Preparation,properties and hydrogen bond exchange mechanism of self-healing polyurethane elastomers
Intrinsic self-healing polyurethane based on hydrogen bond exchange is synthesized with amino-terminated siloxane(ATPS),2,5-dimethyl-2,5-hexanediol(DMHDO),isophorone diisocyanate(IPDI),and hydroxyl-terminated polybutadiene(HTPB).The sample with IPDI∶HTPB∶ATPS∶DMHDO of 1.8∶1∶0.8∶0(P5)achieved a self-healing efficiency of 70％at room temperature;the sample of IPDI∶HTPB∶ATPS∶DMHDO of 1.8∶1∶0.6∶0.2(P4)self-healing efficiency of 90％at 50 ℃.The addition of siloxane reduces steric hindrance and facilitates hydrogen bond exchange.Molecular dynamics simulation was used to explore the dominant hydrogen bond type in the self-healing process.The dominant hydrogen bond of the chain extender is hindered alcohol(P1)which is formed by the urethane bond at the end of the hard segment and the hindered alcohol urethane bond;The chain extender is siloxane(P5)which is formed by the urethane bond at the end of the hard segment.The two chain extenders mixed in equal proportions(P3)has three types dominant hydrogen bonds,which are composed of hard segment end urethane bonds,hindered alcohol urethane bonds and ATPS urea bonds.
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