Atomic force microscopy investigation of interaction forces between polyethylene and asphaltene surfaces

Many petroleum-derived asphalts used for road construction exhibit poor rheological properties. These properties of asphalt can be improved by addition of various polymer fillers to the asphalt blend. Recycled polyolefines, especially polyethylene and polypropylene have been used as the asphalt modifying fillers. Unfortunately the polyolefine-asphalt mixtures are not stable and have a tendency to separate because of the chemical incompatibility of the components. In our research, surfactants were used to improve polymer-asphalt compatibility. Interaction forces between a polyethylene particle and a polyethylene surface and between a polyethylene particle and an asphaltene-surface were measured in surfactant solutions in n-tetradecane and pyridine using the atomic force microscopy colloidal probe technique. Dodecylamine, lauric acid and lauric alcohol (C12E4) were used as surfactants. The most pronounced change the interactions was observed for polyethylene-polyethylene surfaces in the solution of lauric acid. At the same conditions polyethylene-asphaltene interactions were decreased. The most increase was the increase in the repulsion range (to 26 nm) between the spherical PE probe and flat polyethylene surface for 10~3 M n-tetradecane solution of ethoxylated lauryl alcohol (C12E4). In the case of lauric acid the interaction range extended to 24 nm and for dodecylamine to 21 nm. The interaction between the polyethylene sphere and flat asphaltene surface extended to 16 nmfor dodecylamine, to 18 nmfor lauryl alcohol ethoxylated (C12E4) and to 14 nmfor lauric acid.