Study On The Compatibility Between SBS Co-polymers And Asphalt By Dissipative Particle Dynamics

SBS co-polymers can improve the high temperature resistance to rutting,low temperature cracking resistance and aging resistance of asphalt pavement.But it has poor compatibility with asphalt and thus its modification effect is poor.There is serious influence on the road performance of SBS modified asphalt.At present,the compatibility of SBS modified asphalt is mainly measured by experiment.But it is not possible to systematically study the modification mechanism of SBS polymer and the influence of asphalt composition and SBS co-polymer molecular structure on compatibility of SBS modified asphalt in the microcosmic only by experiment.In this paper,molecular dynamics and dissipative particle dynamics are used to study the aggregate morphology of SBS modified asphalt and the influence of content,block ratio and molecular weight of SBS co-polymers as well as asphalt composition on the compatibility of SBS modified asphalt.The specific research conclusions are shown as follows:The asphalt aggregation system was simulated by dissipative particle dynamics.Moreover,the influence of asphalt composition on morphology of aggregation was investigated by concentration distribution curve and radial distribution function.The results showed that,with the increase of asphaltenes,asphaltenes gradually form colloidal nucleus structure.When the content of asphaltenes is 11wt%,colloidal nucleus disperse uniformly.As content of asphaltenes continues to increase,the degree of asphaltenes aggregation becomes more and more serious.Compatibility between saturates and asphaltenes is poor.As the increases of saturates,asphaltenes form colloidal nucleus structure gradually.When content of saturates is 25wt%,colloidal nucleus disperse uniformly.As content of saturates continues to increase,the size of colloidal nucleus becomes larger.Compatibility between aromatics and asphaltenes is good.With the increase of aromatics,the degree of asphaltenes aggregation decrease.When the content of aromatics is 20wt%,colloidal nucleus disperse uniformly,but the size of colloidal nucleus is larger.When the content of aromatics is 30wt%,colloidal nucleus disperses uniformly,and the size of colloidal nucleus is smaller.As content of aromatics continues to increase,the number of colloidal nucleus decreases and asphaltenes disperse more and more uniformly.Resins have good compatibility with asphaltenes.As the content of resins increases,the size of colloidal nucleus becomes smaller,and colloidal nucleus disperse uniformly.The influence of asphalt composition on compatibility between SBS co-polymers and asphalt was simulated by dissipative particle dynamics.The influence of asphalt composition on the compatibility between SBS co-polymers and asphalt was studied by analyzing the interaction energy between SBS co-polymers and asphalt.The results showed that addition of SBS co-polymers is detrimental for asphalt to form stable core structure.SBS co-polymers are mainly dispersed in saturates and aromatics.PB segments of SBS co-polymers adsorb saturates to swell and PS segments of SBS co-polymers adsorb aromatics to swell.With increase of content of saturates,compatibility between SBS co-polymers and asphalt first becomes better,then becomes stable.As content of aromatics increases,compatibility between SBS co-polymers and asphalt becomes better.As content of resins increases,compatibility between SBS co-polymers and asphalt becomes worse.When content of asphaltenes falls in the range of 5wt%-15wt%,compatibility between SBS co-polymers and asphalt first becomes better,then becomes worse.The influence of molecular structure and content of SBS co-polymers on compatibility between SBS co-polymers and asphalt was simulated by dissipative particle dynamics.By analyzing the interaction energy between SBS co-polymers and asphalt,the influence of molecular structure and content of SBS co-polymers on the compatibility between SBS co-polymers and asphalt was investigated.The results showed that when content of SBS polymer is less than 6wt%,SBS co-polymers disperse more uniformly.When content of SBS co-polymers is 6wt-9wt%,SBS co-polymers form network structure,and compatibility between SBS co-polymers and asphalt becomes better.In SBS co-polymers with different block ratios,asphalt and SBS co-polymers with the block ratio(S/B)of 30/70 have the best compatibility.When the block ratio and content of SBS co-polymers are same,with increase of molecular weight of SBS co-polymers,compatibility between SBS co-polymers and asphalt gradually becomes worse.