The effects of acidic components and asphaltenes on the dilational rheological properties of hydrophobically modified polyacrylamide (APP5) have been measured as a function of the time, frequency, bulk concentration, and interfacial pressure by means of a drop shape analysis method. It is established that acidic components and asphaltenes play an important role on the interfacial properties of the APP5/crude oil component mixture at water–kerosene interface. With the addition of acidic components, the dilational modulus of the mixture not only increases with time but is also higher at low concentrations and runs through a maximum at a lower concentration compared to pure APP5. Also, the phase angle of APP5/acidic components is lower compared to pure APP5. The results indicate that the appearance of more elastic films because of the mixed adsorption of acidic components and APP5 molecules. The addition of asphaltenes does not influence the interfacial properties of APP5 at high APP5 concentrations. However, one can observe changes of the interfacial tension and the dilational modulus with the addition of asphaltenes at lower APP5 concentrations. It can be concluded that the behaviors of interfacial layers of the APP5/asphaltene mixture are controlled by APP5 molecules in competition with the asphaltenes at the interface.

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