Structure and Properties of Epoxy/Fly Ash System: Influence of Filler Content and Surface Modification

Epoxy resin composites filled with pristine and organomodified fly ash were prepared and examined. The fly ash used is CaO-rich due to the origin of lignite from the northern Greece area and the power plants in Kozani. As matrix, the epoxy system with curing agent triethylenetetramine was used. A combination of mechanical stirring and ultrasonication was used for highly dispersed fly ash composites. SEM, FTIR spectroscopy and XRD measurements were used to study dispersion homogeneity, structure, degree of aggregation/agglomeration and interface formation of the matrix with the fly ash particles. The properties E′, E″ and relaxations α-(Tg) and β-(Τβ) of the composites were assessed by DMA. Also, DSC and TGA measurements were used to characterize the thermal properties. Interesting results concerning the effect of the surface organomodification of fly ash on the network formation and the thermomechanical properties of the composites were derived. XRD and FTIR measurements reveal that the functional groups present on the surface of fly ash particles play a dominated role to interface formation. DMA results show that the fly ash surface modification affects the thermodynamic properties of the composites. Additionally, there is evidence showing that the short-scale β-relaxation is also affected by the fly ash surface organomodification.