Use Of Rheology Research Articles

Role of Rheology in Morphology Development and Advanced Processing of Thermoplastic Polymer Materials: A Review.

This review presents fundamental knowledge and recent advances pertaining to research on the role of rheology in polymer processing, highlights the knowledge gap between the function of rheology in various processing operations and the importance of rheology in the development, characterization, and assessment of the morphologies of polymeric materials, and offers ideas for enhancing the processabilities of polymeric materials in advanced processing operations. Rheology plays a crucial role in the morphological evolution of polymer blends and composites, influencing the type of morphology in the case of blends and the quality of dispersion in the cases of both blends and composites. The rheological characteristics of multiphase polymeric materials provide valuable information on the morphologies of these materials, thereby rendering rheology an important tool for morphological assessment. Although rheology extensively affects the processabilities of polymeric materials in all processing operations, this review focuses on the roles of rheology in film blowing, electrospinning, centrifugal jet spinning, and the three-dimensional printing of polymeric materials, which are advanced processing operations that have gained significant research interest. This review offers a comprehensive overview of the fundamentals of morphology development and the aforementioned processing techniques; moreover, it covers all vital aspects related to the tailoring of the rheological characteristics of polymeric materials for achieving superior morphologies and high processabilities of these materials in advanced processing operations. Thus, this article provides a direction for future advancements in polymer processing. Furthermore, the superiority of elongational flow over shear flow in enhancing the quality of dispersion in multiphase polymeric materials and the role of extensional rheology in the advanced processing operations of these materials, which have rarely been discussed in previous reviews, have been critically analyzed in this review. In summary, this article offers new insights into the use of rheology in material and product development during advanced polymer-processing operations.

Effect of chest physiotherapy on cystic fibrosis sputum nanostructure: an experimental and theoretical approach

Cystic fibrosis (CF) is a disease characterized by the production of viscous mucoid secretions in multiple organs, particularly the airways. The pathological increase of proteins, mucin and biological polymers determines their arrangement into a three-dimensional polymeric network, affecting the whole mucus and impairing the muco-ciliary clearance which promotes inflammation and bacterial infection. Thus, to improve the efficacy of the drugs usually applied in CF therapy (e.g., mucolytics, anti-inflammatory and antibiotics), an in-depth understanding of the mucus nanostructure is of utmost importance. Drug diffusivity inside a gel-like system depends on the ratio between the diffusing drug molecule radius and the mesh size of the network. Based on our previous findings, we propose the combined use of rheology and low field NMR to study the mesh size distribution of the sputum from CF patients. Specifically, we herein explore the effects of chest physiotherapy on CF sputum characteristic as evaluated by rheology, low field NMR and the drug penetration through the mucus via mathematical simulation. These data show that chest physiotherapy has beneficial effects on patients, as it favourably modifies sputum and enhances drug penetration through the respiratory mucus.Graphical abstract

Rheology-driven design of pizza gas foaming

This paper investigates the production of a yeast-free pizza by gas foaming and the use of rheology to guide the process design. The novel process relies on the use of a gaseous blowing agent and a pressure program to form and stabilize bubbles during baking, avoiding the use of yeast and the associated lengthy leavening stage. The evolution of the dough structure during baking has been studied by a rheological characterization at leavening and baking conditions. These experimental pieces of information have been used to evaluate the time available for blowing agent sorption under pressure during early baking stage, and to guide the pressure release during the final baking, to achieve an optimally foamed pizza.

Combined use of rheology and portable low-field NMR in cystic fibrosis patients

BackgroundAs most cystic fibrosis (CF) patients progress to respiratory failure, lung functionality assessment is pivotal. We previously developed a test that indirectly monitors airways (inflammation/functional test) by measuring the spin-spin relaxation time (T2m) of the water hydrogens present in CF sputum. Here the T2m significance in the monitoring of CF lung disease was further investigated by studying the correlation of T2m with: 1) sputum viscoelasticity, 2) mucociliary clearability index (MCI)/cough clearability index (CCI) and 3) sputum average mesh-size. MethodsSputum samples from 25 consenting CF subjects were analyzed by rheology tests (elastic modulus G and zero shear viscosity η0) and Low Field Nuclear Magnetic (LF-NMR) resonance (T2m). MCI/CCI were calculated from the rheological parameters. The average mesh-size (ξ) of the sputum structure was then evaluated by rheology/LF-NMR, together with FEV1 for each patient. ResultsThere was an inverse correlation between G and η0 versus T2m, indicating that a worsening of the lung condition (T2m-FEV1 drop) is paralleled by an increase in sputum viscoelasticity (G and η0) favoring mucus stasis/inflammation. A direct correlation was also observed between T2m and MCI/CCI, showing that T2m provides information as to airway mucus clearing. Moreover, there was a direct correlation between T2m and the average sputum mesh size (ξ). ConclusionsWe demonstrated a correlation between T2m (measured in CF patient's sputum) and the sputum viscoelasticity/average mesh-size and with MCI/CCI, parameters related to airway mucus clearing. Thus, the present data strengthen the potential of our test to provide indirect monitoring of airway disease course in CF patients as T2m depends on mucus solid concentration and nanostructure.

Developing Chemical Engineering Acumen through Optimization of the Chocolate Process

The United States Military Academy’s Chemical Engineering Chocolate Club increases the interest in the sciences by combining chemical engineering knowledge with the production of a consumable product, chocolate. Cadets design the chocolate process by identifying the product (such as 70% dark chocolate), ingredients, and specific process details such as mixing standards and refinement time. They extend their design to include the use of rheology and a range of rheological models for quality control and assurance.

Assessment of rheological methods to study crystallization of palm oil fractions.

This study provides an evaluation of the use of rheology to characterize soft, semi-hard, and hard fats in relation to determine the crystallization onset, crystallization behavior, as well as microstructure development using either a plate-plate or a starch pasting cell (SPC). The results from this study demonstrate that when applying rheology to study fat crystallization, the results must be interpreted with care. The application of a plate-plate geometry allowed for sensitive evaluation of the initial nucleation phase, which was not possible with an SPC. Both geometries could provide information on crystallization behavior in terms of one-step or two-step crystallization. However, in the late stage of the crystallization process, when the fat crystals form a strong network, the SPC could not describe differences in the rheology of the fat-crystal network, which was a possibility by the use of a plate-plate geometry. Thus, oscillatory rheology with a suitable geometry can be used to evaluate the entire crystallization process.

Combined Use of Rheology, LF-NMR, and MRI for Characterizing the Gel Properties of Hairtail Surimi with Potato Starch

The effects of potato starch (4%, 8%, 12%, 16%, and 20%) on the gel properties of hairtail surimi were investigated by rheology, low-field nuclear magnetic resonance (LF-NMR), and magnetic resonance imaging (MRI). The results indicated that the addition of potato starch markedly improved the gel properties, including the maximum texture profiles, gel strength, and water holding capacity. The addition of potato starch significantly increased both the storage modulus and loss modulus after the formation of gel rather than changed the type of two curves. Furthermore, there was a positive correlation between heat-induced gel properties and rheological properties in the surimi-starch system. The LF-NMR results indicated that the addition of potato starch had a positive effect toward the shortening of T2 spin-spin relaxation time of gel and water exchange from free water to bound water. Additionally, more uniform water distribution in surimi gel contained potato starch was observed from the result of MRI. The overall results suggested that interactions of starch-protein promoted the most favorable properties of hairtail surimi at the addition of 16% potato starch.

Impact of Nitrogen Foamed Stimulation Fluids Stabilized by Nanoadditives on Reservoir Rocks of Hydrocarbon Deposits.

The first objective of this experiment was to improve the stabilization of N2 based foam with nanoparticles as an alternative to typical fracturing fluid, which consists of a gelling agent (HPG—hydroxypropyl guar). The second objective of the project was to investigate the damage caused by nanoparticle–based nitrogen foamed fracturing fluids (F.F) on a reference sandstone, using permeability and porosity tests, optical microscope with a Profilometer, and a scanning electron microscope (SEM). The properties of F.F with two types of SiO2 nanoparticles (hydrophilic fumed silica Areosil 300 and silica sol U-2 obtained by the sol-gel method), such as rheology and core damage, were investigated. The discussion of this research results is based on the stability tests carried out with the use of rheology and the foam half-life, formation damage ratio, and observation of exposed samples using SEM and the Profilometer. The permeability and porosity damage ratios of the damaged core samples were found to decrease when nitrogen foamed fluids were used. These results were confirmed with the Profilometer and SEM images. The experimental data showed that the foam stability increased when silica (SiO2) nanoparticles were added. SiO2 nanoparticle-surfactant-stabilized foam for fracturing is superior to traditional water-based fracturing fluids and causes lower core permeability damage than a traditional F.F.

ВВЕДЕНИЕ В ПРАКТИЧЕСКУЮ РЕОЛОГИЮ ПОЛИМЕРОВ

The article is devoted to the theoretical foundations of the rheology method and its practical aspects in the polymer industry. Examples of the use of rheology for the development and quality control of new and improved materials are given.

The use of rheology to elucidate the granulation mechanisms of a miscible and immiscible system during continuous twin-screw melt granulation

Twin-screw hot melt granulation (TS HMG) is a valuable, but still unexplored alternative to granulate temperature and moisture sensitive drugs in a continuous way. Recently, the material behavior of an immiscible drug–binder blend during TS HMG was unraveled by using a rheometer and differential scanning calorimetry (DSC). Additionally, vibrational spectroscopic techniques proved the link between TS HMG and rheology since equal interactions at molecular level did occur in both processes. This allowed to use a rheometer to gain knowledge of the material behavior during hot melt processing of an immiscible drug–binder blend. However, miscibility of a drug–binder formulation and drug–binder interactions appear to influence the rheological properties and, hence conceivably also the granulation mechanism. The aim of this research was to examine if the TS HMG process of a miscible formulation system is comparable with the mechanism of an immiscible system and to evaluate whether rheology still serves as a useful tool to understand and optimize the hot melt granulation (HMG) process. The executed research (thermal analysis, rheological parameters and spectroscopic data) demonstrated the occurrence of a high and broad tan(δ) curve without a loss peak during the rheological temperature ramp which implies a higher material deformability without movement of the softened single polymer chains. Spectroscopic analysis revealed drug–polymer interactions which constrain the polymer to flow independently. As a result, the binder distribution step, which generally follows the immersion step, was hindered. This insight assisted the understanding of the granule properties. Inhomogeneous granules were produced due to large initial nuclei or adhesion of multiple smaller nuclei. Consequently, a higher granulation temperature was required in order to get the binder more homogeneously distributed within the granules.

The use of Rheology Combined with Differential Scanning Calorimetry to Elucidate the Granulation Mechanism of an Immiscible Formulation During Continuous Twin-Screw Melt Granulation.

Twin screw hot melt granulation (TS HMG) is a valuable, but still unexplored alternative to continuous granulation of moisture sensitive drugs. However, knowledge of the material behavior during TS HMG is crucial to optimize the formulation, process and resulting granule properties. The aim of this study was to evaluate the agglomeration mechanism during TS HMG using a rheometer in combination with differential scanning calorimetry (DSC). An immiscible drug-binder formulation (caffeine-Soluplus(®)) was granulated via TS HMG in combination with thermal and rheological analysis (conventional and Rheoscope), granule characterization and Near Infrared chemical imaging (NIR-CI). A thin binder layer with restricted mobility was formed on the surface of the drug particles during granulation and is covered by a second layer with improved mobility when the Soluplus(®) concentration exceeded 15% (w/w). The formation of this second layer was facilitated at elevated granulation temperatures and resulted in smaller and more spherical granules. The combination of thermal and rheological analysis and NIR-CI images was advantageous to develop in-depth understanding of the agglomeration mechanism during continuous TS HMG and provided insight in the granule properties as function of process temperature and binder concentration.

A review of diet standardization and bolus rheology in the management of dysphagia.

Texture modification is a widespread practice as a strategy for the management of dysphagia and can be very effective in individual cases. However, it is often performed in a qualitative, subjective manner and practices vary internationally according to multiple sets of national guidelines. This article aims to identify best practice by reviewing the theory and practice of texture modification, focussing on recent advances. Instrumental assessment of texture modification in vivo is challenging, and studies including rheology and perception have indicated that fluid viscosity is only one of many factors affecting texture modification in practice. Systematic reviews have identified a historical lack of high-quality clinical evidence, but recent controlled studies are beginning to identify positive and negative aspects of thickened fluids. Research and practice to date have been limited by the lack of control and standardization of foods and drinks. However in 2015 a not-for-profit organization, the International Dysphagia Diet Standardisation Initiative, has published a framework for texture modification from thin liquids to solid foods based on all the existing documentation and guidance, and the - limited - available clinical evidence. Rheology exists in the lab; however, normal practice is often subjective or lacking control and standardization. In the near future, cohesion of practice and the availability of practical standardization tools may increase awareness and use of rheology.

Relaxation and Dynamics in Transient Polymer Model Networks

Supramolecular polymer networks have promising potential to serve as self-healing soft materials. To benefit from this ability, quantitative understanding of the underlying mechanisms of macromolecular dynamics and transient association must be achieved. A key to obtaining such understanding is to understand the dynamics and relaxation of supramolecular polymer networks, which is often complexed by inhomogeneous polymer-network structures. To overcome this limitation, we use a set of regular star-shaped poly(ethylene glycol) polymers end-capped with terpyridine groups that can transiently coordinate to different metal ions, thereby forming transient supramolecular polymer networks with determined homogeneous architectures and determined binding strength. We study these networks in view of their mechanics, dynamics, and relaxation from both macroscopic and microscopic perspectives through the use of rheology, dynamic light scattering, and fluorescence recovery after photobleaching. These studies reveal tha...

Insight into industrial PLA aging process by complementary use of rheology, HPLC, and MALDI

Nowadays, there is a growing availability of biodegradable industrial materials intended to food contact applications whose service life behavior needs to be further investigated. This article is focused on the degradation of two materials based on polylactic acid. The correlation between the rate of degradation and the amount of trapped degradation products was investigated applying three characterization techniques in parallel, namely rheology, high‐performance liquid chromatography (HPLC), and matrix‐assisted laser desorption/ionization (MALDI). The rate of degradation was studied through the evaluation of their rheological properties and calculation of the number of average molecular weights, and weight‐average molecular weights. Water‐soluble oligomers and lactic acid were quantified by HPLC‐ultraviolet. Changes in cyclic and linear oligomers were monitored by MALDI‐time‐of‐flight mass spectrometry. Specimens of 4‐mm thickness of each biopolymer were subjected to hydrolysis in deionized water up to 6 months at two temperatures, simulating service conditions of food packaging. The diminution in viscosity and consequently in molecular weight distribution (20–60%) showed the degradation of the molecular structure of both polylactic acids. The chain scission was followed through the increasing values of lactic acid and hydrolyzed oligomers (twofold to eightfold), and the predominant signal of the linear oligomers over the cyclic ones with aging. Rheology, HPLC, and MALDI showed to be complementary tools to better understand the changes in the molecular structure. The obtained results showed the necessity of adding suitable stabilizers for each particular food packaging application. Copyright © 2013 John Wiley & Sons, Ltd.

The use of rheology in the study of the composition effects on the fresh behaviour of hydraulic lime grouts for injection of masonry walls

The injection of grouts inside multi-leaf stone masonries is a technique widely used for structural consolidation. To ensure an adequate flow of the grout inside the masonry, it is crucial to assure good fresh grout properties, such as good rheological behaviour. The scope of this paper is to provide preliminary indications and valuable data about the effects of specific hydraulic lime grout composition on their rheological behaviour with the purpose of a successful injection process. Through the use of rotational rheometer together with the Taguchi method, it was possible to study the influence of water/binder ratio, the type and dosage of superplasticizer and the partial replacement of hydraulic lime by silica fume, upon the grout rheological properties. The study leads to the conclusion that polycarboxylate-based superplasticizers present better performance from a rheological point of view than the naphthalene-based superplasticizer and that the water/binder ratio and superplasticizer dosage are the most determinant factors in the fresh grout rheological behaviour. On the other hand, silica fume dosage turned out to be the factor with the least contribution to improve the grout rheological behaviour compared to the other two factors reported in this study. The results summarised in this paper are part of a larger study and precede the analysis of the performance of those grouts when injected into different porous media that simulate old masonries.

Effect of Na + and Ca 2+ on the aggregation properties of sieved anaerobic granular sludge

Interactions between fine particles (0–50 μm) of anaerobic granular sludge were investigated by studying the effect of Na + or Ca 2+ supply on the evolution of the zeta potential and viscosity of granular sludge suspensions. In the Na + or Ca 2+ concentration range investigated, the Na + addition affected only slightly the evolution of the viscosity of fine particles of an anaerobic granular suspension. In contrast, Ca 2+ addition strongly modified the evolution of the viscosity of the studied anaerobic granular sludge suspension. The use of rheology combined with zeta potential measurements clearly described the physico-chemical interactions between small anaerobic granules and especially the importance of aggregation phenomena that occur between fine anaerobic particles under Ca 2+ addition. The positive effect of Ca 2+ on the aggregation of non-fed fine anaerobic granular sludge is likely to induce the formation of bigger particles and thus, prevent their wash-out from anaerobic bioreactors.

Use of rheology, dielectric analysis and differential scanning calorimetry for gel time determination of a thermoset

Measurements of gel time of the epoxy system DGEBA( n=0)/ m-XDA were carried out using rheometry and dielectric analysis with the objective of checking the validity of Mangion–Johari equation (DEA) and Harran–Laudouard criterium (rheometry) for gel time determination. In this work, gel times obtained by rheometry and dielectric analysis are compared and conversions at gel time calculated. From the experimental results obtained for gel times it was found a reasonable agreement between the two techniques that lead to gel conversion values very close to those obtained using Flory equation.

Application of rheology for assessment and prediction of the long-term physical stability of emulsions

This review deals with the use of rheology for assessment and prediction of the long-term physical stability of emulsions. It starts with an introduction, highlighting the importance of having accelerated test to predict emulsion stability. This is followed by a section on the stability/instability of emulsion systems, giving a brief summary of the driving force of each instability process and its prevention. The classical techniques that can be applied for assessment of creaming or sedimentation, flocculation, Ostwald ripening, coalescence and phase inversion are briefly described. This is followed by several sections on the application of rheological techniques to assess and predict each of these instabilities. This involves the use of steady state shear stress-shear rate measurements, constant stress (creep) measurements and dynamic (oscillatory) techniques. The last section gives an example of model emulsions to illustrate the correlation between the various break-down processes with the rheological characteristics of the system.

Application of rheology for assessment and prediction of the long-term physical stability of emulsions

This review deals with the use of rheology for assessment and prediction of the long-term physical stability of emulsions. It starts with an introduction, highlighting the importance of having accelerated test to predict emulsion stability. This is followed by a section on the stability/instability of emulsion systems, giving a brief summary of the driving force of each instability process and its prevention. The classical techniques that can be applied for assessment of creaming or sedimentation, flocculation, Ostwald ripening, coalescence and phase inversion are briefly described. This is followed by several sections on the application of rheological techniques to assess and predict each of these instabilities. This involves the use of steady state shear stress-shear rate measurements, constant stress (creep) measurements and dynamic (oscillatory) techniques. The last section gives an example of model emulsions to illustrate the correlation between the various break-down processes with the rheological characteristics of the system.

Use of Rheology in an Industrial Polymer Research Centre

Use of Rheology in an Industrial Polymer Research Centre