A series of aliphatic polyureas with different hard segment contents were synthesized by the reaction of isophorone diisocyanate with Jeffamine D2000 and isophorone diamine as chain extender in solution．The effect of hard segment contents on the morphology and mechanical properties for these polyureas was studied by using DSC and FTIR etc．The experimental results showed that the polyureas exhibited a partial phase separated morphology．The polyurea with higher hard segment contents showed a better compatibility between the soft and hard segments

and a higher degree of hydrogen bonding for the urea carbonyl groups existed in the system

but the values of Tg for the soft segment regions almost did not depend on the hard segment content．The tensile strength

hardness and shear strength of polyurea specimens were enhanced greatly with increasing the hard segment content.