Epoxy/alumina nanoparticle composites. I. Dynamic mechanical behavior

We studied the influence that alumina nanoparticle addition has on the dynamic mechanical spectra of an amino-cured epoxy resin. A suppression of the short-scale cooperative motions related to the beta relaxation and an increase in the activation energy for the beta relaxation of the epoxy matrix was observed as the alumina content increased. This is explained in terms of an antiplasticization effect of the alumina nanoparticles on the epoxy resin. An estimation of the effective thickness of the nanoparticle-matrix interfacial region was done based on the reduced damping. The dependence of the composites' reduced modulus on the alumina nanoparticles content is very well fitted by the generalized Kerner equation. The best-fit parameter values suggest the presence of small and strong agglomerates in the composites at room temperature. At temperatures above the T-g, these agglomerates start to behave as weak ones because of the polymer matrix softening and particle-particle and particle-matrix slippage and friction. (C) 2003 Wiley Periodicals, Inc.