Influence of operating conditions on the surface morphology of microcapsules prepared by in situ polymerization

A series of microcapsules were prepared by in situ polymerization with poly(urea–formaldehyde) as the shell material and glass beads as the core material. Glass beads were chosen as the core material because their size distribution was narrow and their surface was easily changed to be hydrophobic. The respective effects of initial pH value, concentration of wall material and surfactant, stirring rate on the state of microencapsulation were investigated systematically. The results showed that the surface morphology of the microcapsule depends mainly on the final pH value and stirring rate. A higher final pH value and faster stirring rate helped to prepare a smoother microcapsule. Addition of ammonium chloride was found to be very important in preparing of PUF microcapsules. The involvement of ammonium chloride caused a substantial drop in the pH value during reaction and enhanced the deposition of UF nanoparticles onto the surface of microcapsule.