Preparation of a hyperbranched hybrid curing agent for epoxidized novolac resin

Abstract

A hyperbranched hybrid curing agent (CSD) for epoxidized novolac resin (ENR) was prepared by grafting silica nanoparticles modified with poly(amidoamine) (PAMAM) dendritic structure (SD) to carbon nanotube (CNT) using an esterification reaction between the amino functional groups of SD and carboxylic acid functionalities of oxidized CNT. ENR was prepared by a reaction between novolac resin and epichlorohydrin. Curing of ENR was carried out with two different contents of CSD as the hyperbranched hybrid curing component of the epoxidized matrix. The amino-rich structure of CSD could result in its high dispersion in the ENR matrix and consequently high thermal stability of the hybrid composites. Fourier-transform infrared spectroscopy and thermal gravimetric analysis (TGA) showed successful modification of silica nanoparticles and CNT with the PAMAM dendritic structure and SD, respectively. Structure of the resulting hybrid curing agents (SD and CSD) was investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermal investigation of the resulted composites by TGA showed that the cured ENR with higher content of CSD has high thermal properties with a char residue of 44.4% among the other hybrid composites.