A series of polyurethane (PU)

prepared by using uretonimine modified pure 4

4' diphenylmenthane diisocynate (MDI)

and vinyl ester resin (VER) simultaneous interpenetrating polymer networks (SINs) with different compositions have been synthesized. Based upon the DSC

SEM and WAXD observation

the experimental results showed that the chemical bonds between the two networks had great influence on the structure

morphology and mechanical properties of these SINs. For PU/VER SIN in which there are no chemical bonds between the two networks

it is a thermodynamic incompatible system and exhibits phase separation morphology.This is probably related with the different formation rates of the two networks and mixing conditions for forming such SINs.For PU/VER SIN having chemical bonds between the two networks

the compatibility between the two phases and mechanical properties of SINs increased appreciably.Furthermore

the morphology and mechanical property of such SINs are also related with the mixing conditions

i.e hand mixing and reaction injection molding

for forming these SINs.