Improving sphericity of polystyrene capsules with diameter of ignition targets

To improve the sphericity of large-diameter (about 2 mm) polystyrene (PS) capsules for inertial confinement fusion targets, the effects of the interfacial tension between oil phase and outer water phase, the concentration of oil phase, and the speed of rotation flow field on the sphericity of PS capsules were investigated. The results show that, compared with polyvinyl alcohol (PVA), addition of poly(acrylic acid) (PAA) in the outer water phase leads about 10 times increase of interfacial tension between the oil phase and the outer water phase, resulting in a significant improvement of the sphericity of PS capsules. With the replacement of PVA with PAA, the batch yields of PS capsules with out-of-round (OOR) less than 1 m increased from about 5% to above 50%. However, changing the initial concentrations of the oil phase and the speeds of rotation flow field in a wide range did not affect the sphericity of PS capsules remarkably. Under typical operation conditions, the batch yields of the resulting PS capsules with OOR less than 1 m ranges from 40% to 60%.