Preparation And Properties Of Self-repairing Epoxy Resin Based On Quadruple Hydrogen Bonding

Epoxy resins and their composites are increasingly used in the aircraft,automotive,marine,defense and construction industries to penetrate every aspect of our lives.Epoxy resins are susceptible to damage caused by mechanical,chemical,thermal and UV radiation during the process of forming and using,leading to the formation of microcracks and affecting the structural integrity of the polymer,resulting in the performance degradation.Traditional research has focused on the design of new materials and the repair of visible or detectable damage to the polymer structure.Traditional methods of repair are ineffective for invisible micro-cracks in the structure of the material over its useful life.Biology provides a rich system of self-healing,reflecting the guiding principles.According to the repair mechanism,the current self-repair method can be divided into two types: a foreign aid self-repair,relying on material supply,is mixed with the repair agent which inside the microcapsules,liquid core fibersin in the matrix material to achieve self-healing;the other Eigen-type self-healing,relying on energy supply,by means of the introduction of reversible covalent and reversible non-covalent bonds into the polymer,self-healing behavior by breaking and recombining the bonds happened.The former method contains complex methods for repairing the reagent carrier,and has a limited number of repair times,and the release of the repairing agent can form new defects in the original position and can only repair some micro-cracks;the latter can be multiple repairs,and can repair fully fractured materials.However,most of them have the disadvantages of poor mechanical properties,low elastic modulus,low Tg and low breaking strength.In order to solve the contradiction between the material repair efficiency and the mechanical properties,this paper presents a "dynamic quadruple hydrogen bond" based repair mechanism.Polymeric materials with high mechanical strength are prepared using the quadruple hydrogen bonding between UPy.Multiple hydrogen bonds are stable at room temperature and only disconnect when heated or mechanically shocked.Hydrogen bond in the external stimulus will be broken and then reintegrate tu strong quadruple hydrogen bond.The introduction of this strong intermolecular force into the epoxy gives the crosslinked epoxy a thermal repair capability.epoxy resin to provide mechanical properties,supramolecules containing quadruple hydrogen bond to provide self-repair properties,under external conditions(light,heat,etc.)to stimulate the epoxy resin from the glassy state into a rubbery state,the molecular chain mobility increased.Thus,the free supramolecules can rapidly diffuse to the fractured surface of the polymer,recombine at the fracture surface,forming a new polymer network,completing the repair process.It is worth noting that the ability of molecular segments to move by the polymer network crosslinking density and molecular chain rigidity.Based on the "dynamic quadruple hydrogen bond" repair mechanism,it is expected to obtain high repair efficiency,high mechanical properties of repairable polymer materials.Finally,we discuss the microscopic mechanism of self-healing and its influencing factors through the changes of different repair conditions,different supramolecules and different curing agents,and provide the basis for the practical application of such materials.Along with the increase in content of supramolecular,micro phase separation occurs,self repair efficiency increase;Since the heat treatment temperature,repair efficiency increases and then decreases;Only the compatibility of appropriate cause proper micro phase separation to achieve the best effect of repair.