Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Characterization of polyurea microcapsules synthesized with an isocyanate of low toxicity and eco-friendly esters via microfluidics: Shape, shell thickness, morphology and encapsulation efficiency. Chemical Engineering Research and Design, 2022, 182, pp.256-272. ⟨10.1016/j.cherd.2022.03.026⟩. ⟨hal-04063865⟩ Plus de détails...
There are some studies on the synthesis of polyurea microcapsules. However, there is hardly a case where both green solvents and non-toxic isocyanates are used, especially in microfluidics. In this work, an environmentally friendly chemical system of interfacial polymerization (isocyanate: HDB-LV; solvent: octyl salicylate or dibutyl adipate) is tested for the first time to produce polyurea microcapsules. The size of microcapsules is calibrated at 78 μm by microfluidics to quantitatively analyze the relationships among shell thickness, encapsulation efficiency and isocyanate concentrations. The influences of solvent types and reactant concentrations on the shape, morphology and shell thickness of microcapsules are studied. Esters with low water miscibility and low amine concentrations (lower reaction rate) are crucial for the formation of spherical microcapsules. An ester with high water miscibility can diffuse into the continuous phase during encapsulation, which results in broken microcapsules. A high concentration of amine can probably cause cross-linking not only at the interface but also inside the droplet template, which leads to microcapsule deformation. A linear relationship is observed between the shell thickness of microcapsules and the isocyanate concentration. Overall, a high encapsulation efficiency (more than 90%) for octyl salicylate is achieved with polyurea microcapsules.
Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Characterization of polyurea microcapsules synthesized with an isocyanate of low toxicity and eco-friendly esters via microfluidics: Shape, shell thickness, morphology and encapsulation efficiency. Chemical Engineering Research and Design, 2022, 182, pp.256-272. ⟨10.1016/j.cherd.2022.03.026⟩. ⟨hal-04063865⟩
Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Generation of an O/W emulsion in a flow-focusing microchip: importance of wetting conditions and of dynamic interfacial tension. Chemical Engineering Research and Design, 2020, ⟨10.1016/j.cherd.2020.04.012⟩. ⟨hal-02799613⟩ Plus de détails...
6 To date, there is no information on the microfluidic emulsification of dibutyl adipate and 7 n-butyl acetate in water. Since these solvents are very suitable for microencapsulation by 8 interfacial polymerization, it is highly necessary to study the emulsification behavior of these 9 solvents in microchannel. This work shows that the microfluidic emulsification of these sol-10 vents in water may fail to obtain stabilized flow regimes. This is due to droplet coalescence 11 and wall wetting, even if a hydrophilic microchip is used. Hydrodynamic results show that 12 squeezing and dripping regimes are especially affected because of the wall wetting by the 13 dispersed phase. This difficulty can be circumvented by adding a surfactant (here Tween 14 80) into the aqueous phase. However, high surfactant concentrations (ten times the crit-15 ical micelle concentration) should be used for the water-dibutyl adipate system. Indeed, 16 comparison of flow maps for several surfactant concentrations seems to indicate that the 17 dynamic interfacial tension is higher than the one expected (equilibrium), for surfactant 18 concentrations lower than one hundred times the critical micelle concentration. The esti-19 mated diffusion time of Tween 80 is compared to the droplet formation time at different 20 conditions. The choice of more appropriate dimensionless numbers to represent flow maps 21 is also discussed. 22
Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Generation of an O/W emulsion in a flow-focusing microchip: importance of wetting conditions and of dynamic interfacial tension. Chemical Engineering Research and Design, 2020, ⟨10.1016/j.cherd.2020.04.012⟩. ⟨hal-02799613⟩
