Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The incorporation of flexible polycaprolactone (PCL) long chains is intended to enhance the molecular mobility of the epoxy resin. Compared with neat EEC epoxy resin, the PCL-EEC/EEC resin with 20 wt% PCL-EEC loading exhibits an approximately 129% increase in elongation at break, reaching 10.33%. Its tensile strength attains 50.64 MPa, representing a 42% enhancement over that of neat EEC resin (35.66 MPa).

ABSTRACT
This study aims to develop an efficient toughening agent for epoxy resins. Under catalysis, polycaprolactone diol was reacted with epoxy resin to synthesize an epoxy prepolymer containing flexible long chains, which was subsequently introduced into the epoxy curing system and subjected to performance testing. The incorporation of flexible polycaprolactone (PCL) long chains is intended to enhance the molecular mobility of the resin, thereby softening the rigidity of the resin network. Meanwhile, the hydroxyl groups of PCL may participate in the formation of interpenetrating networks or secondary crosslinking points, which refine the three-dimensional crosslinking structure and consequently improve the tensile strength of the resin. Mechanical property tests reveal that, compared with neat EEC epoxy resin, the PCL-EEC/EEC resin with 20 wt% PCL-EEC loading exhibits an approximately 129% increase in elongation at break, reaching 10.33%. Its tensile strength attains 50.64 MPa, representing a 42% enhancement over that of neat EEC resin (35.66 MPa). These results demonstrate that synergistic toughening and strengthening are achieved, while the resin's flowability and processability are well preserved.