Research On The Modification Of Epoxy Resins With Hyperbranched Polymers And Core-shell Particles

Epoxy resins are widely used in aerospace,aircraft,electronic packaging,clean energy,automobile,and structure materials due to their unique properties,such as excellent strength,good adhesive,high modulus,low shrinkage,high thermal stability and ease of processability.However,the high crosslinking density,poor impact resistance and highly britteness of epoxy system resistrict their applications.So it is meaningful to tough the epoxy resins for expanding their applications.In this dissertation,the method and mehanisms of toughening epoxy resins have been reviewed,and a novel route for toughening epoxy resins by hyperbranched polymers(HBPs)and core-shell nanoparticles have been proposed.Main contents and conclusions of this dissertation are as follows:(1)A kind of hyperbranched polymer with hydroxyl groups,HBP-OH,was synthesized through AB2 route using succinic anhydride and diethanolamine as raw materials.Furthermore,a kind of epoxide terminated hyperbranched polymer,HBP-epo,was first prepared through the end-capping reaction between HBP-OH and epichlorohydrin.Moreover,a kind of hyperbranched polymer with amino group,HBP-NH2,was synthesized through AB2 + AB3 route using methyl acrylate and diethanolamine as raw materials.The chemical structures and molecular weights of the three HBPs were characterized by attenuated total internal reflection infrared spectroscopy(ATR-IR),1H Nuclear magnetic resonance spectroscopy(1H NMR)and gel permeation chromatography(GPC).The ATR-IR and 1H NMR spectra show that HBP-OH,HBP-epo and HBP-NH2 have been succefully synthesized.And the molecular weights of HBP-OH,HBP-epo and HBP-NH2,which were obtained by GPC,have been 5963,6345 and 7763 g/mol,respectively.(2)The influences of HBP contents on the mechanical properties,fracture toughness,surface hardness,shrinkage and glass transition temperatures(Tg)of bisphenol A diglycidyl ether epoxy resin system were studied using polyamide as curing agent.The toughening mechanisms of HBPs on epoxy/polyamide system were discussed through field scanning electron microscope(FESEM).HBP could be easy incorporated into the crosslinking network of epoxy/polyamide system due to the good compatibility between HBP and epoxy matrix and resulted in modifying the network,and then improving the toughness of system.Epoxy/polyamide systems modified with HBP-OH,HBP-epo and HBP-NH2 exhibit 1.45,1.55 and 1.61-fold increase in fracture toughness,respectively.FESEM results show that the toughening mechanism has been the shearing deformation toughening mechanism.(3)The effects of silanized zirconium waste nanoparticles on the mechanical properties,fracture toughness,surface hardness and Tg of the epoxy/polyamide/HBP system were studied.The toughening mechanisms of silanized zirconium waste nanoparticles on epoxy/polyamide/HBP system were investigated through FESEM.The resistances of crack initiation and propagation of epoxy/polyamide/HBP system were improved owing to the incorporation of silanized zirconium waste nanoparticles.Furthermore,crack propagation was deflected and terminated.The epoxy/polyamide/HBP-OH,epoxy/polyamide/HBP-epo and epoxy/polyamide/HBP-NH2 systems modified with silanized zirconium waste nanoparticles exhibit 1.15,1.18 and 1.23-fold increase in fracture toughness,respectively.FESEM results indicate that the toughening mechanisms have been the second phase toughening mechanism and shearing deformation mechanism.(4)Inorganic-organic composites,CSP-HBP(CSP-HBP-OH,CSP-HBP-epo and CSP-HBP-NH2)core-shell nanoparticles,were first fabricated through grafting HBP onto the surface of silanized zirconium waste nanoparticles.The particle size,chemical structure and grafting ratio of shell were detected by ATR-IR,1H NMR,transmission electron microscope(TEM)and thermogravimetric analysis(TGA).The influences of CSP-HBP content on the mechanical properties,fracture toughness,surface hardness and Tg of epoxy/polyamide system were investigated.The toughening mechanisms of CSP-HBP core-shell particles were also discussed by FESEM.The ATR-IR and 1H NMR spectra indicate that CSP-HBP-OH,CSP-HBP-epo and CSP-HBP-NH2 have been successfully prepared.TEM images show that the sizes of CSP-HBP-NH2 has been in the range of 60-90 nm.The TGA curves suggest that the grafting ratios of HBP-OH,HBP-epo and HBP-NH2 have been 4.1,9.5 and 29.1%,respectively.The excellent compatibility between core-shell nanoparticles and epoxy matrix,which was due to the functional group in the architecture of CSP-HBP,could improve the interfaces adhesives of CSP-HBP and matrix,increase the shearing deformations,adsorb impact energy and then enhance the toughness.Epoxy/polyamide systems modified with CSP-HBP-OH,CSP-HBP-epo and CSP-HBP-NH2 exhibit 1.63,1.64,and 1.75-fold increase in fracture toughness,respectively.FESEM results also show that the toughening mechanism has been the second phase toughening mechanism.(5)The influence of CSP and HBP on the mechanical properties,fracture toughness,surface hardness and Tg of epoxy/polyamide system were studied.The toughening mechanisms were discussed by FESEM.Epoxy/polyamide systems modified with CSP-HBP-OH and HBP-OH(HBP-epo)exhibit 1.23-fold(1.19-fold)increase in fracture toughness;epoxy/polyamide systems modified with CSP-HBP-epo and HBP-OH(HBP-epo)exhibit 1.26-fold(1.22-fold)increase in fracture toughness;epoxy/polyamide systems modified with CSP-HBP-NH2 and HBP-NH2 exhibit 1.31-fold in fracture toughness.The tensile strength,percent elongation at break,flexural strength,impact strength,surface hardness and Tg have been also simultaneously improved.FESEM results indicate that the toughening mechanism has been the synergetic toughening mecheanism of the second phase mechanism and shearing deformation mechanism.