The Preparation Of Epoxy Resin Cured Materials With Quadruple Hydrogen Bonds And Investigation On Their Healing Properties

As a thermosetting polymer material,epoxy resin has been widely used in coatings,insulating materials and advanced composite materials due to the advantages of high dimensional stability,strong solvent resistance and good thermal stability.However,the epoxy resin has the shortcomings of brittle and hard texture,fragile,poor toughness when high crosslinking density and poor mechanical properties,easy damage when low cross-linking density due to the covalent three-dimensional cross-linked network after curing.The methods of toughening modification,such as the rubber toughening modification,nanoparticle toughening modification,modified curing agent and other toughening modifications,are commonly used to improve the shortcomings of poor toughness of epoxy resin,however they will reduce the the heat resistance and tensile strength of the matrix resin material to varying degrees.The damaged material cannot be repaired due to the covalent cross-linked structure of the resin curing material,resulting in waste of resources and environmental pollution.The goal of this article was to improve the poor toughness of epoxy resin cured materials with high cross-linking density,low elongation and low tensile strength of epoxy cured materials with low cross-linking density at break,and the inability of intrinsic healing after thermosetting resin cured materials were damaged.Utilize the energy absorption and energy consumption characteristics of quadruple hydrogen bond to toughen and strengthen the resin cured material;to achieve intrinsic healing of the thermosetting epoxy resin cured material is stimulated by heat and UV based on the dynamic reversibility of the four hydrogen bonds and disulfide bonds.In view of the above problems,in this paper,2-urea-4[1H]-pyrimidone(UPy)group was introduced into the resin matrix by physical blending and chemical grafting method.The curing materials of E51/593/D2000sp,UPy-E51/D2000,UPy-E51/D 1000/330Nsp,ST3000/UPyD1000/4-AFD,UPy-EHTPB/4-AFD containing quadruply hydrogen bond and disulfide bond were prepared by using polyether amine and 4,4’-diaminodiphenyl disulfide(4-AFD)as curing agent,respectively.The structure,mechanical properties and healing properties of epoxy resin curing materials containing quadruple hydrogen bond and disulfide bond were characterized by DSC,TGA,DMA,SEM,FT-IR and tensile methods.The UPy structure containing quadruple hydrogen bonds was introduced into the E51 resin matrix and the main chain of the resin molecule,the DSC,TGA,DMA and tensile test results showed that the toughness of E51/593/D2000sp and UPy-E51/D2000 epoxy resin cured materials significant increased and the fracture mechanism was obvious ductile fracture,meanwhile the thermal stability and the modulus of the material did not decrease too much due to the energy absorption,consumption of quadruple hydrogen bonds and it can prevent further crack propagation.Tensile test and polarizing microscope results show that E51/593/D2000SP and E51/D1000/330NSP curing materials have good macroscopic and mechanical healing properties based on the mechanism of high temperature dissociation and low temperature reconstruction of dynamic hydrogen bond between UPy dimer,,and the heal efficiency was more than 95%.FT-IR and AFM tests showed that the self-healing properties of the material were caused by the dynamic reversible quadruple hydrogen bond between the UPy dimer.The ST3000/UPy D1000/4-AFD and UPy-EHTPB/4-AFD curing materials was prepared in the low temperature with high repair efficiency with kindliness hydrogenated bisphenol A diglycidyl ether(ST3000 resin)or side chain containing UPy groups modification of epoxy resin poly(1,4-butadiene)(UPy-EHTPB)as the matrix,UPy group single sealing side UPyD1000 or containing dynamic disulfide bond(S-S)4,4-diamino diphenyl disulfide(4-AFD)as curing agent.Reflective infrared and Raman tests showed that the disulfide bond exists in the form of S-S bond in the material.DSC and TGA test results show that the Tg of the material was higher than that of room temperature indicating that the material was solid elastomer at room temperature.The tensile test results showed that the restoration of materials at room temperature with high efficiency due to the motility and diffusivity was stronger of molecular chain segments in low temperature because low Tg of ST3000/UPy-D1000/4-AFD and UPyEHTPB/4-AFD cured materials,so materials at room temperature as the heal time extended and the heal efficiency of material gradually improve,the highest heal efficiency could reach above 90%.