Nonaqueous synthesis of nanosilica in epoxy resin matrix and thermal properties of their cured nanocomposites

Nonaqueous synthesis of nanosilica in diglycidyl ether of bisphenol-A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly with DGEBA epoxy matrix, at 80 degrees C for 4 h under the catalysis of boron trifluoride monoethylamine (BF(3)MEA). BF3MEA was proved to be an effective catalyst for the formation of nanosilica in DGEBA epoxy under thermal heating process. FTIR and Si-29 NMR spectra have been used to characterize the structures of nanosilica obtained from this direct thermal synthetic process. The morphology of the nanosilica synthesized in epoxy matrix has also been analyzed by TEM and SEM studies. The effects of both the concentration of BF3MEA catalyst and amount of TEOS on the diameters of nanosilica in the DGEBA epoxy resin have been discussed in this study. From the DSC analysis, it was found that the nanosilica containing epoxy exhibited the same curing profile as pure epoxy resin, during the curing reaction with 4,4'-diaminodiphenysulfone (DDS). The thermal-cured epoxy-nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221 degrees C, which was almost 50 degrees C higher than that of pure DGEBA-DDS-BF3MEA-cured resin network. Almost 60 degrees C increase in thermal degradation temperature has been observed during the TGA of the DDS-cured epoxy-nanosilica composites containing 40% of TEOS. (c) 2005 Wiley Periodicals, Inc.