Élaboration des émulsions natives issues des graines oléoprotéagineuses et transformation catalytique de la fraction lipidique en biolubrifiants écolabellisables

Les recherches que nous présentons dans ce mémoire s'inscrivent dans le cadre du projet européen IBIOLAB[1] qui vise à la création de biolubrifiants écolabellisables. Tout d'abord, une approche d'ingénierie inverse a été réalisée pour déterminer le rôle des tensioactifs natifs des graines oléoprotéagineuses dans la stabilisation des oléosomes dans l'eau. Ceci a permis par la suite une approche générique avec la mise en œuvre d'un procédé intégré qui permet la libération des lipides sous forme émulsionnée. Une étape optionnelle consiste en l'hydrolyse enzymatique in situ des triglycérides. L'activité de la lipase utilisée a été évaluée lors d'une étude d'estérification des acides gras avec différents alcools par une méthode de séparation triphasique (TPP three-phase partitioning). ABSTRACT : The present work was performed within the framework of the European project IBIOLAB* which aims to create environmentally friendly biolubricants (able to be eco-labelled). First of all, a reverse engineering methodology was developed to understand the role of oilseed native surfactants in the stability of oil-bodies in water. Subsequently, using a general approach, it was possible to develop a process that allows releasing the lipid fraction into an emulsion. If an in-situ enzymatic hydrolysis of triglycerides is added to this process, an emulsion containing the free fatty acids will be obtained. The activity of the remaining lipase in the emulsion was used to study the esterification of free fatty acids with different alcohols using a three-phase partitioning method

Post-harvest tomato plants and urban food wastes for manufacturing plastic films

Poly(vinyl alcohol-co-ethylene) was compounded with 2-10% post-harvest tomato (PHT) plant powder and processed by single-screw extrusion to yield composite films. Upon increasing the filler content, the values of the mechanical properties indicators were found to decrease as follows: Young's modulus from 1797 to 750 MPa, stress at yield from 36 to 15 MPa, maximal stress from 39 to 15 MPa, stress at break from 35 to 14 MPa, and strain at break from 6.6 to 4.3%. The results are discussed in comparison with other composite films containing poly(vinyl alcohol-co-ethylene) and water soluble biopolymers obtained by alkaline hydrolysis of fermented municipal biowastes, and with other commercial materials, such as starch based and low density polyethylene mulch films. Depending on the intended application, the post-harvest tomato blend films may be competitive for cost, performance and sustainability

Parameters affecting enzyme-assisted aqueous extraction of extruded sunflower meal

Microscopic observation of sunflower meal before and after extraction indicated that extensive cellular disruption was achieved by extrusion, but that unextracted oil remained sequestered as coalesced oil within the void spaces of disrupted cotyledon cells. A full factorial design experiment was defined to develop aqueous extraction processing (AEP) with and without enzymes to improve vegetable oil extraction yields of extruded sunflower meal. This experimental design studied the influence of four parameters, agitation, liquid/solid (L/S) ratio, and cellulase and protease addition, on extraction yield of lipid and protein. Agitation and addition of cellulases increased oil extraction yield, indicating that emulsification of oil and alteration of the geometry of the confining cellular matrix were important mechanisms for improving yields. Protease and liquid-solid ratio of the extraction mixture did not have significant effects, indicating key differences with previously established soy oil extraction mechanisms. Maximum yields attained for oil and protein extraction were 39% and 90%, respectively, with the aid of a surfactant

Estudio de los efectos de la temperatura de precalentamiento sobre la microestructura y propiedades mecánicas de aceros ASTM A36 Y ASTM 572 gr. 50 soldados mediante proceso SMAW

El objetivo principal de este trabajo de titulación fue estudiar el efecto de las temperaturas de precalentamiento sobre la microestructura y propiedades mecánicas en juntas soldadas de acero ASTM A36 y ASTM A572 Gr. 50, soldadas mediante proceso SMAW. Se realizó juntas sin precalentamiento y también con temperaturas de precalentamiento de 115ºC, 300ºC y 500ºC. El electrodo empleado fue el E6011. Las temperaturas de precalentamiento se controlaron mediante un pirómetro. Para el precalentamiento se empleó un horno de inducción eléctrico con control de temperatura. Adicionalmente, para el calentamiento de las placas de dimensiones mayores se empleó una antorcha de GLP, con una placa de protección con el fin de que el hollín generado no afecte a las propiedades finales. Posteriormente se realizaron ensayos metalográficos y mecánicos para determinar las propiedades de cada junta. Mediante un análisis metalográfico de las muestras se evidencia que, en la zona afectada por el calor, se forman microestructuras como ferrita acicular y Widmanstaten con presencia de listones de Bainita y a medida que la temperatura de precalentamiento aumenta estos van disminuyendo. Posterior a esto se realizan el ensayo de microdureza Vickers en cada junta, el mismo que evidencia una disminución de valores de microdureza a medida que la temperatura de precalentamiento aumenta esto en el Cordón y la ZAC. En cuanto a propiedades mecánicas, el ensayo de tracción evidenció que mediante la aplicación de un precalentamiento la resistencia a la tracción aumenta. Mientras que, mediante el ensayo de impacto Charpy se evidenció que la resistencia al impacto baja mientras que la temperatura de precalentamiento aumenta. Finalmente, los resultados obtenidos son comprados con el tamaño de grano calculado que se ve refinado a medida que aumenta la temperatura de precalentamiento.The main objective of this research was to study the effect of preheating temperatures on the microstructure and mechanical properties of welded joints made of ASTM A36 and ASTM A572 Gr. 50 steel, welded using the SMAW process. Joints were made without preheating and with preheating temperatures of 115ºC, 300ºC and 500ºC. The electrode used was E6011. Preheat temperatures were monitored by a pyrometer. An electric induction oven with temperature control was used for preheating. Additionally, to heat the plates of larger dimensions, a LPG torch was used, with a protection plate so that the soot generated does not affect the final properties. Subsequently, metallographic, and mechanical tests were carried out to determine the properties of each joint. By means of a metallographic analysis of the samples, it is evidenced that, in the heat affected zone, microstructures such as acicular ferrite and Widmanstaten are formed with the presence of Bainite slats and as the preheating temperature increases, they decrease. After this, the Vickers microhardness test is carried out in each joint, which shows a decrease in microhardness values as the preheating temperature increases this in the Cordon and the HAZ. Regarding mechanical properties, the tensile test showed that by applying a preheating the tensile strength increases. While, through the Charpy impact test, it was evidenced that the impact resistance decreases while the preheating temperature increases. Finally, the results obtained are compared with the calculated grain size that is refined as the preheating temperature increases

Inverse gas chromatography a tool to follow physicochemical modifications of pharmaceutical solids: Crystal habit and particles size surface effects

Powders are complex systems and so pharmaceutical solids are not the exception. Nowadays, pharmaceutical ingredients must comply with well-defined draconian specifications imposing narrow particle size range, control on the mean particle size, crystalline structure, crystal habits aspect and surface properties of powders, among others. The different facets, physical forms, defects and/or impurities of the solid will alter its interaction properties. A powerful way of studying surface properties is based on the adsorption of an organic or water vapor on a powder. Inverse gas chromatography (IGC) appears as a useful method to characterize the surface properties of divided solids. The aim of this work is to study the sensitivity of IGC, in Henry’s domain, in order to detect the impact of size and morphology in surface energy of two crystalline forms of an excipient, d-mannitol. Surface energy analyses using IGC have shown that the α form is the most energetically active form. To study size and shape influence on polymorphism, pure α and β mannitol samples were cryomilled (CM) and/or spray dried (SD). All forms showed an increase of the surface energy after treatment, with a higher influence for β samples (γsd of 40–62mJm−2) than for α mannitol samples (γsd of 75–86mJm−2). Surface heterogeneity analysis in Henry’s domain showed a more heterogeneous β-CM sample (62–52mJm−2). Moreover, despite its spherical shape and quite homogeneous size distribution, β-SD mannitol samples showed a slightly heterogeneous surface (57–52mJm−2) also higher than the recrystallized β pure sample (∼40mJm−2)

Extruded Poly(ethylene–co–vinyl alcohol) Composite Films Containing Biopolymers Isolated from Municipal Biowaste

Single-screw extrusion allows obtaining composite films containing poly(ethylene-co-vinyl alcohol), hereinafter EVOH, and water-soluble lignin-like biopolymers (SLP) isolated from the alkaline hydrolysate of two materials sampled from an urban waste treatment plant. During extrusion, a condensation reaction occurs between the EVOH and SLP. The products are heterogeneous. They contain a mix of EVOH-SLP copolymers with different composition and solubility properties. The films were characterized for tensile strength and water sorption properties. Young modulus and strain at break, respectively, were 2.8 GPa and 14% for neat EVOH vs. 2.1-0.9 GPa and 17–4% for the blends containing 2–15% SLP, with values decreasing upon increasing the % SLP. The blends were more hydrophilic than neat EVOH; their water sorption capacity was found to increase upon increasing the SLP content. Compared to previously reported similar blends obtained by twin-screw extrusion and solvent casting, the data for the single-screw extruded films allows discussing several aspects connected to the valorisation of blends obtained from fossil and biowaste sourced polymers

Effect of temperature on high pressure cellulose compression

The effect of temperature during cellulose compression has been studied using mechanical testing, particle size analysis, density and Pressure-Volume-Temperature (PVT) measurements, crystallinity index, SEM photographs and water sorption isotherms. Commercial cellulose powder samples with different crystallinity levels were compacted at high pressure (177 MPa) for 10 minutes at two different temperatures: 25 and 160 °C. 3 point bending test results for compressed samples are discussed. When pressure was applied directly to powders at room temperature, the cellulose sample with the highest level of crystallinity showed an increase in its crystallinity index of about 5 %, while this was about 22 % for the sample with the lowest level. These increases were even higher at 160 °C attaining 8 and 33 % respectively. Using density measurements, a densification phase related to this crystallinization was observed, and the PVT diagrams from different cellulose samples showed that this was associated with high temperatures. Water sorption isotherms were made on cellulose samples before and after compression. They showed a diminution of cellulose sorption capacity after compression at 160 °C, revealing the effect of temperature on high-pressure cellulose compression, reducing specific surface area. Events of this nature suggest a sintering mechanism, when temperature is associated with high pressure during cellulose compression

Fabrication de panneaux agglomérés de fibres à partir des anas collectés lors de l'extraction mécanique des fibres libériennes de la paille de lin oléagineux

Dans cette étude, des panneaux agglomérés de fibres ont été produits à partir d’anas collectés après extraction mécanique des fibres libériennes de paille de lin oléagineux. Les panneaux ont été mis en oeuvre par thermopressage. Leurs propriétés mécaniques et thermo-mécaniques ont été étudiées ainsi que leur comportement vis-à-vis de l’eau. L’influence d’un prétraitement thermo-mécanique des anas bruts à l’aide d’une extrudeuse bi-vis a été étudiée ainsi que l’ajout de lignine exogène. Tous les panneaux mis en oeuvre possèdent une tenue suffisante pour être manipulés à la main. Le panneau ayant obtenu les propriétés optimales a été obtenu à partir des anas extrudés et sans ajout supplémentaire de lignine. Au regard de ses caractéristiques et du standard NF EN 312, ce dernier remplit complètement les critères d’un panneau aggloméré de type P1 (panneau d’usage général utilisé en milieu sec)

ACOMPAÑAMIENTO ACADÉMICO A ESTUDIANTES DEL NIVEL MEDIO SUPERIOR (ACADEMIC SUPPORT FOR STUDENTS OF THE UPPER MIDDLE LEVEL)

Resumen La deserción escolar en el nivel medio superior se ha incrementado significativamente en los últimos años. Para muchos alumnos es común considerar a las matemáticas un gran obstáculo, pues les generan inseguridades y rechazo, lo cual desencadena situaciones o problemáticas que pueden llegar a ocasionar reprobación, rezago y deserción escolar. En este contexto y con la finalidad de proporcionar apoyo y acompañamiento académico a los alumnos en la asignatura de matemáticas, se decide implementar el uso de la plataforma Khan Academy en alumnos del nivel medio superior, a fin de observar la viabilidad de su uso. Desde la perspectiva docente, se encontró que los contenidos de la plataforma no están alineados a los programas de estudio del Nivel Medio Superior, a fin de proporcionar apoyo didáctico que favorezca el desempeño académico del estudiante. Sin embargo, como resultado de esta experiencia, el alumno reconoce que la plataforma Khan Academy propicia un avance significativo en sus procesos de aprendizaje y mejora la comprensión de los temas revisados motivo por el cual manifiestan que volverían a utilizar la plataforma como apoyo didáctico para la materia de matemáticas. Palabras Clave: acompañamiento académico, desempeño académico, Khan Academy, recursos didácticos. Abstract School dropout at the upper secondary level has increased significantly in recent years. For many students, it is common to consider Mathematics a great obstacle, since they generate many insecurities and rejection, which triggers situations or problems that can lead to failure, lag, and school dropout. In this context and in order to provide support and academic accompaniment to students in the subject of Mathematics, it was decided to implement the use of the Khan Academy platform in upper secondary students, in order to observe the viability of using it. . From the teaching perspective, it was found that the contents of the platform are not aligned with the study programs of the Upper Middle Level, in order to provide didactic support that favors the student's academic performance. However, as a result of this experience, the student recognizes that the Khan Academy platform fosters significant progress in their learning processes and improves understanding of the topics reviewed, which is why they state that they would use the platform again as didactic support for the Mathematics subject. Keywords: academic support, academic performance, Khan Academy, teaching resources

The pressure-volume-temperature relationship of cellulose

Pressure–volume–temperature (PVT) mea- surements of a-cellulose with different water contents, were performed at temperatures from 25 to 180 °C and pressures from 19.6 to 196 MPa. PVT measurements allowed observation of the combined effects of pressure and temperature on the specific volume during cellulose thermo-compression. All isobars showed a decrease in cellulose specific volume with temperature. This densification is associated with a transition process of the cellulose, occurring at a temperature defined by the inflection point Tt of the isobar curve. Tt decreases from 110 to 40 °C with pressure and is lower as moisture content increases. For isobars obtained at high pressures and high moisture contents, after attaining a minimum, an increase in volume is observed with temperature that may be related to free water evaporation. PVT a-cellulose experimental data was compared with predicted values from a regression analysis of the Tait equations of state, usually applied to synthetic polymers. Good correla- tions were observed at low temperatures and low pressures. The densification observed from the PVT experimental data, at a temperature that decreases with pressure, could result from a sintering phenomenon, but more research is needed to actually understand the cohesion mechanism under these conditions