Effect of Viscosity on Solvent-Free Extrusion Emulsification: Molecular Structure

Abstract

A new continuous emulsification technique known as solvent-free extrusion emulsification (SFEE) was recently introduced to prepare submicron particles (100–500 nm) from high viscosity polymers (100–1000 Pa·s) with a twin screw extruder. The present study examined the influence of matrix viscosity on its dispersion mechanism using cross-linked polyester as a viscosity modifier. The investigation used an inline rheometer for transient and steady state viscosity measurements, and offline characterizations including Soxhlet extraction, colorimetric titration, and particle size analysis. Though it remained possible to produce particles close to their target size of 100–200 nm, particle size was notably increased by varying the matrix viscosity from 250 Pa·s for the neat polyester up to 630 Pa·s with the added modifier. The results point to thicker striated lamellae from less effective mixing prior to phase inversion when the matrix viscosity was increased without a corresponding increase in surface active spec...