Rheological and Thermomechanical Characterizations of Fumed Silica-Filled Polybenzoxazine Nanocomposites

The composites of fumed silica-filled polybenzoxazine at various nanofiller contents ranging from 0 to 10 wt% were fabricated. In this study, the rheological and thermomechanical analysis of neat polybenzoxazine and its nanocomposites were performed. The rheograms show the shear thinning behaviours of the melted nanocomposite compound. In addition, the complex viscosity of the nanocomposites revealed that the liquefying temperature of these molding compounds increased with increasing the amount of fumed silica, while the gel-point temperature was not changed even though the amount of nanofiller was increased. The DSC thermograms confirmed that fumed silica loading had neither retarding nor accelerating effect on the thermal curing reaction of the benzoxazine monomer. Furthermore, the flexural modulus and microhardness of the nanocomposites were increased with an increase of the nanofiller. DMA thermograms also revealed that the glass transition temperatures (Tg) of pure polybenzoxazine were shifted from 157oC to higher values from the presence of the fumed silica.