A series of extended-chain ureas(Ui) containing polypropylene glycol(PPG) spacers with different molecular weight were synthesized．The reactive activity

dynamic mechanical behavior

impact property and morphology of the Ui modified E-51／dicy curing system were investigated systematically

the relationships among the dynamic mechanical behavior

impact strength and morphology were also discussed．Results show that the curing activity of modified E-51／dicy curing system was so greatly enhanced that the curing reaction peak temperature decreased from l90 to 140℃

and the apparent activation energy of curing reaction is reduced froml 145.5 kJ／mol to 70～80 kJ／mol．The impact strength of the Ui modified curing system was increased ignificantly

E-51／dicy/U1 (extended-chain area containing PPG flexible spacer with molecular weight 1000) system was 8 times higher than that of the unmodified E-51／dicy curing system

the fracture surfaces of the E-51／dicy/U1 systems displayed tough fracture feature

which is very different from that of the unmodified system．There exist two-phase microstructure for the modified curing systenm．This leads to the significant increasing in impact strength．