The spherulite growth of hard segments in polyurethanes and its relation to the compatibility between the soft and hard segments were studied.DMA and DSC measurements indicate that polyurethane with different soft segments(PCL

PTAM

PTMO and PPO) exhibit different compatibility between their soft and hard segments.The compatibility between hard and soft segmeats in polyurethanes decreases in a sequence of PCL

PTMA

PTMO and PPO.The temperature range for hard segments of polyurethane to grow spherulites in annealing from melt is limited.The better the compatibility between the soft and hard segments

the narrower the temperature range for spherulite formation and the longer the crystallization time.The low temperature limit of spherulite growth is 120℃ for polyurethane with MDI-BDO hard segments and does not change with soft segments.This limit is determined by the hydrogen bonds between the hard segments and soft segments.The high temperature limit of spherulite grouth strongly depends on the compatibility between the soft and hard segments.The worse the compatibility

the higher the high temperature limit Only when the temperature becomes high enough

the compatibility between the soft and hard segments can prevent the forming of spherulite.When the hard segments crystallize from melt

there exist a most appropriate temperature of forming spherulites

at which the amount of hydrogen bonds has a maximum as shown by FTIR In such cases the crystallites and spherulites are more stable.