Fausto Calderas | UNAM Universidad Nacional Autónoma de México (original) (raw)

Papers by Fausto Calderas

Journal of Food Processing and Preservation, Feb 10, 2022

ABSTRACT The rheological parameters: flow behaviour index n, flow consistency index K and effecti... more ABSTRACT The rheological parameters: flow behaviour index n, flow consistency index K and effective viscosity ηe were estimated for the entomoparasitic nematodes Heterorhabditis bacteriophora liquid broth at different culture maturation times. The nematode or nematodes were cultivated during 20 days in a bioreactor, and the growth media inside the bioreactor was enriched with protein and fat sources. Rheological parameters for the heterogeneous suspension were estimated with mixer principles employing a helical ribbon agitator fixed to a rheometer. As the culture matured, n decreased from 0.8 to 0.2 (and nd K increased up to 1200 mPa • sn; ηe showed a non-Newtonian (n<1) behaviour, ηe reached peak values of 0.32 Pa • s for a rotational speed of 0.5 revolutions per second (rps) and 0.048 Pa • s for 2.5 rps. Rheological properties reported here could be more reliable as compared to those reported for non-homogeneous liquid fermentations where estimations were performed with conventional geometries (i.e. concentric cylinders) which are appropriate for homogeneous systems but not for non-homogeneous ones.

Journal of Food Process Engineering

Aloe vera (Aloe barbadensis Miller) is employed as a food supplement containing mucopolysaccharid... more Aloe vera (Aloe barbadensis Miller) is employed as a food supplement containing mucopolysaccharides which contribute to a healthy diet. Aloe vera mucilage is usually obtained through an evaporation process. An alternative process to preserve polysaccharide properties is ultrafiltration (UF), which impedes degradation of the compound by temperature. This work analyses the effect of the UF process on the mechanical and rheological properties of Aloe vera considering the following variables: temperature (T), input feeding rate (V), and transmembrane pressure (ΔPTM). The permeate flux varies according to the operating conditions exhibiting non‐Newtonian effects. The determination of the mass transfer coefficient is based on the analogy of transport phenomena (heat transfer to mass transfer) in non‐Newtonian fluids to obtain the permeate flux. The results show that when the mucilage is fed as a diluted shear‐thinning fluid, the UF efficiency is positively affected. To describe the rheolo...

Chemical Engineering & Technology

The rheological response and the computational hydrodynamic continuous stirred‐tank behavior were... more The rheological response and the computational hydrodynamic continuous stirred‐tank behavior were analyzed to increase the understanding of the bioleaching process in mineral pulps. The rheological properties of the mineral pulps showed that a smaller particle size increases the magnitude of the rheological parameters, shortens the bioleaching process time, and, indirectly, increases the concentration of bacteria in the medium, thus augmenting the gel strength. The bioreactor hydrodynamics results revealed that the best dual‐impeller configuration corresponds to a Rushton (top)/Maxflo (bottom) configuration, generating power savings of ∼9 %. Finally, when analyzing apparent viscosity maps, velocity fields, and streamlines at different stirring speeds, enhanced hydrodynamic conditions were observed at 400 rpm.

Starch - Stärke

The objective of this work is to assess the influence of the concentration of polyglycerol polyri... more The objective of this work is to assess the influence of the concentration of polyglycerol polyricinoleate (PGPR) (at 1%, 1.5%, and 2%) on the physical properties of water in oil gelled emulsions (W/O) and evaluates their efficiency as a delivery vehicle for curcumin. Emulsions are characterized by drop size, centrifugal test, texture, and rheology during 28 days of storage. When the surfactant concentration increases, smaller droplet sizes are obtained (<5 µm), the phase separation (tested by centrifugal force) decreases from 6% to 4% with little variation of the time. The mechanical properties of emulsions show a tendency to decrease as time passed and concentration of PGPR increased. The emulsions increased viscosity as the concentration increased, but the addition of curcumin reduce the viscosity of the emulsions. About controlled release profiles, a low concentration of PGPR shows an increase in the affinity between curcumin and the emulsions, following a pseudo‐Fickian rele...

Polymer Degradation and Stability

Journal of Non-Newtonian Fluid Mechanics, 2021

Abstract In this work we present theoretical and experimental studies on the structure factor in ... more Abstract In this work we present theoretical and experimental studies on the structure factor in micellar systems. Cetyl trimethyl ammonium tosilate (CTAT) solutions in absence of salts exhibit a flow behavior similar to polymer solutions, while upon an increase in the ionic strength with NaCl, their behavior changes to that of a kinetic-controlled breakage-reformation process. The relaxation mechanism thus changes from that of a spectrum of relaxation times into an averaged dominant relaxation mode, representative of reversible kinetics. Micellar solutions exhibit mechanical instabilities under flow, which may be increased by concentration fluctuations. Elastic stresses increase concentration fluctuations, which are experimentally observed by rheo-optical techniques, such as Rheo-SALS, depicting characteristic “butterfly” patterns. Scattering patterns provide information on the structure factor, arising from concentration fluctuations of the flowing solution. Upon addition of salt to a CTAT solution, we observe agreement with the Cox-Merz rule, revealing that the solution is in the fast-breaking regime approaching a single relaxation time kinetics. This behavior cannot be predicted by polymer solution theories which do not incorporate the breakage-reformation kinetics. Here, we propose a kinetic model by which the structure factor can be calculated for these micellar solutions. A shift in the maximum of the scattering patterns as the shear rate is increased is predicted by the new theory, which can be explained by considering flow-induced changes in the structure of the solutions with the underlying kinetics of breakage-reformation. Agreement with experiments is exhibited.

Minerals Engineering, 2019

Bioleaching was used to dissolve zinc, phosphorus, potassium and calcium oxide found in iron conc... more Bioleaching was used to dissolve zinc, phosphorus, potassium and calcium oxide found in iron concentrates using acidophilic microorganisms to enhance the iron yield. Rheological properties of the mineral pulps revealed a maximum in the zero shear-rate viscosity (0.068 Pa s) during day 5 of the process. The mineral concentrate contained hematite (Fe 2 O 3) and magnetite (Fe 3 O 4). Dissolution kinetics were followed in a continuous stirring tank reactor (CSTR) and pulp rheological properties were measured. Various analytical techniques were employed to evaluate the initial and final compositions of the mineral iron concentrates, such as scanning electron microscopy (SEM) and X-ray diffraction using the powder method (XRD). Data obtained from SAOS (small amplitude oscillatory shear) and simple shear were modeled using the multimodal Maxwell model and a kinetic rheological model (BMP), respectively. Up to 72% P, 91% CaO, 74% K and 53% Zn were dissolved in 5 days, where a maximum in both rheological analysis (continuous and oscillatory flow) was observed. This maximum coincided with the end of the microbial growth phase, demonstrating that the microbial growth kinetics influenced the rheological property, which can be modeled using a kinetic-like constitutive equation. The linear viscoelastic response of the pulp is consistent with the appearance of a weak gel at long times (low frequency) with relaxation exponent of n = 0.91 and gel strength of S = 0.0151 Pa s n. A generalized Maxwellian behavior with three relaxation times was observed at high frequency, associated with biofilm-particle interactions. Further investigations may consider other rheological analysis such as LAOS or stress relaxation.

Physics of Fluids, 2019

In this work, a new simplified method to find the fluidity enhancement of a non-Newtonian liquid ... more In this work, a new simplified method to find the fluidity enhancement of a non-Newtonian liquid under a pulsating (time-dependent) pressure gradient is analyzed. The fluidity enhancement is predicted by means of a Taylor series expansion of the flow rate in the vicinity of the applied wall stress. This expansion is shown to render the same results as several perturbation techniques used at length in the literature. Both new and the conventional perturbation methods are equivalent in their predictions of the fluidity enhancement. Even though the flow and rheology behavior are modeled using the Bautista-Manero-Puig constitutive equation, it is shown that the prediction of the fluidity enhancement does not depend on the constitutive model employed, but a condition of shear thinning behavior of the fluid is necessary for it. Flow enhancement is predicted using rheological data for blood since this fluid naturally flows under a pulsatile pressure gradient. The flow enhancement equation ...

Industrial Crops and Products, 2019

Mucilage of Aloe vera (Aloe barbadensis Miller) is an alternative agent for microencapsulation by... more Mucilage of Aloe vera (Aloe barbadensis Miller) is an alternative agent for microencapsulation by spray drying of labile bioactives, such as gallic acid. The microstructure of powders prepared with Aloe vera and maltodextrin (used for comparison purposes) with and without gallic acid revealed defined and undamaged particles. Aloe vera particles without gallic acid exhibited a quasi-modal distribution while the gallic acid loaded samples presented a bimodal distribution (i.e., particle size of 2-3 μm). In maltodextrin samples, the particle size presented a modal distribution (with and without gallic acid), but the mean particle size was almost ten times larger than that of Aloe vera (about 20 μm), as reflected in the low viscosity values of these samples. Under steady-state shear flow, the reconstituted samples depicted a shear-thinning behavior (n < 1). In small-amplitude oscillatory flow the viscous component G" dominated over the storage modulus G'. The FT-IR analysis confirmed the effectiveness of the wall material encapsulating gallic acid. Likewise, antioxidant activity results revealed that the encapsulated phenolic compound retained its antioxidant capacity and stability due to the short contact time in the spray dryer (< 5 s). Comparison of the release profiles (i.e., maximum release time and release percentage) revealed larger magnitudes in samples of Aloe vera containing gallic acid. Thus, the observed release profiles assess the suitability of encapsulation systems based on Aloe vera mucilage for potential applications in functional foods and pharmaceuticals, where maltodextrin is commonly used.

Minerals Engineering, 2018

In this work, we characterize the microstructural and rheological properties of silver manganese ... more In this work, we characterize the microstructural and rheological properties of silver manganese mineral pulps during a bioleaching process in a continuous stirred-tank reactor (CSTR). Analysis of the dissolution kinetics of Manganese in the pulp during the bioleaching process reveals a dissolution level of 20-23% during 36-48 h. This percentage allows the extraction of large percentages of silver (Ag) during the cyanidation process, thus obtaining 64 wt% of Ag. The maximum value of viscosity attained in the medium (especially between 48 and 72 h) is an important parameter, since it may cause processing setbacks such as in-homogeneous agitation and increase in transport energy. Several factors contribute to the continuous change of viscosity in the media such as mineral wearing, the presence of the excreted bacterial exopolysaccharide (EPS), pH changes, particle size modifications due to mineral wear (plus corrosion) and changes in density of the medium. For this reason, it is of great importance to monitor the rheological behavior of the mineral pulp during the bioleaching and cyanidation processes. The mineral pulp behaves as a weak gel as reported in linear viscoelastic measurements.

Korea-Australia Rheology Journal, 2016

In this work, analytical predictions of the rectilinear flow of a non-Newtonian liquid are given.... more In this work, analytical predictions of the rectilinear flow of a non-Newtonian liquid are given. The fluid is subjected to a combined flow: A pulsatile time-dependent pressure gradient and a random longitudinal vibration at the wall acting simultaneously. The fluctuating component of the combined pressure gradient and oscillating flow is assumed to be of small amplitude and can be adequately represented by a weakly stochastic process, for which a quasi-static perturbation solution scheme is suggested, in terms of a small parameter. This flow is analyzed with the Tanner constitutive equation model with the viscosity function represented by the Ellis model. According to the coupled Tanner-Ellis model, the flow enhancement can be separated in two contributions (pulsatile and oscillating mechanisms) and the power requirement is always positive and can be interpreted as the sum of a pulsatile, oscillating, and the coupled systems respectively. Both expressions depend on the amplitude of the oscillations, the perturbation parameter, the exponent of the Ellis model (associated to the shear thinning or thickening mechanisms), and the Reynolds and Deborah numbers. At small wall stress values, the flow enhancement is dominated by the axial wall oscillations whereas at high wall stress values, the system is governed by the pulsating noise perturbation. The flow transition is obtained for a critical shear stress which is a function of the Reynolds number, dimensionless frequency and the ratio of the two amplitudes associated with the pulsating and oscillating perturbations. In addition, the flow enhancement is compared with analytical and numerical predictions of the Reiner-Phillipoff and Carreau models. Finally, the flow enhancement and power requirement are predicted using biological rheometric data of blood with low cholesterol content.

Journal of Bioprocessing & Biotechniques, 2015

The rheological parameters: flow behaviour index n, flow consistency index K and effective viscos... more The rheological parameters: flow behaviour index n, flow consistency index K and effective viscosity ηe were estimated for the entomoparasitic nematodes Heterorhabditis bacteriophora liquid broth at different culture maturation times. The nematode or nematodes were cultivated during 20 days in a bioreactor, and the growth media inside the bioreactor was enriched with protein and fat sources. Rheological parameters for the heterogeneous suspension were estimated with mixer principles employing a helical ribbon agitator fixed to a rheometer. As the culture matured, n decreased from 0.8 to 0.2 (-) and K increased up to 1200 mPa•sn; ηe showed a non-Newtonian (n<1) behaviour, ηe reached peak values of 0.32 Pa•s for a rotational speed of 0.5 revolutions per second (rps) and 0.048 Pa•s for 2.5 rps. Rheological properties reported here could be more reliable as compared to those reported for non-homogeneous liquid fermentations where estimations were performed with conventional geometries (i.e. concentric cylinders) which are appropriate for homogeneous systems but not for non-homogeneous ones.

Applied Clay Science, 2014

In the present work, the effect of sodium montmorillonite (Na + Mt) on the resulting properties o... more In the present work, the effect of sodium montmorillonite (Na + Mt) on the resulting properties of semi-finished (crust) leather has been thoroughly studied. Na + Mt has been added during retanning process of tanned (wetblue) leather in specific conditions. The morphological analysis by scanning electron microscopy has pointed out that Na + Mt particles are homogeneously distributed and finely dispersed within the leather structure. The presence of clay mineral has affected the thermal stability of leather in nitrogen and air (assessed by thermogravimetry), as well. According to the sixty second vertical flammability test results Na + Mt particles have significantly reduced the burning length of the semi-finished leather. A barrier mechanism of the Na + Mt during combustion process is proposed. Mechanical properties (namely, tensile and tear strength) have proven to be considerably improved by using 1 and 3 mass% of Na + Mt; these results have clearly indicated the reinforcing effect of clay mineral platelets that somehow physically interact with leather.

Polymer Engineering & Science, 2013

In this work, the effect of processing conditions on the production of an intumescent flame‐retar... more In this work, the effect of processing conditions on the production of an intumescent flame‐retardant system is studied in polypropylene‐based compounds. Two distinct procedures were used: ultrasonic assisted single screw (with a static mixer die) and twin screw extrusion. The flame‐retardant, thermal, mechanical, morphological, and rheological properties were measured. It was found that the flame‐retardant intumescent content can be diminished from 30 phr (as usually used) to 21 phr using the application of ultrasonic waves during extrusion and with the addition of chemically modified clay to obtain a V0 classification according to UL94‐V standards. In addition, the processed materials presented improvements in the mechanical properties such as impact resistance (Izod Notched), strain at break and tenacity upon ultrasound application. The online application of ultrasound through a die that produces extensional flows improved greatly the dispersion and distribution of the particles ...

Rubber Chemistry and Technology, 2009

It is known that the microstructure of polymer-modified asphalts (PMA) depends strongly of the ch... more It is known that the microstructure of polymer-modified asphalts (PMA) depends strongly of the characteristics of the polymer. The modifier polymer improves the mechanical properties of pure asphalt when used in paved roads. In this work, asphalt is modified using reactive polymers obtained via functionalization of styrene-ethylene/butylene-styrene (SEBS) copolymers in solution using various amounts of benzoil peroxide (BPO) as initiator and maleic anhydride (MAH). The resulting functionalized copolymer (SEBS-g-MAH) with variable amounts of grafting (variable reactivity) is blended with the asphalt at small contents (2–4 wt. %). The amount of MAH grafting was determined by FTIR, 1HNMR, GPC, DSC and by titration with KOH, and this amount is readily correlated with the improvement of the mechanical properties and thermal stability of the asphalt. In addition, the limit of the polymer-asphalt compatibility is determined for these systems.

Polymer Engineering & Science, 2004

In this work, a detailed investigation of the rheological and mechanical properties of nanocompos... more In this work, a detailed investigation of the rheological and mechanical properties of nanocomposites based on polyethylene terephthalate (PET) and montmorillonite clays is presented. A series of additives [maleic anhydride (MAH), pentaerythritol (PENTA), and alkylammonium chlorides from amines of various chain lengths] were used as compatibilizers. The influence of the additives on the mechanical and rheological behavior of the PET matrix was evaluated separately, through their individual contributions. To shed more light on the reported decrease in melt viscosity of organoclay composites with respect to the matrix viscosity, observed in nylon and PET nanocomposites, the polymer molecular weight was related to the resulting rheological and mechanical properties of the systems. Results reveal that the PET nanocomposites behave quite differently in shear as opposed to elongation. The viscoelastic properties in shear present low values when the molecular weight decreases because of th...

Applied Clay Science, 2019

A biocomposite based on montmorillonite clay mineral (MMT) and hybrid biopolymer microparticles (... more A biocomposite based on montmorillonite clay mineral (MMT) and hybrid biopolymer microparticles (MP) carrying atorvastatin (AC), these were designed for oral drug carrier was characterized by scanning and transmission electron microscopy (SEM &TEM), differential scanning calorimetry (DSC) and in vitro biocompatibility by cell viability on fibroblast cells. The rheological synergism relation (by linear oscillatory tests at different pH and frequency) with the mucoadhesive properties revealed interactions between isolated mucin and the MP/MMT biocomposite and those between the mucin and the individual components. Results of these tests showed that the MP/MMT biocomposite provides an improvement in the thermal stability and hence good biocompatibility exhibiting anti-proliferation effects at high concentrations. To our knowledge, no previous reports exist on the determination of the rheological synergism in biocomposites with MMT clay either alone. Moreover, we found a dependence of the rheological synergism on pH and frequency provided by linear viscoelastic data at low frequencies. The MP/MMT biocomposite possesses the highest rheological synergism related to the strongest interaction with mucin at pH 1.6.

Ingeniería Investigación y Tecnología, 2021

En este trabajo, se presentan los estudios de mercado, técnico y económico-financiero, para evalu... more En este trabajo, se presentan los estudios de mercado, técnico y económico-financiero, para evaluar la factibilidad de la manufactura en México de calzado de seguridad, para personal que realiza actividades de combate de incendios forestales. Los requerimientos de diseño y desempeño del calzado se basaron en las especificaciones establecidas por la National Fire Protection Association. El análisis del mercado mexicano se llevó a cabo por medio de la recopilación de fuentes primarias y secundarias. El estudio técnico se enfocó en identificar los principales componentes del calzado, el proceso, la maquinaria y equipo para llevar a cabo la manufactura por la industria del calzado mexicana. Para la determinación de la factibilidad económica y financiera, se estimaron los indicadores del valor actual neto (VAN), la tasa interna de retorno (TIR), el punto de equilibrio y el tiempo de amortización de la inversión. El estudio de factibilidad, muestra nuevas oportunidades de negocio para la ...

Physics of Fluids

In this study, rheological techniques are used to measure the flow properties of blood from 52 pa... more In this study, rheological techniques are used to measure the flow properties of blood from 52 patients with liver cirrhosis. A comparative analysis included a control group (23 persons) to determine the stage of the disease in cirrhotic patients. An important correlation relating the blood biochemical composition with the rheological response was found. Two rheological techniques were employed: simple shear-flow and small amplitude oscillatory shear. The “whole blood viscosity” (WBV) exhibits non-Newtonian shear-thinning behavior. Cirrhotic patients show low WBV levels as well as low values of viscoelastic response compared to those of the control group. Viscosity curves in decompensated cirrhotic patients tend toward a Newtonian behavior (constant viscosity) at high shear rates. Regarding the complex viscosity, there are clear differences between compensated and decompensated patients. The viscoelastic response reveals a change in the slope of the elastic modulus (G′) with frequen...