Thermally insulative, microporous xerogels and aerogels

摘要

Microporous aerogel and xerogel compositions are prepared by a random polymerization reaction of a silanol-terminated polydimethylsiloxane (PDMS) and tetraethoxysilane (TEOS) and/or methyltriethoxysilane (MTEOS) at a molar ratio of at least about 0.012 of the PDMS to TEOS and/or MTEOS to form a gel. The reaction is in the presence of an acid catalyst at a molar ratio of at least about 0.5 acid to TEOS and/or MTEOS, water at a molar ratio in the range of from about 6 to about 15 of the water to TEOS and/or MTEOS and a solvent at a minimum molar ratio of about 4 of the solvent to TEOS and/or MTEOS. In the preparation process, the gel is aged. When elevated temperatures of at least about 40° C. up to the boiling point of the solvent are used in aging, the gel can be aged for a period of at least about 24 hours. At temperatures from ambient up to about 40° C., the gel is aged for a minimum of about 48 hours.