Design,Preparation And Properties Of Self-healing Polyurethane Elastomers

At present,the shortage of non-renewable resources is becoming more and more serious,which restricts the development of economy and society to a certain extent.Polyurethane(PU)is a kind of polymer material which is widely used.It is helpful to extend the service life of PU material by preparing PU material with high self-healing ability.It is of great significance to effectively deal with the current resource crisis and environmental problems and promote the sustainable development of economy and society.Based on the special chemical structure and excellent molecular chain design of PU,a variety of PU materials with excellent self-healing performance are designed and prepared.The specific research contents and results are as follows:1.Self-healing PU elastomer based on reversible hydrogen bonding and flexible block.A new PU chain with flexible blocks with different lengths at both ends is designed and synthesized.These flexible blocks exist at the end of PU chain,which has strong motion ability,and is conducive to the diffusion and self-healing process of the chain in the damaged area.In addition,the existence of hydrogen bond between the imino and carbonyl groups in the carbamate group can further guarantee the effective healing of the damage in these PU materials.2.High self-healing PU elastomers based on strong hydrogen bond network and flexible block.A new PU chain with flexible end chain and 2-urea-4-[1H]-pyrimidine(UPy)group with flexible end chain and reversible quadruple hydrogen bond was designed and prepared.It was found that both PU elastomers with and without UPy group had self-healing ability.In addition,PU without UPy group has strong selfhealing ability at lower temperature,while PU with UPy group has better self-healing effect at higher temperature.The difference of healing ability can be attributed to the comprehensive effect of two key factors(chain segment mobility and hydrogen bond network strength).That is,at low temperature,the mobility of the segments connected with UPy group is relatively poor,which is not conducive to the chain segment diffusion at the fracture,thus the self-healing efficiency is lower;and at high temperature,the movement of the segments connected with UPy group is quite active,that is,the difference of segment movement ability between two kinds of PU elastomers becomes smaller.The reversible qmuadruple hydrogen bonding network between UPy groups becomes the main factor that affects the self-healing of the material fracture,so the PU self-healing effect with UPy group is better.In conclusion,the self-healing behavior of polymer elastomers is determined by the above two key factors.3.The interpenetrating crosslinking PU elastomer with high strength and high selfhealing property based on strong hydrogen bonding network,flexible block and metal ion coordination.Combined with the PU chain containing UPy group,a kind of interpenetrating network of covalent crosslinking network of PU and reversible strong hydrogen bonding network of PU chain containing UPy group was designed and established,and the coordination structure of carboxyl group and zinc ion was introduced to prepare a kind of interpenetrating crosslinking PU material with ultrahigh mechanical strength and ultra-high self-healing performance.It was observed that the existence of cross-linking network and ionic coordination bond provided excellent mechanical properties and thermal stability for the materials.The synergistic effect of ionic coordination bond,reversible strong hydrogen bonding network and high mobility chain segment made up for the adverse effect of covalent cross-linking network on the self-healing performance of the materials to a great extent,even far beyond this effect.