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BACKGROUND Zein as a sole material is not suitable for technological applications since it is not flexible. A possible solution to extend the applications of zein is the formation of zein-polysaccharide complexes. As a first step, sonication parameters were optimized to obtain finer emulsions formulated with zein, rosemary essential oil as food preservative, and sunflower oil, by means of response surface methodology. After the formation of these guar- or diutan-zein complexes the rheological properties of these food emulsions were evaluated. RESULTS An increase in sonication power, sonication time and cycles provoked a decrease in mean droplet size and a lack of recoalescence. The optimized emulsion was the starting point to form two different complexes: zein with diutan gum and zein with guar gum at different concentrations. Rheological properties as well as the microstructure observed by field emission scanning electron microscopy (FESEM) were analyzed. Interestingly, zein-guar gum complexes did not form a rheological gel; as a consequence, emulsions containing them seem to undergo a destabilization process with aging time. In contrast, emulsions formulated with zein-diutan gum presented a 3D network, observed by FESEM technique and proved by rheological measurements. CONCLUSION While emulsions containing zein-guar gum complexes did not form networks to stabilize oil droplets, zein-diutan gum complexes did. This work brings to light the importance of the selection of polysaccharide used in food emulsions formulated with zein. © 2021 Society of Chemical Industry.

Grout injection is a useful repair and strengthening technique to intervene in old masonry buildings. Until now, a very limited amount of work has been reported on the potential of geopolymers for consolidation of old stone masonry walls. In the last decades there has been several research initiatives focus on the development of materials involving a higher volume of supplementary cementitious materials that substitute the traditional binders. Geopolymers that were developed as a part of these efforts, can not only reduce the dependence on traditional binders, but also potentially present materials with less environmental impacts and improved performance. This study investigates the fresh and hardened properties of grouts composed of natural hydraulic lime (NHL) and geopolymer. The experiments were conducted using a geopolymer made of fly ash, sodium hydroxide and water. The effects of the replacement of NHL by the fly ash-based geopolymer (at the dosages of 0, 20, 50, 80 and 100%) on the rheological parameters, stability, water absorption, compressive strength and durability were investigated. The results showed that the geopolymer-based grout has several advantages regarding the mechanical strength, durability and fresh stability, but the improvement of their rheological performances proved to be a challenging task. Overall, the findings of this study will be useful in assessing the design of grouts incorporating alternative binders and consequently contribute to the improvement of the grouting technique.

Several problems and limitations faced in the treatment of many diseases can be overcome by using controlled drug delivery systems (DDS), where the active compound is transported to the target site, minimizing undesirable side effects. In situ-forming hydrogels that can be injected as viscous liquids and jellify under physiological conditions and biocompatible clay nanoparticles have been used in DDS development. In this work, polymer&ndash, clay composites based on Pluronics (F127 and F68) and nanoclays were developed, aiming at a biocompatible and injectable system for long-term controlled delivery of methylene blue (MB) as a model drug. MB release from the systems produced was carried out at 37 &deg, C in a pH 7.4 medium. The Pluronic formulation selected (F127/F68 18/2 wt.%) displayed a sol/gel transition at approx. 30 &deg, C, needing a 2.5 N force to be injected at 25 &deg, C. The addition of 2 wt.% of Na116 clay decreased the sol/gel transition to 28 &deg, C and significantly enhanced its viscoelastic modulus. The most suitable DDS for long-term application was the Na116-MB hybrid from which, after 15 days, only 3% of the encapsulated MB was released. The system developed in this work proved to be injectable, with a long-term drug delivery profile up to 45 days.

Rheology, defined as the science of the deformation and flow of matter, is a multidisciplinary scientific field, covering both fundamental and applied approaches [...]

The injection of grouts is a consolidation technique suitable for overcoming the structural deterioration of old stone masonry walls. Grouting operations involve introducing a suspension (grout) into a masonry core with the aim of improving the load capacity of the wall, as well as reducing its brittle mechanisms. The yield stress of injection grouts will affect the injection pressure and their flow inside the masonry. However, the determination of some rheological properties such as yield stress in hydraulic grout is challenging, due to the combined effects of hydration reactions and interactions between the particles present in the suspension. In this study, the determination of the yield stress of natural hydraulic lime-based grouts with polypropylene fibers was carried out. The changes in yield stress with time, fibers content and hydration were evaluated by two measurement methods using a rotational rheometer. Additionally, the static and dynamic yield stress as well as the critical shear&ndash, strain rate were determined, which provided useful information on the grout design in order to achieve successful grouting operations.

Pluronic PE9400/water binary systems at different concentrations were characterized by means of rheological and microstructural techniques. Temperature ramps revealed a structural transition defined by three zones, which determine time-dependent behaviors. Thus, non-time-dependent, antithixotropic, and thixotropic behaviors were observed depending on Pluronic’s concentration and temperature. These phenomena were analyzed resorting to rheological tools, namely hysteresis loops and transient tests, and supported by Cryo-SEM. The results obtained demonstrated the shear-sensitive character of these systems. All properties presented by these systems make them adequate and interesting for many applications such as injectable systems for tissue repair.

This study discusses the effect of the filler on the fatigue behaviour of bitumen-filler mastics by means of strain controlled fatigue tests, with constant and variable load amplitude, implemented in the DSR. Diluted and concentrated mastics were fabricated with two fillers and two bitumens. The results showed that though the generic behaviour is highly dependent on the bitumen, the effect of the filler is not only related to the increase of stiffness but, more importantly, it is seen in the response to repeated loading. Hence, the fatigue performance was significantly more affected by the increase in content of hydraulic lime than of limestone filler.

Several calamitic reactive mesogens containing only two benzene rings in the molecular core and with or without lateral substitution by the methyl/methoxy groups have been designed and their mesomorphic behaviour was characterised. Depending on the molecular structure, some of the materials exhibit the nematic and the orthogonal smectic mesophases. The reactive mesogens are aimed for further design of the macromolecular materials like polysiloxane-based polymers and elastomers. Beyond the mesomorphic and structural properties, the electrorheological properties within the temperature range of the nematic and smectic A mesophases were studied with and without applied electric field for the selected reactive mesogen. The increase of viscosity was found not to be higher than three times under applied electric field strength of 2 kV/mm. The mesomorphic, structural and rheological properties of the newly designed reactive mesogens are discussed in order to contribute to better understanding of the molec...

Multi-leaf stone masonry walls are among the most vulnerable elements of historic constructions. Grout injection is a common and efficient technique to consolidate such masonries. It consists of introducing a grout into the masonry inner core in order to upgrading the cohesion of the wall by ensuring the transversal bond between the external leaves and improving its monolithic behaviour. Notwithstanding, the recrystallization of salts due to changes in moisture content causes several damages in these masonries, even after the consolidation intervention. This paper aims to assess the potential use of linseed oil in natural hydraulic lime-based grouts to mitigate the water penetration and therefore the damages from salts crystallization. Linseed oil was used in former times as an additive for mortars in order to grant hydrophobicity. In this study several properties of the grouts were evaluated: rheology, mechanical strength, water absorption, adhesion and durability assessed by testing the resistance to sodium chloride. Moreover, this paper also analyses the correlation between non-standard specimens (with reduced size) and standard specimens (40x40x160 mm3). The experimental results revealed that the grouts durability and water transport are significantly improved with added linseed oil. It was also possible to observe a small reduction in mechanical resistance with the presence of linseed oil; however, acceptable strength values to promote an appropriate consolidation were ensured. Furthermore, the reduced size specimens revealed to be a viable alternative to the standard ones.

Rheology, defined as the science of deformation and flow of matter, is a multidisciplinary scientific field, covering both fundamental and applied approaches [...]

A (model) composite system for drug delivery was developed based on a thermoresponsive hydrogel loaded with microparticles. We used Pluronic F127 hydrogel as the continuous phase and alginate microparticles as the dispersed phase of this composite system. It is well known that Pluronic F127 forms a gel when added to water in an appropriate concentration and in a certain temperature range. Pluronic F127 hydrogel may be loaded with drug and injected, in its sol state, to act as a drug delivery system in physiological environment. A rheological characterization allowed the most appropriate concentration of Pluronic F127 (15.5 wt%) and appropriate alginate microparticles contents (5 and 10 wt%) to be determined. Methylene blue (MB) was used as model drug to perform drug release studies in MB loaded Pluronic hydrogel and in MB loaded alginate microparticles/Pluronic hydrogel composite system. The latter showed a significantly slower MB release than the former (10 times), suggesting its potential in the development of dual cargo release systems either for drug delivery or tissue engineering.

Tissue engineering is responsible for developing biological substitutes that restore, maintain or improve tissue function. A solution to achieve this is to implant scaffolds on the affected tissue. These support structures will be responsible for cell protection, oxygenation and nutrition, while supporting mechanical loads during the regeneration process. They should also be biodegradable in order to be gradually replaced by healthy tissue. From the available scaffolds manufacturing techniques, fused filament fabrication has been used recently. This technique does not use organic solvents and has the ability to produce complex geometries. In this paper the influence of manufacturing parameters was assessed. Different temperatures, extrusion speeds, filament offset distances and layer thicknesses were tested and their effect analyzed regarding scaffold morphology and mechanical properties. By decreasing the filament offset distance, three different scaffolds porosities were obtained, increasing the mechanical properties. Combining higher printing temperatures with slow extrusion speeds and low layer thickness, a maximum yield stress of 28 ​MPa and apparent compressive modulus of 942 ​MPa were obtained. With these preferred parameters, two different manufacturing schemes and geometries were tested. While using a double layer printing scheme one obtains an average of 70% increase in mechanical properties, using a staggered configuration can decrease mechanical properties up to 84%.

The newest generation of lubricants needs to adapt to stricter environmental policies. Simple and sustainable formulations with tunable rheological properties under the action of electric potentials may be the key. The present research explored the feasibility of producing electro-sensitive ecolubricants based on nanocellulose (crystalline and fibrillar) or nanoclay (Cloisite 15A montmorillonite and halloysite nanotubes) dispersions in castor oil, at concentrations that ranged from 2 to 6 wt.%. Broadband dielectric spectroscopy (BDS) measurements allowed for a first estimate on the electro-responsive potential of the nanofluids. The nanocelluloses and the montmorillonite suspensions presented a relaxation event in the dielectric loss, &epsilon, &Prime, centered at ca. 2&ndash, 4 kHz, which is related to interfacial polarization. Moreover, their actual electro-rheological (ER) effect under high electric potentials up to 4 kV/mm was assessed by determining the magnitude of the yield stress from steady flow curves at 25 &deg, C. It was found that the nanocelluloses and the montmorillonite showed an enhancement of three orders of magnitude in their yield stress values at 4 kV/m. This enhancement was much greater than in the halloysite nanoclay, which did not exhibit any polarization). This is the starting point for the development of environmentally friendly ER lubricating fluids, based on nanocellulose and montmorillonites (layered nanosilicates), which might assist in reducing the friction and wear through the application of controlled electric fields.

The oscillation frequencies produced by oscillation-type density meters during the density measurements suffer damping due to the viscosity of Newtonian liquids. The effect of viscoelastic behaviour of non-Newtonian liquids in the damping of these oscillations is still not known. So, 7 viscoelastic liquids were rheologically characterized, resorting to a rheometer, and their density measured in order to provide a deeper insight into the damping effects produced by these types of fluids. To do so, oscillatory data was related with the obtained density deviations. The results of this study will give further insights for the knowledge of the measuring behaviour of these density meters when measuring viscoelastic fluids, one of the scopes of the EMPIR Project 17RPT02-rhoLiq.

Fatigue testing of binders is an important subject in asphalt research and in recent decades several test procedures and analysis methods have been proposed. This paper discusses the application of several analysis methods to two different strain-controlled tests, implemented with the DSR. The fatigue laws obtained from the time sweep (TST) and the linear amplitude sweep (LAS) tests with the traditional failure limits, based on a fixed stiffness reduction value, are quite different. Using LAS, with maximum shear stress as failure criterion, gives rise to better results that can be further improved when changing the failure criterion to one based on the dissipated pseudo strain energy evolution.

Two room temperature ionic liquids (ILs) bearing coumarin and p-hydroxycinnamic acid moieties are synthesized, and their photochemistry is studied in solution and neat conditions. Irradiation at absorption maxima leads to photochemical transformations and results in changes of their rheological properties which are evaluated by rotational rheometry. Samples of ionic liquids are also studied by Hyper-Rayleigh scattering, and the effect of their photochemistry on ionic nanoaggregation is discussed.

Gums are often used to increase the viscosity of the continuous phase of oil-in-water emulsions in order to reduce or inhibit some destabilization processes such as creaming. A new type of xanthan gum, advanced performance xanthan gum, which possesses improved rheological properties, has been used as a stabilizer. The addition of advanced performance xanthan gum to egg protein-based emulsions prepared at different homogenization pressures in Microfluidizer was studied. These emulsions showed different droplet size distributions and flocculation degrees. However, all the emulsions studied exhibited the same viscoelastic properties, characterized by a crossover point in the mechanical spectra. This work demonstrates the essential role of this novel gum in the rheology of emulsions. In addition, there is a direct relation between homogenization pressure and flocculation degree. This flocculation led to destabilization by coalescence in these emulsions, being the emulsion processed at the smallest homogenization pressure the most stable.

The financial support received from the Portuguese Foundation for Science and Technology through the strategic project 288 UID/CTM/50025/2013 (Cenimat/I3N) and from the Spanish Ministerio de Economia y Competitividad as well as from V Plan Propio Universidad de Sevilla, and the European Commission (FEDER Programme) is kindly acknowledged. In this paper the rheological characterization of Pluronic/water systems filled with alginate microparticles is presented. The rheological characterization of the Pluronic/water systems allowed for the choice of the best Pluronic concentration taking into account its applications as injectable hydrogels for tissue repair. The effect on the rheological behavior of the addition of alginate microparticles, to be loaded with the drug, was analyzed and the maximum concentration of microparticles determined. publishersversion published

(FCT/MCTES) through the scholarship SFRH/BPD/108427/2015. The authors would like to acknowledge the support from the strategic project UID/CTM/50025/2013. This paper puts forward a new hydrophobic silica fume and assesses its contribution to the performance improvement of grouts for stone masonry consolidation. The experiments were conducted using different dosages of hydrophobic silica fume with natural hydraulic lime grouts in the presence of a polycarboxylate-based high-range water reducer. Results revealed that the effects of hydrophobic silica fume on properties of natural hydraulic lime grouts optimize the use of ordinary silica fume. Remarkable rheological performance was obtained in the presence of hydrophobic silica fume: the plastic viscosity and yield stress were reduced compared with the ordinary silica fume. For mechanical strength aspects, it was found that hydrophobic silica fume slightly affected the flexural and compressive strength; however, the values obtained are suitable for the old stone masonry consolidation purposes. It was also observed that water capillarity was substantially reduced as a result of the water-repellent behavior of hardened grouts. This study suggests that the promising effectiveness of this new silica fume for injection grouts opens the way for it to be used in many other applications. authorsversion published

The oscillation frequencies produced by oscillation-type density meters during the density measurements suffer damping due to the viscosity of newtonian liquids. The effect of viscoelastic behaviour of non-newtonian liquids in the damping of these oscillations is still not known. So, 5 viscoelastic liquids were rheologically characterized, resorting to a rotational rheometer, and their density measured in order to provide a deeper insight into the damping effects produced by these types of fluids. To do so, oscillatory data was related with the obtained density deviations. The results of this study are one of the first insights for the knowledge of the measuring behaviour of these density meters when measuring viscoelastic fluids, one of the scopes of the EMPIR Project 17RPT02-rhoLiq.

The purpose of the present communication is to study the metrological compatibility of measurement results of mass fractions of sodium chloride in aqueous solutions, by different analytical techniques: refractometry and oscillation-type densimetry. In complement pH measurements were made in solutions of NaCl of 3,5 cg g−1 and in a synthetic seawater standard (OSIL). Previously, metrological compatibility of measurement results with refractometer and oscillation-type density meter was showed for aqueous solutions of glucose, from 2 cg g−1 to 42 cg g−1. Due to its interest for the food science and health science, sodium chloride mass fraction in aqueous solution between 0,5 cg g−1 and 7 cg g−1 and for brine systems were also measured. Comparison was displayed between potentiometric pH and pH deduced by salinity experimental value.

The support from the strategic project Pest-C/CTM/LA0025/2011 This paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45-0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the accuracy of the models was experimentally confirmed using random grout compositions. The predicted-to-measured ratio ranged from 0.97 to 1.08, indicating a good agreement between the confirmation results and the expected results from the statistical models. authorsversion published

Asphalt fatigue cracking is one of the phenomena that contribute most to degradation of road pavements and it may initiate within the bitumen or at the bitumen-aggregate interface. The cohesive cracking resistance can be evaluated with bitumen testing. Commonly, the Dynamic Shear Rheometer (DSR) is used for bitumen testing. This paper presents an evaluation of different methods proposed in literature for the estimation of the bitumen fatigue life. A neat and a polymer modified bitumen (PMB) were tested with time sweep tests (continuous and discontinuous loading) and with incremental load amplitude (linear amplitude sweep test). The results are analysed with the traditional approach (Nf,50 corresponding to 50 % initial modulus reduction) and other methodologies, namely the Ratio of Dissipated Energy Change (RDEC) and the Viscoelastic Continuum Damage (VECD) approach. The results obtained showed, as expected, that the PMB has a higher resistance to fatigue than the neat bitumen. The test conditions and the method used to evaluate the fatigue resistance lead to significant differences in the estimated bitumen fatigue life. The plateau value (RDEC) shows very good correlation with Nf,50 obtained from constant strain amplitude tests, regardless of the type of bitumen or test conditions. The fatigue life parameters obtained from the linear amplitude sweep test is very sensitive to the analysis method. Healing during non-loading periods has a large effect on the PMB fatigue life while no effect in the neat bitumen fatigue life for small to intermediate rest periods.

Grout is a concentrated suspension that can be employed for the homogenisation and consolidation of systems presenting pores, voids and cracks, such as inner core of old stone masonries. A grout should be well conceived, taking into account the optimisation of its performance; this means that simple binder and water formulations prove to be inadequate. Hence, the effect of different admixtures and pozzolans, which are traditionally used in concrete, on the fresh and hardened properties of hydraulic lime grouts, were investigated. Hydraulic lime binder plays a role of great importance in the rehabilitation of historic structures, due to its compatibility with pre-existing materials, like mortars. However, hardly any information is presently known regarding the effect of these materials on the behaviour of hydraulic lime grouts. The improvement of their properties through the use of these products is still an open field. Hence, and as a first step, the prediction of grout properties in a laboratory setting were made. The results summarised in this paper are part of a large research project and precede the fine tuning of grout composition according to the characteristics of the masonry to which such a grout is to be injected. publishersversion published

The electrorheological (ER) effect is known as the change in the apparent viscosity upon the application of an external electric field perpendicular to the flow direction. In this work we present the electrorheological behaviour of suspensions in silicone oil of two different dispersed phases: foams of liquid crystal 4-n-penthyl-4′-cyanobiphenyl (5CB) encapsulated in polyvinyl alcohol (PVA) and nano/microspheres of 5CB encapsulated in silica. We will present the viscosity curves under the application of an electric field ranging between 0 and 3 kV mm−1. The ER effect was observed for the suspensions of 5CB/PVA but not in the case of 5CB/silica. For the case of the suspensions of 5CB/PVA, the effect of the viscosity of the continuum phase and the concentration of the dispersed phase was analysed, showing that the enhancement of the viscosity of the suspension increases with the concentration, as expected, however the continuum phase viscosity has no significant effect, at least in the investigated viscosity range.