Mechanical and acoustical properties as a function of PEG concentration inmacroporous silica gels

The pore size of macroporous silica aerogel can be controlled by varying th e concentration of water-soluble organic polymers in the sol. These gels de monstrate a wide array of mechanical and acoustical properties in proportio n to the organic polymer concentration in the sol. Presented in this paper are the resulting mechanical dependencies upon the concentration of high mo lecular weight polyethylene glycol (PEG) in the initial sol. Physical prope rties studied include density, surface area, pore structure, acoustic veloc ity, and mechanical strength. Most of these properties exhibited a large ch ange when a small concentration of PEG was added to the initial sol, correl ating with a strengthening of the solid matrix. Still higher concentrations of PEG progressively weakened the solid matrix. Through examination of the gels containing PEG, experiments have shown an inverse relation of acousti c velocity to PEG concentration while density remains relatively constant. (C) 2001 Elsevier Science B.V. All rights reserved.