Investigation of structure for crosslinked PUU by FTIR showed that the band site for hydrogen bonded NH groups shifted to high wavenumbers

the absorbanee of the band of carbonyl for ordered urea link at 1642 cm-1 was weaker than that of linear PUU

and the absorbanee for the ordered urethane carbonyl wasn’t observed in the spectram for the crosslinked PUU

because of the presence of erosslinks．It was also observed that with the increase of temperature

the absorbanee of hydrogen bonded NH group decreased

while its band site shined to higher wavenumbers．The FFIR results revealed that the mixed degree of the micro hard phase was hisher than that of linear PUU．the resilenee of the erosslinked PUU was lower than that of the linear PUU

and with the increase of temperature

the hyarogen bond among the polar groups was easily destroyed

and the flexibility of the soft segment incleased．and the enhance of the resilenee for the erosslinked PUU was higher than that of the linear PUU The higher the erosslink density．the lower the resilenee of the PUU

and the heat buildup became strong with the increase of erosslink density and the hard segment content．However

the change of the extender molar ratio hardly affected the resilenee and the heat buildup

but it did improve the flexible fatigue properties of the PUU elastomers significantly．