Influence of amine-terminated additives on thermal and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) cured epoxy

The present work accounts for the influence of aromatic amide oligomers on the inherent brittleness of cured epoxy. Aromatic and aliphatic amine-terminated amide oligomers have been prepared by condensation polymerization using isophthaloyl dichloride and two different amines. The oligomers have been characterized using Fourier transform infrared spectroscopy and wide angle X-ray diffraction analysis. Diglycidyl ether of bisphenol A (DGEBA) is cured with a diamine (4,4′-oxydianiline) by using different weight ratio of oligomers. The FTIR of cured epoxy shows ring opening by the disappearance of oxirane ring peak at 913 cm^?1, whereas X-ray diffraction shows its amorphous phase in the cured state. The thermogravimetric analysis of the resultant composites shows that the thermal stability slightly decreases (467–454 °C) with increasing the oligomer content from 5 to 25 wt %, whereas the mechanical parameters (Young's modulus, tensile strength, impact strength, and elongation at break) increase with increase in the oligomer content. DMA shows lower tanδ values for aliphatic amine-terminated oligomers for cured epoxy. Two-phase surface morphology is observed through scanning electron microscopy. Owing to their high mechanical and thermal properties, aromatic amides have observed to greatly influence the mechanical properties of cured epoxy, particularly its brittleness. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48404.