An Epoxy Resin Crosslinked By Dynamic Boronic Ester Bonds And Its Composite

Dynamic covalent polymer network is a new polymer system that combines the characteristics of thermoplastics and thermosets,which shows significant benefits in self-healing,reprocessing,3D printing and other aspects.Boronic ester bond is glucose-responsive and can rapidly exchange in room temperature.It has been used to develop medical sensors or self-healing materialsIn this thesis,a series of dynamic covalent epoxy resins providing various rheological properties and glass transition temperatures(Tg)were prepared,achieving the recycle of epoxy resins.Firstly,a diol group was introduced into an epoxy molecule through a thiol-epoxy click reaction.Secondly,the diol groups were reacted with borate bonds forming dynamic crosslinking netpoints.Effect of the formulation on the properties of the materials was investigated.The rheological properties of the materials can be adjusted by tuning the ratio of non-dynamic crosslinking points and the exchangeable borate bonds.Tg of the polymers can be adjusted from 14.6? to 36.5?by changing the ratio of the fed soft and hard epoxy components.Composites were prepared by introducing the dynamic networks into open porous melamine foams.Such composites can be rapidly self-welded in a few seconds after they had been cut.The welding performance is found to be constant after 20 disassembling-bonding cycles,showing good repeatability.The work also showed that the self-welded strength of the composites increased with the increase of non-dynamic crosslinking points in the matrix.