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The application of quality by design (QbD) is becoming an integral part of the formulation and process development for pharmaceutical products. An essential feature of the QbD philosophy is the design space. In this sense, a new approach to construct a process design space (PDS) for the primary drying section of a freeze-drying process is addressed in this paper. An effective customized design of experiments (DoE) is developed for freeze-drying experiments. The results obtained from the DoE are then used to construct the product-based PDS. The proposed product-based PDS construction approach has several advantages, including (1) eliminating assumptions on the heat transfer coefficient and dried product resistance, as it is constructed from experimental results specifically obtained from a given formulation, yielding more realistic and reliable results and (2) PDS construction based on a narrow range of product temperatures and considering the variations in product temperature and sublimation rate of vials across a shelf. This guarantees the effectiveness and robustness of the process and facilitates the process scale-up and transfer. The PDS developed herein was experimentally verified. The PDS predicted parameters were in excellent agreement with the experimentally obtained parameters.

We examined the rheological and tribological behavior of novel formulations based on castor oil and epoxidized cellulose pulp intended for use as biodegradable lubricating greases. Epoxidized cellulose pulp was found to thicken castor oil to a variable extent depending on its modification degree and the epoxide compound. Greases were subjected to small-amplitude oscillatory shear tests, evaluating the temperature-dependence of the plateau modulus. In addition, friction coefficient and wear were determined in a steel–steel ball-on-three-plates tribological configuration, at two different temperatures (25 and 95 °C), generally obtaining smaller values of both parameters when using aromatic diepoxides instead of aliphatic to modify the cellulose pulp.

The overall objective of this work was to study the combined effect of hydrogen peroxide (H2O2) and light emitting diodes (LED) process assisted by titanium dioxide (TiO2) on the photo-oxidation behaviour of polylactic acid (PLA). The photochemical behaviour of PLA in a TiO2 suspensions was studied by irradiation under photo-oxidative conditions (λ > 454 nm, ambient temperature and with or without the presence of H2O2). The chemical and thermal properties induced by LED irradiation process were analyzed using fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the presence of photoactive TiO2 particles, combined with H2O2 leads to strong impact on the physicochemical properties of the samples during photochemical ageing. A new comprehensive mechanism for the photo-oxidation of PLA for these conditions was discussed.

This paper presents the rheological properties of three types of lime putty, specifying the influence of their origin. The study aims to compare a special lime putty prepared from phosphogypsum with a commercial lime powder and an aged lime putty. The results obtained in terms of chemical composition, crystalline structure, grain size and rheological characterization, (linear viscoelasticity, shear rate and time-dependent flow behaviour) are presented in the study. Putties studied present a similar rheological response, which mainly depends on the particle size and water content. Lower values of the linear viscoelastic functions and viscosity were found for the phosphogypsum lime putty, in agreement with the higher particle size. Transient flow tests reveal a predominant elastic response with no significant shear-induced structural perturbations. However, either a thickening phenomenon over time, i.e. rheopexy, favoured at low shear rates, or a viscosity decrease, i.e. thixotropy, favoured at high shear rates, was observed., The authors would like to thank the aid of CITIUS at the University of Seville for the use of their laboratories for the characterization analyses. A.M.B.-L. has received a Ph.D. Research Grant from the Ministerio de Education, Cultura y Deporte (FPU16/03697).

A method to prepare solvent free castor oil (CO) based polyurethane (PU) adhesives with different ratios of CO and hexamethylene diisocyanate (HMDI) has been developed and the relationships between the microstructure and mechanical properties investigated. Solvent free castor oil-based PU adhesives were synthesized by promoting the reaction between castor oil and HMDI, at room conditions, and by varying the CO/HMDI weight ratio in the range 1:0.032–1:0.32 wt%. The curing of these adhesives did not require any external stimuli such as heat or irradiation treatment and once cured at room temperature they were stable up to 140 °C and water-resistant. A multi-technique approach was used to characterize so-obtained adhesives. The adhesion energy in metal–metal contact was evaluated as a function of the debonding velocity (Vd) through tack experiments. The mechanical properties were influenced by the NCO/ OH ratio, which varies the crosslinking density in the adhesives. Moreover, the structure–mechanical property relationship was explored and the inter-correlation between the storage modulus (G’), adhesion energy (Ead) and correlation length (ξ) detailed, with both G’, Ead increasing while ξ decreased. These solvent-free bio-based adhesives showed capability to adhere different substrates such as wood, paper, textile, and metal, which makes them promising candidates in different industrial and commercial applications.

The main aim of this study was to elucidate the influence of an alkali treatment on the rheological and tribological properties, and microstructure, of cellulose pulp-based gel-like dispersions potentially usable as biodegradable lubricating greases. For this purpose, cellulose pulp was treated with sodium hydroxide under different conditions of alkali concentration (20, 30 and 40%), temperature (20, 45 and 75 °C) and contact time (1 and 2 h). Favourable conditions relative to the rheological response of a commercial lithium lubricating grease used as benchmark were found to be 40% NaOH, 20 °C and 2 h. Gel-like dispersions with acceptable lubrication properties in terms of consistency indices, mechanical stability, and frictional and wear performance, were obtained by using a 6–7% (w/w) proportion of cellulose pulp.

This work advances the development and use of sustainable polyurethane elastomers as green adhesives by providing insights into the mechanisms of humidity-induced changes on adhesive performance. Using a model adhesive prepared from equimolar ratios of castor oil and hexamethylene diisocyanate under facile reaction conditions, we show that the subtle changes in the chemical composition which occur with curing under different humidity environments significantly impact the cohesive integrity of the adhesives and, thus, their performances with different substrates. The curing chemistry was evaluated based on the isocyanate consumption, which was followed using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry. Thermal, mechanical and adhesion properties were evaluated from thermogravimetric analysis, differential scanning calorimetry, rheology, tacking and lap shear tests. Moisture-cured adhesives were less covalently crosslinked, harder, more resistant to deformation, and recovered faster upon shear deformation compared to those cured otherwise. These mechanical properties complimented adhesive lap shear performance with substrates which formed covalent bonds during curing. For substrates with which covalent bonds could not form during curing, however, decreased internal cohesive integrity and associated increased hardness by urea formation resulted in poorer adhesive lap shear performance. This is contrary better tack performances obtained for the moisture-cured adhesives, attributed to their increased polarity and the energy dissipating ability.

On account of the heavy reliance of the adhesive industry on petrochemical derivatives, there is a particular interest in the development of bio-sourced polyurethane adhesives. In this context, a moisture-curable polyurethane adhesive has been synthesized from cellulose acetate and castor oil, using 1,6-hexamethylene diisocyanate as a crosslinker. In particular, this research delves into the rheological and adhesion properties achieved by bio-inspired polyurethanes cured at 20 °C and under different relative humidity conditions (11, 33, 64, and 90.4%). Green shear and peeling strengths on wood and stainless steel as well as chemical structure variations were monitored over curing time. Moreover, fully cured polyurethane-urea adhesives were thermally (thermogravimetric and differential scanning calorimetric analyses) and rheologically characterized within the linear viscoelastic region. The results corroborated the noteworthy impact of environmental humidity throughout the curing process of the synthesized bio-sourced adhesives, favoring the formation of urea linkages, while sharply reducing the crystalline/amorphous ratio. All the bio-based polyurethane-urea copolymers showed a predominant elastic behavior and the time-Temperature superposition principle was found to be applicable up to around 120 °C, due to the thermal rearrangement of the hard segment units. The crosslinking density of the resulting supramolecular structure depends on the humidity-driven balance between the urethane and urea linkages production. As a consequence of the balance between the establishment of bidentate hydrogen bonds and the curing rate, moisture curable polyurethane adhesive cured at 33% relative humidity exhibited the most appropriate shear adhesion performance on wood, while the debonding shear strength on stainless steel increased with the relative humidity due to the higher urea:urethane ratio and larger proportions of non-bonded urethane and urea groups, thus enhancing secondary interactions. Therefore, on the basis of the present study results, it might be concluded that the synthesis of bio-inspired moisture-curable polyurethane can be tuned according to its end-use application through the control of the environmental conditions, and thereby optimizing their adhesion performance, while meeting the Green Chemistry tenets.

8 Pág. Instituto de Ciencias Forestales (ICIFOR), In this study, modified residual lignins from barley and wheat straws submitted to solid-state fermentation with diverse Streptomyces strains were targeted as binders in eco-friendly castor oil-based polyurethane adhesive formulations. The thermo-rheological and adhesion properties of these adhesives were examined and related to the solid-state fermentation yields. Viscoelastic properties were enhanced by lignin addition, and the Streptomyces action generally increased the values of the linear viscoelastic functions. Adhesion performance was dominated by lignin source and further Streptomyces activity and can be correlated with the resulting lignocellulosic composition. Wheat straw lignin-based polyurethane adhesives showed the best performance in metal-textile peeling tests, whereas barley straw lignin provided the best achievements in terms of shear strength in metal-metal and wood-wood joints. Overall, solid-state fermentation with Streptomyces demonstrated to be a suitable pretreatment to conveniently modify and improve residual lignin fractions for application as binders in environmental-friendly polyurethane adhesive formulations., This work was partially funded by two coordinated research MINECO-ERDF projects (CTQ2014-56038-C3-1R and CTQ2014-56038-C3-2R) and the ERDF-Junta de Andalucía 2014-2020 Operational Programme (project UHU-1252599). A.M.B-L. has received a Ph.D. Research Grant from the Ministerio de Educación, Cultura y Deporte (FPU16/03697). The authors gratefully acknowledge the financial support.

In this work, alkali lignin together with different diisocyanates (hexamethylene diisocyanate (HDI), isophorone diisocyanate (IDI), toluene diisocyanate (TDI) and 4,4′-methylenebis (phenyl isocyanate) (MDI)) have been tested as gelling agents in a castor oil medium. A two-step process comprising first lignin functionalization with a diisocyanate and then the formation of a bio-based polyurethane with gel-like characteristics by combining the functionalized lignin with castor was followed. FTIR and thermogravimetry analysis were carried out on both the gelling agents and resulting oleogels. Moreover, oleogel rheological properties were evaluated by means of small-amplitude oscillatory shear (SAOS) tests and viscous flow measurements. The influences of time-temperature processing conditions during oleogel formation, lignin/diisocyanate ratio and functionalized lignin concentration on the rheological properties of oleogels were analyzed using HDI as crosslinker. 30% (w/w) thickener concentration and room temperature processing were selected to prepare oleogels with the rest of diisocyanates considered. Under the same conditions, HDI-functionalized lignin-based oleogels showed the strongest gel-like behavior whereas TDI-, IDI- and especially MDI-functionalized lignin-based oleogels displayed weak gel-like, or even a liquid-like, behaviors as a consequence of the respective chemical structures, which guide to higher steric hindrance, diminishing the formation of urethane linkages and/or Van der Waals forces. In general, oleogels exhibited an internal curing process due to the progressive formation of urethane linkages, which is closely related to the evolving rheological properties. The kinetics of this curing process was studied and an empirical model has been proposed to predict the evolution of the rheological properties with time., This work is a part of two research projects (CTQ2014-56038-C3-1R and TEP-1499) sponsored by the MINECO-FEDER and Junta de Andalucía programmes, respectively.

It is well known that spontaneous oxidation is one of the main drawbacks for the industrial use of eco-friendly vegetable oil-based lubricants. Herein a quick and easy synthesis of different molecules belonging to stilbene family is reported, which together with a number of representative natural sources-derived products with antioxidant (AO) capacity have been tested as additives for improving the oxidative stability of a selected bio-lubricating grease formulation. Thus, different gel-like dispersions based on N-acylated chitosan in castor oil also including these additives have been prepared. Gel-like dispersions were characterized through thermogravimetric analysis (TGA), oxidation onset temperature (OOT) and small-amplitude oscillatory shear (SAOS) rheological measurements. These preliminary results demonstrate that, in general, these antioxidants delay N-acylated chitosan-based gel-like dispersions oxidation. However, the AO activity is more relevant in the case of propyl gallate and ascorbic acid palmitate and not so important in the family of stilbene derivatives. On the other hand, the addition of any antioxidant does not qualitatively affect the rheological response but unexpectedly may significantly modify the values of the SAOS functions. Remarkably, the delay of oxidation reactions occurs by exclusively employing natural resources-derived components, being these formulations environmentally acceptable as a whole and potentially employed in specific industrial applications.

This work has been focused on the preparation and characterization of gel-like dispersions based on sepiolite and castor oil potentially suitable as eco-friendly lubricating greases. Particularity, the effect of sepiolite content exerted on rheological, chemical, thermal and tribological properties was studied. The system exhibited a gel-like behaviour for all the concentrations considered (20–40 wt%) related to the development of a sepiolite three-dimensional colloidal network due to its characteristic nanoscale structure formed by fibers, laths and bundles. The values of both apparent viscosity and viscoelastic functions in the linear viscoelastic region increased with sepiolite content, as a consequence of a strengthening of the gel network. An empirical correlation between viscoelastic modulus and sepiolite concentration was proposed. From tribological point of view, the friction coefficient values and wear marks obtained after the frictional tests became lower when sepiolite concentrations decrease. Gel-like dispersion formulated with 30 wt% sepiolite showed appropriate rheological and tribological behaviour to be used as biolubricating greases.

The frictional and wear properties of novel bio-based greases consisting of epoxide-functionalized alkali lignins (EALs) dispersions in castor oil were examined. EALs used as thickeners were obtained by chemical modification of alkali lignin (AL) with poly (ethylene glycol) diglycidyl ether (PEGDE). The thickener concentrations and epoxy indices used spanned the ranges 2.5–10 wt% and 0.28–0.79 mol/kg, respectively. The influence of both variables on friction and wear was studied. Comparing the frictional behaviour of the biogreases and the base oil revealed that the influence of the thickener on lubrication performance differed with temperature, load, and sliding velocity. The thickener effectively reduced friction and wear, but especially at low concentrations (5 wt% or lower) and high epoxy indices (up to 0.79 mol/kg).

The stability of the thickener microstructure in lubricating greases influences their ability to reduce friction and protect the lubricated surfaces in a tribological system. Shear-induced degradation of the thickener network in lubricating greases that occurs as a result of reduced particle interactions can be considered a process associated with exceeding a critical energy level, i.e. the activation energy. The aim of this experimental study was to investigate the relationship between the activation energy, which represents the amount of energy required to produce shear-induced structural degradation, and the extent of the structural degradation that occurs under different shearing conditions. To this end, rotational transient flow tests were carried out in a rheometer at varying temperatures (25–70 °C) and a constant shear rate to quantify the activation energy of six model greases. The model greases differed in the nature and concentration of the thickener used, and the activation energy was calculated by fitting the rheological energy density to the Arrhenius equation. The activation energy was found to depend on the nature and concentration of the thickener in the greases; higher thickener concentrations resulted in lower activation energies. In addition, oscillation amplitude sweep tests were performed to obtain information about the early stages of shear-induced structural degradation. Lower activation energies were found to result in an earlier onset of shear-induced structural degradation. Finally, correlations between the activation energy and structural degradation of the model greases under different shear situations were presented and discussed. This enhanced understanding of the shear-induced degradation will facilitate the improvement of the service life of lubricating greases.

Several commercially available cellulose derivatives differing in the type of substituent and substitution degree (α-cellulose, methyl cellulose, 2-hydroxyethyl cellulose, methyl 2-hydroxyethyl cellulose and cellulose acetate propionate) have been functionalized with 1,6-hexamethylene diisocyanate (HMDI) and subsequently dispersed in castor oil to obtain chemical oleogels, which can be proposed as lubricating grease formulations completely based on renewable resources. NCO-functionalized cellulose derivatives used as thickening agents and corresponding oleogels were characterized by means of Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Oleogels were also rheologically investigated and gel microstructure determined by atomic force microscope (AFM) observations. Dispersions of the different cellulosic derivatives analyzed provide oleogels with a wide variety of rheological properties, thermal stability and physical appearance. Cellulose derivatives used as thickeners exhibited a reduced thermal resistance after NCO-functionalization due to the inclusion of the HMDI segments in the cellulose structure. However, the resulting oleogels presented suitable thermal resistance. The different rheological responses obtained, from solid-like to weak gels, were found to be basically dependent on the balance between the non-polar and polar substituents molar ratio in the biopolymer structure and the size of these substituents. The presence of non-polar groups reduces cellulose polarity and, therefore, increases the affinity by the oil medium, whereas large substituents seem to hinder the development of the three-dimensional gel network. An empirical correlation between the storage modulus, G ′, and a power function of both the molar ratio [− R polar /− R non-polar ] in each monomer,− R being the different substituents of cellulosic derivatives evaluated, and the ratio of average molecular weight of all substituents to cellulose monomer molecular weight has been proposed to predict the rheological behavior of resulting oleogel formulations.

The overall objective of this work was to study the effect of reprocessing cycles of isotactic polypropylene (PP) on the rheological behavior and microstructure of gel-like dispersions in mineral oil. PP was subjected to 10 reprocessing cycles and oleogel samples were further prepared by using the mixing rheometry technique and characterized from a rheological point of view and polarized light optical microscopy (PLOM). Recycled polymer samples were also characterized by means of rheological measurements, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) to evaluate the property changes induced by reprocessing. The values of different linear viscoelastic functions (elastic modulus and complex viscosity) of recycled PP decrease with the number of reprocessing cycles, which influences oleogel rheological response. An empirical exponential correlation between the storage modulus (G′) of PP samples and the plateau modulus ( G N o ) of oleogels has been proposed to predict the rheological behavior of oleogels. Results were explained considering the scission of PP chains induced by the thermomechanical reprocessing treatment applied.

Summary This work deals with the development and characterization of new formulations based on different types of acylated chitosan, obtained using different acylation protocols and acyl chlorides, which are able to generate stable gel-like dispersions in castor oil. These dispersions can be proposed as promising candidates to replace current non-biodegradable lubricating grease formulations. The biopolymers and gel-like dispersions were characterized through Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). In addition to this, small-amplitude oscillatory shear (SAOS) measurements were performed on gel-like dispersions. The resulting oleogels demonstrated suitable thermal resistance although the inclusion of acyl segments into the polymer structure reduces thermal stabilities. The values of the linear viscoelastic functions and their evolution with frequency for gel-like dispersions of chitosans N -acylated with decanoyl chloride or N - and O -acylated with palmitoyl chloride were very similar to those exhibited for non-biodegradable commercial greases. A significant decrease in the storage and loss moduli was detected as the carbon chain length in the acyl group decreases in both N -acylated and N - and O -acylated chitosans. Moreover, both moduli decrease when the acylation reaction time increases, as a result of a major chitosan acylation degree, which provides weaker gels.

This paper reports a physical characterization of multiple emulsions formulated with a green solvent (2-ethylhexyl lactate) and different HLB amphiphilic block copolymers (Atlas™ G-5000 and Atlox™ 4912), as emulsifiers. 15 wt% 2-ethylhexyl lactate emulsions stabilized by a 1:1 mass ratio of both copolymers were prepared with different copolymer concentrations in one single emulsification step, using a rotor-stator emulsification device. Multiple emulsions were characterized by means of electrolytic conductivity measurements, viscosity, optical microscopy, laser diffraction and multiple light scattering techniques. W/O/W emulsions were obtained in all cases, regardless of the copolymer composition used. All emulsions showed Newtonian behaviour and relatively low viscosity values (2–2.6 times the viscosity of water at 20 °C). Viscosity hardly increased with the overall copolymer concentration. The mean Sauter diameter of O/W globules increased with copolymer concentration, while the evolution of the volumetric mean diameter depended on the occurrence of some recoalescence. The onset of different simultaneous destabilization mechanisms was detected by multiple light scattering. Even though creaming was the predominant destabilization mechanism, a separated layer of oil phase due to coalescence was also observed in most cases after a long aging time. The destabilization kinetics was slowed down by increasing the total copolymer concentration when both types of copolymers were used.

The overall objective of this work was to study the influence of vinyl acetate (VAc) content on the rheological properties and microstructure of polymer gels based on conventional and high-oleic sunflower vegetable oils and ethylene-vinyl acetate copolymer (EVA). The mechanical properties during gel preparation can be in situ monitored through the evolution of torque with processing time by using the mixing rheometry technique. Linear viscoelastic measurements, as well as differential scanning calorimetry (DSC) tests and morphological observations, were performed on the resulting gels. From the experimental results, it can be concluded that VAc content and melt flow index of the EVA copolymer significantly affect the rheological and thermal responses of polymer gels. VAc content, mainly affecting EVA degree of crystallinity, and melt flow index influence the linear viscoelastic behaviour in opposite directions. On the contrary, the extension of the linear viscoelastic regime and gel-like to liquid-like response transition temperatures are mainly dominated by EVA degree of crystallinity, as confirmed through calorimetry tests and microscopy observations. The different fatty acid profile in sunflower oils tested does not exert an important influence on process rheokinetics and rheological behaviour.

This work deals with the development and rheological characterization of a variety of green lubricating grease formulations based on different combinations of vegetable oil-derived basestocks and biopolymers obtained from renewable resources. Castor oil, high-oleic sunflower acid oil (HOS-AO) and a ricinoleic acid-derived estolide were tested as basestocks, whereas chitosan and Kraft cellulose pulp, apart from traditional lithium soap, were selected as thickener agents. Rheological behaviour was characterized by means of small-amplitude oscillatory shear (SAOS) and viscous flow measurements. In addition to these, some standard mechanical tests were carried out in order to evaluate the suitability of these formulations for lubricant applications. The rheological response depends on the type of vegetable oil-derived basestocks and thickener agent. Higher values of the SAOS functions were obtained for chitosan-based formulations. High viscosity and consistency were particularly achieved by combining the estolide sample and lithium hydroxide. On the contrary, soft greases and generally higher flow indexes were found in cellulose pulp-based formulations. The effect of the different basestocks on the rheological response was explained attending to the influence exerted by oil viscosity and basestock-thickener polar interactions, as well as the chemical reaction between the basestock carboxylic moieties and lithium hydroxide to form different thickener structures.

In this work, the capability of organo-bentonite (OBent)/recycled polypropylene (PP) and mineral oil blends to form gel-like dispersions potentially applicable as lubricating greases was explored. Specifically, the effect of both thickener concentration ratios on the rheology, thermal and some lubricant performance properties of the resulting gel-like dispersions was studied. The rheological response was qualitatively similar for all the samples studied and also similar to that found in standard lubricating greases. The plateau modulus G°N, of OBent/PP dispersions in mineral oil showed negative deviation from the additivity line and minimum values were observed for intermediate OBent/PP concentration ratios, excepting at the highest temperature studied (150 °C), where a continuous increase of this viscoelastic parameter with OBent content was found. The degree of crystallinity of recycled PP in the sample was influenced by the presence of OBent. Samples formulated with lower values of OBent/PP concentration ratio yield gel-like formulations with appropriate mechanical stabilities to be used as lubricating greases. The friction coefficient evaluated in a ball-on-plate tribological contact decreased with OBent content.

In this study, cellulose acetate and castor oil have been used to synthesize new eco-friendly alternatives to traditional polyurethane adhesives. First, cellulose acetate (CA) was modified with diphenylmethane-4,4′-diisocyanate (MDI) at different NCO:OH molar ratios, ranging from 2 to 4.53, and then the resulting biopolymers were mixed with castor oil (CO) at 1:1 wt ratio. The fully cured bio-sourced adhesives were rheologically characterized by applying dynamic oscillatory torsional tests at different temperatures (from −30 up to 200 °C). Furthermore, their adhesion performance on stainless steel and poplar wood substrates was analyzed, by conducting standardized mechanical tests, namely single-lap shear and 180° peel strengths, at room temperature and 100 °C. Fourier transform infrared spectroscopy-attenuated total reflectance along with differential scanning calorimetry and thermogravimetric analysis were also performed. Above a critical NCO:OH ratio, a thermo-rheological simplicity was found within the whole temperature range considered, being able to apply the t-T superposition principle. However, an increase in the temperature led to a depletion in their mechanical performance, thus reducing their temperature range of application. Thermal and spectroscopic analysis corroborated the complete disappearance of free isocyanate during the first few days of curing, and a segmented structure, typical of polyurethanes. Optimum thermo-rheological behaviour and adhesion performance on wood and stainless steel of the bio-sourced polyurethanes studied were found for NCO:OH molar ratios higher than 3.5, which was related to the higher compatibility between hard and soft microdomains.

This work reports the influence of solid-state fermentation (SSF) of two agricultural residues, wheat and barley straws, by using Streptomyces MDG301 strain, on their capacity to thicken and structure castor oil via crosslinking with hexamethylene diisocyanate in order to obtain gel-like systems. The analytical composition of the lignocellulosic residues and the enzymatic profile of the strain on both substrates were screened in order to establish the best conditions to achieve optimal oleogel properties. A different rheological response was found for oleogels obtained from each residue. This result could be explained in terms of the different enzymatic profile observed when the microorganism grow on these substrates. Thus, a notable difference in the production levels of CMCase and xylanase activities were detected. The assessment of the resulting oleogels as potential lubricating grease formulations was carried out by means of rheological characterization at different temperatures and tribological and mechanical stability tests. Overall, these oleogels demonstrate to possess similar rheological and tribological characteristics compared to other commercial lubricating greases.

This work deals with the viscous, thermal and tribological characterization of a variety of estolides, obtained from both oleic and ricinoleic acids, using different acid-catalysed synthesis protocols, and their blends with vegetable (high-oleic sunflower, HOSO, and castor, CO) oils. Estolides with molecular weights between 4.4 and 6.9 times higher than the originating fatty acids were obtained. Polymerization degree was larger when using the sulphuric acid-catalysed synthesis protocol. Estolides obtained from oleic acid displayed higher freezing temperatures than the fatty acid, whereas the crystallization process was delayed in estolides obtained from ricinoleic acid, yielding improved low-temperature properties. Ricinoleic acid-derived estolides showed much higher viscosity values than those prepared from the oleic acid, with values of kinematic viscosity up to around 6700 mm 2 /s. In general, viscosities were related to estolide molecular weight. Significant increments in HOSO and CO viscosities were found when they were blended with estolides, especially those prepared from the ricinoleic acid using the sulphuric and p -toluensulphonic acids-catalyzed methods. Relative increments in kinematic viscosities up to 1500% and 700% were obtained for HOSO and CO, respectively. HOSO's viscosity-temperature dependence was significantly improved when it was blended with different estolides, whereas CO/oleic acid-derived estolides blends showed a more moderate improvement of CO thermal dependence. The sulphuric acid-catalysed method influences friction and wear in the ball-on-plates contact lubricated with estolides. The addition of the different estolides to HOSO or CO does not modify their frictional behavior, resulting in just one single Stribeck curve for all samples, and significantly reduces wear.

This work focuses on the development of gel-like formulations for use as lubricating greases. These dispersions were formulated using mineral oil and recycled/amorphous polypropylene blends. In particular, the influence of the polypropylene concentration ratio (Wi) on the rheology, thermal and some lubricant performance properties of polymer/oil blends were studied. The rheological responses of these systems were quite different, influenced mainly by the concentration of amorphous polypropylene. At intermediate temperatures (25 °C, 50 °C) and high recycled polypropylene concentrations (Wi > 0.5), the evolution of small-amplitude oscillatory shear (SAOS) functions was very similar to those found with other commercial lubricating greases. Samples with lower concentrations of amorphous polypropylene (12.5%) present maximum G N ° values in the temperature range studied. An Arrhenius-type equation can be used to quantify the thermal dependence of the linear viscoelastic functions of these gel-like dispersions. In general, sample formulations studied exhibited values of the friction coefficient comparable to those found for traditional lithium lubricating greases.

This work has been focused on the development of polyolefins/oil blends potentially suitable as lubricating greases by studying the effect that some thermo-mechanical processing variables exert on their rheological properties and microstructure. Polyolefin/oil blends have been prepared by dispersing recycled and virgin polyolefins such as high-density polyethylenes (HDPEs) and polypropylenes (PPs) in mineral lubricating oil. Linear viscoelasticity functions have been significantly influenced by processing conditions. The nature of polymers used, specially the content of HDPE, has been found to modify the microstructure of blends yielding lower mechanical stability but, on the other hand, higher values of linear viscoelastic functions.

Microalgae are one of the most promising sources for new food and functional food products, and can be used to enhance the nutritional value of foods, due to their well-balanced chemical composition. Knowing their physicochemical characteristics is fundamental for the selection of the most suitable microalgae to specific food technology applications and consequently successful novel foods development. The aim of this study is to screen the chemical composition (e.g., proteins, pigments, fatty acids) and thermogravimetry properties of five microalgae species with potential application in the food industry: Chlorella vulgaris (green and carotenogenic), Haematococcus pluvialis (carotenogenic), Spirulina maxima, Diacronema vlkianum and Isochrysis galbana. C. green and S. maxima presented high protein (38% and 44%, respectively), low fat content (5% and 4%, respectively). The carotenogenic C. vulgaris and H. pluvialis showed a higher carotenoid content, higher fat, low protein and better resistance to thermal treatment. D. vlkianum and I. galbana presented high protein (38–40%) and fat (18–24%) contents with PUFA's ω3, mainly EPA and DHA. Finally, the results from microalgae chemical and thermal analysis were grouped and correlated through Principal Components Analysis (PCA) in order to determine which variables better define and differentiate them.

7 páginas, 5 figuras, 1 tabla, Yessotoxins (YTXs) production along the culture growth of three strains of the dinoflagellate Protoceratium reticulatum isolated from seawater of Galician Rias Baixas, Spain was investigated. Quantification and toxin profile determination in both cells and culture medium along the growth curve were performed by liquid chromatography–mass spectrometry (LC–MS3) analysis. The YTX profile was very similar among strains, the three algal strains produce mainly YTX and also some YTX analogs. Among the strains the maximum toxin production ranged between 416 and 576 ng mL−1. This is the first report about YTX production by P. reticulatum isolated in Galician coast, NW Spain., This study was supported by project AGL2005-07924-CO4-01/02 with the collaboration of the project ACU-02-005 INIA and culture CCVIEO.[SS]

This work is focused on the development of gel-like formulations, potentially applicable as biodegradable lubricating greases obtained by dispersing eucalyptus Kraft cellulose pulp, or its methylated derivative, in an ethyl cellulose/castor oil medium. The effects that concentration and weight ratio of the different cellulosic derivatives exert on the rheological properties, thermal resistance and mechanical stability of these oleogels were studied. The evolution of linear viscoelasticity functions with frequency was very similar to that found for traditional lubricating greases. In general, linear viscoelastic functions increase with Kraft cellulose pulp or methylcellulose concentrations and ethyl cellulose/Kraft cellulose pulp weight ratio. However, the relative elasticity of gel-like dispersions based on ethyl cellulose/Kraft cellulose pulp is not affected by the composition of these thickener blends, which allows the application of an empirical superposition method to obtain generalized master curves for describing the viscoelastic response of these formulations. On the contrary, the relative elasticity of methylcellulose-based gel-like dispersions depends on the composition of methylated cellulose pulp/ethyl cellulose blends. An Arrhenius-type equation can be used to quantify the linear viscoelastic functions thermal dependence of these gel-like dispersions. Moreover, formulations prepared using Kraft cellulose pulp/ethyl cellulose blends show appropriate mechanical stabilities to be used as bio-lubricating greases.

Microalgae represent an alternative and innovative source of natural ingredients that can be used in the development of novel food products. Biologically active compounds (e.g. carotenoids) are naturally encapsulated within microalgal cells, being able to resist harsh technological conditions involved in food technology processes. The aim of this work was to study the effect of adding Haematococcus pluvialis and Spirulina maxima microalgal biomass on the linear viscoelastic behaviour of vegetarian food gels prepared from pea protein, κ-carrageenan and starch. The gelation process was monitored in situ through dynamic oscillatory measurements, under different thermal profile conditions. Increasing temperature (70–90 °C, 5 min) resulted in more structured gels, while the effect of time (5–30 min, at 90 °C) was less pronounced. The effect of heating and cooling rates on gel setting was also studied. Haematococcus gels were highly structured and less dependent on gel setting conditions. Spirulina gels presented lower values of viscoelastic functions than the control (gel matrix without microalgae), but this was overcome when using lower heating/cooling rates.

Low temperature performance is one of the main constraints concerning the use of vegetable oils as lubricants, more than mineral or synthetic oil-based lubricants. In this work, the low-temperature behaviour of a variety of vegetable oil basestocks for lubricating applications, as well as their blends with some viscosity improvers and pour point additives, was studied through pour point determinations, thermal analysis (DSC) and viscosity measurements at low temperature. The concentration of polyunsaturated fatty acids (PUFAs) was found a predominant parameter influencing the low-temperature properties of vegetable oil-based lubricants. The pour point depressant (PPD) additives used had a positive influence by lowering the pour point and increasing the low-temperature performance of the vegetable oils studied, which was found dependent on vegetable oil fatty acid composition. In this sense, the most striking result was shown by the sunflower (SO)/PPD blend, whose pour point temperature reached −36 °C in comparison to −18 °C for the neat oil. By contrast, the worst result was obtained for the high oleic sunflower oil (HOSO)/PPD blend (−21 °C) in comparison with HOSO (−18 °C). On the other hand, it was found that the ethyl cellulose (EC), used as viscosity modifier, induces a delay in HOSO crystallization, producing a similar effect than PPD tested, besides increasing the viscosity. However, the ethylene–vinyl acetate copolymer (EVA) induces an undesirable increase in HOSO viscosity at around 13 °C.

The purpose of the present work is to evaluate the effect that different polyolefins, used as additives in small proportions, exert on the rheological properties of standard lithium lubricating greases. Grease formulations containing several polyolefins, differing in nature and molecular weight, were manufactured and rheologically characterized. The influence of the type of polymer, molecular weight, crystallinity degree and vinyl acetate content has been analyzed. Small-amplitude oscillatory shear (SAOS) and viscous flow measurements, as well as calorimetric (DSC) and thermogravimetric (TGA) analysis, were carried out. In general, the addition of polymers such as HDPE, LDPE, LLDPE and PP to lithium lubricating greases significantly increases the values of the rheological parameters analyzed, consistency and mechanical stability. However, the use of polyolefins as rheology modifiers does not significantly affect the friction coefficient determined in a tribological contact. The crystallinity degree, mainly dependent on the nature of the polymer, has been found the most highly influencing parameter on the rheology of the lubricating greases studied. However, the rheological modification exerted by EVA copolymers mainly depends on the vinyl acetate content. Thus, a negative effect in both apparent viscosity and linear viscoelastic functions of greases was obtained when polymer vinyl acetate content is higher than 28% (w/w).

Nowadays the lubricating market is demanding new biodegradable or more environmentally acceptable products based on renewable resources as a consequence of progressively more strict environmental regulations. In this framework, this study deals with the design of gel-like dispersions potentially applicable as environmentally friendly lubricating greases. These dispersions were formulated using castor oil and ethyl cellulose/α-cellulose or ethyl cellulose/methyl cellulose blends. In particular, the influence of cellulosic derivatives concentration ratio on the linear viscoelasticity and mechanical stability of the resulting oleogel formulations was studied. The modification of ethyl cellulose/α-cellulose or ethyl cellulose/methyl cellulose weight ratios allows obtaining some formulations with suitable rheological characteristics and mechanical stability for potential lubricating applications. An important decrease in the values of the linear viscoelasticity functions down to a minimum value was found by increasing ethyl cellulose/α-cellulose or ethyl cellulose/methyl cellulose weight ratios ( W ) up to a critical value, which depends on both nature of the cellulosic derivatives employed and temperature. Above this critical value, the linear viscoelastic functions increase with W , at temperatures in the range 0–75 °C, and continuously decrease at higher temperatures, i.e. 125 °C. Thermal susceptibility is significantly dampened by reducing ethyl cellulose concentration. Gel-like dispersions formulated with ethyl cellulose/methyl cellulose blends showed appropriate mechanical stabilities to be used as bio-lubricating greases.

Microalgae are an enormous biological resource, representing one of the most promising sources for the development of new food products and applications. Pea protein/κ-carrageenan/starch gels, interesting vegetarian alternatives to dairy desserts, served as model systems to study the addition of microalgal biomass, its effect, and subsequent rheological behaviour. Spirulina and Haematococcus gels presented a markedly different rheological behaviour compared to the control mixed biopolymer gelled system. The present goal is to clarify how these microalgae affect the gelation and interact with each biopolymer present in the complex mixed gel system. Hence, the aim of the present work is to study the effect of Spirulina and Haematococcus microalgal biomass addition on the rheological behaviour of pea protein, κ-carrageenan and starch simple gels, as well as in pea protein/κ-carrageenan and pea protein/starch systems. The gelation process was monitored in-situ through dynamic oscillatory measurements (temperature, time and frequency sweep tests) for a 24 h maturation period, and rheological results were supported with fluorescence optical microscopy observations. The addition of Spirulina and Haematococcus to biopolymer gelled systems induced significant changes in the gels’ rheological behaviour and microstructure. In general, it was observed that the gelling mechanism is ruled by the biopolymers, while microalgae seem to be embedded in the gel network acting as active particle fillers. The addition of Haematococcus resulted in more structured gels in comparison to the control and Spirulina systems. In the case of κ-carrageenan gels, both microalgae induced a large increase in the rheological parameters, which should be related to the high ionic content of microalgal biomass. Spirulina addition on starch systems promoted a decrease in the gels’ rheological parameters. This should be related to the starch gelatinization process, probably by competing for water binding zones during the granules’ hydration process.

This work deals with the development of new gel-like formulations prepared from natural resources, which could be potentially applicable as environmentally friendly lubricating greases. In particular, the use of chitin, chitosan and acylated derivatives as thickener agents of vegetable oils, which may represent an alternative to the traditional metallic soaps or polyurea derivatives, was explored. Biopolymers used to obtain oleogels were chemically and thermally characterized. Oleogels thermal and rheological behaviours were studied by means of TGA and DSC tests, and linear viscoelasticity measurements, respectively. Moreover, some lubricant performance properties were evaluated. The evolution of linear viscoelasticity functions with frequency was very similar to that found for standard lubricating greases. In general, linear viscoelasticity functions increased with biopolymer concentration, whilst they decreased when acylated chitosan or soybean oil were used in the oleogel formulation. The use of acylated chitosan with a degree of acylation of around 0.3 provides oleogels with very similar rheological properties than those shown by traditional lubricating greases, as a consequence of reducing the biopolymer polarity. However, chitin and chitosan-based oleogels show higher thermal stabilities than formulations containing acylated chitosan. In general, oleogel samples studied exhibited values of the friction coefficient comparable to those found for standard lithium greases. However, most of these oleogels generally display a quite poor mechanical stability in rolling elements.

Dysphagia, or abnormal swallowing of foods and/or liquids, may result as a consequence of different common diseases. Management of dysphagia is commonly done by the prescription of texture-controlled diets. The aim of the present study was to characterize the rheological behaviour, as a function of ageing, of a new ready-to-serve dysphagia diet food with spoon-like consistency (pudding). Linear (small amplitude oscillatory shear) and non-linear (steady-state flow and relaxation) material functions were measured as a function of product shelf-life at different storage temperatures. From the experimental results obtained, it may be concluded that both linear viscoelasticity moduli and viscosities of the commercial pudding studied always increase with ageing, showing maximum values for samples stored at 40 °C. A power-law model describes the frequency dependence of pudding elastic modulus. The power-law index shows minimum values for the sample stored at 40 °C, and does not depend on ageing. Linear viscoelasticity functions versus frequency curves, as a function of ageing, can be superposed into a master one. The non-linear relaxation modulus is factorable into time and strain dependent components. Commercial pudding Sauter’s diameter increases with ageing and storage temperature. However, the differences are not large enough to explain the significant increase in the rheological functions found during storage at high temperature. Protein aggregation enhancement in the continuous phase, during storage at high temperature, may explain the experimental results obtained.

This work deals with the design of new gel-like formulations based on blends of cellulosic derivatives and castor oil, which could be potentially applicable as environmentally-friendly lubricating greases. In particular, the influence of ethyl cellulose molecular weight, blended with α-cellulose or methylcellulose, on the thermal and rheological properties of the resulting gel-like dispersions was explored. Thermal and rheological behaviours were characterized by means of TGA tests and linear viscoelasticity (SAOS) measurements. Moreover, some standard mechanical tests, usually performed on commercial lubricating greases, were carried out in order to evaluate the suitability of these oleogels for lubricant applications. From the experimental results obtained, it can be deduced that SAOS functions of gel-like dispersions are not significantly influenced by ethyl cellulose molecular weight below a critical threshold value (Mw

During these last years, special attention has been paid to the protection of the environment against pollution exerted by lubricants and hydraulic fluids based on mineral oils. Thus, vegetable oil-based lubricants are being actively demanded for many green industrial activities. Although vegetable oils have some excellent properties for their potential use as lubricants, some inconveniences should be technologically improved, i.e. limited range of viscosities available. Consequently, environmental friendly viscosity modifiers should be included in the lubricant formulation. In this paper, ethylene–vinyl acetate copolymer (EVA) has been successfully tested as viscosity modifier for several common vegetable oils, yielding potentially environmental friendly lubricants for some applications. EVA addition always yields an important increase in vegetable oil viscosity. The most important viscosity increments have been found for low-viscosity vegetable oils, i.e. sunflower oil (SO), high-oleic sunflower oil (HOSO) and soybean oil (SYO), at moderate temperatures. Viscosity increments up to 330–420% respecting the original oil have been obtained for these vegetable oil/EVA blends at 40 °C. On the contrary, the lowest increments correspond to castor oil/EVA blends, mainly at low temperature. Furthermore, ternary blends of high-oleic sunflower oil, castor oil (CO) and EVA may be used to design enhanced bio-lubricant formulations for some specific applications. In this sense, some CO/HOSO/EVA ternary blends (CO/HOSO weight ratios >1) show kinematic viscosities, at 40 °C, higher than 320 cSt, which may be considered a threshold viscosity value for gearboxes and four-strokes engine applications.

27 páginas, 4 tablas, 4 figuras, Diarrhetic Shellfish Poisoning (DSP) is a specific type of food poisoning, characterized by severe gastrointestinal illness due to the ingestion of filter feeding bivalves contaminated with a specific suite of toxins. It is known that the problem is worldwide and three chemically different groups of toxins have been historically associated with DSP syndrome: okadaic acid (OA) and dinophysistoxins (DTXs), pectenotoxins (PTXs) and yessotoxins (YTXs). PTXs and YTXs have been considered as DSP toxins because they can be detected with the bioassays used for the toxins of the okadaic acid group, but diarrhegenic effects have only been proven for OA and DTXs. Whereas, some PTXs causes liver necrosis and YTXs damages cardiac muscle after intraperitoneal injection into mice. On the other hand, azaspiracids (AZAs) have never been included in the DSP group, but they cause diarrhoea in humans. This review summarizes the origin, characterization, structure, activity, mechanism of action, clinical symptoms, method for analysis, potential risk, regulation and perspectives of DSP and associated toxins produced by marine dinoflagellates., This work was funded b yGrants AGL2005-07924-C04- 01/02 and CTQ2008-0754-C04-01/04 from the MEC of Spain.

The main goal of this work was to study the feasibility of using a low-density polyethylene (LDPE) as additive to improve the rheological properties of lithium lubricating greases. The combined effect that both soap and LDPE concentrations exerts on the rheology of lithium lubricating greases and its relationship with grease microstructure were studied according to an experimental design based on the response surface methodology (RSM). Different lubricating grease formulations were manufactured by modifying lithium 12-hydroxystereate and LDPE concentrations. Small-amplitude oscillatory shear (SAOS) and viscous flow measurements, as well as mechanical stability tests, were performed. In addition to these, environmental scanning electronic microscopy (ESEM) was used to determine grease microstructure. LDPE was found to be a useful additive to modify grease rheology, acting as filler in the entangled soap network. The values of both apparent viscosity and linear viscoelasticity functions increase with soap and LDPE concentration. However, the addition of LDPE distorts soap microstructural network, yielding greases with lower relative elastic characteristics.

Benthic dinoflagellates of the genus Ostreopsis are important components of subtropical and tropical marine coral reef–lagoonal environments. Currently, as a result of global warming and trade globalization, they are also distributed worldwide. These microalgae are shown to produce palytoxin, one of the most potent non-protein marine toxins known. The haemolytic assay is a very easy, rapid and sensitive method to determine palytoxin. However, under the conditions reported in previous works this assay is inadequate for a rigorous dose–response treatment, since: (1) it produces degenerate sigmoidal profiles, with a pronounced slope which makes the calculation of the ED50 very sensitive to the experimental error; (2) at the usual work temperature, the in vitro stability of the system is low, which accentuates the variability and ambiguity of the response. To resolve these problems haemolysis of sheep erythrocytes is studied, including it's toxicological dynamics, kinetics, inhibition by ouabain and response to temperature. The results show that, to obtain a smoother, more stable and reproducible response, it is necessary to apply two resources simultaneously: operation at a moderate temperature and partial inhibition of the palytoxin by ouabain. It also produces highly reliable parameters and allows strict equivalencies to be established with the mouse bioassays, a traditional reference point, though bioethically questionable and 20 times less sensitive than the bioassay proposed here.

This work deals with the influence that the addition of poly(1,4-butanediol) tolylene 2,4-diisocyanate terminated prepolymer (PBTDI) at different stages during the manufacturing process of a traditional lithium lubricating grease exerts on its rheological and morphological characteristics. With this aim, the reaction between terminal isocyanate groups and the hydroxy group located in the hydrocarbon chain of the 12-hydroxystearate lithium soap was intended to be promoted during lubricating grease processing. Several PBTDI-based greases just differing in the process stage at which this polymer was added were prepared. The polymer used and the final lubricating greases were characterized by FTIR spectroscopy and DSC techniques. The effect of PBTDI addition at different processing stages was tested on final greases by performing small-amplitude oscillatory shear (SAOS) measurements as well as atomic force microscopy (AFM) observations. Addition of PBTDI significantly increased the values of the linear viscoelasticity functions when it was added during the final cooling stage of the manufacturing process. It was demonstrated that this increment in relation to the values found for the additive-free lubricating grease was only observed when PBTDI chemically interacted with the soap network. However, the effectiveness of PBTDI as rheology modifier was much lower when the addition took place at earlier steps of the manufacturing process. Some competitive reactions due to either the presence of water or the high temperatures applied have been proposed to explain this loss of effectiveness depending on the lubricating grease processing stage at which PBTDI was added.

The recovery of plastic waste but also its applicability in product development may be an incentive to industry, since the use of such plastics represents a cheaper source of raw material. The aim of the present paper is to study the feasibility of recycling polyolefins as additives to improve the rheological properties of lithium 12-hydroxystearate lubricating greases. The effects that both soap and recycled low-density polyethylene (LDPE) concentration exert on the rheology of lithium lubricating greases and its relationship with grease microstructure are discussed in this work. In this way, different lubricating grease formulations were manufactured by modifying the concentration of lithium 12-hydroxystearate and content of recycled LDPE, according to a RSM statistical design. These lubricating greases were rheologically characterized through small-amplitude oscillatory shear (SAOS) and viscous flow measurements. In addition to these, scanning electronic microscopy (SEM) observations and mechanical stability tests were also carried out. Recycled LDPE was found to be an effective additive to modify grease rheology, acting as filler in the soap entangled microstructure. The values of both apparent viscosity and viscoelastic functions in the linear viscoelastic region increase with soap and recycled polymer concentrations. However, the addition of recycled LDPE distort the microstructural network of these greases resulting greases with less relative elastic characteristics and poorer mechanical properties as LDPE content increases.

Evaluation of wall slip phenomena during the horizontal pipeline flow of air/lubricating grease mixtures was investigated. With this aim, pressure drop measurements have been carried out along pipelines with different diameter and roughness. A modified Jastrzebski's equation for the slip velocity, based on the introduction of the relative roughness, has been used to correct wall slip effects for a lithium lubricating grease/air system. This expression has been introduced in the classical Rabinowitsch–Mooney treatment and applied to the superficial liquid velocity instead of the single-phase average velocity following a single-phase treatment analogy. Thus, the non-slip flow curve data for the two-phase mixture were obtained from roughened pipes and compared with those obtained from pipes with smooth internal surfaces. The effect of air on the extension of wall slip has been established as a function of air flow rate. Thus, the consideration of the reduction of the wetted pipe surface as air is injected allows an adequate explanation of this phenomenon, confirmed by the reduction of the effective slip contribution on the observed apparent shear rate. A power-law relationship between the slip velocity and the wall shear stress has been deduced, although this tends asymptotically to linearity as air flow rate is increased.

The prediction of the pressure drop gradient and the evaluation of the drag reduction phenomenon observed during the piping multiphase flow of a lubricating grease/air mixture have been investigated. With this aim, viscous flow tests in rotational rheometers and pressure drop measurements in pipelines have been carried out using different geometries with both smooth and rough surfaces. The Sisko model has been used to predict the pressure drop gradient. The drag ratio, as a function of air flow rate, for highly viscous pastes such as lubricating greases, significantly differs, qualitative and quantitatively, from that found in the literature for other non-Newtonian fluids with viscosities of around 200 times lower. The pressure drop gradient in the intermittent multiphase flow regime can be predicted by modifying the classical approach of Lockhart and Martinelli with an empirical correction factor. An empirical model, with a combination of power-law and sigmoidal-type equations, has been proposed to describe the experimental evolution of the drag ratio as a function of Re L ′ / Re TP ′ . The accuracy of the proposed model has been tested by estimating the classical Fanning friction factor for a non-Newtonian fluid, f = 16/Re′, once the pressure loss has been corrected with the drag ratio previously obtained.

The overall objective of this work was to evaluate the evolution of the microstructure and rheology of a lubricating grease during its manufacturing process. With this aim, lithium lubricating greases were prepared by inducing the saponification reaction between 12-hydroxystearic acid and hydrated lithium hydroxide within a naphtenic lubricating oil medium, applying a controlled-temperature programme. The manufacturing process was followed through the mixing rheometry technique by measuring the evolution of torque with processing time. Samples of incipient and finished grease were taken from the stirred tank at different processing times. Rheological (linear viscoelasticity and viscous flow) and mechanical stability tests, as well as morphological studies, were carried out on each sample. The changes found in the microstructure and rheology of a lubricating grease during its processing have been related to the soap concentration in the reacting mixture, the waxy soap transition at high temperatures and the further cooling steps. From the experimental results obtained, we may conclude that a suitable lithium lubricating grease is a highly structured system, based on the development of a three-dimensional network due to the presence of metallic soap crystallites.

Prediction of pressure drop gradient and evaluation of wall slip and air bubbles entrainment effects observed during the piping flow of lubricating greases were investigated. With this aim, viscous flow tests in rotational rheometers and pressure drop measurements in pipelines were carried out using different geometries with both smooth and rough surfaces. The Sisko model was applied in the experimental range of flow rates for predicting pressure drop gradient. Air entrainment occurring when the pumping system was primed with a highly viscous material as lubricating greases significantly decreases pressure drop gradient. This air entrainment effect can be corrected using a modified expression to evaluate the drag ratio defined for non-Newtonian liquid/air intermittent flows. On the other hand, a new expression based on the internal relative roughness of pipelines was proposed to correct wall slip effect. Eliminating these two effects, the classical definition of the friction factor for a non-Newtonian fluid, f = 16/Re′, can be applied to predict pressure drop of grease flow in pipelines.

The overall objective of this work was to evaluate the manufacture of lubricating greases through the mixing rheometry technique, by studying the effect of some processing variables such as rotation speed, intensity and duration of the homogenization treatment and thermal profile applied, in terms of the power-draw characterization and rheological behaviour of the final product. With this aim, lithium lubricating greases were prepared by inducing the saponification reaction between 12-hydroxystearic acid and hydrated lithium hydroxide within a naphtenic lubricating oil medium in an open vessel. The saponification reaction occurred until neutralization by stirring with a controlled-rotational speed mixing rheometer using an anchor impeller. Different rotational speeds were selected. Finally, a highly intensive homogenization treatment was applied using a rotor-stator turbine in order to reduce crystal sizes. Different homogenization treatments and cooling profiles were applied on the incipient greases. The manufacture of lubricating greases was always followed through the evolution of torque with processing time. The experimental results obtained demonstrate that the mechanical behaviour of a lubricating grease strongly depends on some of the processing variables studied. Some exponential models have been proposed to evaluate the influence of the processing variables on both the consistency index and the linear viscoelastic plateau modulus of the lubricating greases.