Preparation And Performance Of Schiff Base/Epoxy Self-healing Materials

Thermosetting resin materials,such as epoxy resin,because of its brittleness,it is easy to be damaged by impact at room temperature.This kind of damage will reduce the mechanical properties and service life of the materials.Schiff base is an organic compound with dynamic imine structure,which is synthesized by condensation of aldehydes or ketones with primary amines.With the advantages of simple synthesis?environmental friendliness and no pollution,Schiff base has incomparable advantages and wide application prospects in the self-healing field of polymer materials.In this paper,a series of linear Schiff base segments with two imine structures were synthesized by one pot method using TPA(A2),DETA(B3)and D-230(B2)as raw materials:one is the imine segment condensed by A2 and B2,the other is the imine segment containing unreacted secondary amine(-NH)condensed by A2 and B3.This paper studies from the following two aspects.1.Different kinds of Schiff base/E-51 materials were prepared by curing epoxy resin(E-51)with secondary amine group in Schiff base chain segment as ring opening agent of anhydride.The effects of different types and contents of linear Schiff base segments on the properties of polymer materials were studied.It was found that the mechanical strength,thermodynamic properties and self-healing ability of Schiff base/E-51 materials could be effectively adjusted by changing the type and content of linear Schiff base.It can design materials according to the requirements,and can effectively control the self-healing temperature of materials.At the same time,the material has self-healing at room temperature,and the first and second self-healing efficiency is as high as 93.6% and 91.3%.After two repair cycles,the material still has high fracture tensile strength.The high self-healing ability at room temperature is due to the dynamic balance of imine bond in the system,which can improve the self-healing ability of the material and take into account the mechanical strength and service environment of the material,so as to endow the crosslinked epoxy resin with self-healing ability.2.The secondary amine group in the chain segment of Schiff base was used as the crosslinking point,and the synthesized epoxy resin containing DA bond was introduced as the permanent crosslinking agent.The dynamic imine DA joint network was constructed,and different types of Schiff base/EP-DA materials were prepared.The effects of crosslinking degree on the properties of polymer materials were studied.It is found that the mechanical strength,self-healing ability and degradation rate of the material can be effectively regulated by adjusting the content of the secondary amine crosslinking point in Schiff base.The highest self-healing efficiency of the material can reach 70.1%.This type of material has good self repair ability.The main chain of the system contains imine structure,under a certain temperature and acid conditions,this type of material can be completely degraded,which also provides the possibility for the recovery of materials.The material can be completely degraded in a short time.The introduction of DA bond in crosslinking agent makes the material have the ability of high temperature remodeling.This kind of network polymer material has excellent mechanical strength,good remolding molding and degradability,which provides a new way for the design of dynamic covalent network polymer.