Silicone Resin Coating of Micro-Sized Ferrite Particles Using Supercritical Carbon Dioxide

Idzumi Okajima,Tatsuya Kanie,Takeshi Sako

doi:10.3390/polym12092012

Abstract

An environmentally friendly and efficient polymer coating method for micro-sized particles was developed using supercritical CO2. Because this method used supercritical CO2 as the solvent to dissolve the coating material, we avoided environmental pollution from organic solvents, saved the energy required to evaporate/remove organic solvents, realized a uniform coating film on the fine particles, and prevented agglomeration of the coating particles. The solubilities of the five silicone resins used as coating materials were measured using the flow method, and the data were well correlated by Chrastil’s equation with an average deviation of 5.7%. Resins comprising numerous methyl-group side chains exhibited high solubilities and were suitable coating materials. A new semi-flow-type coating method using supercritical CO2 was also developed, which deposited a film with a uniform thickness of 0.2–1.3 μm on whole fine particles. Notably, in this method, the film thickness was easily controlled. A simple and rapid technique was developed for measuring the coating thickness using X-ray fluorescence analysis. The model for calculating the coating film thickness was based on the material balance of the coating material. This model satisfactorily predicted the thickness with an average error of 0.085 μm by measuring the solubility of the coating material in supercritical CO2, integrated flow volume of supercritical CO2, particle diameter, density and charged weight of the fine particle, and coating material density.

Highlights

Polymer coating is important for surface functionalization and fabricating composite coatings of micro- and nano-sized particles
This technology is used in many fields, such as medicine, food, cosmetics, smart materials, and electronics; the most notable application is in drug delivery [1,2], in which the dissolution time of a drug in the human body is controlled, and the internal absorption or decomposition of the drug is suppressed by encapsulating it in a harmless polymer
The solubility of this resin did not depend on the flow rate of supercritical CO2 in this flow rate range, because dissolution equilibrium was achieved in the rate of supercritical CO2 in this flow rate range, because dissolution equilibrium was achieved in the saturator across the entire flow rate range

Summary

Introduction

Polymer coating is important for surface functionalization and fabricating composite coatings of micro- and nano-sized particles This technology is used in many fields, such as medicine, food, cosmetics, smart materials, and electronics; the most notable application is in drug delivery [1,2], in which the dissolution time of a drug in the human body is controlled, and the internal absorption or decomposition of the drug is suppressed by encapsulating it in a harmless polymer. Supercritical CO2 has been studied in several fields because it is an environmentally friendly solvent that acts as a promising alternative to toxic and flammable organic solvents It has moderate critical constants (Tc = 304.3 K, Pc = 7.38 MPa), large solvating power for organic materials, low viscosity, high diffusivity, and near-zero surface tension [5].

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