Preparation And Characterization Of Grafted SBS And Its Compatibility With Asphalt

SBS modified asphalt has been widely applied due to its favourable road performance.However, the chemical activity of C=C double bond and its-H in SBS molecular structureresults in their easily oxidization property, and thus the storage stability and the anti-agingproperties of SBS modified asphalt were reduced. These phenomena can be improved bysynthesizing graft-modified SBS using polar monomer. It not only can increase the polarity ofthe SBS molecule, promoting the compatibility between SBS and asphalt, and also destroypart of C=C double bond of SBS, improving the storage stability and the anti-aging propertiesof SBS modified asphalt.Based on this consideration, in this dissertation, three polar monomers (marked A, B andC) were chose to synthesize grafted SBS by using solution polymerization. Three kinds ofgrafted SBS were named SBS-g-A, SBS-g-B and SBS-g-C, respectively, and further toprepare modified asphalt by using them as asphalt modifiers. Compared with SBS modifiedasphalt, polar monomer C was determined ultimately to synthesize grafted SBS according totheir dissolved situation in the asphalt. Using C as a grafting monomer, SBS-g-C withdifferent graft ratio were synthesized by changing the addition amount of monomer. FTIR,1HNMR and XPS were used to characterize the chemical structure of the grafted product. GPCwas carried on to calculate the graft ratio of monomer. Two thermodynamic parameters,solubility parameter and surface tension, of SBS, SBS-g-C and asphalt were measured andcalculated, to analysis the influence on the compatibility between SBS and asphalt of graftcopolymerization of SBS.The results show that the polar monomer C was grafted on the SBS main chainsuccessfully. The molecular weight and distribution of grafted SBS obtained by GPC showthat grafting rate is up to20.32%.Solubility parameter of asphalt, grafted SBS and SBS are9.14(4.1868J/cm~3)1/2,9.10(4.1868J/cm~3)1/2and8.97(4.1868J/cm~3)1/2, while surface tension were49.06mN/m、51.57mN/m and29.50mN/m, respectively. The solubility parameter and surface tension of the grafted SBS is higher comparing with SBS, which means that the grafting effect increases thesolubility parameters and the surface tension of SBS, more close to asphalt’s.