Application Of Itaconic Based Hyperbranched Polymer In Self-healing And Recyclable Epoxy Resins

As an important type of thermosetting resin,epoxy resin is difficult to recycle due to its insoluble and infusible characteristics.If dynamic covalent bonds or degradable covalent bonds are inserted into the epoxy resin cross-linking network,the epoxy resin can not only exhibit the properties of traditional thermosetting resins,but also exhibit the characteristics of self-repair and recycling.However,the mechanical properties of self-healing recyclable epoxy resins are often low.Hyperbranched polymers have been used to enhance and toughen epoxy resins,and are known for their good fluidity and compatibility.Therefore,adding hyperbranched polymers to the self-healing and recyclable epoxy resin system is expected to achieve the enhancement of mechanical properties.In this paper,two hyperbranched polymers were synthesized and used to modify bisphenol A epoxy resin(DGEBA),and the mechanical properties and recycling properties of the modified epoxy resin were studied in detail.(1)Itaconic based hyperbranched polyester(ITA-HBP-12)was prepared by using itaconic and trimethylolpropane.The molecular structure and molecular weight of ITA-HBP-12 was characterized by FT-IR,1H-NMR,12C-NMR and GPC.The curing mechanism of ITA-HBP-12 modified bisphenol A epoxy resin(ITA-HBP-12/DGEBA)was studied by FT-IR and DSC.The dynamic of ITA-HBP-12/DGEBA was studied by DMA.The self-healing performance of ITA-HBP-12/DGEBA was studied by optical microscope.The repetitive processing performance of ITA-HBP-12/DGEBA was studied using DMA,PALS and AFM.Finally,the degradation mechanism of ITA-HBP-12/DGEBA was studied by LC-MS,FT-IR and 1H-NMR.Research indicates: Compared with ITA/DGEBA/TBD resin,the tensile strength,impact strength,flexural strength and bending modulus of ITA-HBP-12/DGEBA resin were increased by 49%,111%,42% and 41%,respectively,the stress relaxation time at 120?,130?,140?,150? and 160? was shortened by 46%,25%,25%,50% and 48% respectively.ITA-HBP-12/DGEBA resin has fast self-healing performance and great water resistance,acid resistance and solvent resistance.The retention rates of tensile strength,impact strength,bending strength and bending modulus of ITA-HBP-12/DGEBA resin were all over 90% after repeated processing for three times.ITA-HBP-12/DGEBA resin can be rapidly degraded into a carboxylic terminated polyester(r-ITA-HBP)with branch structure in 1mol/L Na OH solution at 80?.r-ITA-HBP can re-cure DGEBA,and the mechanical properties of the cured resin are similar to that of ITA-HBP-12/DGEBA resin.(2)Itaconic based hyperbranched epoxy resin(EHBP)was successfully synthesized through itaconic derivatives(DOPO-ITA),and the molecular structure and molecular weight of EHBP were characterized by FT-IR,1H-NMR,and GPC.The strengthening and toughening mechanism of EHBP on EHBP modified bisphenol A epoxy resin(EHBP/DGEBA)was studied by DMA and PALS.The effect of EHBP content on the heat resistance of EHBP/DGEBA was studied by TGA.Finally,the degradation mechanism of EHBP/DGEBA was studied by GC-MS,FT-IR and 1H-NMR.Research indicates: The mechanical properties of EHBP/DGEBA resin increased first and then decreased with the increase of EHBP content,and reached the maximum value when adding 10 phr EHBP.The impact strength,tensile strength and flexural strength of 10 phr EHBP/DGEBA resin were increased by 285%,58%,63% and 35%,respectively.The strengthening and toughening mechanism of EHBP/DGEBA resin belongs to in-situ strengthening and toughening mechanism.The EHBP/DGEBA resin was completely degraded in 0.5mol/L phosphoric acid solution at 90? for 2h.The degradation product of EHBP/DGEBA resin can be used as curing agent to cross-link with DGEBA.The tensile strength of regenerated epoxy resin can reach 79.02 MPa.EHBP/DGEBA resin has realized the closed-loop recovery of epoxy resin.