Reactive & Functional Polymers, Vol.142, 44-52, 2019
Electrospraying technique under pressurized carbon dioxide for hollow particle production
Fabrication of polyvinylpyrrolidone (PVP) particles by an electrospraying process under pressurized carbon dioxide (CO2) used as an anti-solvent was studied. The process was carried out at a constant temperature with CO2 pressures ranging from 1 to 6 MPa. A fixed applied voltage (17 kV) was employed to generate electric field. PVP powder dissolved in dichloromethane (DCM) at concentrations of 4, 6, and 8 wt% was used as the starting material. Scanning electron microscopy observations indicated that the electrosprayed PVP particles produced at 1-3 MPa using 8 wt% PVP solutions have spherical morphologies. At a similar concentration, increasing the CO2 pressure up to 6 MPa resulted in particle strings and strings as major products. Interestingly, hollow core particles formed when ethanol was added as a secondary solvent for controlling the evaporation rate of DCM during the electrospraying process under pressurized CO2. The FT-IR spectra revealed that the structural properties of PVP did not change after the electrospraying process. This work demonstrates that electrohydrodynamic processes under pressurized CO2 are likely to be fruitful for the fabrication of organic polymers with hollow cores.