Fabrication of thermally expandable core–shell microcapsules using organic and inorganic stabilizers and their application

Thermally expandable core–shell microcapsules (TEM) were fabricated with an organic steric stabilizer and an inorganic Pickering emulsifier. In order to fabricate a TEM, acrylonitrile (AN) and metacrylonitrile (MAN) were used as monomers. Halloysite nanotubes (HNTs) and poly(vinylpyrrolidone) (PVP) were used as the inorganic Pickering emulsifier and the organic stabilizer, respectively. The liquid hydrocarbon content in the core, and the thermal and expansion properties, of TEMs with two different emulsifiers were compared. The mechanical properties of polypropylene (PP) foams containing TEMs prepared with two types of stabilizers were analyzed. The TEMs polymerized with PVP showed a finer expanded cell, while those fabricated with HNTs resulted in a larger expanded cell in the PP matrix.