PurposeTo evaluate the improvement of mechanical and thermal properties of cured epoxy modified with amine functional aniline formaldehyde condensate (AFAFC) along with the optimum result of modified epoxy.Design/methodology/approachFor effective toughening, different compositions were made by adding various concentration of AFAFC to epoxy. The impact, adhesive, tensile and flexural strengths of the modified and the unmodified epoxy were characterized by dynamic mechanical analysis. Thermo gravimetric of modified epoxy was also reported.FindingsThe modification of epoxy resin using AFAFC showed significant enhancement of mechanical strength over unmodified epoxy. The reason behind this is that in the initial stage of cure the AFAFC are miscible with the epoxy and form a homogeneous solution. This good mixing promotes the chemical reaction and network formation. During the curing process, as the molecular weight increases, the component separates with in the reaction medium to form a second dispersed phase.Research limitations/implicationsThe toughening agent AFAFC have been synthesized by using aniline and formaldehyde. Besides this, by changing the amine and aldehyde, another toughening agent could be synthesized and the efficiency of modification of epoxy resin using these could also be studied.Originality/valueAFAFC modified epoxy could be used in the field of coating, casting, adhesives, potting and encapsulation of semiconductor devices.