Particle Formation by Emulsion Inversion Method: Effect of the Stirring Speed on Inversion and Formation of Spherical Particles

Abstract

Summery: Phase inversion emulsification technique was employed in this work as a practical method to form epoxy particles. The effect of stirring speed on the inversion behaviour and the morphological aspects of the resulting solid epoxy particles are investigated. Emulsion inversion was induced by increasing the amount of initially dispersed deionized water in the presence of a non-ionic block copolymer surfactant at a fixed concentration. The process of inversion was followed by monitoring the variations in the rotational speed of the stirrer caused by the viscosity variations of the emulsifying system throughout the process. It was shown that the mixing speed plays an important role in controlling the size and size distribution of the resulting emulsion particles. Below a critical stirring speed, spherical particles could not be formed and the inversion process resulted in macroscopically non-homogeneous multi shape structures. Fully spherical particles were formed above this critical speed. Further increase in the rotational speed of the mixer, significantly reduced the size of these spherical particles with a wide and random size distributions controlled and considerably narrowed by the stirring speed. Dynamic light scattering analysis and scanning electron microscopy were used to study the particle size and size distributions. In addition, study of the rotational speed variations of the stirrer, which is directly related to the viscosity changes of the emulsifying system, revealed that a correlation between the physical aspects of the inversion behaviour and the viscosity changes during the emulsion inversion process could be established.

Coencapsulation of Polyphenols and Anthocyanins from Blueberry Pomace by Double Emulsion Stabilized by Whey Proteins: Effect of Homogenization Parameters

“…Thus, the disruptive forces generated by mixing at both speeds probably exceeded the cohesive forces. When stirring is energetic enough, the droplet and eddy scale is reduced, and translational Brownian motion of the emulsifier is high because surfactant diffusion from the bulk is partly substituted by convection, which enables rapid adsorption of the emulsifier at the oil-water interface [ 51 ]. High stirring speeds, however, also increase the likelihood of droplet coalescence by increasing droplet velocity and collision rate.…”

“…Our findings indicate that increasing the homogenization speed is beneficial only when a critical speed is not exceeded, in agreement with previous findings regarding particle size and emulsion stability. Most studies have focused on simple emulsions with great variations in stirring speeds (e.g., 100–1300 rpm [ 51 ] and 10,000–15,000 rpm [ 54 ]) and emulsion composition. Liyana et al [ 54 ] found that the stability of O/W emulsions was improved by increasing the stirring speed from 10,000 to 15,000 rpm, but they did not measure particle size.…”

Preparation and characterization of curcumin–piperine dual drug loaded nanoparticles

“…Fully spherical particles were formed above critical stirring speed. Further increase in the rotational speed of the mixer, significantly reduced the size of the spherical particles with a wide and random size distributions controlled and considerably narrowed by the stirring speed [19] . The result of the emulsion polymerization method has confirmed that increase in stirring speed from 100 to 500 rpm has significantly decreased the average particle size to around 700 nm and further increase in stirring speed in Fessi method from 500 to 1 000 rpm has reduced the average particle size below 100 nm which is mainly due to high shear rate [20] .…”

Replication of anisotropic dispersed particulates and complex continuous templates

“…This is caused by the minimization of the interfacial free energy usually resulting in spherical microparticles. 44 However, despite this challenge a variety of easily dissolvable anisotropic polymeric colloids have recently been prepared, including ellipsoids, 45 corpuscle-shaped, 46 and tetrahedral particles. 47 In most cases, anisotropic microparticles are fabricated by fine tailoring the colloidal procedure developed for spherical colloids.…”