Chemische Synthese von Resorcin‐Formaldehyd‐Aerogelkompositen

Abstract

Resorcinol‐formaldehyde‐aerogel‐composites are synthesized and characterized in regard to properties which are interesting for industry. Density, thermal conductivity, specific surface and the compression strength are determined and the structure is investigated by scanning electron microscopy. A standard RF‐recipe are used which contains the molar ratios of resorcinol to formaldehyde (R/F) of 0.7, resorcinol to water (R/W) of 0.04 and resorcinol to catalyst (R/C) of 1500. RF/cellulose‐composites are synthesized by adding cellulose fibers in RF‐solution which fibers are untreated or pretreated with sodium hydroxide to swell or dissolve. Beside RF/cellulose‐composites are synthesized with cellulose‐hydrogel which is immersed into a RF‐solution (with different R/C‐values) while it gels. After aging these composites, the gels are dried supercritical. Furthermore, RF/silica‐composites are synthesized with hydrophobic silica‐aerogels with different grain sizes (1 to 4 mm) by mixing silica with a highly viscous RF‐solution. By employing the same synthesis procedures for RF/Silicacomposites, RF/silica/cellulose‐composites are synthesized with untreated cellulose. All the gels are dried under ambient conditions except the RF/cellulose‐composites with cellulose‐gel.