Controlling the structure of a porous polymer by coupling supercritical CO₂ and single screw extrusion process

Abstract

A study on the extrusion of Eudragit E100 was carried out using supercritical carbon dioxide (scCO 2 ) as plasticizer and foaming agent. ScCO 2 modifies the rheological properties of the material in the barrel of the extruder and acts as a blowing agent during the relaxation when flowing through the die. For experiments, a singlescrew extruder was modified to be able to inject scCO 2 within the extruded material. The aim is to determine a correlation between operating conditions and foam structure. The effect of three parameters was studied: the temperature in the die and in the metering zone, the screw speed, and the volumetric flow rate of CO 2 . An increase in temperature enhances the expansion rate and the average pore diameter and appears to be the most significant parameter. The effect of CO 2 concentration is significant at small concentrations only: the higher the CO 2 concentration, the lower the pore density and the higher both the pore diameter and the expansion rate. The effect of the screw speed is tricky because a variation of this speed involves a decrease of CO 2 weight ratio. This study shows that the structure of the extrudates does not evolve with a coupling of screw speed increase and a subsequent CO 2 weight ratio decrease.

Challenges and Strategies in Thermal Processing of Amorphous Solid Dispersions: A Review

“…Finally, each of the polymers investigated exhibited increased dissolution rates when processed with CO 2 injection due to the increased porosity and foaming effect of the expanding gas upon exiting the extruder die. Other investigators have found that the pore size is a function of the processing temperature and CO 2 concentration (89).…”

Use of supercritical CO2‐aided and conventional melt extrusion for enhancing the dissolution rate of an active pharmaceutical ingredient

“…[9,10] The single-screw extruder has a 30-mm screw diameter and a length to diameter (L/D) ratio of 35 (Rheoscam, SCAMEX, Crosne, France). A large L/D ratio generally allows increasing not only the capacity of mixing and melting but also energy consumption.…”

“…[8] Lately, Nikitine et al studied the correlation between operating conditions and foam structures of Eudragit E100. [9] This work was also completed by the study of the influence of scCO 2 on the polymer flow of Eudragit E100 in the extruder. [10][11][12] Lipid soluble chemicals, such as carvedilol (CAR), are almost insoluble in water.…”

“…[9] The aim was to obtain similar drug release rate of CAR as it was achieved by nanoprecipitation and to investigate the potential advantages of applying scCO 2 during the extrusion process. For achieving rapid dissolution, the feasibility of an amorphous solid dispersion or solution of CAR and Eudragit E100 was investigated in order to avoid the necessity of overcoming the crystal lattice energy of CAR.…”

Capillary rheometry of a binary mixture polymer/CO2 in a single screw extruder

“…Using a new sc CO 2 assisted extrusion process, microcellular foams of a biocompatible amorphous polymer were elaborated [8]. However, understanding and improving such a process requires the knowledge of physical properties, like the solubility of CO 2 into the polymer, the diffusion coefficient and the viscosity of the mixture.…”