Isothermal cure characterization of fumed silica/epoxy nanocomposites: The glass transition temperature and conversion

The glass transition temperature (T-g) and conversion (alpha) were measured for a cycloaliphatic epoxy/anhydride system incorporated with different contents of hydrophobic fumed silica Samples isothermally cured at varying cure temperatures and times were analyzed by differential scanning calorimetry (DSC) T-g vs In(time) data at an arbitrary reference temperature were superposed by time-temperature shifts to forma master curve for the kinetically controlled reaction, and the shift factors Overt: used to Calculate ail Arrhenius activation energy Influence of the hydrophobic fumed silica was investigated from T-g and alpha data For low conversions, the incorporated fumed silica may reduce segmental mobility, giving rise to an increase in T-g For high conversions, there was a significant depression of T-g which may be associated with the presence of residual hydroxyl groups on the surface of hydrophobic furled silica The positive and negative effects of the furled silica on T-g and alpha are discussed (C) 2009 Elsevier Ltd All rights reserved