Journal of Supercritical Fluids, Vol.151, 8-14, 2019
Synthesis of highly cross-linked uniform polyurea aerogels
Polyurea (PUA) aerogel is a kind of advanced material with excellent thermal and mechanical properties. In this paper, uniform and highly cross-linked PUA aerogels are synthesized at ambient temperature, 0 degrees C and -20 degrees C respectively. Solid content and synthesis temperature of the aerogels were as the main factors of the study. Synthesis temperature can regulate the solubility of monomers in solution, thereby reducing the size of particles and causing more contacts between the particles to form the fibers of polymers. It's resulted that the microstructure of PUA aerogels becomes more uniform. Meanwhile the specific surface area and pore volume of the materials increase correspondingly. The linear shrinkage, bulk density and thermal conductivity are also improved. PUA aerogel synthesized at -20 degrees C has the largest specific surface area of 240 m(2)/g, the highest pore volume of 1.13 cm(3)/g, the lowest linear shrinkage of 5.67 +/- 0.05% and the density of 0.084 +/- 0.001 g/cm(3). In addition, the PUA aerogel has a low thermal conductivity of 0.0192 +/- 0.0002 W/(m K) with the density of 0.109 +/- 0.003 g/cm(3). (C) 2019 Elsevier B.V. All rights reserved.