Investigation On The Preparation And Properties Of Epoxy Resin Based Vitrimer

Self-healing thermosetting material is currently a very popular research direction.Due to the ‘insoluble and infusible' properties,once they are damaged during use,they only can be scrapped for overall replacement.The self-healing properties can extend its service life.This technology can be widely used in different fields,from sophisticated flexible electronic devices to large load-bearing structural parts,especially in the aerospace field where humans can not enter and exit at will,thus self-healing is particularly valuable.In this paper,two kinds of vitrimer materials with different systems were prepared by epoxy resin E-51,methyl tetrahydrophthalic anhydride curing agent,adipic acid curing agent and zinc acetylacetonate catalyst.The mechanical properties such as bending strength and toughness,thermal properties such as glass transition temperature were studied.The rheological experiment was used to establish a model to analyze the stress relaxation behavior,and the fitting data was used to guide the thermal welding experiment to study their thermal-welding ability.The shape recovery ability was studied by a self-made simple shape memory test device.The study found that the addition of moderate amount of catalyst can increase the bending strength of the material.After replacing some of the anhydride with adipic acid,the bending strength of the material decreases with the increase of the adipic acid fraction,but the toughness is gradually improved.The stress relaxation of the vitrimer material is a double relaxation behavior,which is dominated by the relaxation of the normally crosslinked polymer in the early stage,and dominated by the relaxation caused by the transesterification reaction in the latter stage.It is the superposition of two relaxation.The relaxation behavior is related to temperature and thermal treatment time.The transesterification rate of both systems increase with the elevated temperature,and the relaxation time decreases overall.The difference is that with the increasing experiment times,the decomplexation of the complex product of the anhydride and catalyst leads to further post-cure,which results in the system that cannot be completely relaxed.In theanhydride-diacid complex system,the post-cure reaction disappears due to the reduction of the complex product,and it can be completely relaxed,but it need a relatively longer time.Therefore,the welding repair ability of the two systems is not infinite.The introduction of self-repair performance does not have much influence on the shape memory performance of the two systems,and both have excellent shape recovery ability,which are consistent with the inverse S-shaped curve of the Bolyzmann model.