Strong aliphatic crosslinked polyureas synthesized through a non-isocyanate route and a Michael addition with an aliphatic bismaleimide

A simple and convenient non-isocyanate route is described to synthesize strong aliphatic crosslinked polyureas (cPUreas). A ring-opening reaction of mixed diamines with ethylene carbonate was carried out at 100 degrees C, and a transurethane polycondensation was followed at 170 degrees C, with different amino terminated polyurea oligomers (H2N-o-PUrea-NH(2)s) prepared. cPUreas were prepared further through a crosslinking reaction of H2N-o-PUrea-NH(2)s with 1,5-bis(maleimide)-2-methylpentane. The cPUreas were characterized by FT-IR, dynamic mechanical analysis, thermogravimetric analysis, and tensile test. Different curing conditions were adopted to study the influence on the properties. The cPUreas exhibited tensile strength up to 91 MPa, glass transition temperature between 96 and 182 degrees C, and initial decomposition temperature at over 288 degrees C. Aliphatic cPUreas with excellent thermal and mechanical properties were successfully synthesized.