A C-13 NMR and DSC study of the amorphous and crystalline phases in asphalts

The amorphous and crystalline phases in asphalt have been identified and st udied using low-temperature solid-state carbon-13 CP/MAS NMR and DSC techni ques. The NMR mass percent of the crystalline methylene carbons was shown t o correlate linearly with the mass percent of crystalline wax in asphalts m easured using DSC. While the internal methylene carbon content of long-chai n alkanes in the crystalline phase in the asphalts varied, the internal met hylene carbon content of the long-chain alkanes in the amorphous phase rema ined relatively constant. The NMR crystalline methylene carbon content was plotted against a low-temperature cracking parameter, the fracture temperat ure of an asphalt. It was found that 1% or less of aliphatic carbons in the crystalline phase has little effect on the fracture temperature. For these asphalts, the fracture temperature depends mainly on the initial amount of mobile aliphatic carbons in the amorphous phase at 23 degrees C. For aspha lts containing 1% or more of crystalline aliphatic carbons, the fracture te mperature increases with increasing crystalline methylene carbon content.