Enhanced thermal stability and mechanical performance of epoxy resin with amine-terminated aromatic amide oligomer: unveiling the ring-opening curing phenomenon

Abstract

Amine-terminated aromatic amide oligomer (ATAAO) was used to cure diglycidyl ether of bisphenol A epoxy resin. P-phenylenediamine (PPDA) and isophthaloyl chloride (IPC) underwent a condensation reaction to synthesize the oligomer using dimethyl acetamide (DMAc) as the solvent. The successful synthesis and semi-crystalline nature of oligomer was confirmed using ¹HNMR, FT-IR, and X-ray diffraction, respectively. The curing reaction was carried out by mixing ATAAO and diglycidyl ether of bisphenol A (DGEBA) epoxy resin in DMAc, followed by curing at 363.15 K and 393.15 K for 30, 60, 90 and 120 min, respectively. Moreover, the ring-opening curing phenomenon in epoxy was confirmed by ¹HNMR and FT-IR. XRD analysis revealed the amorphous nature of the cured epoxy. Thermal analysis revealed an increase in thermal stability (553.21 K to 580.32 K) and glass transition temperature (423.21 K to 481.61 K) with increasing curing temperature (363.15 K to 393.15 K) and curing duration (30 min to 120 min). Stress–strain analysis revealed an increase in Young’s modulus (5.93 MPa to 41.09 MPa) and stress at the break (7.79 MPa to 31.92 MPa) of cured epoxy films with changing curing conditions. Moreover, a homogeneous surface of cured epoxy films containing slight bumps and small globular without any phase separation was observed in scanning electron micrographs.