of tetraethylene glycol diacrylate (TEGDA) (0, 10, and 30 wt %). Fourier transform infrared analysis, tensile, and dynamic mechanical tests are carried out on UV post-cured resins, and the results are correlated with the amount of TEGDA. A higher content of TEGDA gives rise to an increase in conversion and glass-transition temperature. Tests on pure BisDA_{n = 2} and mixtures of BisDA_{n = 2} and BisDA_{n = 4} (BisDA_{n = 2 + 4}) show that with increasing TEGDA content, the crosslink density increases. An increase in molecular weight of the acrylate monomer changes the final mechanical properties of UV-cured products. A material having a rubber behavior is the result of this change. Next to UV post-curing, the effect of thermal post-curing is studied. The results show that thermal treatments affect the mechanical properties mainly if the polymer has a low crosslink density. Formulations highly loaded with TEGDA lead to polymers with high crosslink density, low network mobility, and consequently low mechanical properties if thermally treated. Correlations between, on the one hand, resin formulation and process conditions and, on the other hand, the final mechanical properties of UV-cured systems are established allowing to optimize the structure–mechanical properties relationship in acrylate networks. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48498.     

The Interplay Between the Main Flour Constituents in the Rheological Behaviour of Wheat Flour Dough

There is still considerable debate in the literature about the respective roles of starch and gluten in both the linear and non-linear rheology of wheat flour dough. Hence, to elucidate the individual contributions of gluten and starch to the overall dough behaviour, the rheological properties of dough and mixtures of different gluten-starch ratios were studied systematically in shear and extension, by means of an adequate rheological toolbox consisting of linear small amplitude oscillatory shear tests and non-linear tests such as creep-recovery in shear and uniaxial extension. The starch component plays a pivotal role in linear dough rheology. With increasing starch content, the linearity limit observed in oscillatory shear tests decreases as a power-law function. Starch also clearly affects the extensional viscosity at small strains. Consequently, in the linear region differences between different gluten systems may become obscured by the presence of starch. As breadmaking qualities are known to be intrinsically linked to the gluten network, it is imperative to probe the non-linear behaviour of dough in order to expose differences in flour quality. The quality differences between a strong and a weak flour type were revealed most clearly in the value of the strain-hardening index in uniaxial extension and the total recovery compliance in non-linear creep-recovery tests. Notwithstanding its earlier successful application to pure gluten gels, the accuracy of the critical gel model in predicting the linear rheological properties of dough was found to be limited, due to dough having a small linearity limit and a finite longest relaxation time.     

Rheology of Concentrated Tomato-Derived Suspensions: Effects of Particle Characteristics

In the present work, the effect of particle properties on the rheological behaviour of tomato-derived suspensions was investigated systematically. Hereto, a range of relatively monodisperse suspensions, containing either cell fragments or single cells with varying average particle size (～148, 267, 303 and 393 μm) and pulp content (from 25 to 60 wt.%), was prepared by the reconstitution of tomato tissue-based particles in water. The effect of the presence of a serum phase on the rheological properties of tomato-derived suspensions was investigated by the comparison of the rheology of reconstituted tomato purées in water with those in serum. All the tomato-derived suspensions were non-Newtonian liquids exhibiting a yield stress. The flow behaviour could be described well by the Herschel–Bulkley model. The undisrupted network structure of all suspensions could be classified as a weak gel with a rather low critical strain. Particle concentration, size and morphology (surface/shape) turned out to be key structural properties controlling the rheological parameters of these tomato-derived suspensions. Increase in yield stress and storage modulus with particle concentration could be fitted to a power law model. The ratio of static yield stress to dynamic yield stress turned out to be larger for particles with a more irregular, less intact surface, showing the enhanced tendency of the latter particles to build up structure in rest conditions. A unique linear relation was found between the static yield stress and the maximal elastic stress in oscillatory tests, independent of the particle properties. Finally, replacing the serum phase by water led to a substantial decrease in network strength, especially in quiescent conditions.