Effect of Reactive Diluents and Kaolin on the Mechanical Properties of Epoxy Resin

Epoxy resin was modified using phenyl diglycidyl ether (POE), xylene and kaolin. The impact strength (IS), critical stress intensity factor (K(C)), flexural strength and glass transition temperature (Tg) were evaluated as functions of the modifier content. It was found that the addition of diluents led to a significant reduction of both viscosity and Tg. A three-fold increase of IS was obtained with the addition of 2.5% POE. Moreover, the addition of 15% POE resulted in about 145% enhancement of the K(C) parameter. However, the addition of xylene had no significant effect on these properties. Furthermore, the addition of 10% kaolin to epoxy resin gave compositions with the highest fracture toughness. Maximum K(C) values were obtained with epoxy hybrid compositions containing 10% kaolin and 2.5% POE and 10% kaolin and 5% POE respectively. All tested compositions had higher energy at break than nonmodified epoxy resin. SEM micrographs of fractured surfaces of modified epoxy compositions revealed the presence of plastic deformations, which can be considered as the main source of the mechanical properties enhancement.