Characteristics and release property of polylactic acid/sodium monofluorophosphate microcapsules prepared by spray drying

Abstract

Microcapsules composed of polylactic acid (PLA)/corrosion inhibitor sodium monofluorophosphate (MFP) were prepared by spray drying, and the effects of processing parameters on the morphology and encapsulation efficiency of the microcapsules were investigated. The results showed that low viscous PLA solution only resulted in porous microcapsules with low encapsulation efficiency, whereas filamentous substances were produced instead of microcapsules once PLA solution content exceeded 5%. When spray pressure exceeded 0.4MPa, the microcapsule surface was wrinkled due to high evaporation rate of the atomized droplets. The spray pressure less than 0.3MPa created larger atomized droplets and yielded the adhesive microcapsules with lower encapsulation efficiency. The optimal emulsion parameters were as follows: PLA concentration, 5%; water-oil ratio, 1:9; inlet air temperature, 50°C; and spray pressure, 0.4MPa. The resulting microcapsules exhibited a good sustained-release behavior in a simulated concrete pore solution.