Influence of fluorobenzene mass transfer on the qualities of poly-α-methylstyrene shells

Abstract

Polymer shells prepared by the microencapsulation technique with perfect sphericity and defect-free surface finish are demanded in inertial confinement fusion (ICF) experiments. The sphericity and surface finish are some of the hardest specifications to fulfill. Driven by the need to improve qualities of the polymer shells to meet the critical specifications, the effects of fluorobenzene (FB) mass transfer rate on sphericity and surface finish were investigated and the mechanisms of the effects of FB mass transfer on sphericity and surface finish of poly-a-methylstyrene (PAMS) were also discussed. The sphericity and surface finish of the PAMS shells are greatly improved by decreasing the FB mass transfer rate. The calculative frequency of the final shells with an out-of-round (d OOR ) of less than 2 mm increases from 30% to 80%, while the power spectra density (PSD) plot gets closer to the specification of the national ignition facility (NIF). The tracking experiments show that the curing process is extended and the percolation transition is also postponed by decreasing the FB mass transfer rate. Therefore, the interfacial tension can work sufficiently, helping make double droplets become spherical, since the double droplets' stay in the liquid state is effectively extended. Moreover, the Marangoni instabilities at the O-W2 boundary are also restrained by controlling the mass transfer, due to the diffusivity of FB being slowed down. Both the results and methods presented in this work provide a more in-depth understanding of the curing process and the mass transfer, to the benefit of fabricating polymer shells with high sphericity and defect-free surface finish used in ICF experiments.

Droplet Evaporation Process of a Fluorobenzene + n-Octane + Polystyrene Mixture

“…However, certain issues exist in practical processes, such as non-uniform capsule sizes and difficulties in controlling the evaporation rate of solvents. Chen et al [4] studied the influence of the FB mass transfer rate on the sphericity and surface smoothness of PAMS products, as well as discussing the mass transfer mechanism. In a subsequent study, Chen et al [5] introduced hexadecane (C16) into the O phase to reduce the evaporation rate of FB and improve the surface smoothness of the PAMS microspheres.…”

Improvement of the Sphericity and the Thickness Uniformity of the Polystyrene (PS) Shell Microsphere during Curing Process

“…By using polyacrylic acid (PAA) instead of polyvinyl alcohol (PVA), the interfacial tension between the milk particles and the external water phase was increased, and the spheroidization of the compound droplets was strengthened to improve the quality of the solidified microspheres. The rotating curing system is mostly applied to the curing process of the compound droplets [22,23]. However, the detailed flow field inside the rotating container, as well as the effects of the rotation rate and the liquid level on the quality of the microspheres, are less understood.…”