Preparation Of Phenolic Modified Epoxy Vitrimer Composite And Its Investigation On Self-healing Performance

As one of the three major thermosetting materials,epoxy resin has made great progress from technical and economic point of view due to its unique chemical structure and properties.Due to the infusible and insoluble properties of thermosetting materials,once the materials are damaged during use or reach service life,they cannot be reprocessed to realize recycling.So we can only replace the whole product.Therefore,self-healing thermosetting materials have become the focus of research.The self-healing performance can extend the service life of materials and reduce the consumption of raw materials,which is particularly important in the current social environmental due to oil resources are scarce.In this paper,epoxy vitirmer material was prepared by epoxy resin E-51,methyl tetrahydrophthalic anhydride as curing agent,stannous isocaprylate as catalyst,after that linear phenolic resin was used to modify it,and various properties of the two systems were explored.The curing reaction process was discussed,and the mechanical properties such as bending strength,tensile strength and the change of glass transition temperature of the material were studied.The stress relaxation behavior of the material was studied by rheometer,and a multivariate model was established to describe the stress relaxation behavior.Then the self-healing performance of the material was studied through thermal welding and scratch repair,and the shape memory ability was studied by monitoring the relationship between the recover angle and recover time.The study found that the increase of the catalyst content improved the repair ability of the material,promoted the transesterification reaction rate of the material,and made the stress relaxation time shorter.At the same time,when the catalyst content is 7%,the bending strength of the sample is the highest,which is 87.5 MPa.The stress relaxation behavior of the material is the superposition of two stress relaxation behavior.At the beginning of relaxation,the small units of the polymer chain respond faster,and then the slow relaxation process is caused by the transesterification reaction.In the pure anhydride/epoxy system,the low hydroxyl content limited the progress of the transesterification reaction and made the stress relaxation cannot be completely relaxed.The vitrimer system is modified by linear phenolic resin,a certain amount of hydroxyl is introduced to the material,promoted the transesterification reaction and improved the repair ability of the material.The shear strength of five repetitive welding at high temperature is above 2 MPa,essentially unchanged.The addition of phenolic resin promoted the curing of the system,made the curing of the material more complete,the bending strength of the material could reach 127 MPa.But the addition of excessive phenolic resin would lead to the decrease of the crosslinking density and affect the mechanical properties of the material.The study found that the two vitrimer systems have excellent shape recovery performance,and the change curves of the recovery angle with time are consistent with Bolyzmann model.