Microstructure And Rheological Properties Of Bitumen Modified By Polyethylene And Its Blend

In this thesis,bitumen modified by polyethylene(PE)or polymer blend including PE was studied.The phase separation structure was regulated by changing the molecular weight of PE,composition ratio of polymer blend and so on,in order to endow bituminous materials high modulus and high elasticity.Accordingly,the rutting resistance would be enhanced.A further study on the bitumen modified by waste PE was also explored which contributes to the production of environmentally-friendly bituminous materials.The effect of PE molecular weight on bitumen properties was investigated.The modulus and the viscosity is higher,the phase angle is lower of the modified bitumen with the molecular weight increasing.The lower molecular PE-rich droplets phase is dispersed in the bitumen-rich matrix,which can be regarded as droplet-matrix(dispersed-matrix phase)structure.The higher molecular PE modified bitumen still exhibits droplet-matrix structure.But the PE-rich droplets are irregular and partially elongated.It was found that the highest molecular weight PE modified bitumen has the highest melting point temperature and good stability by DSC testing.Accordingly,the highest modulus and viscosity is endowed,reflecting better rutting and deformation resistance.Based on the results of the previous,the best anti-rutting PE modifier and thermoplastic elastomer SBS(PE/SBS blends)was selected to endow further improvable elasticity(recover from deformation)in bituminous materials.It is noticed that the modified bitumen is more dependent on temperature when SBS is the main component.PE-rich phase has a large melting enthalpy(crystallization-amorphous phase transition)when the crystallization PE is main,resulting in stable rheology “platform” within a certain range below the melting point of PE.Accordingly,the temperature sensitivity is improved and high temperature resistance to rutting is enhanced.Based on the above,the third component(chloroprene rubber(CR),thermoplastic bomb(SBS),polyethylene compatibilizer(PEC))is added to study waste polyethylene(WPE)modified bitumen.The modulus and elasticity is higher with the third component increasing.The system with 4wt.% PEC forms a highly crosslinked sponge-like gel structure.The special phase structure makes good thermodynamics stability,high modulus and high viscosity,low phase angle,reflecting good resistance to rutting and deformation.