@article{2818723,
    title = "Millimeter-Size Spherical Polyurea Aerogel Beads with Narrow Size Distribution",
    author = "Despoina Chriti and Grigorios Raptopoulos and Maria Papastergiou and Patrina Paraskevopoulou",
    journal = "Gels",
    year = "2018",
    volume = "4",
    number = "3",
    pages = "66",
    publisher = "MDPI",
    issn = "2310-2861",
    keywords = "aerogels, Desmodur N3300, ethylenediamine, polyurea, spherical beads",
    abstract = "We report the room temperature synthesis of spherical millimeter-size polyurea (PUA) aerogel beads. Wet-gels of said beads were obtained by dripping a propylene carbonate solution of an aliphatic triisocyanate based on isocyanurate nodes into a mixture of ethylenediamine and heavy mineral oil. Drying the resulting wet spherical gels with supercritical fluid (SCF) CO2 afforded spherical aerogel beads with a mean diameter of 2.7 mm, and a narrow size distribution (full width at half maximum: 0.4 mm). Spherical PUA aerogel beads had low density (0.166 +- 0.001 g cm–3), high porosity (87% v/v) and high surface area (197 m2 g–1). IR, 1H magic angle spinning (MAS) and 13C cross-polarization magic angle spinning (CPMAS) NMR showed the characteristic peaks of urea and the isocyanurate ring. Scanning electron microscopy (SEM) showed the presence of a thin, yet porous skin on the surface of the beads with a different (denser) morphology than their interior. The synthetic method shown here is simple, cost-efficient and suitable for large-scale production of PUA aerogel beads."
}