Rapid fabrication of low density melamine-formaldehyde aerogels

Low density melamine-formaldehyde (MF) aerogels were fabricated rapidly by adding the alkali to low concentration MF sol precursor before the formation of cross-linking. The gelation of the MF sol with the precursor concentration as low as 4% could be accomplished by the modified method. The gelation time for MF wet gels could be also reduced to even 5 h. After solvent exchanging and CO2 supercritical drying, the MF areogel with the lowest density of about 55 mg/cm(3) could be prepared. The samples were also characterized by scanning electron microscopy, transmittance electron microscope, Fourier transform infrared spectroscopy and nitrogen adsorption-desorption isotherms. The results indicated that the addition of the alkali to the MF sol precursor not only sped up the gelation process without changing the reaction mechanism, but also accomplished the low density MF aerogel.