Polar asphaltenes facilitate the flow improving performance of polyethylene-vinyl acetate

Herein, four asphaltenes in distinguished polarities were first fractionated from heavy crude oil by the solventprecipitation method (that is, C5I asphaltenes) and characterized, and the effects of asphaltenes on the polyethylene-vinyl acetate (EVA) PPD's performance for the model waxy oil were evaluated. Results show that the asphaltenes in lower polarities contain a greater number of aliphatic groups and present a higher H/C ratio, hence exhibiting better oily compatibility and the greater synergistic performance with EVA in improving the waxy oil flowability at low temperatures. The competition between the co-crystallization and nucleation effect of additives determines the wax precipitating temperature (WPT). Adding asphaltenes delays the wax precipitation, but increases wax crystal number just below WPT, especially together with EVA. According to the micro-observation and isothermal titration tests, EVA can adsorb onto the asphaltene aggregates to form the composite EVA/asphaltene particles, and the adsorption gradually reaches saturated with the EVA injecting. The composite particles act as the heterogeneous crystallizing templates for wax molecules to precipitate, triggering the formation of wax crystal flocs with large size, spherical-like morphology, and compact structure. Reducing the asphaltenes polarity strengthens the stronger interactions among asphaltenes, EVA and paraffin wax molecules, and hence improves the EVA/asphaltene synergistic performance.