Synthesis And Properties Of Selenium Containing Polyurethane Based Self-healing Materials

Polyurethane is widely used in many fields due to its excellent performance.However,the material causes various damages due to external influences during use,reducing the service life of the material or wasting resources.Thus,polyurethane materials with self-healing properties are receiving increasing attention.In recent years,there have been many reports on polyurethane self-healing materials,but most of the materials have strictly healing conditions,slow healing rate and low mechanical properties.This thesis aims to synthesize polyurethane self-healing materials based on dynamic diselenide bonds with high mechanical properties,fast healing speed,mild healing conditions and recyclability.The specific research content is as follows:1.Isocyanate-terminated urethanes were synthesized by using different molecular weight polypropylene glycols(PPG2000,PPG3000)and isophorone diisocyanate.Alkyl diselenide functionalized diamine is effectively used as a dynamic crosslinker for the design of self-healing polyurethane.Different polyurethanes were synthesized by adjusting the molar ratio of di-isocyanate-terminated urethane to tri-isocyanate-terminated urethane.The reaction was monitored by FTIR spectroscopy.The mechanical properties and self-healing effects of polyurethane materials with different crosslink density are compared.Tensile testing and healing experiments show that the tensile strength of polyurethane materials can reach up to 12 MPa due to the combination of urea bond and amide bon.As the proportion of flexible segments of polyurethane increases,the mechanical properties of the elastomer decreases.At the same time,the self-healing efficiency is increased.The minimum time required for the healing efficiency of polyurethane materials to reach 100%at 25? was explored.The effect of temperature on healing efficiency was also examined.The experimental results show that 100%healing efficiency can be obtained in only one hour;the healing efficiency also increases as the temperature rises.From the tensile test results showed that temperature was important for the self-healing efficiency of current material.As high as 100%of the initial mechanical property was recovered at 50? after 10 min.The alkyl diselenide has been incorporated into polyurethane networks using a para-substituted amine diphenyl alkyl diselenide.The resulting materials not only exhibit faster self-healing properties than the corresponding disulfide based materials,but also show the ability to be processed as temperatures as low as 60? and do not cause a decline in mechanical properties.2.Graphene was used as a modification agent to enhance the mechanical properties of the above polyurethane self-healing material.In order to improve the compatibility of graphene with polyurethane matrix and the dispersion of graphene in polyurethane matrix,firstly,3-aminopropyltrimethoxysilane was reacted with graphene oxide,and then hydrazine hydrate was reduced to obtain functionalized graphene.Functionalized graphene exhibits excellent dispersion in THF solution,providing better conditions for film formation.Since the functionalized graphene introduces a reactive group which can react with the isocyanate group,a chemical bond interaction can be generated with the polyurethane matrix,so that good compatibility is exhibited.Tensile tester and thermo gravimetric analyzer characterized the properties of the composites.The results show that compared with pure polyurethane materials,the tensile strength of composites containing 0.2 wt.%functionalized graphene increased by 87.2%,the strain increased by 47%,and the thermal decomposition temperature is increased by nearly 50?.It is noteworthy that due to the dynamic diselenide bond in the composite system,excellent self-healing properties are still maintaining.3.Isocyanate-terminated urethanes were synthesized by isophorone diisocyanate and using different molecular weight polypropylene glycols(PEG600,PEG1000),having excellent biocompatibility.Alkyl diselenide is effectively used as a dynamic crosslinker for the design of self-healing polyurethane and it has strong mechanical properties.At 37?,after 3 hours of spontaneous healing,85%of initial mechanical property was recovered respectively.It can be proved by cell viability experiments that the synthesized polyurethane material has good biocompatibility.