Le phénomène de mouillage partiel dans les mélanges de polymères non miscibles ternaires et quaternaires

Quelques exemples intéressants de matériaux polymères microstructurés -- L'origine des forces capillaires et de la tension interfaciale -- L'utilisation des copolymères pour modifier les propriétés interfaciales -- Les systèmes capillaires -- Notions fondamentales sur la modification des interfaces avec des copolymères -- La courbe d'émulsion -- La microscopie électronique en transmission -- Mesurer la tension interfaciale modifiée -- Méthodes expérimentales -- Nouvelle structure compacte auto-assemblée de gouttelettes à l'interface dans des mélanges ternaires de polymères -- Novel self-assembling close-packed droplet array at the interface in ternary polymer blends -- Mesure In-Situ de tensions interfaciales dans des mélanges ternaires et quaternaires d'homopolymères non miscibles ayant une microstructure de type mouillage partiel -- In-situ measure of interfacial tensions in ternary and quaternary immiscible polymer blends demonstrating partial wetting -- Mesure In-Situ de tension interfaciales modifiées dans des mélanges de polymères ternaires ayant une structure de type mouillage partiel -- Modified interfacial tensions measured In-Situ in ternary polymer blends demonstrating partial wetting -- La migration du copolymère à l'interface PS/HDPE dans les mélanges ternaires PS/PP/HDPE -- La valeur des angles de contact lorsque la coupe effectuée au faisceau ionique n'est pas perpendiculaire à la ligne triphasée -- Effet de la géométrie de la microstructure sur la coalescence des phases -- Le développement de la microstructure dans les mélanges quaternaires

Is the Maxwell–Garnett continuum model valid to predict the thermal conductivity of particle-stabilized (Pickering) emulsions?

An experimental heat transfer measurement apparatus is constructed to measure the thermal conductivity in two-phase systems using an internal standard. This apparatus is validated and used to obtain the thermal conductivity of glass-bead-stabilized oil-in-water (o/w) emulsions. The experimentally obtained values are found to be in good agreement with the predictions from the Maxwell–Garnett continuum model, thus confirming that no preferential heat-transfer route is formed through the glass beads in the emulsions

Polylactic acid (PLA) foaming: Design of experiments for cell size control

ABSTRACT: In this study, a design of experiments (DoE) approach was used to develop a PLA open-cell foam morphology using the compression molding technique. The effect of three molding parameters (foaming time, mold opening temperature, and weight concentration of the ADA blowing agent) on the cellular structure was investigated. A regression equation relating the average cell size to the above three processing parameters was developed from the DoE and the analysis of variance (ANOVA) was used to find the best dimensional fitting parameters based on the experimental data. With the help of the DoE technique, we were able to develop various foam morphologies having different average cell size distribution levels, which is important in the development of open-cell PLA scaffolds for bone regeneration for which the control of cell morphology is crucial for osteoblasts proliferation. For example, at a constant ADA weight concentration of 5.95 wt%, we were able to develop a narrow average cell size distribution ranging between 275 and 300 μm by varying the mold opening temperature between 106°C and 112°C, while maintaining the foaming time constant at 8 min, or by varying the mold foaming time between 6 and 11 min and maintaining the mold opening temperature at 109°C

A mechanism for the synergistic gelation properties of gelatin B and xanthan gum aqueous mixtures

Gelatin B and xanthan gum aqueous mixtures (GB/XG, (0.2-2%)/0.2% w/v) exhibit enhanced gelling properties compared to their pure component solutions at similar compositions. The mixed gels comprise co-localized networks of GB and XG–rich domains. Our results show that these domains are composed of intermolecular complexes and their aggregates stabilized by the neutralization effect of GB, and linked together by formation of GB triple helices. GB/XG mixtures display composition-dependent microstructural transitions: from discontinuous aggregates (GB/XG ratio ≤ 1) to a continuous GB/XG network (ratio = 2-6), followed by network fragmentation (ratio = 8-10). Increasing the GB Bloom index accelerates network formation and results in higher elastic modulus (G’), while increasing the XG molecular weight causes the opposite effect due to diffusion limitations. This work provides a set of fundamental guidelines to design novel thickeners and/or gelling agents based on proteins and polysaccharides, for food or pharmaceutical applications

One-step processing of highly viscous multiple Pickering emulsions

ABSTRACT: Hypothesis Solid-stabilized Pickering emulsions have attracted a lot of attention recently due to their surfactant-free character, and exceptional stability. At the moment, how the viscosities of the liquid phases impact the processing of Pickering emulsions remain to be clearly understood – it is however an important parameter to consider when developing chemical engineering processes employing these multiphase liquids. Our first assumption was that the amount of emulsified dispersed phase would drastically decrease as viscosity increases. Experiments and findings In this work, we demonstrate that double water-in-oil-in-water (W/O/W) Pickering emulsions are obtained in a single processing step when using very high viscosity silicone oils (≥10,000 cSt) and a single type of sub-μm silica particles modified with two grafted silanes and sodium alginate. The formation of water sub-inclusions proceeds via a phase-inversion mechanism. These sub-inclusions are subsequently stabilized and retained in the oil phase due to its viscosity, limiting sub-inclusions mobility, and the presence of adsorbed particles forming dense layers at oil-water interfaces, acting as barriers. The process we present is simple, requires a minimum number of components, and allows the preparation of multiple emulsions which could then be used to efficiently protect and/or transport a variety of sensitive encapsulated compounds

The control of hydroxyl density on glass particulates surface: Application to anionic polymerization of polyamide 6

Monomer polymerization after the impregnation of reinforcements is a relevant option for the manufacturing of thermoplastic composites by liquid processes (infusion or RTM). In the case of polyamide 6 (PA6) synthesized by this process, the system is composed of the monomers, the catalyst, and the activator, which react within the fibrous environment. Therefore, controlling the chemistry of the fiber surface is crucial because it influences not only the polymerization and crystallization processes, but it also controls the fiber-matrix adhesion and the resulting mechanical properties. However, the hydroxyl groups typically present on the glass fiber surface inhibit the polymerization process. The objective of this project is to adapt and control the surface chemistry of glass particulate reinforcements in order to promote the polymerization and crystallization processes of PA6. This work was carried out with glass microbeads comparable in size to the diameter of glass fibers. First, the evolution of the hydroxyl groups surface density on the glass beads, as a function of calcination time, was monitored by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The hydroxyl groups surface density was then tuned in order to allow thesynthesis of anionic polyamide 6 (PA6), which was monitored by differential scanning calorimetry (DSC). Next, in order to further promote the polymerization and crystallization of PA6, and to improve interfacial adhesion between the PA6 and glass particulates, the grafting process of an amino-silane coupling agent at the particulates surface was investigated by TGA and FTIR. The results demonstrate that the competition between re-hydroxylation and condensation of the silane on the surface during the grafting process needs to be carefully balanced in order to maintain fast polymerization kinetics, as revealed by DSC analysis. Overall, the systematic methodology presented in this work can be adapted for various combinations of reactive resins and solid fillers, allowing for the preparation of high performance (nano)composite materials

Sodium alginate-grafted submicrometer particles display enhanced reversible aggregation/disaggregation properties

In this article, we demonstrate that submicrometer particles with surface-grafted sodium alginate (SA) display enhanced and reversible aggregation/disaggregation properties in aqueous solution. 300 nm silica particles were first functionalized with an aminosilane coupling agent, followed by the grafting of pH-sensitive SA, as confirmed by zeta potential, XPS and FTIR analyses. The SA-modified particles show enhanced aggregation properties at acidic pH compared to unmodified silica, with a 10 times increase in average aggregate diameter. The process is reversible, as the aggregates can be broken and dispersed again when the pH is increased back to 7.0. As a result, the sedimentation rate of SA-modified particles at pH 3.0 is both significantly faster and complete compared to the unmodified particles. This enhanced aggregation is most likely due to the formation of intermolecular hydrogen bonds between neighboring SA-modified particles. This work illustrates how surface-grafted macromolecules of natural origins can be used to tune interparticle interactions, in order to improve separation processes

Tailoring glass fiber surface for the polymerization and crystallization of anionic PA6

Monomer polymerization after the impregnation of reinforcements is a relevant option for the manufacturing of thermoplastic composites by liquid processes (infusion or RTM). In the case of polyamide 6 synthesized by this process, the systems composed of monomers, catalyst and activator react within the fibrous environment. Therefore, fiber sizing is a crucial parameter because it not only influences the polymerization and crystallization processes, but also controls the fiber-matrix adhesion

Tailoring glass fiber surface for the polymerization and crystallization of anionic polyamide 6

Monomer polymerization after the impregnation of reinforcements is a relevant option for the manufacturing of thermoplastic composites by liquid processes (infusion or RTM). In the case of polyamide 6 synthesized by this process, the system composed of monomers, catalyst and activator reacts within the fibrous environment. Therefore, fiber surface chemistry is a crucial parameter because it does not only influence the polymerization and crystallization processes, but it also controls the fiber-matrix adhesion

Tuning particle–particle interactions to control Pickering emulsions constituents separation

We demonstrate that the separation and recovery of solid-stabilized (Pickering) emulsion constituents are significantly improved via a simple filtration approach – without any additional chemical agent – by initially grafting sodium alginate (SA), a natural polysaccharide, onto silane-modified sub-micrometer silica particles. The combination of surface-grafted trimethoxy(propyl)silane (TMPS) and (3-aminopropyl)trimethoxysilane (APTMS) controls particle wettability, verified via zeta potential and contact angle measurements. Rheometry and filtration experiments reveal that further grafting of SA via APTMS enhances particle–particle and droplet–droplet interactions. This work provides an approach towards the design of environmentally friendly Pickering emulsion based chemical engineering processes with easy-to-separate and reusable particles, allowing waste reduction and reduced toxicity advantages