Synthesis And Properties Of Crosslinked Polyureas Through A Non-isocyanate Route

Two simple non-isocyanate routes synthesizing crosslinked polyureas(cPUreas)are described in the paper.Ring-opening reaction of diamines(DAs)with ethylene carbonate(EC)was carried out at a DA/EC molar ratio of(m+l)/m at 100 0C.Transurethane polycondensation was followed at 170?,and a series of amino terminated poly urea oligomers(H2N-o-PUrea-NH2s)were prepared.H2N-o-PUrea-NH2s were polymerized with a hexanediamine-tetraester(HDATE)or a bismaleimide(BMI)to form cPUreas.The properties of cPUreas were studied by DSC,DMA,TG and tensile test.The research contents are described as follows:1.HDA-o-PUreas were synthesized from 1,6-hexanediamine(HDA),isophoronediamine(IPDA)and ethylene carbonate(EC)at different EC/DA molar ratios.The amino value of HDA-o-PUreas range from 440 to 498 mgKOH/mol,and the yield after dissoluting in diethyl ether is 69%-76%.HD A-c-PUreas were prepared with HDA-o-PUreas and HDATE through a bulk polycondensation reaction at 170?.HDA-o-PUreas exhibited a To above 73?initial decomposition temperature(Ti)higher than 230? and tensile stress from 68 to 73MPa,strain at break range from 17%to 19%.Changing the molar ratio of EC/DAs has little effect on the performance of HDA-o-PUreas.2.D230-o-PUreas were synthesized from poly(propylene glycol)bis(2-aminopropyl ether)(D230),isophoronediamine(IPDA)and ethylene carbonate(EC)at different IPDA/D230 molar ratios.D230-o-PUreas reacted with HD ATE to get D230-c-PUreas at 170?.The Tg and tensile stress increase when more IPDA were introduced into D230-c-PUreas,while strain at break decrease.D230-c-PUreas exhibited a good damping properties with a damping temperature range(tan?>0.3)up to 67?.3.BMI-c-PUreas were synthesized from D230-o-PUreas and BMI through Michael addition at 170?.Curing by BMI could introduce a large amount of N heterocyclic structure into the system.The networks were more compact,and the performance of BMI-c-PUreas were improved.BMI-c-PUreas exhibited a glass transition temperature(Ta)of 96-182C°,initial decomposition temperature(Ti)of 289?,tensile strength from 73 MPa to 91 MPa,and strain at break from 16%to 13%.The effect of curing temperature and time on the properties of BMI-c-PUreas was discussed.Increasing the curing temperature or prolonging the curing time can significantly increase the crosslink density(?e)and glass transition temperature(Ta)of the polymer,but has little effect on the tensile strength and strain at break.