| Popis: |
Eight asphalts selected for intensive study in the Strategic Highway Research Program have been separated into neutral, basic, and acidic fractions by means of ion exchange chromatography. Each asphalt exhibits a characteristic fractionation pattern into neutral, acidic, and basic components. The separations into chemical types were verified by elemental analysis and infrared methods. Separations were reasonably repeatable, and recoveries were acceptable. Large enough amounts of asphalts could be separated so that properties of interest of the fractions could be studied. In all cases, neutral fractions comprised at leaBt one-half of the asphalts. These neutral fractions are the least aromatic and contain the lowest percentages of heteroatoms and metals compared with the polar fractions. They also are much lower in molecular weight. The viscosities of the neutral fractions are at least two orders of magnitude lower than parent asphalt viscosities measured at the same temperature and rate of shear.... |
