Investigation On Microstructures And Properties Of Epoxy Asphalts Modified By SBS Containing Various Structures And Functionalized SBS

Epoxy asphalt(EA)is a kind of reactive polymer modified asphalt(PMA)with outstanding performances.Nowadays,EA has been widely used in paving of roads for special uses.Styrene-butadiene-styrene triblock copolymer(SBS),as one of the most important thermoplastic modifiers,has been also worldwidely applied in asphalt modifications.In this thesis,SBS and functionalized SBS were chosen to modify epoxy asphalt binder(EAB).The micro structures and properties of epoxy SBS modified asphalt(ESBA)with various styrene(S)/butadiene(B)structures were studied.Then brominated SBS(BrSBS)was added into EAB to enhance its flame resistance.Another functionalized SBS,epoxidized SBS(ESBS)with different degrees of epoxidation,was synthesized.The phase-separated microstructure and properties of epoxy ESBS modified asphalt(EESA)were researched.Firstly,ESBAs were prepared with epoxy oligomer,curing agent and SBSmodified asphalts(SBAs)with various styrene-butadiene structures,which in turn were subjected to laser scanning confocal microscopy(LSCM),viscous measurements,thermal analysis and tensile tests.The LSCM results revealed that both polymer-rich phase and fluorescent particle-rich phase were observed in the asphalt matrix.Moreover,the number of SBS particles in SBAs increased with the increase of styrene contents.The presence of SBS decreased the size of dispersed domains in the continuous epoxy phase of the neat EAB.For ESBAs,a double phase separation occurred between SBA and epoxy and between asphalt and SBS in the dispersed SB A phase.Both number and size of SBS domains in the dispersed SBA phase of ESBAs increased with the increase of styrene contents.The inclusion of styrenic polymers increased the viscosity of the neat EAB.The viscosity of ESBAs increased with the increase of average molecular weights of the styrenic polymers.The addition of styrenic polymers increased the glass transition temperature(Tg)and storage modulus(E')of the neat EAB.Meanwhile,the inclusion of styrenic polymers weakened the damping properties of the neat EAB.The styrene-butadiene structures had little effect on the Tg and damping properties of ESBAs.The E' of ESBAs decreased with the increase of styrene contents.The presence of SBS enhanced the thermal stability of the neat EAB.Tensile results showed that the addition of SBS increased the tensile strength of the neat EAB.Then,BrSBS was added into EAB to produce epoxy BrSBS modified asphalt(EBrSA).Due to the persistence,bioaccumulation and toxicity impact to environment,several most common-used flame retardants may face severe scrutiny or even prohibition in a few years.BrSBS derives from the bromination of SBS,which is ecofriendly due to its huge molecule weight.In present thesis,the phase-separated microstructure,viscosity,flame retardancy,thermal,damping and mechanical properties of EBrSAs were studied.Double phase separation occurred in EBrSAs.BrSBS modified asphalt(BrSA)-rich phase dispersed in the continuous epoxy-rich phase when the BrSBS contents were lower.However,phase-inverted morphology appeared when the BrSBS contents were higher.In other words,the epoxy-rich phase dispersed in the continuous BrSA-rich phase.The incorporation of BrSBS greatly increased the viscosity of the neat EAB.The flame retardancy of the neat EAB was significantly improved with the inclusion of BrSBS.The presence of BrSBS lowered the thermal stability,damping and mechanical properties of the neat EAB.However,the addition of BrSBS notably increased Tg of the neat EAB.At last,SBS was epoxidized by H2O2 with different concentrations to prepare ESBSs with various degrees of epoxidation.The degrees of epoxidation and characteristic groups of ESBS were determined by nuclear magnetic resonance(NMR)spectrometer and Fourier transform infrared(FT-IR)spectrometer.The mixtures of ESBS and epoxy oligomer were mixed with asphalt and curing agent to prepare EESA.The results of NMR and FT-IR showed that SBS had been epoxidized.The LSCM micrographs of EESA revealed that polymer domains together with asphalt domains dispersed in the continuous epoxy resin phase.When the degree of epoxidation of ESBSs was low,polymer domains dispersed at the edge of asphalt phase and epoxy phase.With the increase of degree of epoxidation of EESA,polymer domains moved to asphalt domains and the modified asphalt domains dispersed more uniformly in the continuous epoxy phase.The incorporation of ESBS increased the viscosity of the neat EAB and decreased its thermal stability.On the other hand,ESBS greatly enhanced the elongation at break of the neat EAB,and when the degree of epoxidation of ESBSs was high,the toughness of the neat EAB had been significantly improved with the inclusion of ESBS.