PISOX was modified by polyurethane prepolymer which was synthesized by MDI and PTMG-2000 to
strengthen toughness. The variation of resin mechanical properties with different I/ E ratio and content of prepolymer
were characterized. The composite mechanical properties and the heat resistant property of modified resin and unmodi-
fied resin investigated by universal testing machine and DMTA, were compared. The variation of micromorphology was
observed by SEM to speculate toughening mechanisms. The results suggested that the composite material had the best
mechanics performance when I/ E ratio is 1. 8 and the content of prepolymer is 15%. The bending strength, bending
modulus, impact strength is 60. 92 MPa, 2 295 MPa, 6. 40 kJ/ m 2 , respectively. The DMTA showed that the addition
of prepolymer had little effect on the heat resistance of the resin at high temperature. The glass transition temperature
is 258℃. Composite material prepared by this resin had better mechanical properties and interfacial properties. By
comparing the microstructure of the cured material, we can conclude that the modified system is two phase structure,
rubber phase played the role of absorbing impact energy and terminating crack, whic can improve the toughness of the
material effectively.