Epoxy Resin-modified, Urea-formaldehyde/Silicon Networks for High Impact Strength and Thermal Stability

Abstract

A variety of toughening agents are used to modify epoxy resins that improve the fracture toughness of the epoxy systems. The basic goal in toughening cross-linked epoxy resins that are normally brittle at room temperature is to improve crack resistance and toughness without significantly decreasing other important inherent properties, such as the flexural modulus and the thermomechanical properties of the original epoxy resins. In the present study, thermally stable epoxy resin modified urea-formaldehyde/silicon blends have been prepared by in situ polymerization technique. The materials were modified with triethylenetetramine (hardener) to obtain highly cross-linked thermosetting resins. The physical properties of the resulting blends were evaluated by measuring the impact strength, which is found to be increased by more than 25% of that of the cured and blank epoxy resin. The impact fracture surfaces are examined using scanning electron microscopy (SEM) to reveal the morphological changes. The hardness was found to be high in the case of modified epoxy resin as compared to blank epoxy. The influence on the thermal properties and the behavior of different curing agents on resins were investigated by thermogravimetrc analysis (TGA) and differential scanning calorimetry (DSC). The results of the modified epoxy resins showed remarkably high thermal stability as well as a higher degree of solvent resistance as compared with blank epoxy resin.