Effect of Hydrophobically Modified Polyacrylamide on Interfacial Dilational Rheological Properties of Crude Oil Components

The effect of hydrophobically modified polyacrylamide (HMPAM) on the dilational rheological properties of interfacial films containing acidic components or asphaltenes in petroleum crude oil was investigated by drop shape analysis method. The influence of surface. active component concentration on the dilational rheological behavior was investigated. Experimental results show that the dilational modulus is approximately 100 mN.m(-1) for a 1750 mg.L-1 HMPAM solution. This is due to the formation of an interfacial structure by a hydrophobic interaction among HMPAM molecules. As the interfacial film ages, the acidic component molecules adsorb onto the interface and form mixed complexes with the hydrophobic parts of the HMPAM molecules. These interactions reduce the dilational modulus by a fast exchange process and the elasticity of the structure improves because of an enhanced hydrophobic interaction among the HMPAM molecules. For asphaltenes, the nature of the interfacial film is controlled by both the structure of HMPAM and the interfacial complex formed by pure asphaltene molecules because of their relatively larger molecular sizes as well as their strong intermolecular interactions, which leads to a slight decrease in the dilational modulus compared with the pure HMPAM system.