Rapid Self-healing System Based On Microencapsulated Thiourea Modified Polyamine And Epoxy

Epoxy-based materials have been widely used in engineering due to their excellent properties.However,the thermosetting polymer is highly sensitive to defects or cracks.When being impacted by the outside,the microcracks inside the matrix will rapidly expand and gradually destroy the properties of the material,eventually leading to the macroscopic destruction of the material.Therefore,the realization of self-repairing function in epoxy resin material,thereby extending its service life and reducing its maintenance cost,has become a current research hotspot.The two-component homogeneous self-healing epoxy resin based on epoxy microcapsules and amine microcapsules has the advantages of low toxicity,low cost,complete autonomy,homogeneity,high efficiency,and long-term stability.It is considered to be a kind of potential practical value Self-healing system.However,the lower repair rate limits its further practical development.How to increase the repair rate under the premise of ensuring repair efficiency and achieve a balance between repair efficiency and speed is a necessary prerequisite for its practical application.In order to solve the above problems,this subject proposes to use thiourea chemically modified amine curing agent to improve the repair rate of the system,and develop a new fast self-healing ring based on thiourea modified polyamine microcapsules and epoxy microcapsules.Oxygen resin system.The main contents of this paper are as follows:First,using diethylene triamine(DETA),polyether amine(T403),and thiourea(TU)as raw materials,the polyamine and thiourea are polycondensed at a certain temperature,and sulfur atoms are introduced into the molecular chain(S)to prepare thiourea modified polyamines(TU-DETA and TU-T403).Test and characterize the molecular structure of modified polyamines by infrared spectroscopy(FTIR),nuclear magnetic resonance(13CNMR),liquid phase-mass spectrometry(LC-MS)and thermogravimetric analysis(TGA),and solidify them The kinetics of epoxy monomers were studied.The experimental results show that through modification,C=S groups are successfully introduced into the molecular chains of TU-DETA and TU-T403 and their molecular weights are significantly increased.In manual premixed repair,the repair efficiency of using TU-DETA at 25°C for 4 hours is about 140%,and the repair efficiency of using TU-T403 at room temperature(25°C)for 24 hours is about143%,which is comparable to that of unmodified DETA and T403.Compared with the modification,the repair rate and efficiency have been significantly improved after modification,which provides a prerequisite for the development of a new fast and efficient self-repair system.Secondly,using electrostatic spray-interfacial polymerization microencapsulation technology,the synthesis and performance control of the preparation of thiourea-modified polyamine microcapsules have been deeply studied.The feasibility of microencapsulation of thiourea-modified polyamines and the influence of process parameters such as the content of shelling agent,injection voltage,polarity of reaction solution and reaction time on the quality of microcapsules were investigated.The morphology,wall thickness,effective core material content,dispersion and long-term stability of the modified polyamine microcapsules were tested and characterized by scanning electron microscope(SEM),thermogravimetric analyzer(TGA)and other characterization methods.The experimental results show that the electrostatic spray-interfacial polymerization method can successfully encapsulate thiourea-modified polyamines.The prepared microcapsules have the advantages of shell-core structure,controllable size,high effective core material content and good thermal stability.The twocomponent rapid self-healing system based on thiourea modified polyamine microcapsules and epoxy microcapsules has laid the technical foundation.Finally,based on the prepared thiourea-modified polyamine microcapsules and epoxy resin microcapsules,the performance and control of self-healing epoxy resins based on these two microcapsules were studied.Experimental results show that the highest self-repair efficiency of self-healing epoxy resin containing TU-DETA microcapsules is 50%,and the repair rate is doubled,but the repair efficiency is low and cannot meet the requirements of practical self-healing materials.Using self-healing epoxy resin containing TU-T403 microcapsules for 48 hours at room temperature,the highest self-healing efficiency can reach103%.When the repair time is 24 h,the repair efficiency of the system is 91%,which is basically close to complete repair and double the repair rate compared with T403 microcapsules,which proves that the microcapsule-type self-repair system has basically satisfied the practical selfrepairing system.Requirements for restoration materials.In addition,this subject also studied the repair performance of the system at low temperatures.The results show that the self-healing efficiency of the system is 90% when the repair temperature is 15?,and the T403 microcapsules can hardly be repaired at this temperature,which proves the great advantages and advantages of the self-healing system based on TU-T403 microcapsules.Development potential.In summary,improving the repair rate and efficiency through thiourea modified polyamine has proved to be an effective method,which solves the problem of slow repair rate of epoxypolyamine chemical system.The electrostatic spray-interfacial polymerization method can realize the preparation of large quantities of high-quality modified polyetheramine microcapsules,which meets the needs of microcapsule industrialization.The successful development of the self-repair system will greatly promote the practical development of the microcapsule self-repair system.