Preparation Of Self-Healing Polymer Based On Disulfide Exchange Reaction And Its Recovery Performance

Traditional thermoset polymer materials do not have self-healing properties.During long-term use,micro-cracks or degradation aging can occur inside the materials,which not only reduces the materials properties,but also reduces the service life of the materials.The introduction of dynamic covalent bonds into polymeric materials imparts reproducible,remodelable and recyclable properties to conventional polymeric materials.This new type of polymer materials has a wide range of applications in microelectronics,biomimetic medicine,coatings and other related fields.In order to solve the problem of recycling of acrylic resins,an elastomers having repairing and remolding properties was prepared by a thiol-olefin click addition reaction using an acrylate monomer and a polysulfide rubbers.Firstly,the effects of four different catalytic systems,such as free radical catalytic system,alkali catalytic system,redox catalytic system and photocatalytic system,on the structure of acrylate elastomers were compared.Infrared spectrometer(FTIR)and nuclear magnetic resonance spectroscopy(~1H-NMR)were used.Characterizing the degree of reaction,the results show that the base catalyst system and the redox catalyst system show better catalytic effects than the other two catalyst systems.Secondly,the thermodynamic properties were characterized by differential scanning calorimetry(DSC),thermogravimetric(TGA)and dynamic thermomechanical(DMA).The results show that the acrylate elastomers under different catalytic systems have higher thermal stability and Lower glass transition temperature.Then the effects of different reactant systems,different oxidants,reducing agents and self-repairing accelerators on the mechanical properties and repair efficiency of acrylate elastomers were compared.The mechanical properties of the acrylate elastomers before and after repair and remodeling were tested by a tensile machine.The results show that the acrylate elastomers exhibits higher tensile strength and repair efficiency than the other catalyst systems under the base catalyst system;1,8-Diazabicyclo[5.4.0]undec-7-ene(DBU)is used as a reducing agent,the toughness and repair efficiency of the materials can be greatly improved.Finally,the mechanism of exchange of disulfide bonds under high temperature is discussed.The disulfide bond in the crosslinked network undergoes dynamic reversible exchange reaction at high temperature.The rearrangement of the dynamic network structure at high temperatures gives the materials excellent self-healing,reshaping and reprocessing capabilities,and achieves the recycling of acrylic resins.To solve the problem of recycling of thermosetting epoxy resins.A novel epoxy resins containing aβ-hydroxy ester is synthesized by reacting a commercial epoxy resins with a dicarboxylic acid,and is crosslinked by an aromatic amine curing agent(4-AFD)containing a disulfide bond.4-AFD as a hard segment and a dicarboxylic acid as a soft segment,a dynamic crosslinked epoxy resin network with a dual repair mechanism of disulfide exchange reaction and transesterification was constructed.The structure of self-healing epoxy resin materials was first studied,and the degree of reaction was characterized by FTIR and ~1H-NMR.The results show that the epoxy resins and the dicarboxylic acid reacted within 3 h and completely reacted with4-AFD.Secondly,the thermodynamic properties were characterized by DSC and TGA.The results show that the self-repairing epoxy resins materials with different ratios of soft and hard segments have different glass transition temperatures and high thermal stability.By changing the proportion of soft and hard segments,the mechanical properties and recovery properties of self-healing epoxy resins materials under different soft and hard segment ratios were systematically studied.The mechanical properties before and after remodeling were tested using a stretching machine.The results show that the tensile strength of the material increases with the increase of the hard segment ratio;the chemical structure and mechanical properties of the materials do not change significantly with the increase of the number of remodeling.The recovery of the self-healing epoxy resins materials in 1 wt%4-dimethylaminopyridine(DMAP)in dichloromethane was then investigated.The results show that the chemical structure of the self-healing epoxy resin materials before and after solvent recovery has no obvious change,which provides a new way for the recycling of epoxy resins.Finally,the switch mechanism of epoxy resins materials with double repair mechanism under high temperature is discussed,which has better solid phase recovery performance than self-healing materials with single repair mechanism.